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Lectotypifications of Eriobotrya ambigua, E. bengalensis f. contracta, E. bengalensis f. multinervata, Opa metrosideros (synonym of E. metrosideros), Photinia griffithii (synonym of E. griffithii), E. prionophylla are designated here, and a neotype is designated for Mespilus bengalensis (≡ E. bengalensis). The protologues of these names and the original materials are evaluated. Nomenclatural notes discussing the selection of type specimens are given for each name and known isotypes are also cited.

Rapid ʻŌhiʻa Death (ROD) is a deadly disease that is threatening the native Hawaiian keystone tree species, ʻōhiʻa lehua (Metrosideros polymorpha Gaudich). Ambrosia beetles (Curculionidae: Scolytinae) and their frass are hypothesized to play a major role in the spread of ROD, although their ecological niches and frass production within trees and across the landscape are not well understood. We characterized the beetle communities and associated frass production from bolts (tree stem sections) representative of entire individual ʻōhiʻa trees from multiple locations across Hawaiʻi Island by rearing beetles and testing their frass for viable ROD-causing fungi. Additionally, we estimated frass production for three beetle species by weighing their frass over time. We found that Xyleborinus saxesenii (Ratzburg), Xyleborus affinis Eichhoff, Xyleborus ferrugineus (Fabricius), Xyleborus perforans (Wollaston), and Xyleborus simillimus Perkins were commonly found on ROD-infected ʻōhiʻa and each produced frass containing viable Ceratocystis propagules. The Hawaiʻi Island endemic beetle and the only native ambrosia beetle associated with ʻōhiʻa, X. simillimus, was limited to high elevations and appeared to utilize similar tree heights or niche dimensions as the invasive X. ferrugineus. Viable Ceratocystis propagules expelled in frass were found throughout entire tree bole sections as high as 13 m. Additionally, we found that X. ferrugineus produced over 4× more frass than X. simillimus. Our results indicate the ambrosia beetle community and their frass play an important role in the ROD pathosystem. This information may help with the development and implementation of management strategies to control the spread of the disease.

Resistance to the pandemic strain of Austropuccinia psidii was identified in New Zealand provenance Leptospermum scoparium, Kunzea robusta, and K. linearis plants. Only 1 Metrosideros excelsa-resistant plant was found (of the 570 tested) and no resistant plants of either Lophomyrtus bullata or L. obcordata were found. Three types of resistance were identified in Leptospermum scoparium. The first two, a putative immune response and a hypersensitive response, are leaf resistance mechanisms found in other myrtaceous species while on the lateral and main stems a putative immune stem resistance was also observed. Both leaf and stem infection were found on K. robusta and K. linearis plants as well as branch tip dieback that developed on almost 50% of the plants. L. scoparium, K. robusta, and K. linearis are the first myrtaceous species where consistent infection of stems has been observed in artificial inoculation trials. This new finding and the first observation of significant branch tip dieback of plants of the two Kunzea spp. resulted in the development of two new myrtle rust disease severity assessment scales. Significant seed family and provenance effects were found in L. scoparium, K. robusta, and K. linearis: some families produced significantly more plants with leaf, stem, and (in Kunzea spp.) branch tip dieback resistance, and provenances provided different percentages of resistant families and plants. The distribution of the disease symptoms on plants from the same seed family, and between plants from different seed families, suggested that the leaf, stem, and branch tip dieback resistances were the result of independent disease resistance mechanisms.

In palynology and other laboratory-based disciplines, methodological literature often lags the development and adoption of new practices. Here we highlight the lack of literature on the application of heavy liquid density separation for pollen preparations, a technique that has become common practice in recent years. In a study of Holocene-age sediments from Lake Pupuke, northern New Zealand, we found that the density of the heavy liquid used to separate pollen from the minerogenic fraction, within the range of reported practice, affected pollen counts. When a relatively low density was used (2.0 g/cm3), buoyant pollen grains such as Prumnopitys taxifolia and Dacrydium cupressinum were overrepresented, whereas small, compact pollen grains such as Libocedrus and Metrosideros were underrepresented. This result raises wider concerns, as heavy liquid densities reported in the literature range from 1.88 to 2.40 g/cm3. We draw attention to this problem and recommend steps that palynologists can take to ensure that their enumerated pollen assemblages are representative and do not lead to spurious interpretations.

Some of the most spectacular adaptive radiations begin with founder populations on remote islands. How genetically limited founder populations give rise to the striking phenotypic and ecological diversity characteristic of adaptive radiations is a paradox of evolutionary biology. We conducted an evolutionary genomics analysis of genus Metrosideros, a landscape-dominant, incipient adaptive radiation of woody plants that spans a striking range of phenotypes and environments across the Hawaiian Islands. Using nanopore-sequencing, we created a chromosome-level genome assembly for Metrosideros polymorpha var. incana and analyzed whole-genome sequences of 131 individuals from 11 taxa sampled across the islands. Demographic modeling and population genomics analyses suggested that Hawaiian Metrosideros originated from a single colonization event and subsequently spread across the archipelago following the formation of new islands. The evolutionary history of Hawaiian Metrosideros shows evidence of extensive reticulation associated with significant sharing of ancestral variation between taxa and secondarily with admixture. Taking advantage of the highly contiguous genome assembly, we investigated the genomic architecture underlying the adaptive radiation and discovered that divergent selection drove the formation of differentiation outliers in paired taxa representing early stages of speciation/divergence. Analysis of the evolutionary origins of the outlier single nucleotide polymorphisms (SNPs) showed enrichment for ancestral variations under divergent selection. Our findings suggest that Hawaiian Metrosideros possesses an unexpectedly rich pool of ancestral genetic variation, and the reassortment of these variations has fueled the island adaptive radiation.

Species radiations should be facilitated by short generation times and limited dispersal among discontinuous populations. Hawaii’s hyper-diverse, landscape-dominant tree, Metrosideros, is unique among the islands’ radiations for its massive populations that occur continuously over space and time within islands, its exceptional capacity for gene flow by both pollen and seed, and its extended life span (ca. >650 years). Metrosideros shows the greatest phenotypic and microsatellite DNA diversity on Oʻahu, where taxa occur in tight sympatry or parapatry in mesic and montane wet forest on 2 volcanoes. We document the nonrandom distributions of 12 taxa (including unnamed morphotypes) along elevation gradients, measure phenotypes of ~6-year-old common-garden plants of 8 taxa to verify heritability of phenotypes, and examine genotypes of 476 wild adults at 9 microsatellite loci to compare the strengths of isolation across taxa, volcanoes, and distance. All 8 taxa retained their diagnostic phenotypes in the common garden. Populations were isolated by taxon to a range of degrees (pairwise FST between taxa: 0.004–0.267), and there was no pattern of isolation by distance or by elevation; however, significant isolation between volcanoes was observed within monotypic species, suggesting limited gene flow between volcanoes. Among the infraspecific taxa of Metrosideros polymorpha, genetic diversity and isolation significantly decreased and increased, respectively, with elevation. Overall, 5 of the 6 most isolated taxa were associated with highest elevations or otherwise extreme environments. These findings suggest a principal role for selection in the origin and maintenance of the exceptional diversity that occurs within continuous Metrosideros stands on Oʻahu.

