Search

Fragmentation of natural vegetation is currently one of the largest threats to plant populations and their interactions with pollinators. Plant reproductive susceptibility to habitat fragmentation has been investigated in many species; however, the response of wild mass‐flowering species is poorly known, with research limited to mainly boreal plant species.Here, we studied twelve remnant populations of the threatened mass‐flowering shrub Conospermum undulatum in the southwest Australian biodiversity hotspot, each presenting different population size, level of isolation, and floral display. We assessed the impact of fragmentation on (a) fruit and seed production; and (b) seed germination. To gain a deeper understanding of factors influencing the reproductive success of C. undulatum, we performed pollinator exclusion and self‐pollination treatments to experimentally assess the mating system of this threatened shrub.We found C. undulatum to be strictly self‐incompatible and totally reliant on pollinators visiting with an outcrossed pollen load to complete the reproductive cycle. Further, we found that fruit production dropped from 35% to, Plant reproductive susceptibility to habitat fragmentation has been investigated in many species; however, the response of wild mass‐flowering species is poorly known. Here, we studied the reproductive output and mating system of twelve remnant populations of the threatened mass‐flowering shrub Conospermum undulatum in the southwest Australian biodiversity hotspot, each presenting different population size, level of isolation, and floral display. Fragmentation has a significant effect on the reproductive output of C. undulatum, and size, isolation, and floral display of populations are important factors to be considered when planning conservation actions.

Understanding the timescales that shape spatial genetic structure is pivotal to ascertain the impact of habitat fragmentation on the genetic diversity and reproductive viability of long-lived plant populations. Combining genetic and ecological information with current and past fragmentation conditions allows the identification of the main drivers important in shaping population structure and declines in reproduction, which is crucial for informing conservation strategies. Using historic aerial photographs, we defined the past fragmentation conditions for the shrub Conospermum undulatum, a species now completely embedded in an urban area. We explored the impact of current and past conditions on its genetic layout and assessed the effects of genetic and environmental factors on its reproduction. The historically high structural connectivity was evident in the genetics of the species. Despite the current intense fragmentation, we found similar levels of genetic diversity across populations and a weak spatial genetic structure. Historical connectivity was negatively associated with genetic differentiation among populations and positively related to within-population genetic diversity. Variation partitioning of reproductive performance explained ~ 66% of the variance, showing significant influences for genetic (9%), environmental (15%), and combined (42%) fractions. Our study highlights the importance of considering the historical habitat dynamics when investigating fragmentation consequences in long-lived plants. A detailed characterization of fragmentation from 1953 has shown how low levels of genetic fixation are due to extensive gene flow through the non-fragmented landscape. Moreover, knowledge of the relationships between genetic and environmental variation and reproduction can help to implement effective conservation strategies, particularly in highly dynamic landscapes.

Specialization to extreme selective situations promotes the acquisition of traits whose coadaptive integration may compromise evolutionary flexibility and adaptability. We test this idea in the context of the foliar stoichiometry of plants native to the South African Cape. Whereas foliar concentrations of nitrogen, phosphorus (P), potassium (K), calcium, magnesium, and sodium showed strong phylogenetic signal, as did the foliar ratios of these nutrients to P, the same was not true of the corresponding soil values. In addition, although foliar traits were often related to soil values, the coefficients of determination were consistently low. These results identify foliar stoichiometry as having a strong genetic component, with variation in foliar nutrient concentrations, especially [P] and [K], being identified as potentially adaptive. Comparison of stoichiometric variation across 11 similarly aged clades revealed consistently low foliar nutrient concentrations in lineages showing specialization to extremely low-nutrient fynbos heathlands. These lineages also display lower rates of evolution of these traits as well as a reduced tendency for foliar [P] to track soil [P]. Reduced evolutionary lability and adaptability in the nutritional traits of fynbos-specialist lineages may explain the floristic distinctness of the fynbos flora and implies a reduced scope for edaphically driven ecological speciation.

As climates change, restoration programmes need to maximize the capacity of regenerating ecosystems to adapt to new environments, particularly when planting long-lived trees. By using a combined phenotypic and genomic approach, we assessed evidence of adaptation capacity in Eucalyptus loxophleba ssp. lissophloia, a mallee eucalypt important for restoration and oil production in Western Australia. Assessment of leaf traits in nine wild populations across a rainfall gradient showed that two traits were correlated with long-term moisture availability. Populations in more arid environments had lower specific leaf area and lower stomatal conductance, consistent with a stable plastic or adaptive response. Other leaf size and shape traits were correlated with short-term climate variables, suggesting a dynamic plastic response. Genome-wide scans with 4851 DArTseq markers and outlier analysis detected 50 markers showing signals of disruptive selection, consistent with local adaptation. Sixteen markers showed allele frequencies correlated with aridity; three were also associated with differences in stomatal conductance. Multivariate analysis and marker-environment associations signalled secondary directions of adaptation associated with maximum temperatures and soil phosphorus. We suggest that adaptation and acclimation are both likely determinants of functional phenotype in E. loxophleba, and argue that aridity is a critical driver of adaptation in this widespread species.

Widespread species spanning strong environmental (e.g., climatic) gradients frequently display morphological and physiological adaptations to local conditions. Some adaptations are common to different species that occupy similar environments. However, the genomic architecture underlying such convergent traits may not be the same between species. Using genomic data from previous studies of three widespread eucalypt species that grow along rainfall gradients in southern Australia, our probabilistic approach provides evidence that adaptation to aridity is a genome-wide phenomenon, likely to involve multiple and diverse genes, gene families and regulatory regions that affect a multitude of complex genetic and biochemical processes.

Premise Recent habitat fragmentation is posing a risk to the wavy-leaved smokebush, Conospermum undulatum (Proteaceae), a rare plant species endemic to southwestern Western Australia. Microsatellite markers are required to characterize the genetic diversity and structure of the species for conservation purposes and to facilitate ecological studies. Methods and results Illumina MiSeq high-throughput sequencing was used to develop 20 novel microsatellite markers for C. undulatum. Polymorphism at each locus was assessed using 72 individuals from three natural populations. Nineteen markers were polymorphic, with the number of alleles per locus ranging from two to 21, and observed and expected heterozygosity ranging from 0.000 to 1.000 and 0.117 to 0.919, respectively. All markers successfully amplified in three congeneric species (C. stoechadis, C. canaliculatum and C. triplinervium). Conclusions The microsatellite markers will be useful for revealing patterns of genetic diversity, dispersal dynamics, and hybridization events for C. undulatum to inform future conservation efforts.

