Global climate change is a major threat to biodiversity. The most common methods for predicting the response of biodiversity to changing climate do not explicitly incorporate fundamental evolutionary and ecological processes that determine species responses to changing climate, such as reproduction, dispersal, and adaptation. We provide an overview of an emerging mechanistic spatial theory of species range shifts under climate change. This theoretical framework explicitly defines the ecological processes that contribute to species range shifts via biologically meaningful dispersal, reproductive, and climate envelope parameters. We present methods for estimating the parameters of the model with widely available species occurrence and abundance data and then apply these methods to empirical data for 12 North American butterfly species to illustrate the potential use of the theory for global change biology. The model predicts species persistence in light of current climate change and habitat loss. On average, we estimate that the climate envelopes of our study species are shifting north at a rate of 3.25 +/- 1.36 km/yr (mean +/- SD) and that our study species produce 3.46 +/- 1.39 (mean +/- SD) viable offspring per individual per year. Based on our parameter estimates, we are able to predict the relative risk of our 12 study species for lagging behind changing climate. This theoretical framework improves predictions of global change outcomes by facilitating the development and testing of hypotheses, providing mechanistic predictions of current and future range dynamics, and encouraging the adaptive integration of theory and data. The theory is ripe for future developments such as the incorporation of biotic interactions and evolution of adaptations to novel climatic conditions, and it has the potential to be a catalyst for the development of more effective conservation strategies to mitigate losses of biodiversity from global climate change.

Organismal dispersal through mountain passes should be more constrained by temperature‐related differences between lowland and highland sites in montane environments. This may lead to higher rates of diversification through isolation of existing lineages toward the tropics. This mechanism, proposed by Janzen, could influence broad‐scale patterns of biodiversity across mountainous regions and more broadly across latitudinal gradients. We constructed two complementary analyses to test this hypothesis. First, we measured topographically‐derived thermal gradients using recently‐developed climatic data across the Americas, reviewing the main expectations from Janzen's climatic model. Then, we evaluated whether thermal barriers predict assemblage similarity for amphibians and mammals along elevational gradients across most of their latitudinal extent in the Americas. Thermal barriers between low and high elevation areas, initially proposed to be unique to tropical environments, are comparably strong in some temperate regions, particularly along the western slopes of North American dividing ranges. Biotic similarity for both mammals and amphibians decreases between sites that are separated by elevation‐related thermal barriers. That is, the stronger the thermal barrier separating pairs of sites across the latitudinal gradient, the lower the similarity of their species assemblages. Thermal barriers explain 10–35% of the variation in latitudinal gradients of biotic similarity, effects that were stronger in comparisons of sites at high elevations. Mammals' stronger dispersal capacities and homeothermy may explain weaker effects of thermal barriers on gradients of assemblage similarity than among amphibians. Understanding how temperature gradients have shaped gradients of montane biological diversity in the past will improve understanding of how changing environments may affect them in the future.

Aim We test macroecological hypotheses (H1: long‐term climate stability; H2: climate seasonality; H3: climate distinctiveness or rarity; and, H4: spatial heterogeneity in contemporary climate, topography or habitat) proposed to explain broad‐scale patterns of total species endemism. Location Continental areas worldwide and zoogeographical realms. Methods Using species distribution maps for mammals and amphibians, we calculated five metrics of species endemism, based on inverse and median range size, and range size cut‐offs. We performed multi‐model averaging. We tested the accuracy of fitted models using cross‐validation, comparing observed versus predicted values of endemism among zoogeographical realms. Results Model averaging showed that species endemism for amphibians and mammals was statistically related to all set of predictors (H1, H2, H4 and richness), except for climate distinctiveness (H3). Effect sizes for spatial heterogeneity were larger and more consistent among zoogeographical realms than the effect sizes of climate stability. The effect of species richness on species endemism varies widely and depends on the metric of endemism and taxonomic group used in the analysis. Cross‐validation across all zoogeographical realms showed that predictions of endemism systematically fail for both taxa. In most cases, low to moderate endemism is predicted reasonably well. However, areas with high numbers of endemic species are systematically under‐predicted. Main conclusions Our results are not consistent with any of the processes hypothesized to create and maintain global patterns of endemism. Although we found statistically significant relationships, they failed the stronger test of a causal relationship: accurate prediction in independent data. The inconsistent effect of richness in our models suggests that patterns of endemism are not driven by the same variables as total richness. Patterns of endemism have no consistent relationships with climatic stability among zoogeographical realms, so suggestions that endemism reflect climatic stability are likely due to collinearity with other factors, especially spatial heterogeneity.

Aim Geographical variations in species richness are highly correlated with current temperature. The tropical niche conservatism hypothesis proposes that this relationship is driven by the evolutionarily conserved ancestral tolerances of species to the warm environments in which most clades originated. The hypothesis predicts that the slope of the richness–temperature gradient is positively related to the temperature of the period during which the clade originated. Here, we test this prediction for bird and mammal families in the Americas and by revisiting a global analysis of 343 groups of organisms (Romdal et al., 2013, Global Ecology and Biogeography, 22, 344–350). Location The Americas and world‐wide. Methods We computed the slope of the species richness–current temperature relationship within each bird and mammal family in the Americas. We used palaeoclimate reconstructions to estimate temperature at the time of the family's origination, taken from the fossil record. We then tested how much of the among‐family variance in the richness–temperature slope could be explained by the temperature at the time of family origination. We repeated this test for the 343 groups of organisms world‐wide. Results Contrary to the prediction of tropical niche conservatism, the temperature at which bird and mammal families originated does not explain variations in the richness–temperature relationships. Similarly, we show that, although the predicted relationship was statistically detected in a broad range of groups of organisms in a previous study, it in fact statistically explains only 1.2–2.9% of the variance among groups in the slope of richness gradients. Main conclusions We found evidence inconsistent with the hypothesis that tropical niche conservatism is the main mechanism underlying the ubiquitous richness–climate relationship.