Seed banks serve the purpose of maintaining germplasm for ex situ species preservation. Herbarium vouchers may be a viable source of unique and/or additional seeds for restoration as they can somet...

A long-standing goal of evolutionary biology is to understand the mechanisms underlying the formation of species. Of particular interest is whether or not speciation can occur in the presence of gene flow and without a period of physical isolation. Here, we investigated this process within Hawaiian Metrosideros, a hypervariable and highly dispersible woody species complex that dominates the Hawaiian Islands in continuous stands. Specifically, we investigated the origin of Metrosideros polymorpha var. newellii (newellii), a riparian ecotype endemic to Hawaii Island that is purportedly derived from the archipelago-wide M. polymorpha var. glaberrima (glaberrima). Disruptive selection across a sharp forest-riparian ecotone contributes to the isolation of these varieties and is a likely driver of newellii’s origin. We examined genome-wide variation of 42 trees from Hawaii Island and older islands. Results revealed a split between glaberrima and newellii within the past 0.3–1.2 My. Admixture was extensive between lineages within Hawaii Island and between islands, but introgression from populations on older islands (i.e., secondary gene flow) did not appear to contribute to the emergence of newellii. In contrast, recurrent gene flow (i.e., primary gene flow) between glaberrima and newellii contributed to the formation of genomic islands of elevated absolute and relative divergence. These regions were enriched for genes with regulatory functions as well as for signals of positive selection, especially in newellii, consistent with divergent selection underlying their formation. In sum, our results support riparian newellii as a rare case of incipient ecological speciation with primary gene flow in trees.

Understanding microsite preferences of species at the sapling stage is crucial for successful forest restoration, as efforts can be concentrated onto the most promising sites, and invaded sites can be manipulated toward more suitable conditions for target species. The Hawaiian Lowland Wet Forest is a highly endemic and endangered ecosystem that has received limited attention in terms of research on recruitment dynamics. Our study combined density records and sapling-based measurements within a forest reserve, an invaded forest, a traditional restoration project and a novel restoration project. We recorded substrate type, soil depth, surface roughness, and light availability for 382 saplings of the four native tree species Metrosideros polymorpha, Myrsine lessertiana, Pipturus albidus, and Psychotria hawaiiensis, and 146 spots where the target species were absent. The invaded forest had the lowest native sapling density, lower light availability, and lower surface roughness than the remaining management units. The novel restoration project had more moss/nurselog sites and higher light availability than the remaining management units. The traditional restoration project was mainly characterized by rocky substrate. Metrosideros and Pipturus showed significantly higher light demand than Myrsine and Psychotria. Pipturus was associated with rough microsites and Metrosideros with moss/nurselog substrates. Our findings suggest that restoration strategies considering manipulation of the canopy light environment and microsite preferences of target species can better facilitate native recruitment into heavily invaded forests.

Some of the most spectacular adaptive radiations begin with founder populations on remote islands. How genetically limited founder populations give rise to the striking phenotypic and ecological diversity characteristic of adaptive radiations is a paradox of evolutionary biology. We conducted an evolutionary genomic analysis of genusMetrosideros, a landscape-dominant, incipient adaptive radiation of woody plants that spans a striking range of phenotypes and environments across the Hawaiian Islands. Using nanopore-sequencing, we created a chromosome-level genome assembly forM. polymorphavar.incanaand analyzed wholegenome sequences of 131 individuals from 11 taxa sampled across the islands. We found evidence of population structure that grouped taxa by island. Demographic modeling showed concordance between the divergence times of island-specific lineages and the geological formation of individual islands. Gene flow was also detected within and between island taxa, suggesting a complex reticulated evolutionary history. We investigated genomic regions with increased differentiation as these regions may harbor variants involved in local adaptation or reproductive isolation, thus forming the genomic basis of adaptive radiation. We discovered differentiation outliers have arisen from balancing selection on ancient divergent haplotypes that formed before the initial colonization of the archipelago. These regions experienced recurrent divergent selection as lineages colonized and diversified on new islands, and hybridization likely facilitated the transfer of these ancient variants between taxa. Balancing selection on multiple ancient haplotypes–or time-tested variants–may help to explain how lineages with limited gene pools can rapidly diversify to fill myriad ecological niches on remote islands.Significance statementSome of the most spectacular adaptive radiations of plants and animals occur on remote oceanic islands, yet such radiations are preceded by founding events that severely limit genetic variation. How genetically depauperate founder populations give rise to the spectacular phenotypic and ecological diversity characteristic of island adaptive radiations is not known. We generated novel genomic resources for HawaiianMetrosideros––a hyper-variable incipient adaptive radiation of woody taxa—for insights into the paradox of remote island radiations. We found thatMetrosideroscolonized each island shortly after formation and diversified within islands through recurrent selection on ancient variations that predate the radiation. Recurring use of ancient variants may explain how genetically depauperate lineages can diversify to fill countless niches on remote islands.

Shifts in flowering time have the potential to act as strong prezygotic reproductive barriers in plants. We investigate the role of flowering time divergence in two species of mountain rose (Metrosideros) endemic to Lord Howe Island, Australia, a minute and isolated island in the Tasman Sea.Metrosideros nervulosaandM. sclerocarpaare sister species and have divergent ecological niches on the island but grow sympatrically for much of their range, and likely speciatedin situon the island. We used flowering time and population genomic analyses of population structure and selection, to investigate their evolution, with a particular focus on the role of flowering time in their speciation. Population structure analyses showed the species are highly differentiated and appear to be in the very late stages of speciation. We found flowering times of the species to be significantly displaced, withM. sclerocarpaflowering 53 days later thanM. nervulosa. Furthermore, the analyses of selection showed that flowering time genes are under selection between the species. Thus, prezygotic reproductive isolation is mediated by flowering time shifts in the species, and likely evolved under selection, to drive the completion of speciation within a small geographical area.This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.

