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It is critical that we understand the effects of climate change on natural systems if we ever hope to predict or mitigate consequent changes in diversity and ecosystem function. In order to identify coherent 'fingerprints' of climate change across Earth's terrestrial and marine ecosystems, various reviews have been conducted to synthesize studies of climate change impacts on individual species, assemblages and systems. These reviews help to make information about climate change impacts accessible for researchers as well as for the general public and policymakers. As such, these reviews can be highly influential in setting the direction of policy and research. Unfortunately, due to limited data availability, the majority of reviews of climate change impacts suffer from severe taxonomic and geographic biases. In particular, tropical and marine systems are grossly underrepresented, as are plants and endothermic animals. These biases may preclude a comprehensive understanding of how climate change is affecting Earth's natural systems at a global scale. In order to advance our understanding of climate change impacts on species and ecosystems, we need to first assess the types of data that are and are not available and then correct these biases through directed studies and initiatives.

Tropical species may be highly vulnerable to climate change [Also see Report by Chan et al. ] Early Victorian naturalists marveled at the profusion of diversity they encountered as they traveled from temperate to tropical latitudes. The inverse relationship between latitude and species richness that these naturalists first observed is now referred to as the latitudinal diversity gradient. Various ecological and evolutionary explanations have been proposed for the latitudinal diversity gradient. Of these, perhaps none are more relevant to contemporary conservation issues than Janzen's hypothesis of latitudinal differences in species' climatic tolerances and thermal selectivity ( 1 ). On page 1437 of this issue, Chan et al. ( 2 ) advance Janzen's early theories by elucidating some of the potential selective pressures imposed by climate and climate variability.

Due to global warming, many species will face greater risks of thermal stress, which can lead to changes in performance, abundance, and/or geographic distributions. In plants, high temperatures above a species-specific critical thermal maximum will permanently damage photosystem II, leading to decreased electron transport rates, photosynthetic failure, and eventual leaf and plant death. Previous studies have shown that plant thermal tolerances vary with latitude, but little is known about how they change across smaller-scale thermal gradients (i.e., with elevation) or about how these thermal tolerances relate to species' local performances and geographic distributions. In this study, we assess the maximum photosynthetic thermal tolerances (T50) of nearly 200 tropical tree species growing in 10 forest plots distributed across a >2,500 m elevation gradient (corresponding to a 17°C temperature gradient) in the northern Andes Mountains of Colombia. Using these data, we test the relationships between species' thermal tolerances and (1) plot elevations and temperatures, (2) species' large-scale geographic distributions, and (3) changes in species' abundances through time within the plots. We found that species' T50 do in fact decrease with plot elevation but significantly slower than the corresponding adiabatic lapse rate (−0.4 vs. −5.7°C km−1) and that there remains a large amount of unexplained variation in the thermal tolerances of co-occurring tree species. There was only a very weak association between species' thermal tolerances and their large-scale geographic distributions and no significant relationships between species' thermal tolerances and their changes in relative abundance through time. A potential explanation for these results is that thermal tolerances are adaptations to extreme leaf temperatures that can be decoupled from regional air temperatures due to microclimatic variations and differences in the species' leaf thermoregulatory properties.

Collaboration can improve conservation initiatives through increases in article impact and by building scientific understating required for conservation practice. We investigated temporal trends in collaboration in the tropical ecology and conservation literature by examining patterns of authorship for 2271 articles published from 2000 to 2016 in Biotropica and the Journal of Tropical Ecology. Consistent with trends in other studies and scientific disciplines, we found that the number of authors per article increased from 2.6 in 2000 to 4.2 in 2015 using a generalized linear model (glm). We modeled changes in multinational collaboration in articles using a glm and found that the mean number of author-affiliated countries increased from 1.3 (±0.6 SD) to 1.7 (±0.8 SD) over time and that increases were best explained by the number of authors per article. The proportion of authors based in tropical countries increased, but the probability of tropical–extratropical collaboration did not and was best explained solely by the number of authors per article. Overall, our analyses suggest that only certain types of collaboration are increasing and that these increases coincide with a general increase in the number of authors per article. Such changes in author numbers and collaboration could be the result of increased data sharing, changes in the scope of research questions, changes in authorship criteria, or scientific migration. We encourage tropical conservation scientists continue to build collaborative ties, particularly with researchers based in underrepresented tropical countries, to ensure that tropical ecology and conservation remains inclusive and effective. to build collaborative ties, particularly with researchers based in underrepresented tropical countries, to ensure that tropical ecology and conservation remains inclusive and effective.

Functional traits are increasingly used to understand the ecology of plants and to predict their responses to global changes. Unfortunately, trait data are unavailable for the majority of plant species. The lack of trait data is especially prevalent for hard-to-measure traits and for tropical plant species, potentially owing to the many inherent difficulties of working with species in remote, hyperdiverse rainforest systems. The living collections of botanic gardens provide convenient access to large numbers of tropical plant species and can potentially be used to quickly augment trait databases and advance our understanding of species' responses to climate change. In this review, we quantitatively assess the availability of trait data for tropical versus temperate species, the diversity of species available for sampling in several exemplar tropical botanic gardens and the validity of garden-based leaf and root trait measurements. Our analyses support the contention that the living collections of botanic gardens are a valuable scientific resource that can contribute significantly to research on plant functional ecology and conservation. This article is part of the theme issue ‘Biological collections for understanding biodiversity in the Anthropocene’.

Phylogenetic constraints on ecophysiological adaptations and specific resource requirements are likely to explain why some taxonomic/functional groups exhibit different richness patterns along climatic gradients. We used interpolated species elevational distribution data and climatic data to describe gymnosperm species richness variation along elevational and climatic gradients in the Himalayas. We compared the climatic and elevational distributions of gymnosperms to those previously found for bryophytes, ferns, and angiosperm tree lineages to understand the respective drivers of species richness. We divided our study location into three regions: Eastern; Central; and Western Himalayas, in each calculating gymnosperm species richness per 100-m band elevational interval by determining the sum of species with overlapping elevational distributions. Using linear regression, we analyzed the relationship between species’ elevational mid-point and species’ elevational range size to test the Rapoport’s rule for gymnosperms in the Himalayas. Generalized linear models were used to test if potential evapotranspiration, growing degree days, and the number of rainy days could predict the observed patterns of gymnosperm species richness. We used the non-linear least squares method to examine if species richness optima differed among the four taxa. We found supporting evidence for the elevational Rapoport’s rule in the distribution of gymnosperms, and we found a unimodal pattern in gymnosperm species richness with elevation, with the highest species richness observed at ca. 3000 m. We also found a unimodal pattern of gymnosperm species richness along both the potential evapotranspiration and growing degree day gradients, while the relationship between species richness and the number of rainy days per year was non-significant. Gymnosperm species richness peaked at higher elevations than for any other plant functional group. Our results are consistent with the view that differences in response of contrasting plant taxonomic groups with elevation can be explained by differences in energy requirements and competitive interactions.