Jon C. Barlow

We assessed changes in fundamental climate‐niche space for lizard and snake species in western North America under modeled climate scenarios to inform natural resource managers of possible shifts in species distributions. We generated eight distribution models for each of 130 snake and lizard species in western North America under six time‐by‐climate scenarios. We combined the highest‐performing models per species into a single ensemble model for each scenario. Maps were generated from the ensemble models to depict climate‐niche space for each species and scenario. Patterns of species richness based on climate suitability and niche shifts were calculated from the projections at the scale of the entire study area and individual states and provinces, from Canada to Mexico. Squamate species' climate‐niche space for the recent‐time climate scenario and published known ranges were highly correlated (r = 0.81). Overall, reptile climate‐niche space was projected to move northward in the future. Sixty‐eight percent of species were projected to expand their current climate‐niche space rather than to shift, contract, or remain stable. Only 8.5% of species were projected to lose climate‐niche space in the future, and these species primarily occurred in Mexico and the southwestern U.S. We found few species were projected to lose all suitable climate‐niche space at the state or province level, although species were often predicted to occupy novel areas, such as at higher elevations. Most squamate species were projected to increase their climate‐niche space in future climate scenarios. As climate niches move northward, species are predicted to cross administrative borders, resulting in novel conservation issues for local landowners and natural resource agencies. However, information on species dispersal abilities, landscape connectivity, biophysical tolerances, and habitat suitability is needed to contextualize predictions relative to realized future niche expansions.

An ongoing challenge in evolutionary and ecological research focuses on testing biogeographic hypotheses for the understanding of both species' distributional patterns and of the factors influencing range limits. In this study, we described the climatic niches of Neotropical humid montane forest birds through the analysis of factors driving their evolution at inter‐ and intraspecific levels; and tested for differences among allopatric lineages within Aulacorhynchus, Chlorospingus, Cardellina, and Eupherusa. We employed ecological niche models (ENMs) along with an ordination approach with kernel smoothing to perform niche overlap analyses and test hypotheses of niche equivalence/similarity among lineages. In addition, we described the potential distributions of each lineage during the Late Pleistocene climate fluctuations, identifying historical range expansions, connectivity, and stability. Overall, we observed differences in environmental variables influencing climatic requirements and distributional patterns for our selected species. We detected the highest values of niche overlap mainly between Eupherusa and some Chlorospingus lineages. At both interspecific and intraspecific levels, sister lineages showed non‐identical environmental niches. Our results offer weak support to a moist forest model, in which populations followed the expansion and contraction cycles of montane forests, leading to a lack of niche conservatism among lineages (they tend to occupy not identical climatic environments) throughout Mesoamerica. Therefore, historical climatic conditions may act as ecological barriers determining the distributional ranges of these species.

Here, we explored how variations in the allopatric speciation scenario, specifically ecological vs. vicariant allopatry, relate to climatic niche change in sister species. We selected two sister species pairs of North American hummingbirds (Calypte anna, C. costae, Basilinna leucotis, B. xantusii) that diverged 2.5 and 3.6 million years ago, under ecological (arid climate tendency during Pliocene) and vicariant (Baja California peninsula separation) allopatric processes, respectively. We constructed the climatic niche of each species using occurrence records and estimated the distance, similarity, and unique fraction of climatic niche between sister species. Calypte species showed moderate niche divergence (Euclidean distance between centroids = 1.94, Sørensen index of similarity = 0.080, unique fraction of hypervolume in C. costae = 0.57, and C. anna = 0.95). However, contrary to expectations, Basilinna species, which diverged under a vicariant scenario, displayed clear niche divergence (Euclidean distance between centroids = 3.78, Sørensen index of similarity = 0.0001, and unique fraction of hypervolume in B. xantusii = 0.98, and B. leucotis = 0.99). We explained dissimilarity in climatic niches between Basilinna species by the ecological divergence between habitats of disjunct populations, which would have also been associated with increased aridity during the Pliocene.

Biogeography has as a central theme, which is the study of geographic ranges of species that are determined by evolutionary history, abiotic factors, and biotic interactions. Understanding the influence of biotic interactions on geographic ranges is a topic that has been little explored, especially in a way that compares species that vary in intensity of interaction. Here, we assessed interaction intensity as a determinant of geographic range overlap between ant-following birds and army ants in Mexico and Central America. We hypothesized that the intensity of the interaction between army ants and ant-following birds, obligate or facultative, predicts the overlap of geographic ranges of interacting species, as well as the extension of geographic ranges. We generated species distribution models with MAXENT and estimated the percentage of overlap between two species of army ants and 10 species of ant-following birds. Contrary to our predictions, Bayesian regression models found no support for an estimated higher range overlap for obligate ant-following birds and army ants, or wider geographic ranges for facultative ant-following bird species. However, our results suggested trends for higher percentages of range overlap between obligate ant-following birds and army ants, and for geographic ranges of facultative ant-following birds extending to areas without the presence of army ants. Our research encourages further exploration of the biogeography of biotic interactions as part of a quantitative gradient of intensities and not as qualitative categories, integrating spatial and temporal variation in the intensity of interaction.