Fungal endophyte (FE) communities can be shaped by environmental conditions and/or host-plant affinities. Hawaiʻi's landscape-dominant woody genus Metrosideros (Myrtaceae) comprises several vegetatively distinct taxa that are non-randomly distributed across environments, and their FE communities are poorly known. We examined the relative importance of Metrosideros taxon and environment (elevation) on FE communities on Oʻahu. ITS1 rDNA barcoding and sequencing of 113 trees detected a richness of 1,637 FEs representing 5 phyla, 223 genera, and 200 species. Variation in FE diversity was significantly explained by host taxon and site with considerable overlap in FE communities among taxa. FE communities did not vary between pubescent and glabrous taxa or across elevations, possibly due to the relatively narrow range of environmental conditions represented on Oʻahu relative to taller islands. A significant pattern of isolation by distance in FE composition was detected both among and within sites, consistent with restricted dispersal of FEs across the island.

As the most remote archipelago in the world, the Hawaiian Islands are home to a highly endemic and disharmonic biota that has fascinated biologists for centuries. Forests are the dominant terrestrial biome in Hawai‘i, spanning complex, heterogeneous climates across substrates that vary tremendously in age, soil structure, and nutrient availability. Species richness is low in Hawaiian forests compared to other tropical forests, as a consequence of dispersal limitation from continents and adaptive radiations in only some lineages, and forests are dominated by the widespread Metrosideros species complex. Low species richness provides a relatively tractable model system for studies of community assembly, local adaptation, and species interactions. Moreover, Hawaiian forests provide insights into predicted patterns of evolution on islands, revealing that while some evidence supports “island syndromes,” there are exceptions to them all. For example, Hawaiian plants are not as a whole less defended against herbivores, less dispersible, more conservative in resource use, or more slow-growing than their continental relatives. Clearly, more work is needed to understand the drivers, sources, and constraints on phenotypic variation among Hawaiian species, including both widespread and rare species, and to understand the role of this variation for ecological and evolutionary processes, which will further contribute to conservation of this unique biota. Today, Hawaiian forests are among the most threatened globally. Resource management failures – the proliferation of non-native species in particular – have led to devastating declines in native taxa and resulted in dominance by novel species assemblages. Conservation and restoration of Hawaiian forests now rely on managing threats including climate change, ongoing species introductions, novel pathogens, lost mutualists, and altered ecosystem dynamics through the use of diverse tools and strategies grounded in basic ecological, evolutionary, and biocultural principles. The future of Hawaiian forests thus depends on the synthesis of ecological and evolutionary research, which will continue to inform future conservation and restoration practices.

Premise of the Study: The capsular-fruited genus Metrosideros (Myrtaceae) is one of the most widely distributed flowering plant genera in the Pacific but is extinct in Australia today. The center of geographic origin for the genus and the reason for and timing of its extinction in Australia remain uncertain. We identify fossil Metrosideros fruits from the newly discovered Golden Fleece fossil flora in the Oligo-Miocene of Tasmania, Australia, shedding further light on these problems. Methods: Standard paleopalynological techniques were used to date the fossil-bearing sediments. Scanning electron microscopy and an auto-montage camera system were used to take high-resolution images of fossil and extant fruits taken from herbarium specimens. Fossils are identified using a nearestliving-relative approach. Key Results: The fossil-bearing sediments are palynostratigraphically dated as being Proteacidites tuberculatus Zone Equivalent (ca. 33-16 Ma) in age and provide a confident Oligo Miocene age for the macrofossils. Two new fossil species of Metrosideros are described and are here named Metrosideros dawsonii sp. nov. and Metrosideros wrightii sp. nov. Conclusions: These newly described fossil species of Metrosideros provide a second record of the genus in the Cenozoic of Australia, placing them in the late Early Oligocene to late Early Miocene. It is now apparent not only that Metrosideros was present in Australia, where the genus is now extinct, but that at least several Metrosideros species were present during the Cenozoic. These fossils further strengthen the case for an Australian origin of the genus.

Whereas disruptive selection imposed by heterogeneous environments can lead to the evolution of extrinsic isolating barriers between diverging populations, the evolution of intrinsic postzygotic barriers through divergent selection is less certain. Long‐lived species such as trees may be especially slow to evolve intrinsic isolating barriers. We examined postpollination reproductive isolating barriers below the species boundary, in an ephemeral hybrid zone between two successional varieties of the landscape‐dominant Hawaiian tree, Metrosideros polymorpha, on volcanically active Hawai'i Island. These archipelago‐wide sympatric varieties show the weakest neutral genetic divergence of any taxon pair on Hawai'i Island but significant morphological and ecological differentiation consistent with adaptation to new and old lava flows. Cross‐fertility between varieties was high and included heterosis of F1 hybrids at the seed germination stage, consistent with a substantial genetic load apparent within varieties through low self‐fertility and a lack of self‐pollen discrimination. However, a partial, but significant, barrier was observed in the form of reduced female and male fertility of hybrids, especially backcross hybrids, consistent with the accumulation of genetic incompatibilities between varieties. These results suggest that partial intrinsic postzygotic barriers can arise through disruptive selection acting on large, hybridizing populations of a long‐lived species.

The Hawaiian psyllids (Psylloidea, Triozidae) feeding on Metrosideros (Myrtaceae) constitute a remarkable radiation of more than 35 species. This monophyletic group has diversified on a single, highly polymorphic host plant species, Metrosideros polymorpha. Eleven Metrosideros-feeding species included in the Insects of Hawaii by Zimmerman are redescribed, and an additional 25 new species are described. Contrary to previous classifications that placed the Metrosideros-feeders in two genera, Trioza Foerster, 1848 and Kuwayama Crawford, 1911, all 36 named species are placed in Pariaconus Enderlein, 1926; and the relationship of this genus to other Pacific taxa within the family Triozidae, and other Austro-Pacific taxa feeding on host plants in Myrtaceae is clarified. The processes of diversification in Pariaconus include shifts in galling habit, geographic isolation within and between islands, and preferences for different morphotypes of the host plant. Four species groups are recognized: the bicoloratus and minutus groups are free-living or form pit galls, and together with the kamua group (composing all of the Kauai species) form a basal assemblage; the more derived closed gall species in the ohialoha group are found on all major islands except Kauai. The diversification of Pariaconus has likely occurred over several million years. Within island diversification is exemplified in the kamua group, and within species variation in the ohialoha group, but species discovery rates suggest this radiation remains undersampled. Mitochondrial DNA barcodes are provided for 28 of the 36 species. Genetic divergence, intraspecific genetic structure, and parallel evolution of different galling biologies and morphological traits are discussed within a phylogenetic framework. Outgroup analysis for the genus Pariaconus and ancestral character state reconstruction suggest pit-galling may be the ancestral state, and the closest outgroups are Palaearctic-Australasian taxa rather than other Pacific Metrosideros-feeders.

