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Assessing within-species variation in response to drought is crucial for predicting species' responses to climate change and informing restoration and conservation efforts, yet experimental data are lacking for the vast majority of tropical tree species. We assessed intraspecific variation in response to water availability across a strong rainfall gradient for 16 tropical tree species using reciprocal transplant and common garden field experiments, along with measurements of gene flow and key functional traits linked to drought resistance. Although drought resistance varies widely among species in these forests, we found little evidence for within-species variation in drought resistance. For the majority of functional traits measured, we detected no significant intraspecific variation. The few traits that did vary significantly between drier and wetter origins of the same species all showed relationships opposite to expectations based on drought stress. Furthermore, seedlings of the same species originating from drier and wetter sites performed equally well under drought conditions in the common garden experiment and at the driest transplant site. However, contrary to expectation, wetter-origin seedlings survived better than drier-origin seedlings under wetter conditions in both the reciprocal transplant and common garden experiment, potentially due to lower insect herbivory. Our study provides the most comprehensive picture to date of intraspecific variation in tropical tree species' responses to water availability. Our findings suggest that while drought plays an important role in shaping species composition across moist tropical forests, its influence on within-species variation is limited., Competing Interests: Competing interests statement:The authors declare no competing interest.

Resolving the consequences of pollinator foraging behaviour for plant mating systems is a fundamental challenge in evolutionary ecology. Pollinators may adopt particular foraging tactics: complete trapline foraging (repeated movements along a fixed route), sample-and-shift trapline foraging (a variable route that incorporates information from previous experiences) and territorial foraging (stochastic movements within a restricted area). Studies that integrate these pollinator foraging tactics with plant mating systems are generally lacking. We investigate the consequences of particular pollinator foraging tactics for Heliconia tortuosa. We combine parentage and sibship inference analysis with simulation modelling to: estimate mating system parameters; infer the foraging tactic adopted by the pollinators; and quantify the impact of pollinator foraging tactics on mating system parameters. We found high outcrossing rates, ubiquitous multiple paternity and a pronounced departure from near-neighbour mating. We also found that plants repeatedly receive pollen from a series of particular donors. We infer that the pollinators primarily adopt complete trapline foraging and occasionally engage in sample-and-shift trapline foraging. This enhances multiple paternity without a substantial increase in near-neighbour mating. The particular pollinator foraging tactics have divergent consequences for multiple paternity and near-neighbour mating. Thus, pollinator foraging behaviour is an important driver of the ecology and evolution of plant mating systems., (© 2022 The Authors. New Phytologist © 2022 New Phytologist Foundation.)

Premise: Reconciling the use of taxonomy to partition morphological variation and describe genetic divergence within and among closely related species is a persistent challenge in phylogenetics. We reconstructed phylogenetic relationships among Cedrela odorata (Meliaceae) and five closely allied species to test the genetic basis for the current model of species delimitation in this economically valuable and threatened genus., Methods: We prepared a nuclear species tree with the program SNPhylo and 16,000 single-nucleotide polymorphisms from 168 Cedrela specimens. Based on clades present and ancestral patterns ADMIXTURE, we designed nine species delimitation models and compared each model to current taxonomy with Bayes factor delimitation. Timing of major lineage divergences was estimated with the program SNAPP., Results: The resulting analysis revealed that modern C. odorata evolved from two genetically distinct ancestral sources. All species delimitation models tested better fit the data than the model representing current taxonomic delimitation. Models with the greatest marginal likelihoods separated Mesoamerican C. odorata and South American C. odorata into two species and lumped C. angustifolia and C. montana as a single species. We estimated that Cedrela diversified in South America within the last 19 million years following one or more dispersal events from Mesoamerican lineages., Conclusions: Our analyses show that the present taxonomic understanding within the genus obscures divergent lineages in C. odorata due in part to morphological differentiation and taxonomic distinctions that are not predictably associated with genetic divergence. A more accurate application of taxonomy to C. odorata and related species may aid in its conservation, management, and restoration efforts., (© 2022 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Forest conversion and habitat loss are major threats to biological diversity. Forest regeneration can mitigate the negative effects of old-growth forest loss on species diversity, but less is known about the extent to which forest loss reduces genetic diversity in remnant populations and whether secondary forests play a role in the maintenance of genetic diversity. We quantified genetic diversity in a tropical hummingbird-pollinated understorey herb, Heliconia tortuosa, across a landscape mosaic of primary and secondary forest regrowth. Using microsatellite genotypes from >850 adult and juvenile plants within 33 forest patches and extensive bird surveys, we examined the effect of contemporary and historical landscape features including forest age (primary vs. secondary forest), stand isolation and pollinator assemblages on genetic diversity and levels of inbreeding in H. tortuosa. We found that inbreeding was up to three times higher in secondary forest, and this effect was amplified with reductions in primary forest in the surrounding landscape through reduced observed heterozygosity in isolated fragments. Inbreeding in forest patches was negatively correlated with the local frequency of specialist long-distance foraging traplining hummingbirds. Traplining hummingbirds therefore appear to facilitate mating among unrelated plants-an inference we tested using empirically parameterized simulations. Higher levels of inbreeding in H. tortuosa are therefore associated with reduced functional diversity of hummingbirds in secondary forests and forest patches isolated from primary forests. Our findings suggest a cryptic consequence of primary forest loss and secondary forest regeneration through the disruption of mutualistic interactions resulting in the erosion of genetic diversity in a common understorey plant., (© 2022 John Wiley & Sons Ltd.)

Identifying key traits that can serve as proxies for species drought resistance is crucial for predicting and mitigating the effects of climate change in diverse plant communities. Turgor loss point (π tlp ) is a recently emerged trait that has been linked to species distributions across gradients of water availability. However, a direct relationship between π tlp and species ability to survive drought has yet to be established for woody species. Using a manipulative field experiment to quantify species drought resistance (i.e., their survival response to drought), combined with measurements of π tlp for 16 tree species, we show a negative relationship between π tlp and seedling drought resistance. Using long-term forest plot data, we also show that π tlp predicts seedling survival responses to a severe El Niño-related drought, although additional factors are clearly also important. Our study demonstrates that species with lower π tlp exhibit higher survival under both experimental and natural drought. These results provide a missing cornerstone in the assessment of the traits underlying drought resistance in woody species and strengthen π tlp as a proxy for evaluating which species will lose or win under projections of exacerbating drought regimes., (© 2022 The Authors. Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

As extreme climate events are predicted to become more frequent because of global climate change, understanding their impacts on natural systems is crucial. Tropical forests are vulnerable to droughts associated with extreme El Niño events. However, little is known about how tropical seedling communities respond to El Niño-related droughts, even though patterns of seedling survival shape future forest structure and diversity. Using long-term data from eight tropical moist forests spanning a rainfall gradient in central Panama, we show that community-wide seedling mortality increased by 11% during the extreme 2015-16 El Niño, with mortality increasing most in drought-sensitive species and in wetter forests. These results indicate that severe El Niño-related droughts influence understory dynamics in tropical forests, with effects varying both within and across sites. Our findings suggest that predicted increases in the frequency of extreme El Niño events will alter tropical plant communities through their effects on early life stages., (© 2021 John Wiley & Sons Ltd.)