Biogeographic studies have generally relied on methods that use a few, large predefined areas, which may overlook fine‐scale patterns. Here we test previous hypotheses about the biogeographic history of a diverse bat clade regarding its association with major Neotropical geological formations, particularly the Antilles, the South American Dry Diagonal, the Andes and the Panamanian land bridge, by applying a recently available method that uses actual distributions instead of predefined areas. We compiled and curated spatially explicit, georeferenced data of 173 bat species (Mammalia: Chiroptera: Noctilionoidea) from the online database Global Biodiversity Information Facility. By taking a previous comprehensive phylogeny as an evolutionary framework, we performed computationally intensive analyses using the Geographically‐explicit Event Model. This method uses the observed species distributions to reconstruct the ancestral areas and biogeographic events at each phylogeny node. We found that sympatric speciation was the most frequently reconstructed event, and involved mainly the Panamanian Isthmus and northern South America (SA), but all sympatry reconstructions were different and specific to each node. Allopatric events were important in the Andes; vicariance caused both west/east and north/south disjunctions that went unnoticed previously. Founder events indicated bidirectional dispersal between the mainland and the Antilles since the Miocene, and across the incomplete Panamanian bridge and the SA Dry Diagonal since the early Pliocene. Overall, we found support for previous hypotheses on the influence of major Neotropical paleogeographic events in the diversification of the group, but additionally revealed multi‐scale patterns that are embedded within the mainland and were previously overlooked. Our results highlight a trans‐isthmian centre of diversification in the biogeographic history of Noctilionoidea including the Panamanian Isthmus and Northern SA.

Conservation status assessments for Cassin’s Sparrow (Peucaea cassinii) show considerable variability across the species’ North American range. In this study, we combine data from NASA’s Modern-Era Reanalysis for Research and Applications, Version 2 (MERRA-2; M2) with field observations spanning the past 40 years to investigate Cassin’s Sparrow’s response to multi-decadal changes in climatic suitability that could help explain this variability. We examine two time- and variable-specific time series using MaxEnt. The M2 time series uses a mix of microclimatic and ecosystem functional attributes; the MERRAclim-2 (MC) time series uses MERRA-2-derived bioclimatic variables. Trend analysis reveals complex patterns of slowly increasing climatic suitability over 69.5% of the study area in the MC time series accompanied by decreases over 24.4% of the area. Shifts in the study area–wide weighted centroid for suitability show a northwesterly, 40-year displacement of 1.85 km/yr. The M2 time series indicates a less favorable history with increasing and decreasing trends over 54.9% and 40.1% of the study area, respectively, and a westerly centroid shift of 2.60 km/yr. Increasing winds, drying land surface conditions, and variability in North American monsoon rainfall appear to be dominating, climate-related influences on the species. These variables also demonstrate complex patterns of non-constant spatial and temporal trends across the study area. We conclude that modeled estimates of climatic suitability for Cassin’s Sparrow can vary widely depending on the temporal frame, spatial extent, and environmental drivers considered; that the species’ response to non-constant trends in key environmental drivers is a potential source of this variability; that this variability mirrors the inconsistencies seen in the literature regarding the species’ conservation status; and that retrospective ecological niche modeling that combines time and variable specificity, as we have done here, can be a useful adjunct to assessments of a species’ conservation status.

AbstractAimDue to its complex biogeographical and ecological history, the seasonally dry forests (SDF) of Mesoamerica are considered a biodiversity hotspot. SDF are currently distributed in relatively large and continuous, but isolated areas, in which there are both high total and endemic species numbers. Among birds, few species are shared across SDF patches; other species are endemic to one of these; and for two species currently endemic to one patch, fossils have been recovered in a different one, suggesting a former widespread distribution in so species, implying that current distributional patterns are probably recent.LocationMesoamerican seasonally dry forests.MethodsWe assessed the role of niche divergence/conservatism in the evolution of bird distributional patterns. Using an ecological niche modelling approach, we estimated palaeodistributions for two species currently endemic to the SDF of Yucatan Peninsula (YP), two to the Mesoamerican Pacific Slope (MPS) with fossil record in the YP and two more showing an allopatric pattern. For comparison, we simulated virtual species (VS) matching each pattern, assuming they represent the expected distribution of species in each SDF patch. To test hypothesis of niche conservatism, we assessed the niche equivalence/similarity between the patches represented by the VS, and in each bird species and its VS distributional counterpart.ResultsOur results showed three patterns: (i) no past geographical connectiveness among suitable areas; (ii) niche conservatism, but not equivalence, despite low niche overlap and geographical distance; and (iii) potential niche divergence.Main ConclusionsFor birds currently endemic to the MPS, our results suggest that the absence from the YP may be attributed to the loss of their environmental niche. Widespread species showed either niche conservatism or divergence. YP endemics showed niche divergence. Our results underline the role of niche divergence/conservatism in the evolution of distributional patterns in Mesoamerican SDF avifauna.