Anecdotal theories about traditional uses of Polynesian woods in relation to social and religious practices were tested using comparative wood identification. The woods used to make 135 figure carvings from the Hawaiian archipelago were identified and compared with 23 figure carvings from elsewhere in Polynesia (especially Tahiti and the Marquesas). Prior to this study, the majority of Hawaiian images were believed to have been made from wood ofMetrosideros polymorpha, the commonest forest tree on the archipelago. The results confirm thatMetrosideroswas relatively popular in Hawaii (13% of Hawaiian carvings, compared with 4% in central and south-eastern Polynesia). However, more unexpectedly, over 18 different genera were utilized for figure carvings in Hawaii. The genusCordiaaccounted for 20% of Hawaiian figure carvings identified here, compared with 26% elsewhere in Polynesia, andThespesiafor 4%, compared with 30% in Marquesas. Use of some woods, such as species ofAcacia, was not previously recorded for this purpose, including the first record ofArtocarpuswood for large Hawaiian temple images. Many species—especially those that were less popular for ritual figure carving—were also used for various other purposes, including food, canoe building and medicines. This study demonstrates that the early Polynesian settlers brought with them traditions of using certain trees, but also took advantage of elements of the extensive indigenous flora.

International audience; Compared to traditionally used plastid or ribosomal markers, nuclear gene markers provide many advantages for molecular systematics of plants, and high-throughput sequencing technologies are making large nuclear datasets available at an unprecedented rate. We used targeted amplicon sequencing of 44 nuclear genes to construct a time-calibrated phylogeny of genus Metrosideros (Myrtaceae), evaluate recent systematic revisions, and assess whether phylogenetic signal within the Hawaiian Archipelago is correlated with island biogeography or morphological diversification. We generated a final dataset of 40 nuclear genes for 187 specimens, used multiple search heuristics and species-tree analysis to estimate a phylogeny, and incorporated new fossils for the genus to estimate divergence times across the dataset. All analyses supported the monophyly of Metrosideros, including Carpolepis and Tepualia. Hawaiian Metrosideros were monophyletic and dated to 3.1 MYA using new fossils for the genus, which is intermediate to previous estimates based on nuclear ribosomal/chloroplast loci and calibrated with island ages. Within the Hawaiian Metrosideros clade, we observed short branch lengths and unresolved relationships, and phylogenetic patterns were not concordant with biogeographic hypotheses of island progression, or the delineation of taxa or morphotypes. Average nucleotide diversity was relatively consistent across the Hawaiian Islands with the exception of slightly lower diversity on Kaua'i. These results provide a data-rich estimate of the timing of a single introduction of Metrosideros to Hawai'i and highlight the need for molecular markers with higher evolutionary rates for resolution of relationships within this recent radiation.

A long-standing goal of evolutionary biology is to understand the mechanisms underlying the formation of species. Of particular interest is whether or not speciation can occur in the presence of gene flow and without a period of physical isolation. Here, we investigated this process within HawaiianMetrosideros, a hyper-variable and highly dispersible woody species complex that dominates the Hawaiian Islands in continuous stands. Specifically, we investigated the origin ofMetrosideros polymorphavar.newellii(newellii), a riparian ecotype endemic to Hawaii Island that is purportedly derived from the archipelago-wideM. polymorphavar.glaberrima(glaberrima). Disruptive selection across a sharp forest-riparian ecotone contributes to the isolation of these varieties and is a likely driver of newellii’s origin. We examined genome-wide variation of 42 trees from Hawaii Island and older islands. Results revealed a split between glaberrima and newellii within the past 0.3-1.2 million years. Admixture was extensive between lineages within Hawaii Island and between islands, but introgression from populations on older islands (i.e.secondary gene flow) did not appear to contribute to the emergence of newellii. In contrast, recurrent gene flow (i.e.primary gene flow) between glaberrima and newellii contributed to the formation of genomic islands of elevated absolute and relative divergence. These regions were enriched for genes with regulatory functions as well as for signals of positive selection, especially in newellii, consistent with divergent selection underlying their formation. In sum, our results support riparian newellii as a rare case of incipient ecological speciation with primary gene flow in trees.Author summaryA long-standing question in evolution is whether or not new species can arise in the presence of gene flow, which is expected to inhibit the formation of reproductive isolating barriers. We investigated the genomics underlying the origin of a Hawaii Island-endemic riparian tree and purported case of incipient sympatric speciation due to disruptive selection across a sharp forest-riparian ecotone. We find extensive evidence of ongoing gene flow between the riparian tree and its closest relative along with local genomic regions resistant to admixture that likely formed through selection on genes for ecological adaptation and/or reproductive isolation. These results strongly suggest that where disruptive selection is strong, incipient speciation with gene flow is possible even in long-lived, highly dispersible trees.

International audience; Inoculation of arbuscular mycorrhizal fungi (AMF) as plant growth promoters has mostly been conducted using single-species inoculum. In this study, we investigated whether co-inoculation of different native AMF species induced an improvement of plant growth in an ultramafic soil. We analyzed the effects of six species of AMF from a New Caledonian ultramafic soil on plant growth and nutrition, using mono-inoculations and mixtures comprising different numbers of AMF species, in a greenhouse experiment. The endemic Metrosideros laurifolia was used as a host plant. Our results suggest that, when the plant faced multiple abiotic stress factors (nutrient deficiencies and high concentrations of different heavy metals), co-inoculation of AMF belonging to different families was more efficient than mono-inoculation in improving biomass, mineral nutrition, Ca/Mg ratio, and tolerance to heavy metals of plants in ultramafic soil. This performance suggested functional complementarity between distantly related AMF. Our findings will have important implications for restoration ecology and mycorrhizal biotechnology applied to ultramafic soils.

Whole genome sequences, which can be provided even for non-model organisms owing to high-throughput sequencers, are valuable in enhancing the understanding of adaptive evolution. Metrosideros polymorpha, a tree species endemic to the Hawaiian Islands, occupies a wide range of ecological habitats and shows remarkable polymorphism in phenotypes among/within populations. The biological functions of genetic variations observed within this species could provide significant insights into the adaptive radiation found in a single species. Here de novo assembled genome sequences of M. polymorpha are presented to reveal basic genomic parameters about this species and to develop our knowledge of ecological divergences. The assembly yielded 304-Mbp genome sequences, half of which were covered by 19 scaffolds with >5 Mbp, and contained 30 K protein-coding genes. Demographic history inferred from the genome-wide heterozygosity indicated that this species experienced a dramatic rise and fall in the effective population size, possibly owing to past geographic or climatic changes in the Hawaiian Islands. This M. polymorpha genome assembly represents a high-quality genome resource useful for future functional analyses of both intra- and interspecies genetic variations or comparative genomics.