• Disruption of pollination services has been investigated in many species; however, fragmentation-induced effects on endemic plants that rely on species-specific invertebrate pollinators are still unclear. While honeybees can forage over long distances, many native bees with small body size are unable to extend their foraging range, making habitat fragmentation the largest threat to such systems. • Here, we defined the pollinator assemblage of our target species, Conospermum undulatum (Proteaceae), among remnant populations characterized by different degrees of fragmentation. We explored the impact of fragmentation on flower visitation in eleven populations of C. undulatum. Lastly, we took advantage of the fragmentation gradient to tease apart the influences of pollen quantity and quality on pollen limitation. • Small populations showed an impoverished pool of weakly effective pollinators. Flower visitation increased from 1.5% to 74.3% with increasing floral display index, while it increased from 1.3% to 5.6% with increasing connectivity levels of populations. We found evidence of pollen quantity limitation across all the populations; however, the overall pollen limitation was greater in small fragments where genetic factors limited the quality of pollen. • Native bees were absent in small isolated remnants. Our study highlights the importance of such pollinators for plants that coevolved with them. The availability of compatible pollen is limited in small remnant populations and native pollinators appeared unable to maintain an adequate inter-population pollen flow in heavily fragmented landscapes. The effects of habitat fragmentation can be exacerbated in small and isolated populations of plants that rely on species-specific pollinators for sexual reproduction.

Human-wildlife conflicts around the loss and use of habitat are common reasons for species being listed as threatened. In order to reduce such conflicts it is important to have a clear understandin...

Citizen science monitoring programmes are making increasingly important contributions to wildlife conservation, often at spatial and temporal scales unachievable by individual or teams of researchers. They are particularly valuable in estimating population trends and management impacts, and thus informing effective conservation decisions for declining species. The quality and potential biases of citizen science data are of concern, however, and appropriate experimental design and analysis are needed to ensure that the maximum scientific value is extracted. We investigated these issues in a citizen science survey of the Endangered Carnaby's black-cockatoo Calyptorhynchus latirostris. Since 2010, citizen scientists have conducted synchronized annual counts of Carnaby's black-cockatoo at roost sites to estimate the population trend. Survey effort was substantial, with c. 150 sites surveyed by > 260 volunteers each year. Relatively few sites were occupied, however, and only 42 (16%) of the 265 sites surveyed in total accounted for 95% of all observations. Many sites were empty and survey effort was often inconsistent. Taking these issues into account, analysis showed a statistically significant decline in roost occupancy rate and a non-significant decline in the mean size of roosting flocks, with an estimated overall trend of 14% decline per annum in the number of roosting birds. We highlight three important issues for citizen science monitoring programmes: the need to maintain regular surveys of sample sites to avoid patchy data, use an appropriate model that accounts for variable survey effort, high frequency of zero counts, and sampling site turnover, and incorporate information on site characteristics to help explain variation.

Plant interaction studies provide a good understanding of the roles of key species, which can assist restoration of natural ecosystems. Among the interactions, facilitation and competition are known to affect ecosystem structure and function. We investigated whether a deep-rooted species could positively affect surrounding seedlings through hydraulic redistribution during dry months. We conducted two experiments in which seedlings from two species were growing together or isolated from source plants (field experiment) and where plants were isolated from source plants that were connected to or separated from a water table (glasshouse experiment). Survival, growth, water relations and soil water content were measured. We also applied δ2H enriched water adjacent to, or into, the roots of source plants to track water movement between plants. Soil water content was higher in shallow layers where source plants could interact with seedlings (field) and when accessing water tables (glasshouse). Seedlings from all treatments had an increase in leaf δ2H. Seedlings of Banksia attenuata that were isolated from source plants had the highest survival, growth and stomatal conductance rates. Seedlings of Gompholobium tomentosum presented higher stomatal conductance rates when growing with source plants than when isolated from them during the first months, but this relationship reversed towards the end of summer. These results suggest that source plants and seedlings competed, but the influence of facilitation and competition might change during the year, at least for the shallow-rooted species. Therefore, competition for water and/or other limiting factors must be considered when planning ecological restoration in such areas.

Invasive species may outperform native species by acquiring more resources or by efficiently using limited resources. Studies comparing leaf traits as a metric of carbon capture strategies in native and invasive species have come to different conclusions. Some studies suggest that invasive species are better at acquiring resources, but that native and invasive species use resources similarly. Other studies have found that native and invasive species differ in resource use efficiency, which implies different biochemical or physiological mechanisms of carbon capture. To resolve this debate, we examined relationships among four leaf traits (photosynthetic rate, specific leaf area, foliar nitrogen, foliar phosphorus) in co-occurring native and invasive species from eight plant communities across five Mediterranean-climate ecosystems. We performed standardized major axis regression for all trait combinations within and across sites, testing for slope homogeneity and shifts in elevation (y-intercept) or along a common slope between species groups. Across the global dataset, native and invasive species had similar carbon capture strategies (i.e., similar slopes), with invasive species occupying a position of greater resource acquisition. However, these patterns did not hold when regions were analyzed individually. Regional differences may be driven by differences in life form between native and invasive species, and variation in soil resource availability among regions. Our context-dependent results reveal not only that management of invasive species will differ across regions but also that global comparisons of invasive and native species can be misleading.

Where threatened species persist in multiple use landscapes, management activities, such as prescribed burning, may influence the availability of resources for those species. We examined how time since fire can influence food resources for the endangered Carnaby’s cockatoo (Calyptorhynchus latirostris) in banksia woodlands of southwestern Australia. Tree density and cone productivity of dominant plant species, Banksia attenuata and Banksia menziesii, were compared across 44 sites of varying post-fire aged vegetation. The number of Carnaby’s cockatoos that could be supported in banksia woodlands was estimated using the bird’s energetic requirements and seed energy content. Banksia attenuata produced more cones at sites aged 10–30 years since fire in both survey years, while cone productivity for B. menziesii was highest in very old sites (>35 years since fire) in one year only. Higher numbers of Carnaby’s cockatoos were predicted to be supported in vegetation aged between 14–30 years since fire, peaking in vegetation aged 20–25 years. The current distribution of post-fire aged vegetation within this area (>60% burnt within the last 7 years) is predicted to support ∼2725 Carnaby’s cockatoos, representing 25–35% of the estimated birds reliant on the area. Our results indicate that food resources are influenced by time since fire and, consequently, if optimising food resources was an objective, may be manipulated by altering burning patterns. While human and asset protection is a priority for prescribed burning, management of landscapes for improved persistence of threatened species is also important and complex trade-offs will have to be considered.

Patterns of adaptive variation within plant species are best studied through common garden experiments, but these are costly and time-consuming, especially for trees that have long generation times. We explored whether genome-wide scanning technology combined with outlier marker detection could be used to detect adaptation to climate and provide an alternative to common garden experiments. As a case study, we sampled nine provenances of the widespread forest tree species, Eucalyptus tricarpa, across an aridity gradient in southeastern Australia. Using a Bayesian analysis, we identified a suite of 94 putatively adaptive (outlying) sequence-tagged markers across the genome. Population-level allele frequencies of these outlier markers were strongly correlated with temperature and moisture availability at the site of origin, and with population differences in functional traits measured in two common gardens. Using the output from a canonical analysis of principal coordinates, we devised a metric that provides a holistic measure of genomic adaptation to aridity that could be used to guide assisted migration or genetic augmentation.

