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Highlights • Seed recalcitrance occurred in 721 species, 297 genera and 84 families. • The trait was apomorphic in numerous extant lineages. • There is evidence of a radiation of recalcitrant taxa from the Miocene onwards. • Transition rates from orthodox to recalcitrant state were lower than vice versa. • Time spent in the recalcitrant state is shorter than that of the orthodox state. Abstract This analytical review builds on previous descriptions of the recalcitrant seed trait's taxonomic and phylogenetic coverage and provides new insights into the recalcitrant seed trait's apomorphic or plesiomorphic character state, transition rates and residence time in relation to Earth's geological history. A comprehensive global list of recalcitrant-seeded species (RSS) was compiled to assess taxonomic and phylogenetic coverage. Plesiomorphic character state (orthodox or recalcitrant) was established via a comparison of the species stem ages of RSS and orthodox-seeded species (OSS) within specific lineages. Using a previously published tree, frequency by which transitions between OSS and RSS occur and the average time spent in each state was calculated. The recalcitrant seed trait occurred in 721 species, 297 genera and 84 families, with 92% of RSS being tropical phanerophytes. The recalcitrant seed trait was apomorphic in numerous extant lineages, with the earliest representative species appearing in the late Cretaceous. The ratio of RSS to OSS divergence changes from favouring recalcitrance in the late Cretaceous, to the Eocene, when it favoured orthodoxy, reaching the highest difference in the Pleistocene and abating in the Holocene. Transition rates from the orthodox to the recalcitrant state were lower than vice versa. The average time RSS spent in the recalcitrant state is considerably shorter than that spent by OSS in the orthodox state. Recalcitrance is more likely a consequence of gradual adaptation and taxa appear to be more likely to transition from recalcitrant to orthodox than the reverse. By occurring in relatively warm and wet environments, RSS need not invest in desiccation tolerance mechanisms, constituting a metabolic 'saving'. However, some RSS persist in arid and temperate regions, and have arisen during and survived periods associated with major climatic changes. This, together with their representation in numerous ancient lineages, suggests that RSS are 'evolutionary survivors'. [ABSTRACT FROM AUTHOR]

Abstract: Relatively few studies have investigated mistletoe infestation of tree species in urban settings, and even fewer considered infestation of alien tree species. Here, mistletoe infestation incidence and intensity were studied in Durban, South Africa. The relationship of infestation to tree CBH and height was examined in detail for the mistletoe species Erianthemum dregei. Although E. dregei is known to have a wide range of host taxa, we report E. dregei infestation on 27 new host species for the first time. E. dregei occurred on 30 host species with a preference for the alien host tree Melia azedarach in our study area. The relationship between infestation and CBH indicated that the trees (irrespective of species) of ≥200cm were more susceptible to the mistletoe attack. The implications of this pattern, as well as those of high host diversity and especially of infestation of alien trees are discussed in a conservation perspective. [Copyright &y& Elsevier]

• Urban green spaces hosted many alien and invasive aliens. • Shrubs and herbs from Asteraceae, Fabaceae, Verbenaceae are dominant aliens. • Disturbance and informal settlements influence invasive alien species composition. • The Alien Invasive Index developed identified hotspots of invasiveness. • The Alien Invasive Index can be used to prioritise green spaces for alien control. Urban natural green spaces are becoming increasingly impacted by anthropogenic disturbances, promoting alien plant invasions. Using a rapidly developing city in South Africa as a case study, we related distribution, composition, and ordering of alien plant species to environmental and anthropogenic factors to identify drivers of invasiveness. Vegetation surveys were used to identify and quantify (in terms of composition and density) alien species within 30 natural green spaces. Floristic characteristics were then related to levels of non-natural disturbance and selected abiotic parameters. Based on the relationships observed, selected floristic parameters were used to develop an Alien Invasive Index to identify 'invasive alien hotspots'. Collectively, 80 alien plant species (from 30 families) were found, 35 of which are invasive. The most speciose families were Asteraceae > Fabaceae > Verbenaceae. Their representatives, specifically the invasive shrubs Lantana camara (Verbenaceae) and Chromolaena odorata (Asteraceae) and alien herbs Conyza sumatrensis , Bidens pilosa and Tagetes minuata (Asteraceae) were also the most dominant in terms of frequency across sites and density. A Principal Component Analysis showed invasive alien plant species composition to be most strongly related to level of disturbance, followed by distance to informal settlement and soil moisture content. The Alien Invasive Index could discriminate between sites with low and high levels of invasiveness, and its suitability was validated by the fact that sites with very high index values were in close proximity to informal settlements. The study demonstrates the value of combining classical in situ vegetation surveys and overlay analysis using Geographic Information System for prioritising green spaces and alien species for management in cities that are limited in terms of financial resources. [ABSTRACT FROM AUTHOR]

