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Neotropical seasonal dry forest (NSDF) is one of the most threatened ecosystems according to global climate change predictions. Nonetheless, few studies have evaluated the global climate change impacts on diversity patterns of NSDF plants. The lack of whole biome-scale approaches restricts our understanding of global climate change consequences in the high beta-diverse NSDF. We analysed the impact of global climate change on species distribution ranges, species richness, and assemblage composition (beta diversity) for 1,178 NSDF species. We used five representative plant families (in terms of abundance, dominance, and endemism) within the NSDF: Cactaceae, Capparaceae, Fabaceae, Malvaceae, and Zygophyllaceae. We reconstructed potential species distributions in the present and future (2040-2080), considering an intermediate Shared Socioeconomic Pathway and two dispersal ability assumptions on the taxa. Using a resource use scores index, we related climate-induced range contractions with species' water stress tolerance. Even under a favourable dispersal scenario, species distribution and richness showed future significant declines across those sites where mean temperature and precipitation seasonality are expected to increase. Further, changes in species range distribution in the future correlated positively with potential use of resources in Fabaceae. Results suggest that biotic heterogenization will likely be the short-term outcome at biome scale under dispersal limitations. Nonetheless, by 2080, the prevailing effect under both dispersal assumptions will be homogenization, even within floristic nuclei. This information is critical for further defining new areas worth protecting and future planning of mitigation actions for both species and the whole biome.

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Climate change has physiological consequences on organisms, ecosystems and human societies, surpassing the pace of organismal adaptation. Hibernating mammals are particularly vulnerable as winter survival is determined by short-term physiological changes triggered by temperature. In these animals, winter temperatures cannot surpass a certain threshold, above which hibernators arouse from torpor, increasing several fold their energy needs when food is unavailable. Here, we parameterized a numerical model predicting energy consumption in heterothermic species and modelled winter survival at different climate change scenarios. As a model species, we used the arboreal marsupial monito del monte (genus Dromiciops), which is recognized as one of the few South American hibernators. We modelled four climate change scenarios (from optimistic to pessimistic) based on IPCC projections, predicting that northern and coastal populations (Dromiciops bozinovici) will decline because the minimum number of cold days needed to survive the winter will not be attained. These populations are also the most affected by habitat fragmentation and changes in land use. Conversely, Andean and other highland populations, in cooler environments, are predicted to persist and thrive. Given the widespread presence of hibernating mammals around the world, models based on simple physiological parameters, such as this one, are becoming essential for predicting species responses to warming in the short term.

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Background: Maize (Zea mays L.) is a staple crop cultivated on a global scale. However, its ability to feed the rapidly growing human population may be impaired by climate change, especially if it has low climatic niche and range lability. One important question requiring clarification is therefore whether maize shows high niche and range lability. Methods: We used the COUE scheme (a unified terminology representing niche centroid shift, overlap, unfilling and expansion) and species distribution models to study the niche and range changes between maize and its wild progenitors using occurrence records of maize, lowland teosinte (Zea mays ssp. parviglumis) and highland teosinte (Zea mays ssp. mexicana), respectively, as well as explore the mechanisms underlying the niche and range changes. Results: In contrast to maize in Mexico, maize did not conserve its niche inherited from lowland and highland teosinte at the global scale. The niche breadth of maize at the global scale was wider than that of its wild progenitors (ca. 5.21 and 3.53 times wider compared with lowland and highland teosinte, respectively). Compared with its wild progenitors, maize at global scale can survive in regions with colder, wetter climatic conditions, as well as with wider ranges of climatic variables (ca. 4.51 and 2.40 times wider compared with lowland and highland teosinte, respectively). The niche changes of maize were largely driven by human introduction and cultivation, which have exposed maize to climatic conditions different from those experienced by its wild progenitors. Small changes in niche breadth had large effects on the magnitude of range shifts; changes in niche breadth thus merit increased attention. Discussion: Our results demonstrate that maize shows wide climatic niche and range lability, and this substantially expanded its realized niche and potential range. Our findings also suggest that niche and range shifts probably triggered by natural and artificial selection in cultivation may enable maize to become a global staple crop to feed the growing population and adapting to changing climatic conditions. Future analyses are needed to determine the limits of the novel conditions that maize can tolerate, especially relative to projected climate change.

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The role of historical factors in establishing patterns of diversity in tropical mountains is of interest to understand the buildup of megadiverse biotas. In these regions, the historical processes of range fragmentation and contraction followed by dispersal are thought to be mediated by the interplay between rugged relief (complex topography) and climate fluctuations and likely explain most of the dynamics of diversification in plants and animals. Although empirical studies addressing the interaction between climate and topography have provided invaluable insights into population divergence and speciation patterns in tropical montane organisms, a more detailed and robust test of such processes in an explicit spatio-temporal framework is still lacking. Consequently, our ability to gain insights into historical range shifts over time and the genomic footprint left by them is limited. Here, we used niche modeling and subgenomic population-level datasets to explore the evolution of two species of warbling finches (genus Microspingus) disjunctly distributed across the Montane Atlantic Forest, a Neotropical region with complex geological and environmental histories. Population structure inferences suggest a scenario of three genetically differentiated populations, which are congruent with both geography and phenotypic variation. Demographic simulations support asynchronous isolation of these populations as recently as ∼40,000 years ago, relatively stable population sizes over recent time, and past gene flow subsequent to divergence. Throughout the last 800,000 years, niche models predicted extensive expansion into lowland areas with increasing overlap of species distributions during glacial periods, with prominent retractions and isolation into higher altitudes during interglacials, which are in line with signs of introgression of currently isolated populations. These results support a dual role of cyclical climatic changes: population divergence and persistence in mountain tops during warm periods followed by periods of expansion and admixture in lower elevations during cold periods. Our results underscore the role of the interplay between landscape and climate as an important mechanism in the evolution of the Neotropical montane biota.