The food resource utilisation of six species of Banksia by the endangered Carnaby’s cockatoo (Calyptorhynchus latirostris) was investigated on the Swan coastal plain, Western Australia, over a 12-month period. The energy yield from the seeds harvested by the cockatoos was determined and the information was combined with data on the number of infructescences produced per hectare, the average seed yield per infructescence and the average rate of harvest of that species of seed by the cockatoos to calculate estimates of the number of infructescences required to support a single cockatoo per day under a range of scenarios. Over 65% of infructescences of each species of Banksia handled by the cockatoos were consumed for seed. Banksia sessilis had the largest number of infructescences and follicles manipulated by Carnaby’s cockatoos. The energy content of Banksia seed was 20–23 kJ g–1. Seed weight varied from 0.075 ± 0.016 (s.e.) g for B. attenuata to 0.007 ± 0.002 (s.e.) g for B. sessilis. The number of infructescences required to meet the birds’ daily energy intake ranged from 14 for B. grandis to 3821 for B. sessilis. The results have important implications for the continued capacity of the Swan coastal plain to support Carnaby’s cockatoos, for the future survival of obligate seeding Banksia spp. and for anthropogenic revegetation programs utilising Banksia spp.

The idea that dominant invasive plant species outperform neighboring native species through higher rates of carbon assimilation and growth is supported by several analyses of global data sets. However, theory suggests that native and invasive species occurring in low-resource environments will be functionally similar, as environmental factors restrict the range of observed physiological and morphological trait values. We measured resource-use traits in native and invasive plant species across eight diverse vegetation communities distributed throughout the five mediterranean-climate regions, which are drought prone and increasingly threatened by human activities, including the introduction of exotic species. Traits differed strongly across the five regions. In regions with functional differences between native and invasive species groups, invasive species displayed traits consistent with high resource acquisition; however, these patterns were largely attributable to differences in life form. We found that species invading mediterranean-climate regions were more likely to be annual than perennial: three of the five regions were dominated by native woody species and invasive annuals. These results suggest that trait differences between native and invasive species are context dependent and will vary across vegetation communities. Native and invasive species within annual and perennial groups had similar patterns of carbon assimilation and resource use, which contradicts the widespread idea that invasive species optimize resource acquisition rather than resource conservation. .

Understanding the interactive effects of global change drivers on vegetation is critical for ecosystem management and restoration, particularly in the Mediterranean-climate biodiversity hotspots of the world. Climate change, habitat loss and nitrogen deposition have been identified as the key threats to biodiversity loss in these regions, yet their combined effects are poorly understood. We measured the interactive effects of rainfall manipulation (reduction, control, addition) and nitrogen deposition (N addition, N 1 P addition, and unfertilised) on the establishment of 19 Banksia-woodland species planted at three sites in southwestern Australia. Seedling survival and aboveground biomass was increased with water addition but was not affected by rainfall reduction. N addition alone did not impact seedling survival and growth, but interacted with rainfall manipulation and site in unpredictable ways. Treatment effects were context dependent, which we attributed to historic nutrient enrichment and competitive exotic species that prevented seedling establishment. Plant species (n 5 6) varied greatly in their water-use efficiency and nitrogen-use efficiency responses to the imposed treatments, which underscores the difficulty of generalising results to larger numbers of species. Despite our finding that rainfall manipulation and nutrient addition have complex, and in some cases antagonistic effects on seedling survival and growth in Banksia woodlands, our results suggest that local context (i.e. invasive species, land-use history) will have as much influence on seedling establishment as global changes in climate and nitrogen deposition. We call for more field experiments and predictive models to explore further the importance of ecological context in determining the interactive effects of multiple global change drivers on ecosystems. Finally, to realize effective biodiversity conservation, local management interventions that address invasive species and associated habitat degradation will be as critical in the future as they are now.

Aim Interpretations of global-scale patterns in foliar N and P concentrations and N:P ratios across climatic gradients and biomes often ignore complications imposed by taxonomic and phylogenetic structure in the nutrient concentrations of the constituent taxa. We analysed foliar N and P concentrations and N:P ratios of species from similar climate zones, but with contrasting soil fertility, to determine the relative importance of phylogeny and geographic region in driving foliar nutrient concentrations. Location Mediterranean climate regions. Methods Mean foliar N and P concentrations of 564 species from five mediterranean climate regions were compiled. Regional comparisons of foliar N and P concentrations and N:P ratios were performed using a phylogenetically independent contrasts (PIC) procedure. We also evaluated phylogenetic structuring in these variables, determining for each clade whether (1) the mean trait value and (2) the variance in trait values deviate significantly from chance expectation. Results Foliar N and P concentrations were found to vary between regions, a result confirmed using PIC. Tests of phylogenetic structure identified lineages having unusually high or low N and P concentrations, these being largely consistent amongst two of the regions. There was a general pattern of conservatism in foliar N and P concentrations and N:P ratios with localized instances of overdispersion. Main conclusions Our findings identify soil fertility as a strong environmental filter which has led to the dominance of low-nutrient adapted lineages in the South African Cape and Western Australia. There is also a pronounced clade-specific ‘stoichiometric homeostasis’ in foliar N and P concentrations and N:P ratios and this strong phylogenetic conservatism, together with the narrow range of foliar concentrations, is an evolutionary outcome of factors associated with developmental and physiological nutrient requirements specific to each lineage. Our results reinforce the need to include phylogenetic considerations in discussions of the biological stoichiometry of plants if we are to expand our current knowledge of foliar N and P concentrations and N:P patterns from an ecological to a biogeographic scale.

The presence of grazers on grazing lawns in East Africa and North America often alters nitrogen cycling and availability. Grazing lawns can be defined as areas where grasses are kept in a short, actively growing, palatable state by the action of grazers. Our aim was to test whether lawns have enhanced leaf nitrogen (N) concentrations, total soil N and δ15N when compared to tall grass areas in a South African savannah. Previous studies have used ecosystem δ15N as a proxy of N availability, and enriched δ15N values have been suggested to indicate higher N availability or higher N transformation rates. Across all sites, foliar N concentrations (but not soil N) were higher when compared to tall grass areas, and evidence of enriched foliar and soil δ15N values was found on the lawns. These results suggest that grazers may be involved in altering the rates of N transformations directly on grazing lawns. Regardless of whether these N transformations included increased net N mineralization, higher N concentrations in above-ground foliage attract grazers back to the lawns, encouraging their maintenance. Resume La presence de brouteurs sur les pâturages « grazing lawns » d’Afrique de l’Est et d’Amerique du Nord modifie souvent le cycle et la disponibilite de l’azote. On peut definir ces grazing lawns comme des endroits ou l’herbe est maintenue courte et nutritive, en croissance active, sous l’action du broutage. Notre but etait de tester si ces lawns avaient des concentrations plus fortes en azote (N) dans les feuilles, et en azote total N et en δ15N dans le sol, par comparaison avec les zones de hautes herbes d’une savane d’Afrique du Sud. Des etudes anterieures ont utilise le δ15N de l’ecosysteme comme proxy pour la disponibilite en azote, et on a suggere que des valeurs superieures de δ15N indiquaient une plus grande disponibilite en azote ou un taux plus eleve de transformation de l’azote. Dans tous les sites, la concentration foliaire en azote (mais pas l’azote du sol) etait superieure a celle des zones d’herbes hautes, et l’on a trouve des preuves de valeurs de δ15N enrichies dans les feuilles et le sol de ces prairies. Ces resultats laissent penser que les herbivores peuvent etre directement impliques dans la modification du taux de la transformation de l’azote dans les grazing lawns. Que ces transformations incluent ou non une plus forte mineralisation nette en azote, de plus hautes concentrations d’azote dans les feuilles aeriennes attirent les herbivores vers les lawns, ce qui favorise leur maintien.