Heteroblastic and homoblastic woody plants from the New Zealand flora provide a rich playground for testing hypotheses relating to phase change and flowering.

The genus Metrosideros (Myrtaceae) comprises 50–60 species found largely across the Pacific Islands. The relationships within this genus, including the circumscriptions of the subgenera Mearnsia and Metrosideros and their relationships with the other members of the tribe Metrosidereae (namely the New Caledonian endemic genus Carpolepis and the South American Tepualia), are poorly understood. Phylogenetic analyses were carried out using previously published ITS sequences, covering most species of the tribe, and new sequences of five single-copy nuclear genes with a reduced taxon sampling. The independent and combined analyses of the five nuclear genes using a range of approaches, including Bayesian single-gene, concatenated (MrBayes), concordance (BUCKy) and coalescent (*BEAST) analyses, yielded different topologies, indicating important conflicts among phylogenies based on individual genes. The deep relationships within the tribe Metrosidereae remain poorly resolved, but our results indicate that...

Tamaki Estuary is an arm of the Hauraki Gulf situated on the eastern side of central Auckland. Over the last 100 years, Tamaki catchment has evolved from a nearly rural landscape to an urbanised and industrialised area. Pollen, 14C and glass shards analyses, were carried out on three cores collected along the estuary with the aim to reconstruct the estuary's history over the last ∼8000 years and trace natural and anthropogenic effects recorded in the sediments. Glass shard analysis was used to establish key tephra time markers such as the peralkaline eruption of Mayor Island, ∼6000 years BP. During the pre-Polynesian period (since at least 8000 years BP), regional vegetation was podocarp/hardwood forest dominated by Dacrydium cupressinun, Prumnopits taxifolia, and Metrosideros. Major Polynesian settler impact (commencing ∼700 yr BP) was associated with forest clearance as indicated by a sharp decline in forest pollen types. This coincided with an increase in bracken (Pteridium esculentum) spores and grass pollen. Continuing landscape disturbance during European settlement (commencing after 1840 AD) was accompanied by the distinctive appearance of exotic pollen taxa such as Pinus.

This paper addresses the question of transition states in the Hawaiian rainforest ecosystem with emphasis on their initial developments. Born among volcanoes in the north central Pacific about 4 million years ago, the Hawaiian rainforest became assembled from spores of algae, fungi, lichens, bryophytes, ferns and from seeds of about 275 flowering plants that over the millennia evolved into ca. 1000 endemic species. Outstanding among the forest builders were the tree ferns (Cibotium spp.) and the 'ōhi'a lehua trees (Metrosideros spp.), which still dominate the Hawaiian rainforest ecosystem today. The structure of this forest is simple. The canopy in closed mature rainforests is dominated by cohorts of Metrosideros polymorpha and the undergrowth by tree fern species of Cibotium. When a new lava flow cuts through this forest, kipuka are formed, i.e., islands of remnant vegetation. On the new volcanic substrate, the assemblage of plant life forms is similar to the assemblage during the evolution of this system. In open juvenile forests, a mat-forming fern, the uluhe fern (Dicranopteris linearis), becomes established. It inhibits further regeneration of the dominant 'ōhi'a tree, thereby reinforcing the cohort structure of the canopy guild. In the later part of its life cycle, the canopy guild breaks down often in synchrony. The trigger is hypothesized to be a climatic perturbation. After the disturbance, the forest becomes reestablished in about 30–40 yr. As the volcanic surfaces age, they go from a mesotrophic to a eutrophic phase, reaching a biophilic nutrient climax by about 1–25 K yr. Thereafter, a regressive oligotrophic phase follows; the soils become exhausted of nutrients. The shield volcanoes break down. Marginally, forest habitats change into bogs and stream ecosystems. The broader 'ōhi'a rainforest redeveloping in the more dissected landscapes of the older islands loses stature, often forming large gaps that are invaded by the aluminum tolerant uluhe fern. The 'ōhi'a trees still thrive on soils rejuvenated from landslides and from Asian dust on the oldest (5 million years old) island Kaua'i but their stature and living biomass is greatly diminished.

Foliar architecture of Myrtaceae native species of the Argentinian flora IV. Tribes Myrteae and Metrosidereae and key based on foliar characters. This work completes the leaf architecture of native species of Myrtaceae from Argentina. In this contribution are studied two native genus of the tribe Myrteae with uncertain position in the past, and the only one native genus of tribe Metrosidereae in SouthAmerica. One species of Blepharocalyx and two species of Eugenia are simple, with variable apex and base, leathery texture and entire margin. First vein pinnate, simple and straight, without agrophic veins,second veins broquidodromous, with or without paramarginal and intramarginal veins, third and fourth veins random reticulate or percurrent, and fifth vein random reticulate, percurrent or dichotomized. With or without areoles, with venules branching one, two or more times. The last marginal venation can be complete or incomplete. The leaves of genus Metrosideros are characterized by simple, with acute apex and cuneate base, leathery texture and entire margin. First vein category suprabasal-acrodromous, with agrophic veins, second vein cladodromous or branched, without paramarginal veins and intramarginal veins, and third vein dichotomized. Not develop areoles. Venules branched two or more times. The last marginal venation can be incomplete. Finally, is presented a key to differentiate all native Argentinian species of Myrtaceae, based on characters or character combinations of foliar architecture.

Simultaneous salinity and boron (B) excess often occur due to irrigation with water containing high levels of salts, including B. The effects of excess of NaCl and B in the nutrient solution on some agronomical and physiological parameters of Viburnum tinus (laurustinus) and Metrosideros excelsa (metrosideros) were studied. Potted plants were grown in a factorial combination of B (1 and 6 mg/l) and NaCl (2 and 6 dS/m). B toxicity (6 mg/l) caused tip/edge burn in the lower leaves of laurustinus, while these symptoms were absent in metrosideros. Toxicity by B reduced dry biomass in the two species, particularly the aerial part in metrosideros and the roots in laurustinus. Metrosideros accumulated a similar content of B in all leaves, while the laurustinus tended to accumulate more B in the lower leaves. The leaf B content in laurustinus was reduced by salinity to a greater extent than in metrosideros; however, this was not sufficient to prevent injuries to the laurustinus photosynthetic system.