The predicted 2–5 °C increase in global temperatures by the end of this century could enhance the invasive potential of some alien plant species. It is unclear whether aliens that originate from and/or are naturalised in warm areas are predisposed to respond positively to this increase. This study assessed the propagule and seedling responses of three alien plant species ( viz . Oenothera biennis , Syncarpia glomulifera and Petiveria alliacea ) naturalised in a subtropical region in South Africa to elevated temperatures. The species were characterised in terms of propagule (seed/achene) traits related to invasiveness before these were sown at ambient (daily maximum: 26.2 ± 0.3 °C; daily minimum: 17.9 ± 0.2 °C) and elevated (daily maximum: 30.6 ± 0.5 °C; daily minimum: 21.2 ± 0.3 °C) temperatures to assess germination capacity and rate. Seedlings subsequently produced were grown at these temperatures to assess growth and performance. Propagules of all species possess traits that facilitate persistent seed banks but their small size may not favour seedling survival under harsh conditions. Only O. biennis and P. alliacea exhibited high seed viability but elevated temperatures enhanced germination capacity and rate in all species. Seedlings of both O. biennis and S. glomulifera exhibited signs of stress at elevated temperatures ( e.g. reduced biomass) though. However, while seedling production and survival were reduced at elevated temperatures in O. biennis , these parameters were enhanced at elevated temperatures in S. glomulifera (possibly due to increased shoot emergence rate). Elevated temperatures did not affect seedling production in P. alliacea but did enhance seedling survival, possibly by inducing biomass allocation patterns that enhance productivity. The ability of naturalised species to become invasive in a changing climate may be more dependent on phenotypic plasticity than the possession of a syndrome of invasive traits. Species that originate from, and are naturalised in, warmer climates may not be predisposed to respond positively to elevated temperatures. [ABSTRACT FROM AUTHOR]

• El Niño Southern Oscillation induced drought reduces the growth of indigenous tree seedlings/saplings. • The microtopographic positions within a reforestation site influence tree seedlings/saplings response to drought. • Drought tolerant pioneer tree species should be used for reforestation in dry and drought-prone areas. The selection of reforestation species that promote rapid forest establishment has now become more challenging as a result of global climate change. This is because a recent increase in droughts associated with the El Niño Southern Oscillation is presenting a critical challenge to forest seedling survival and growth, thus threatening biodiversity and ecosystem services supply. The severe drought associated with the 2014–2016 El Niño Southern Oscillation event presented an opportunity to assess its impact on the reforestation success of a subtropical forest in Durban, South Africa. We assess how microtopographic positions (specifically, dry and moist microhabitats) influenced seedling/sapling survival and growth performance (stem diameter and height, and canopy width) of four dominant planted tree species (Bridelia micrantha, Erythrina lysistemon, Millettia grandis, and Vachellia natalitia) under a severe drought, measured a month after transplanting and 13 months post-transplanting, after the drought began. Survival ranged from 73% to 93%, but seedlings/saplings in the moist microhabitat had higher survival rates and higher growth rates than species in the dry microhabitat. A higher survival rate exhibited by M. grandis followed by V. natalitia and E. lysistemon in both the dry and moist microhabitats suggests these three species are good pioneers for reforestation in areas that are predicted to experience frequent and intense droughts. Results from this study highlight the importance of considering microtopographic positions, as well as understanding species-specific habitat requirements when selecting reforestation species under the current and future climatic conditions. [ABSTRACT FROM AUTHOR]