Climate change is one of the main threats to biodiversity in the 21st century. However, the effects that it may have on different mammal species are unknown, making it difficult to implement conservation strategies. In this paper, we used species distribution models (SDM) to assess the effect of global climate change on the potential distribution of the 8 of the 9 marsupial species in Mexico, and analyzed their distribution in the current system of natural protected areas (NPAs). We used presence records for each species and bioclimatic variables from the present and the future (2050 and 2080) with 2 contrasting possible scenarios (representative concentration pathways RCP 4.5 and 8.5). We found that Tlacuatzin canescens would have the most stable potential range under any climate change scenario, while the remaining species (Caluromys derbianus, Chironectes minimus, Didelphis marsupialis, D. virginiana, Philander opossum, Marmosa mexicana, and Metachirus nudicaudatus) would undergo notable range losses in the future, though there would not only be losses—according to our SDMs, for all species there would be some range gain under the different climate scenarios, assuming the vegetation cover remained. The current system of NPAs in Mexico currently protects and under the 2 future scenarios would protect less than 20% of the potential range of marsupials, so a reevaluation of their areas beyond the NPAs is highly recommended for the long-term conservation of this group. Our results provide relevant information on the estimated effects of global climate change on marsupials, allowing us to design more effective methodologies for the protection of this portion of the mammalian fauna in Mexico.

Human‐induced climate change has intensified negative impacts on socioeconomic factors, the environment, and biodiversity, including changes in rainfall patterns and an increase in global average temperatures. Drylands are particularly at risk, with projections suggesting they will become hotter, drier, and less suitable for a significant portion of their species, potentially leading to mammal defaunation. We use ecological niche modelling and community ecology biodiversity metrics to examine potential geographical range shifts of non‐volant mammal species in the largest Neotropical dryland, the Caatinga, and evaluate impacts of climate change on mammal assemblages. According to projections, 85% of the mammal species will lose suitable habitats, with one quarter of species projected to completely lose suitable habitats by 2060. This will result in a decrease in species richness for more than 90% of assemblages and an increase in compositional similarity to nearby assemblages (i.e., reduction in spatial beta diversity) for 70% of the assemblages. Small‐sized mammals will be the most impacted and lose most of their suitable habitats, especially in highlands. The scenario is even worse in the eastern half of Caatinga where habitat destruction already prevails, compounding the threats faced by species there. While species‐specific responses can vary with respect to dispersal, behavior, and energy requirements, our findings indicate that climate change can drive mammal assemblages to biotic homogenization and species loss, with drastic changes in assemblage trophic structure. For successful long‐term socioenvironmental policy and conservation planning, it is critical that findings from biodiversity forecasts are considered.

Background Carnivore mammals are animals vulnerable to human interference, such as climate change and deforestation. Their distribution and persistence are affected by such impacts, mainly in tropical regions such as the Amazon. Due to the importance of carnivores in the maintenance and functioning of the ecosystem, they are extremely important animals for conservation. We evaluated the impact of climate change on the geographic distribution of carnivores in the Amazon using Species Distribution Models (SDMs). Do we seek to answer the following questions: (1) What is the effect of climate change on the distribution of carnivores in the Amazon? (2) Will carnivore species lose or gain representation within the Protected Areas (PAs) of the Amazon in the future? Methods We evaluated the distribution area of 16 species of carnivores mammals in the Amazon, based on two future climate scenarios (RCP 4.5 and RCP 8.5) for the year 2070. For the construction of the SDMs we used bioclimatic and vegetation cover variables (land type). Based on these models, we calculated the area loss and climate suitability of the species, as well as the effectiveness of the protected areas inserted in the Amazon. We estimated the effectiveness of PAs on the individual persistence of carnivores in the future, for this, we used the SDMs to perform the gap analysis. Finally, we analyze the effectiveness of PAs in protecting taxonomic richness in future scenarios. Results The SDMs showed satisfactory predictive performance, with Jaccard values above 0.85 and AUC above 0.91 for all species. In the present and for the future climate scenarios, we observe a reduction of potencial distribution in both future scenarios (RCP4.5 and RCP8.5), where five species will be negatively affected by climate change in the RCP 4.5 future scenario and eight in the RCP 8.5 scenario. The remaining species stay stable in terms of total area. All species in the study showed a loss of climatic suitability. Some species lost almost all climatic suitability in the RCP 8.5 scenario. According to the GAP analysis, all species are protected within the PAs both in the current scenario and in both future climate scenarios. From the null models, we found that in all climate scenarios, the PAs are not efficient in protecting species richness.