Predominant frameworks for understanding plant ecology have an aboveground bias that neglects soil micro-organisms. This is inconsistent with recent work illustrating the importance of soil microbes in terrestrial ecology. Microbial effects have been incorporated into plant community dynamics using ideas of niche modification and plant-soil community feedbacks. Here, we expand and integrate qualitative conceptual models of plant niche and feedback to explore implications of microbial interactions for understanding plant community ecology. At the same time we review the empirical evidence for these processes. We also consider common mycorrhizal networks, and propose that these are best interpreted within the feedback framework. Finally, we apply our integrated model of niche and feedback to understanding plant coexistence, monodominance and invasion ecology.

The availability of nitrogen (N) is an important determinant of ecosystem and community dynamics for grasslands and savannas, influencing factors such as biomass productivity, plant and herbivore composition, and losses of N to waters and the atmosphere. To better understand the controls over N availability at landscape to regional scales, we quantified a range of plant and soil characteristics at each of 330 sites in three regions of South Africa: Kruger National Park (KNP), private game reserves adjacent to KNP (private protected areas – PPAs) and Hluhluwe-iMfolozi Park (HiP). In comparing regions and sites within regions, grazing appeared to have a strong influence on N availability. Sites in the PPAs adjacent to KNP as well as sodic and alluvial sites in general typically had the highest N availability. The high N availability of these sites was not generally associated with greater potential N mineralization, but instead with less grass biomass and more forb biomass that indicated greater grazing pressure. Whereas sodic sites had a long history of high N availability as evidenced by their high soil δ15N, the greater N availability in the PPAs over the two parks appeared to be relatively recent. Grazer biomass, average potential mineralization rates and grass biomass for HiP were greater than KNP, yet there were no differences in N availability as indexed by soil and foliar δ15N between sites in the two parks. Although the short-term increase in N availability in PPAs is not necessarily deleterious, it is uncertain whether current productivity levels in those ecosystems is sustainable. With differences in management causing herbivore biomass to be 150% greater in the PPAs than the adjacent KNP, changes in plant communities and nitrogen cycling might lead to long-term degradation of these ecosystems, their ability to sustain herbivore populations, and also serve as an economic resource for the region.

Herbivory can change the structure and spatial heterogeneity of vegetation. We ask whether all species of grazers in a savanna ecosystem can have this effect or whether megaherbivores (>1000 kg) have a ‘special‘ role that cannot be replicated by other species of grazers. We performed a replicated landscape scale experiment that examined the effects of White Rhino on the grass sward, on other species of grazing mammals and on the movement of fire through the landscape. White Rhino maintained short grass (‘lawn‘) patches in mesic areas (750 mm pa) with increases in grass sward height when they were removed. Other species of grazers were unable to maintain short grass communities when White Rhino were removed. In semi-arid areas (600 mm pa) other, smaller grazers were able to maintain short grass communities in the absence of White Rhino and sward height did not increase. White Rhino removals affected fire by increasing fuel loads and fuel continuity. This resulted in larger, less patchy fires. We propose that the White Rhino acts as an influential ecosystem engineer, creating and maintaining short grass swards, which alter habitat for other grazers and change the fire regime. These results indicate the existence of context-dependent facilitation between White Rhino and other grazers in mesic, but not in semi-arid, savannas. Such top down effects on the ecosystem may have been much more widespread before the extinction of large grazers in the Pleistocene.

Investments in ecological restoration are estimated at $US 2 trillion per annum worldwide and are increasing rapidly ( Cunningham, 2008 ; Williams et al., 2014 ). These investments are occurring in an environment of accelerated climate change that is projected to continue into the next century, yet they currently take little account of such change. This has significant implications for the long-term success of restoration plantings across millions of hectares, with germplasm used in current restoration efforts potentially poorly-adapted to future climates. New approaches that optimize the climate-resilience of these restoration efforts are thus essential ( Breed et al., 2013 ; Williams et al., 2014 ; Havens et al., 2015 ). A promising, but as yet untapped, opportunity for enhancing the climate-resilience of restoration investments rests in the exploitation of natural genetic variability of plant species. The capacity of plants to adapt to environmental change through plasticity, selection, or gene flow is only beginning to be explored ( Nicotra et al., 2010 ; Hoffmann and Sgro, 2011 ; Aitken and Whitlock, 2013 ; Alberto et al., 2013 ). Informed strategies for sourcing germplasm that capitalize on inherent genetic diversity and adaptive capacity offer significant promise for improving the success of extensive plantings to restore landscapes that are eroded, salinized, desertified, highly fragmented or degraded through introduced competitors, herbivores, or diseases. Here we describe a new strategy for sourcing germplasm for ecological restoration to promote adaptation in a changing climate. We argue that a "climate-adjusted" provenancing strategy (Figure 1A ) should combine genetic diversity and adaptability, targeting projected climate change directions whilst allowing for uncertainty in such projections as well as unforeseen selective agents. We introduce climate-adjusted provenancing in the context of historical approaches to provenancing, and highlight emerging research to test this strategy.

The introduction of exotic plants can have large impacts on ecosystem functions such as soil nutrient cycling. Since these impacts result from differences in traits between the exotic and resident species, novel physiological traits such as N cycling may cause large alterations in ecosystem function. It is unclear, however, whether all members of a given functional group will have the same ecosystem effects. Here we look at a within functional group comparison to test whether an annual (Lupinus luteus) and a perennial (Acacia saligna) N-fixing exotic species cause the same effects on soil N cycling in the fynbos vegetation of South Africa. We measured litterfall quantity and quality, and soil total nitrogen and organic matter for each vegetation type as well. Available nitrogen was quantified using ion exchange resin bags monthly for 1 year. We used microcosms to evaluate litter decomposition. Although both exotic species increased the available nitrogen in the soil, only Acacia increased the total soil N and organic matter. This could be explained by the slow decomposition of Acacia litter in the microcosm study, despite the fact that Acacia and Lupinus litter contained equivalent N concentrations. Presumably, low carbon quality of Acacia litter slows its decomposition in soil, resulting in retention of organic nitrogen in Acacia stands after clearing for restoration purposes. The differences in long term impacts of these annual and perennial species highlight the fact that not all N-fixing exotic species exert equivalent impacts. Ecologists should consider multiple traits rather than broadly defined functional groups alone when predicting invader impacts.