An updated, annotated list of earthstars found in the Hawaiian Islands is presented that includes 19 species of Geastrum and Myriostoma coliforme. Favored habitats for these gasteroid fungi include periodically wet windward coastal Casuarina groves, windward Leucaena thickets, and leeward coastal Prosopis groves. In contrast to these nonnative vegetation zones, earthstars such as Geastrum minimum, G. campestre, and G. corollinum are found also in largely native leeward montane Sophora/Myoporum forests, whereas Geastrum velutinum and G. reticulatum appear in montane native Acacia koa/Metrosideros forests. Eighty-two percent of the collections were made between September and February, although Geastrum triplex may be found earlier during the summer months. Two species, Geastrum litchiforme Desjardin & Hemmes and Geastrum reticulatum Desjardin & Hemmes, are described as new, accompanied by illustrations and comparisons with allied taxa. Geastrum xerophilum, originally published without Latin diagnosis, is formally validated. Specific collections are documented and island distribution and preferred habitats of the various species are listed. An artificial dichotomous key to aid in identification is provided.

Lestari DA, Santoso W (2011) Inventory and habitat study of orchids species in Lamedai Nature Reserve, Kolaka, Southeast Sulawesi. Biodiversitas 12: 28-33. Orchid is one of the ornamental plants which have been high commercial value. Therefore, orchid often has been over exploitation. Finally, some of orchid species are becoming threatened or even endangered. Purwodadi Botanical Garden as an institute of ex-situ conservation play role with it. The aim of this research is to inventory orchid’s species in Lamedai Nature Reserve, Kolaka, Southeast Sulawesi by explorative method. Observation for habitat study was focused on some ecological factors supported to orchids growth like host tree, zone growth on host tree, abundance of sunlight, thickness of substrate (moss), orchid species and number of individual species. The result showed that there were 27 orchids species, consist of, 25 species (16 genera) epiphytic orchid and 2 species terrestrial orchid such as Eulophia keithii var. celebica and Goodyera rubicunda (Blume) Lindl. The host preference for theepiphytic orchid is the group of Myrtaceae family like Syzygium sp., Metrosideros vera Niederen and Metrosideros sp. They mostly grow on the main stem of the tree zone 1 on thick substrate (moss) and get a little abundance of sunlight (calm).

The risk posed to New Zealand native flora by the recently-established pest of Australian origin Uraba lugens Walker (Lepidoptera: Nolidae) (gum leaf skeletonizer) was assessed. Weed biological control host range testing methods were applied to identify those New Zealand plant species potentially at risk. Native plants tested were primarily in the Myrtaceae, the family that contains all the Australian hosts of U. lugens. 2 Experimental methods included no-choice larval feeding assays and field cage and laboratory oviposition trials. Difficulty in ascertaining reliable oviposition preference data from cage oviposition trials limited the confidence with which the invader's field host range could be predicted. 3 Field surveys of plants attacked by U. lugens in the infested area supported the initial predictions but only some of the at-risk native Myrtaceae were present in the area. 4 The risk to native New Zealand plants is presented in terms of two mechanisms: development of self-sustaining populations and temporary spill-over of solitary larvae. Development of self-sustaining populations of the pest within native forests is deemed to be highly improbable. 5 Temporary spill-over impacts are most likely in urban areas within mixed species plantings or boundaries between native/exotic forests and coinciding with the mobile larval life stages. Spill-over impacts from U. lugens have only been recorded to date on Metrosideros excelsa.

Metrosideros Banks ex Gaertner (1788: 170, Myrtaceae) is one of the most widespread tree genus across the Pacific islands and is an emerging model for the study of speciation in tropical trees (Papadopulos et al. 2011; Stacy et al. 2014). The material housed at the Muséum National d’Histoire Naturelle in Paris (P) was recently reviewed in order to prepare the evaluation of the New Caledonian species for the IUCN redlist (IUCN 2017) and apply some recent taxonomic changes in the genus (Pillon et al. 2015). A new species from Vanuatu came to light and is described below.

The Hawaiian endemic Metrosideros polymorpha is known for its high levels of morphological diversity and localized adaptation to a range of habitats. At the ecotone between bogs and forests, individuals exhibiting morphological extremes can be found within a few metres of each other. The objective of this study was to examine the genetic diversity and structure of morphologically distinct neighbouring populations of M. polymorpha, growing in bogs and adjacent forests across multiple islands. We explored these relationships using the molecular technique of inter-simple sequence repeats (ISSRs). The majority (90.79%) of genetic variation was found within populations, 8.53% of the differentiation among populations can be attributed to differences between microhabitat types within islands and very little of the genetic differentiation is explained by the differences among islands (0.68%). These high levels of genetic homogeneity across populations could be the result of extensive gene flow and/or recent isolation of populations. We introduce a nearest genetic neighbour (NGN) analysis to examine detailed relationships of dispersal within and among populations by habitat and island. Using this approach, we provide evidence for habitat fidelity within bog populations and a positive correlation between island age and the proportion of same-island NGNs. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162, 558–571.

Rapid ‘Ōhi‘a Death (ROD) is a disease aggressively killing large numbers of Metrosideros polymorpha (‘ōhi‘a), a native keystone tree species on Hawaii Island. This loss threatens to deeply alter the biological make-up of this unique island ecosystem. Spatially explicit information about the present and past advancement of the disease is essential for its containment; yet, currently such data are severely lacking. To this end, we used the Carnegie Airborne Observatory to collect Laser-Guided Imaging Spectroscopy data and high-resolution digital imagery across >500,000 ha of Hawaii Island in June–July 2017. We then developed a method to map individual tree crowns matching the symptoms of both active (brown; desiccated ‘ōhi‘a crowns) and past (leafless tree crowns) ROD infection using an ensemble of two distinct machine learning approaches. Employing a very conservative classification scheme for minimizing false-positives, model sensitivity rates were 86.9 and 82.5, and precision rates were 97.4 and 95.3 for browning and leafless crowns, respectively. Across the island of Hawaii, we found 43,134 individual crowns suspected of exhibiting the active (browning) stage of ROD infection. Hotspots of potential ROD infection are apparent in the maps. The peninsula on the eastern side of Hawaii known as the Puna district, where the ROD outbreak likely originated, contained a particularly high density of brown crown detections. In comparison, leafless crown detections were much more numerous (547,666 detected leafless crowns in total) and more dispersed across the island. Mapped hotspots of likely ROD incidence across the island will enable scientists, administrators, and land managers to better understand both where and how ROD spreads and how to apply limited resources to limiting this spread.