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PREMISE: Past climate fluctuations during the Holocene and Pleistocene shaped the distribution of several plant species in temperate areas over the world. Wild maize, commonly known as teosinte, is a good system to evaluate the effects of historical climate fluctuations on genetic diversity due to its wide distribution in Mexico with contrasting environmental conditions. We explored the influence of contemporary factors and historical environmental shifts on genetic diversity, including present and three historical periods using neutral markers. METHODS: We used 22 nuclear microsatellite loci to examine the genetic diversity of 14 populations of Zea mays subsp. parviglumis and 15 populations of Zea mays subsp. mexicana (527 individuals total). We implemented genetic structure analyses to evaluate genetic differentiation between and within subspecies. We applied coalescent-based demographic analysis and species distribution modeling to evaluate the effects of historical environmental shifts. RESULTS: We found 355 alleles in total for the two subspecies and variable levels of diversity in each (Z. mays subsp. parviglumis expected heterozygosity HE = 0.3646-0.7699; Z. mays subsp. mexicana HE = 0.5885-0.7671). We detected significant genetic structure among populations (DEST = 0.4332) with significant heterozygote deficiency (FIS = 0.1796), and variable selfing rates (sg2 = 0.0-0.3090). The Bayesian assignment analysis differentiated four genetic groups. Demographic and species distribution modeling analysis suggested that environmental shifts were influential in the amount of genetic diversity. CONCLUSIONS: Our analyses suggest that the current genetic diversity in teosinte is shaped by factors such as local adaptation and genetic isolation, along with historical environmental fluctuations.

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Experimental investigation of the intensity of potential competitive interactions among increasingly abundant tropically-associated grey Lutjanus griseus and lane snapper Lutjanus synagris and resident northern Gulf of Mexico (nGOM) red snapper Lutjanus campechanus was undertaken in large outdoor mesocosms. In pair-wise interaction trials, compared with L. synagris, L. campechanus demonstrated significantly increased roving behaviour and predatory activity. While no significant difference in these activities was observed between L. campechanus and L. griseus, when all three snappers (Lutjanidae) were grouped together L. campechanus swimming activity significantly decreased in the presence of both tropically-associated species. Overall, L. campechanus were more active and aggressive predators and appear to be competitively resistant to L. griseus and L. synagris. As lower latitude species have continued to become increasingly prevalent in nGOM habitats and regional warming continues to affect resident reef-associated fishes, these findings contribute to the assessment of the effects of warming-related species shifts upon nGOM fishes and document current partial resilience of L. campechanus to climate-related expansions of tropical confamilials.

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Parallel studies of nesting colonies in Mexico and the United States show that Elegant Terns (Thalasseus elegans) have expanded from the Gulf of California Midriff Island Region into Southern California, but the expansion fluctuates from year to year. A strong inverse relationship between nesting pairs in three Southern California nesting areas [San Diego saltworks, Bolsa Chica Ecological Reserve, and Los Angeles Harbor (1991 to 2014)] and Isla Rasa in the Midriff (1980 to 2014) shows that terns migrate northward when confronting warm oceanographic anomalies (>1.0°C), which may decrease fish availability and hamper nesting success. Migration pulses are triggered by sea surface temperature anomalies localized in the Midriff and, secondarily, by reductions in the sardine population as a result of intensive fishing. This behavior is new; before year 2000, the terns stayed in the Midriff even when oceanographic conditions were adverse. Our results show that terns are responding dynamically to rapidly changing oceanographic conditions and fish availability by migrating 600 km northwest in search of more productive waters.

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Global climate change is driving species poleward and upward in high-latitude regions, but the extent to which the biodiverse tropics are similarly affected is poorly known due to a scarcity of historical records. In 1802, Alexander von Humboldt ascended the Chimborazo volcano in Ecuador. He recorded the distribution of plant species and vegetation zones along its slopes and in surrounding parts of the Andes. We revisited Chimborazo in 2012, precisely 210 y after Humboldt's expedition. We documented upward shifts in the distribution of vegetation zones as well as increases in maximum elevation limits of individual plant taxa of >500 m on average. These range shifts are consistent with increased temperatures and glacier retreat on Chimborazo since Humboldt's study. Our findings provide evidence that global warming is strongly reshaping tropical plant distributions, consistent with Humboldt's proposal that climate is the primary control on the altitudinal distribution of vegetation.

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Historically, many species moved great distances as climates changed. However, modern movements will be limited by the patterns of human-dominated landscapes. Here, we use a combination of projected climate-driven shifts in the distributions of 2903 vertebrate species, estimated current human impacts on the landscape, and movement models, to determine through which areas in the western hemisphere species will likely need to move to track suitable climates. Our results reveal areas with projected high densities of climate-driven movements - including, the Amazon Basin, the southeastern United States and southeastern Brazil. Some of these regions, such as southern Bolivia and northern Paraguay, contain relatively intact landscapes, whereas others such as the southeastern United States and Brazil are heavily impacted by human activities. Thus, these results highlight both critical areas for protecting lands that will foster movement, and barriers where human land-use activities will likely impede climate-driven shifts in species distributions.

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