In this study the contribution of climatic factors and phylogenetic relationships affecting the geographical distribution of C 3 and C 4 genera of the Cyperaceae in South Africa was investigated. The δ 13 C values of herbarium specimens of 68 southern African species from 22 genera and eight tribes were used to assign the species to either the C 3 or C 4 photosynthetic pathway. Geographical distribution data for the Cyperaceae were used to investigate relationships between climatic factors and the number of species and proportional abundance of C 4 species per region. The number of Cyperaceae species per 2° X 2° square across South Africa varied from less than five in the north-western regions to more than 15 in the south-western and north-eastern regions of South Africa where rainfall exceeds 800 mm y -1 . Of the 68 species investigated, 28 had C 4 photosynthesis and these were scattered among nine genera of four tribes (Cypereae, Scirpeae, Abildgaardieae and Rhyncosporeae). The proportional abundance of C 4 species ranged from 14% in the winter rainfall regions of the south-west of South Africa to 67% in the summer rainfall areas of the north-east. The geographical distribution of species was related to their phylogenetic position such that the distributions of C 3 and C 4 species in Cypereae, Scirpeae and Schoeneae was quite distinct. Linear regression analysis showed that the transition temperatures (equal C 3 and C 4 species numbers) for the Cyperaceae were different to those obtained for the Poaceae from the same region. No strong relationships were found between the proportional abundance of C 4 species and other climate factors such as altitude and rainfall. Our analysis of the current geographical distribution of C 4 Cyperaceae in southern Africa in a phylogenetic context suggests that the ecological advantages conferred by the C 4 pathway differ amongst the different plant groups.

Recent efforts to clear invasive plants from the fynbos of South Africa forces managers to think about how N2-fixing invasives have altered ecosystem processes and the implications of these changes for community development. This study investigated the changes in nitrogen (N) cycling regimes in fynbos with the invasion of Acacia saligna, the effects of clear-cutting acacia stands on soil microclimate and N cycling, and how altered N resources affected the growth of a weedy grass species. Litterfall, litter quality, soil nutrient pools, and ion exchange resin (IER)-available soil N were measured in uninvaded fynbos, intact acacia, and cleared acacia stands. In addition, a bioassay experiment was used to ascertain whether the changes in soil nutrient availability associated with acacia would enhance the success of a weedy grass species. Acacia plots had greater amounts of litterfall, which had higher concentrations of N. This led to larger quantities of organic matter, total N, and IER-available N in the soil. Clearing acacia stands caused changes in soil moisture and temperature, but did not result in differences in IER-available N. The alteration of N availability by acacias was shown to increase growth rates of the weedy grass Ehrharta calycina, suggesting that secondary invasions by nitrophilous weedy species may occur after clearing N2-fixing alien species in the fynbos. It is suggested that managers use controlled burns, the addition of mulch, and the addition of fynbos seed after clearing to lower the levels of available N in the soil and initiate the return of native vegetation.

Climatic and geological change may play a key role in stimulating biological radiations. Here, we use phylogenetic data to test whether the comparatively high diversity of ehrharteoid grasses in the Cape region of South Africa is the result of rapid radiation associated with the onset of a seasonally arid climate during the late Miocene. A phylogenetic hypothesis based on morphological and nucleotide sequence (nuclear ITS1 and plastid trnL-F) data confirms the monophyly of the African Ehrharta species and shows that the diversification of this lineage was centered in the Cape region. Sequence divergence data (ITS1 + trnL-F) indicate a pulse of rapid speciation, which may explain poor phylogenetic resolution within the African Ehrharta clade. Alternative calibrations yield a broad range of time estimates for the start and end of this radiation, most of which indicate a radiation inside the last 11 million years. A calibration based on the age of Ehrhartoideae suggests that radiation started 9.82 +/- 0.20 million years ago and ended 8.74 +/- 0.21 million years ago. Under alternative calibrations, estimated speciation rates during the period of radiation range between 0.87 and 4.18 species per million years. Parsimony optimization of habitat parameters reveals that radiation was correlated with the occupation of seasonally arid succulent karoo environments, wet heathy (fynbos) environments being ancestral. These data support earlier suggestions that late Miocene climatic change stimulated floristic radiation at the Cape, and highlight the potential importance of environmental change in powering diversification in continental floras.

Summary 1We conducted a fertilization–defoliation experiment to investigate postfire flowering in Ehrharta capensis, a cormous grass native to the Cape fynbos. 2Combined fertilization and defoliation produced a strong flowering response in E. capensis, suggesting that the strong postfire flowering pattern of this species can be explained largely by the effect of fire on soil nutrients and vegetation cover. Flowering was absent in control plants, and sparse in plants receiving single treatments. 3Comparable treatment dependence of flowering was not observed in two congeneric species that lack specialized storage structures and in which flowering is not apparently fire-dependent. 4In E. capensis, flowering did not significantly reduce the dry mass of corms persisting from previous years, or the amounts of reserves these contained. We conclude that corm-stored reserves do not contribute substantially to inflorescence production. 5Flowering E. capensis plants produced significantly larger replacement corms than did nonflowering plants, indicating that sexual reproduction does not occur at a cost to asexual persistence. 6The lack of a trade-off between sexual and asexual reproduction may explain why E. capensis, and possibly other clonal geophytes, flower only when resource availability is high. Cost–benefit models, which predict a trade-off, do not properly describe resource allocation in these species.