Many tropical island forest ecosystems are dominated by non-native plant species and lack native species regeneration in the understorey. Comparison of replicated control and removal plots offers an opportunity to examine not only invasive species impacts but also the restoration potential of native species. In lowland Hawaiian wet forests little is known about native species seed dynamics, recruitment requirements, or the effects of management. In a heavily invaded lowland wet forest, we examined the relationship between seed presence and seedling establishment in control and removal plots. Non-native species were competitively superior because they had higher germination percentages and dominated the seed bank; only seven out of 33,375 seedlings were native. In contrast, the seed rain contained native seed, but native seedling recruitment was almost exclusively limited to removal plots, suggesting that optimum establishment conditions are not met in the presence of a dense mid-storey of non-native species. Non-native species dominance was altered and biomass significantly decreased over time resulting in a reduced weeding effort (12.38–0.77 g day 1 ). We suggest that with opening of the canopy through non-native species removal and subsequent weeding, it may be possible to reduce the seed bank enough to skew the regeneration potential towards native species. Our results suggest that germination success and lack of a seed bank are the main bottlenecks for native species. We conclude that without invasive species control, future regeneration of Hawaiian lowland wet forests is likely to be almost entirely

Wildfires are rare in the disturbance history of Hawaiian forests but may increase in prevalence due to invasive species and global climate change. We documented survival rates and adaptations facilitating persistence of native woody species following 2002–2003 wildfires in Hawaii Volcanoes National Park, Hawaii. Fires occurred during an El Nino drought and were ignited by lava flows. They burned across an environmental gradient occupied by two drier shrub-dominated communities and three mesic/wet Metrosideros forest communities. All the 19 native tree, shrub, and tree fern species demonstrated some capacity of postfire persistence. While greater than 95% of the dominant Metrosideros trees were top-killed, more than half survived fires via basal sprouting. Metrosideros trees with diameters >20 cm sprouted in lower percentages than smaller trees. At least 17 of 29 native woody species colonized the postfire environment via seedling establishment. Although the native biota possess adaptations facilitating persistence following wildfire, the presence of highly competitive invasive plants and ungulates will likely alter postfire succession.

The scale insect families Asterolecaniidae and Eriococcidae are discussed from New Caledonia. One new genus Oacoccus gen. nov., and a new species Oacoccus nothofagi sp. nov. on Nothofagus sp., are described in the Asterolecaniidae, and a new species Eriococcus millei sp. nov. is described in the Eriococcidae. A new genus Rhopalotococcus gen. nov., and two new species Rhopalotococcus dugdalei sp. nov. and Rhopalotococcus metrosideri sp. nov., are also described in the Eriococcidae. Both species induce leaf galls on Metrosideros sp. Keys are provided for all the New Caledonian genera and species in the families Asterolecaniidae and Eriococcidae.

A multiproxy analysis of back-dune sediment cores from Rangihoua Bay, northern New Zealand, provides an environmental history of the Late Quaternary, placing human impacts on the site into a geomorphological and ecological context. The inferred paleoecological significance of the trends is generally coeval between proxies. The history commences with a Late Pleistocene deposit that formed part of a river terrace during lower sea level. The dryland vegetation at that time was dominated by Fuscospora forest. The record recommences at ca. 7400 YBP, by which time Fuscospora had been replaced by podocarp-hardwood forest, comprising mainly Dacrydium and Prumnopitys taxifolia emerging through a Metrosideros canopy. One of the core sites was a lagoon fringed with mainly Cyperaceae, Leptospermum, and Dodonaea. Redox-sensitive elements reflect phases of anoxia related to variation in lagoon depth. Transition from lagoon to peat swamp, due to natural infilling and/or climate change, occurred after ca. 5500 Y...

A new species of fly, Fergusonina metrosiderosi Taylor sp.n. (Diptera: Fergusoninidae) [and its associated nematode, Fergusobia pohutukawa Davies sp.n. (Tylenchida: Neotylenchidae)], is described from unilocular basal shoot-bud galls on Pohutukawa (New Zealand Christmas Tree), Metrosideros excelsa Banks ex Gaertn. (Myrtaceae). The fly is characterized by the short, sclerotized postabdomen of the female, distinctly grey wings, reduction in length of the reclinate orbital, postocellar and vertical setae, undifferentiation of the ocellar setae, supernumerary setation of the genae, and three pairs of scutellar setae rather than two. The dorsal shield is restricted to a few raised sclerotized spicules on the first to third thoracic segments of the larva and epidermis of the puparium. The nematode is characterized by the combinations of arcuate shape, small ‘a’ ratio, swollen cuticle, small cephalic region with elevated circum-oral area with a flat tip, coarse annulation and relatively slender conical tail of the parthenogenetic female, and coarse annulation, long bursa and angular spicule with short, broad, offset manubrium of the male. Fergusonina metrosiderosi sp.n. and Fergusobia pohutukawa sp.n. represent the first record of the fly-nematode association from the host genus Metrosideros, and the first record from New Zealand. Aspects of the biology and biogeography of the fly-nematode association are discussed.

Genomewide markers enable us to study genetic differentiation within a species and the factors underlying it at a much higher resolution than before, which advances our understanding of adaptation in organisms. We investigated genomic divergence in Metrosideros polymorpha, a woody species that occupies a wide range of ecological habitats across the Hawaiian Islands and shows remarkable phenotypic variation. Using 1659 single nucleotide polymorphism (SNP) markers annotated with the genome assembly, we examined the population genetic structure and demographic history of nine populations across five elevations and two ages of substrates on Mauna Loa, the island of Hawaii. The nine populations were differentiated into two genetic clusters distributed on the lower and higher elevations and were largely admixed on the middle elevation. Demographic modelling revealed that the two genetic clusters have been maintained in the face of gene flow, and the effective population size of the high-altitude cluster was much smaller. A FST -based outlier search among the 1659 SNPs revealed that 34 SNPs (2.05%) were likely to be under divergent selection and the allele frequencies of 21 of them were associated with environmental changes along elevations, such as temperature and precipitation. This study shows a genomic mosaic of M. polymorpha, in which contrasting divergence patterns were found. While most genomic polymorphisms were shared among populations, a small fraction of the genome was significantly differentiated between populations in diverse environments and could be responsible for the dramatic adaptation to a wide range of environments.