Summary This study evaluates the importance of soil characteristics in determining the periodic dominance and scarcity of legumes in fynbos environments in South Africa. To do this we investigated (i) whether the soil nutrient status of 9 recently burned areas facilitated the establishment and success of 15 Aspalathus spp., which are the most species rich group of legumes in the region, (ii) whether patterns of nodulation were species specific and unrelated to environmental controls, and (iii) what the contribution of the fixation process to the nitrogen capital of selected Aspalathus spp. and fynbos stands was. In order to answer these questions we investigated soil nutrient status of recently burned and adjacent unburned fynbos stands. This was then related to nodulation patterns and estimates of nitrogen contributed from fixation for all Aspalathus spp. Significant differences among the 9 experimental sites in terms of soil total nitrogen were found however within sites there were no consistent changes in total nitrogen with age of vegetation since the last fire. Soil phosphorus, pH and organic matter contents were also very similar across sites. Average nodulation of Aspalathus spp. in the field showed considerable variation among the species sampled. These patterns appeared to be species specific rather than environmentally controlled since multiple regression analyses showed that only 12.9% of the variation in nodule mass could be explained by these factors. Despite the short duration presence of Aspalathus spp. (generally Muster der Knollchenbildung von funfzehn Aspalathus- Arten und ihre okologische Rolle in der Fynbos-Vegetation von Sudafrika In dieser Arbeit wird die Bedeutung von Bodenmerkmalen fur die periodische Dominanz und Seltenheit von Leguminosen in der Fynbos-Vegetation von Sudafrika untersucht. Wir analysierten (i) ob der Nahrstoffstatus des Bodens in neuen, vor kurzem abgebrannten Gebieten die Etablierung und den Erfolg von 15 Aspalathus-Arten fordert, welche die artenreichste Gruppe der Leguminosen in dieser Region sind, (ii) welche Muster der Knollchenbildung artspezifisch und unabhangig von Umweltfaktoren sind und (iii) welches der Beitrag des Fixierungsprozesses fur das Stickstoff-Kapital ausgewahlter Aspalathus-Arten und das Fynbos-Gebiet war. Um diese Fragen zu beantworten, untersuchten wir den Nahrstoffstatus von vor kurzem abgebrannten und benachbarten, nicht abgebrannten Fynbos-Gebieten. Diese Untersuchungen wurden auf das Muster der Knollchenbildung bezogen und fur die Schatzung der Stickstoffmenge genutzt, die durch die Fixierung aller Aspalathus-Arten beigetragen wurde. Signifikante Unterschiede im Gesamtgehalt an Bodenstickstoff wurden zwischen den neun Untersuchungsflachen gefunden, allerdings gab es innerhalb der Flachen keine konsistenten Veranderungen im Stickstoff-Gesamtgehalt mit dem Alter der Vegetation seit dem letzten Feuer. Der Phosphorgehalt im Boden, der pH-Wert und der Gehalt an organischem Material war auch ahnlich zwischen den Flachen. Die mittlere Knollchenbildung der Aspalathus-Arten im Feld zeigte eine erhebliche Variation zwischen den Arten. Dieses Muster schien eher artspezifisch als durch die Umwelt kontrolliert zu sein, da multiple Regressionsanalysen zeigten, dass nur 12,9% der Variation in der Knollchenmasse durch diese Faktoren erklart werden konnte. Trotz der geringen Dauerhaftigkeit der Aspalathus-Arten nach dem Feuer (im allgemeinen

Nonstructural carbohydrate allocation patterns in response to different frequencies of simulated browsing (leaf and twig removal) were studied in the following semi-arid shrubs: Osteospermum sinuatum, a dwarf deciduous shrub, Pteronia pallens, a dwarf evergreen shrub, and Ruschia spinosa, a dwarf leaf-succulent shrub. Simulated browsing at all frequencies resulted in the elevation, or had no effect, on total nonstructural carbohydrate (TNC) concentrations of O. sinuatum plant parts, and resulted in the decrease in TNC concentrations of R. spinosa plant parts. The responses of P. pallens were intermediate with elevations as well as declines in TNC concentrations of plant parts measured in response to various clipping frequencies. At the low frequency of simulated browsing (every 26 weeks) elevations in plant TNC content were measured in the two non-succulent shrubs O. sinuatum and P. pallens. It was concluded that the overcompensation with respect to TNC accumulation observed in the two non-succulent species represents one of the ways in which excess photosynthate is utilized by browsed shrubs with a limited regiowth potential. Simulated browsing was the least detrimental with respect to biomass production to the non-succulent O. sinuatum and P. pallens, and most injurious to the leaf-succulent shrub, R. spinosa. The observed TNC allocation patterns could not adequately explain the variation among species in the production of new growth and it was concluded that some factor(s) other than the carbon resource was limiting regrowth.

This study examines the impacts of woody, N2-fixing invasive Acacia spp. on the patterns of nutrient cycling in two invaded ecosystems of differing nutrient status in the Cape floristic region. Patterns of soil nutrient mineralization were measured by a field incubation method while the significance of the fixation process in altering nutrient cycling was assessed by the δ15N natural abundance technique. The results confirm earlier reports that invasion by woody shrubs results in organic matter and nutrient enrichment of surface soils of both ecosystems. However, patterns of nutrient availability (phosphorus and nitrogen) were not necessarily enhanced. In the more fertile strandveld both phosphorus and nitrogen (significant at P

Summary Environmental hypotheses accounting for the distribution of succulents are many and varied and include the notion that this leaf type is more common in regions of low but predictable rainfall and saline areas but is absent or rare in regions with regular frosts. This paper tests the low temperature control of distribution hypothesis on all 5 varieties of the widely distributed succulent Cotyledon orbiculata in southern Africa to determine whether it has morphological and physiological attributes which confer tolerance to low temperatures. The low temperature survival limits (−6.1 to −10.4 °C) of this species are very similar to those determined for other desert succulents on other continents. In addition, the current geographical range of C. orbiculata cannot be predicted from the temperature tolerances of even the most resistant organs examined in this study and no special modifications could be found to explain the occurrence of this species in regions with regular frosts (up to 90 nights per year). The results of the study caution against making predictions concerning the distribution of succulents in relation to past and future climate changes without more experimental evidence.

Nara ( Acanthosicyos horridus ) is a dioecious phreatophyte endemic to the Namib Desert. This plant, because of its sand-binding characteristics, forms micro-ecosystems within the dunes. These micro-ecosystems provide both shelter and food for a variety of detritivores, herbivores, omnivores, and carnivores. Nara, a leafless cucurbit, provides a source of water with many of its plant parts containing > 80% water by weight. The new stem tips, flowers, and seeds provide high sources of both nitrogen and phosphorus. The pulp of the melons, besides providing a high source of water, also offers a significant amount of carbohydrates. Considering the nutrient-poor environment nara occurs in, its stoichiometric relationships of C/N and C/P are unusually low.

While seasonal redistribution of fine root biomass in response to fluctuations in groundwater level is often inferred in phreatophytic plants, few studies have observed the in situ growth dynamics of deep roots relative to those near the surface. We investigated the root growth dynamics of two Banksia species accessing a seasonally dynamic water table and hypothesized that root growth phenology varied with depth, i.e. root growth closest to the water table would be influenced by water table dynamics rather than surface micro-climate. Root in-growth bags were used to observe the dynamics of root growth at different soil depths and above-ground growth was also assessed to identify whole-plant growth phenology. Root growth at shallow depths was found to be in synchrony with above-ground growth phenophases, following increases in ambient temperature and soil water content. In contrast, root growth at depth was either constant or suppressed by saturation. Root growth above the water table and within the capillary fringe occurred in all seasons, corresponding with consistent water availability and aerobic conditions. However, at the water table, a seasonal cycle of root elongation with drawdown in summer followed by trimming in response to water table rise and saturation in winter, was observed. The ability to grow roots year-round at the capillary fringe and redistribute fine root biomass in response to groundwater drawdown is considered critical in allowing phreatophytes, in seasonally water-limited environments, to maintain access to groundwater throughout the year.

In most documented examples of adaptive radiation, the processes underlying divergence in form and function are poorly explored and remain speculative. Here, data from a comparative seedling growth experiment are used to explore growth form divergence in Ehrharta, a group of grasses that radiated in seasonally arid environments of the Cape region of South Africa. Seedlings of eight Ehrharta species of variable growth form were grown in liquid culture under conditions of high resource availabilty for 56 d, during which time changes in dry mass, allocation, and leaf parameters were measured. The results of this experiment reveal the existence of distinct seedling growth patterns that are associated with differences in adult plant form and seasonal drought survival strategy. Specifically, species that utilize a reseeding strategy have higher seedling growth rates and flower earlier than species that persist by vegetative means. A correlation between species' growth rates and their native substrates suggests that edaphic heterogeneity has been central in directing the evolution of alternative persistence strategies and growth forms. Parsimony reconstruction identifies slow growth and an association with nutrient-deficient sandstone-derived soils as ancestral in Ehrharta, with fast growth evolving after a transition to richer shale- and granite-derived soils. The emergence of annual species in two fast-growth lineages suggests that the latter is a key step in the evolution of an ephemeral strategy. An association between plant function and habitat identifies the radiation of Ehrharta as adaptive.

Allocation of carbon to chemical defences has often been suggested to be a direct response to browsing or grazing by herbivores. This study quantitatively compares total polyphenol and tannin production in response to simulated browsing of three karoo shrubs in order to test this induced defence hypothesis. The three species studied responded to browsing either by rapid regrowth or by increasing polyphenol production in the remaining tissues. The patterns did not follow any phylogenetic relationships but were weakly associated with the palatability of each species. The highly palatable deciduous species Osteospermum sinuatum, which is capable of rapid regrowth, showed no or very low levels of constitutive and browsing-induced total polyphenols, condensed tannins and protein-precipitating tannins. The evergreen sclerophyllous species Pteronia pallens showed a limited regrowth capacity and had intermediate levels of polyphenols, while the evergreen succulent species Ruschia spinosa showed almost no regrowth over the study period. R. spinosa contained the highest constitutive and browsing-induced levels of polyphenols, condensed tannins and protein-precipitating tannins. In two of the species more than one anti-herbivore defence feature co-occur. P. pallens foliage contains both hepatotoxins and polyphenols while R. spinosa has both structural (spines) and chemical defences. Responses of karoo shrubs to simulated browsing are interpreted as the result of passive alterations in plant chemistry rather than as an active defence response to herbivores.

The interaction of density and mycorrhizal effects on the growth, mineral nutrition and size distribution of seedlings of two perennial members of the Fabaceae was investigated in pot culture. Seedlings of Otholobium hirtum and Aspalathus linearis were grown at densities of 1, 4, 8 and 16 plants per 13-cm pot with or without vesicular-arbuscular (VA) mycorrhizal inoculum for 120 days. Plant mass, relative growth rates, height and leaf number all decreased with increasing plant density. This was ascribed to the decreasing availability of phosphorus per plant as density increased. O. hirtum was highly dependent on mycorrhizas for P uptake but both mycorrhizal and non-mycorrhizal A. linearis seedlings were able to extract soil P with equal ease. Plant size distribution as measured by the coefficient of variation (CV) of shoot mass was greater at higher densities. CVs of mycorrhizal O. hirtum plants were higher than those of non-mycorrhizal plants. CVs of the facultatively mycorrhizal A. linearis were similar for both mycorrhizal and non-mycorrhizal plants. Higher CVs are attributed to resource preemption by larger individuals. Individuals in populations with high CVs will probably survive stress which would result in the extinction of populations with low CVs. Mass of mycorrhizal plants of both species decreased more rapidly with increasing density than did non-mycorrhizal plant mass. It is concluded that the cost of being mycorrhizal increases as plant density increases, while the benefit decreases. The results suggest that mycorrhizas will influence density-dependent population processes of faculative and obligate mycorrhizal species.

Symbiotic methods for germinating Eulophia Lindl. and Polystachya Hook. seeds from terrestrial and epiphytic habitats respectively were established. Cultures, initiated from the seeds were grown on 2% oats medium and germination medium, alone, or oats medium supplemented with 10 g.L 1banana fruit homogenate and 0.2 g.L' activated charcoal. The highest germination/differentiation, which took place after 7 days of inoculation, was obtained on the 2% oats medium with glucose (2 g.L-') and NH4NVO4H20 (1.0 mM.L') as a source of inorganic nitrogen and supplemented with the additives. Development of protocorms in compatible orchid-fungus combination took place after the second subculture (30 days) from which seedling developed. Irrespective of the fact that the orchids showed possible specificity patterns at population level with their fungal partners in their natural habitats the in vitro symbiotic seed germination also showed significant tendency towards fungal specificity. Since germination took a shorter time by this technique to develop protocorms, propagation of endangered orchids could be done and used for ex situ conservation programmes.

The importance of competition and soil factors in determining the distributions of fynbos species was assessed by means of a three-yr experiment. Three pairs of Proteaceae shrub species were selected as case studies. For each pair, one species replaces the other along a transect representing an edaphic gradient across the landscape. These species were grown in cleared plots arranged along the corresponding transect, in monoculture and mixture at a range of total densities. Site effects (soil factors), density and monoculture/mixture effects on survival and above-ground biomass were determined after three yr. Site effects were the major determinants of the survival of all species, although the pattern corresponded well with adult distributions of only three species. Biomass was related primarily to site effects for three species (corresponding with adult distributions) and, for the other three, to density effects. Although all species showed reduction of biomass with increasing density, differences between intra- and interspecific competition were generally small. While competition may be important in determining growth and the spatial arrangement of individuals within communities (as indicated by density effects), this work suggests that it may be relatively unimportant in determining fynbos species distributions. As no conclusive evidence was found for one species competitively excluding the other from part of its range, it was concluded that the distribution of these species across this landscape is determined primarily by soil factors.

1. An etiolated regrowth technique was used to examine the dependence of regrowth of Osteospermum sinuatum, a semiarid shrub native to South Africa, on its carbon reserves. Regrowth as well as changes in reserve carbon pool sizes of four plant parts were compared between clipped plants (80% of leaf and twig biomass removed) growing in the light and in the dark. 2. Distinct temporal and spatial patterns of reserve carbon use were found, with reserve carbon of twigs being used before stem and below-ground storage carbohydrates. Leaf reserve carbon was also utilized in the absence of photosynthesis. 3. Regrowth of clipped Osteospermum sinuatum plants was dependent initially on carbon reserves but subsequent leaf growth and refilling of partially depleted carbohydrate reserves relied on photosynthates produced by new and remaining leaves. Most regrowth was derived from stored carbon (60%) during the first 2 weeks following clipping. 4. Results suggest that the production of new leaves in this shrub is dependent on carbon reserves to a greater extent than is the case for grasses. The difference between grasses and shrubs, with respect to the relative importance of reserve carbon for regrowth, possibly explains the poor competitive ability of grasses, and the persistence of shrubs in graminoid-shrub communities subjected to severe grazing pressures.