Five unusual C-methylflavonoids lacking B-ring oxygenation (2′,4′-dihydroxy-3′,5′-dimethyl-6′-methoxychalcone, 2′,4′-dihydroxy-3′-methyl-6′-methoxychalcone, 2′,6′-dihydroxy-3′-methyl-4′-methoxychalcone, 2′-hydroxy-3′-methyl-4′,6′-dimethoxychalcone and 5,7-dihydroxy-6,8-dimethylflavanone) were found for the first time in Metrosideros excelsa. The flavanone was the major constituent in leaves, whereas 2′,6′-dihydroxy-3′-methyl-4′-methoxychalcone dominated all other aerial plant parts studied. Other Metrosideros species were investigated for these five flavonoids. C19–C36 aldehydes and C22–C32 alcohols were also identified from the dried seed capsules of M. excelsa.

Nutrient resource availability and host-plant foliar pubescence both influence arthropod food webs, but multifactor studies are needed to under- stand their interdependence and relative importance. Arthropods were sampled by clipping foliage from Metrosideros polymorpha (Myrtaceae) trees of pubescent, glabrous, and intermediate leaf forms on fertilised and unfertilised plots. 2. Fertilisation decreased leaf mass per area (LMA) but did not change the relative mass of pubescence within leaf morphological classes. 3. Fertilisation increased densities of individuals in four taxonomic orders, densities of individuals and species of all trophic levels, and the biomass of Collembola and Homoptera. Herbivore relative diversity (Shannon H 0 ) also increased with fertilisation, but detritivore diversity declined due to increasing dominance of Salina celebensis (Schaeffer) (Collembola). 4. Detritivore density, driven again by S. celebensis, increased with decreasing leaf pubescence, but Heteroptera and Acari were most abundant on the inter- mediate pubescence class, and Psocoptera density and biomass increased with increasing pubescence. Trophic-level species density did not change with leaf morphological class, but relative diversity of all arthropods and of detritivores increased with increasing pubescence. 5. Both resource availability and leaf pubescence affected Metrosideros arthro- pod communities. However, the pervasive positive influence of fertilisation did not translate to compositional shifts, and there were no interactions with leaf morphological class. In contrast, the effects of leaf pubescence on arthropod density, biomass, and diversity were more restricted taxonomically, and non- parametric MANOVA and redundancy analyses demonstrated significant differen- tiation in community composition on the pubescent morphology.

A 2.34 m sediment profile from the base of the crater of Mt St John volcano (a small basaltic cone on Auckland Isthmus) provides a partial environmental record of the Late Quaternary. The record highlights potential age control problems with sediment cores taken directly from archaeological sites. Two distal tephras were recorded: 9.5 ka Rotoma and 7 ka Tuhua. A date of 16 309 ± 90 14C yr BP from the basal scoria of the profile provides a minimum date for the eruption of Mt St John. Pollen was present only in the upper 0.33 m of the profile, in a layer of peat and soil which caps highly weathered silts and clays eroded from the crater walls. In early Polynesian times (most likely after c. 800 14C yr BP), vegetation of the crater swamp was dominated by Cyperaceae sedges and Paesia ground fern. Dacrycarpus trees were also present. Podocarp‐hardwood forest, dominated by Metrosideros, grew on the rim and inner slopes of the crater. Elaeocarpus, Griselinia, and Cyathea were also present. A decline in ...

Documented chromosome numbers are reported for 187 taxa (170 species, 9 subspecies, 8 varieties), 5 hybrids (four putative, one artificial), and 18 of uncertain rank from 50 families (84 genera; 2 lycophyte, 11 pterophyte and 71 anthophyte). Of these, 189 counts are new for the New Zealand flora (167 of these are from named taxa). Many of the counts reported are from more poorly investigated families (e.g., Cyperaceae, Lycopodiaceae, Pota‐mogetonaceae) and genera (e.g., Desmoschoenus, Freycinetia, Lycopodiella, Lycopodium, Potamo‐geton, Schoenus), indigenous to New Zealand, or from nationally uncommon and/or threatened taxa (e.g., Eleocharis neozelandica, Hebe societatis, Myriophyllum robustum, and Pittosporum dallii), and/or newly described plants (e.g., Gingidia gri‐sea, Olearia adenocarpa), while three counts are from naturalised species (Alternanthera sessilis, Nephrolepis cordifolia, and Senecio skirrhodon), and one from a cultivated plant of Metrosideros nervulosa. In the majority of genera...

Carnivore (top-down) and resource (bottom-up) influences in food webs are strong and pervasive, but few studies have investigated their interactive effects in species-rich terrestrial ecosystems. This study focused on arthropods associated with the dominant tree species, Metrosideros polymorpha (Myrtaceae), in Hawaiian forests. Severe soil nutrient limitation on a 120-yr-old lava flow was removed by fertilization and combined with bird predator exclusion cages in a randomized block design. Arthropod densities were measured from clipped foliage at the outset and conclusion of a 33-mo experiment, and their biomass was estimated using regression equations. Metrosideros foliar nitrogen, tree growth, and biomass increased directly in response to fertilization but did not change with bird exclusion. Fertilization increased detritivore densities but not biomass, and both density and biomass of herbivores, while bird exclusion increased both density and biomass of carnivores. Fertilization also increased spider density and biomass, but bird exclusion increased spider numbers (15 species) only in high resource plots. Overall, trophic level biomass responses were less pronounced than density because smaller bodied individuals responded more to enrichment. Bottom-up factors controlled basal trophic levels, and detritivores comprised the largest fraction of arthropod density and biomass. Conversely, top-down impacts were apparent but variable, limited to higher order consumers, and did not cascade to the level of primary producers. These experimental results were consistent with the view that complex forest ecosystems are structured on a bottom-up template.

Because of its remoteness and mid-latitude position, New Zealand lacks access to the tropical climates that might have ensured straightforward survival for frost-sensitive species during glacial times. Nevertheless, the New Zealand lowland flora retains a substantial complement of plants sourced in the tropics. While there have been extinction pulses for elements of the frost-sensitive flora under glacial/stadial regimes, the surviving remnants have been able to recolonize large areas of habitat during successive warm climate periods. Refugia for such species in stadial New Zealand are likely to have been localized and ecologically suboptimal. To examine these relationships we have applied chloroplast DNA sequence data to the investigation of phylogeographical pattern for five endemic species of Metrosideros subg. Metrosideros, a wide-ranging group of mostly frost-sensitive woody plants in New Zealand. The results of this research verify the location of two generally mooted stadial refugia for the country and provide support for the existence of a third. A simple pattern of chloroplast haplotype diversity was recorded in extra-refugial areas, compared with a greater complexity in the vicinity of the identified refugia. This pattern was independently repeated in both main islands. The proposed refugia correspond to contemporary localities of high average winter temperatures. The sharing of chloroplast haplotypes between the different species of Metrosideros examined suggests that there has been a history of repeated hybridization and introgression for these plants, possibly initiated by periods of refugial confinement. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 83, 399–412.