To test whether differences in water relations were responsible for differences in species distributions across a landscape, we investigated patterns of water use (water potential, transpiration) of Protea susannae (associated with deep soil) and Protea compacta (associated with shallow soil) in the field (mature plants) and in the laboratory (seedlings). Adults of P. susannae had more extensive root systems and less conservative water use than those of P. compacta, suggesting greater access to water. However, no substantial differences in water potential or transpiration were found, for either species, between plants in deep and shallow soils. Germination, seedling growth and water relations were compared under controlled-environment conditions. Protea compacta seedlings were much larger with greater root depth and transpiration rate (per plant). The consequence of this was a drying out of the soil profile leading to greater dependence on the water table. Protea susannae seedlings were initially conservative in water use but, after 30 weeks, had a similar rate of transpiration (per plant) to P. compacta seedlings, despite a much smaller leaf area. Both species were found to experience switches in water-use strategy between seedling and adult stages : from conservative to water spending in P. susannae and from water spending to conservative in P. compacta. These switches, together with differences in water relations, particularly at the seedling stage, suggest that habitat specialization could play a critical role in determining these species distributions.

1. The influence of seed reserves on seedling growth and phosphorus acquisition of 14 vesicular-arbuscular mycorrhizal (VAM) shrub species belonging to the Rosidae and indigenous to the flora of the nutrient-poor soils of the Cape Fynbos, South Africa, was studied in the presence or absence of mycorrhizal inoculum. 2. It is expected that among potentially VAM plant species found in a low-nutrient, high-light environment those with small seed reserves will have a higher dependency on mycorrhizas for seedling establishment than larger-seeded species. 3. Growth of the seedlings when non-mycorrhizal was strongly controlled by seed reserves. Most non-mycorrhizal plants were unable to acquire soil phosphorus unless they possessed alternative nutrient-acquiring root modifications. 4. Mycorrhizal responses in terms of mass and phosphorus content of inoculated plants compared to uninoculated plants are negatively correlated with the logarithm of seed mass and phosphorus content. Thus, it is suggested that seed size among the Rosidae in a low-nutrient environment is a trade-off between dispersal distances and the ability to establish a competitive presence in the absence of mycorrhizal inoculum, with no single seed size conferring an absolute advantage to VAM plant species. 5. The simultaneous evolution of cluster roots and large seeds in low-nutrient environments is proposed as a mechanism allowing for the adoption of the non-mycorrhizal state in some members of the Rosidae

We analysed distribution records of mistletoes (Loranthaceae and Viscaceae) in South Africa in terms of host taxa and geographic patterns. Few species are found in nutri- ent-poor Cape shrublands (fynbos) and in the southern ever- green forests on nutrient-poor sands. The most species-rich areas are the nutrient-rich mesic savannas (including Valley Bushveld, a subset of savanna). Mistletoe species richness is significantly correlated with the average nitrogen levels of the woody plants in any biome, suggesting that the overall nutri- ent status of a biome influences mistletoe species richness. The analysis of host-choice of mistletoes also indicates a non-random distribution; thirty-three genera in twenty-two plant families host from three to twenty-four different mistle- toe species, suggesting that parasitism is not related to phylo- genetic position. The most important host genera are Acacia (hosting twenty-four spp. mistletoes), followed by Combretum (fourteen), Maytenus (thirteen) and Rhus (twelve). The species richness of mistletoes on host genera is significantly correlated with mean host N, and in four of five areas sampled, the number of mistletoes on host trees was significantly correlated with host N.

Levels of infection in the roots of vesicular-arbuscular mycorrhizal (VAM) plants growing in three lowland evergreen shrublands of the Cape Floristic Region, South Africa, were studied and used to assess mycorrhizal activity in these natural ecosystems. Average infection was significantly different between vegetation types. VAM infection levels were lowest in strandveld which has high soil phosphorus contents, intermediate in fynbos (very low phosphorus levels) and highest in renosterveld plants where plant-available phosphorus levels are very low due to competition for the moderately high total phosphorus present in soil. Infection intensity was very variable amongst individual plants, suggesting that mycorrhizal inoculum is patchily distributed in the soil (...)

(1) Seedling development under nutrient-deficient conditions was investigated for five bradysporous members of the Proteaceae to test the hypothesis that large seed size and high embryo nutritional quality reflect the outcome of selection favouring propagules suited for establishment in infertile soils characteristic of those natural environments dominated by members of the Proteaceae. (2) Seeds of Protea lorifolia, Protea cynaroides, Leucadendron laureolum, Hakea sericea and Banksia laricina were germinated and grown on nutrient-deficient sand for 200 days. Every forty days ten seedlings of each species were harvested to determine growth, allocation patterns and nutrient use. Seedling parts were dried, weighed and analysed for N, P, K, Ca and Mg. . (3) Seedlings of all Proteaceae species were able to survive prolonged periods of nutrient scarcity irrespective of seed size. (4) Rapid germination of Proteaceae seeds does not appear to be a significant means of increasing seedling fitness. (5) Seed mass was positively correlated with seedling size. (6) No correlation between relative growth rates and seed size was found. (7) Seeds of members of the Proteaceae show selective storage of specific nutrients (N and P) such that seed chemical composition is unbalanced for optimum seedling growth. These elements complement the rich sources of cations Ca,Mg and K found in soils of post-fire environments when maximal recruitment of proteoid species occurs.

Leucospermum conocarpodendron (L.) Buek (Proteaceae) seedlings were excavated several months after a fire in Cape fynbos. Seedlings under burnt parental skeletons had short hypocotyls (mean 25 mm) indicating passive dispersal whereas seedlings in the open were more deeply buried (mean 48 mm) by ants. Soil nutrient concentrations at the site of germination were negatively related to depth of burial and distance from parent. Ant dispersal resulted in seedlings emerging in soils with lower nutrient concentrations than passively dispersed seeds. Tissue analysis supported the soil results with lower P content in seedlings from open (ant dispersed) sites. Seedling survival in the first year of establishment was also lower in open sites, but not significantly so. However seedlings were slightly taller in the open. The results of this study, the first on naturally occurring intraspecific variation in myrmecochory, strongly contradict current explanations for the high incidence of myrmecochory in nutrient poor environments.

(1) Results are presented to the atmospheric deposition of phosphorus over a 1 year period in coastal fynbos vegetation on aeolian sandy soils of low phosphorus content. (2) Annual precipitation during 1980-8 1 was 381 mm. (3) Phosphorus input was estimated as 0. 19 kg ha-' year-'; it occurred mainly during the winter. (4) It is concluded that phosphorus input from bulk precipitation is an important contribution to the fynbos biome.