Adam C. Algar

Plague, the zoonotic vector-borne disease caused by the bacterium Yersinia pestis, shows seasonal infection patterns across the Central Highlands of Madagascar. The disease persists within a complex ecological network involving host and vector species, all influenced by climate. Due to this complexity, links between climate, Y. pestis ecology and human infection remain incomplete. This study developed microclimate-based models to assess climatic impacts on growth cycles of plague vectors Xenopsylla cheopis and Synopsyllus fonquerniei. Using microclimatic modelling, the vector development index (VDI) was calculated to estimate annual developmental phases for each flea species. The uncorrected VDI suggested that development rates were highly variable for X. cheopis compared to S. fonquerniei, which shows greater temporal consistency. Elevated VDI slopes, representing an increased rate of vector development, correlated with plague cases across 61.8–14.7% of areas, implying possible climatic influence on vector-driven disease cycles. However, these associations were not maintained after adjusting modelled temperatures using limited field validation. These findings highlight the complex interactions between climate, vector dynamics and Y. pestis transmission, and emphasize the need for further investigation into burrow microclimates and their seasonal epidemiological roles.

Aim: The evolution of montane species provides critical insights into the drivers of adaptation and diversification. Topographic complexity, a defining feature of many mountainous landscapes, promotes ecological and geographic isolation, often accelerating speciation rates. However, the extent to which topographic complexity directly shapes diversification remains unresolved. Here, we investigate the evolutionary dynamics of Anolis lizards across Neotropical mountain ranges to test two hypotheses: (1) higher elevation environments promote higher speciation rates in species that inhabit them; and (2) greater topographic complexity and climatic stability (i.e., lower past climatic‐change velocity) positively influence speciation rates. Location: The Americas. Time Period: Present. Major Taxa Studied: Anolis lizards. Methods: We gathered topographic complexity and past climatic‐change velocity data for 303 anole species and performed phylogenetic analyses to assess how speciation rates change across mountain ranges in the Americas. Results: We found that topographic complexity and past climatic‐change velocity do not significantly influence speciation rates, diverging from prior studies that link rugged landscapes or past climatic‐change velocity to high diversification rates. Main Conclusions: Our findings challenge assumptions about the direct role of topographic complexity in speciation, highlighting the need to consider multifaceted ecological and biogeographical factors driving evolutionary processes. By disentangling the relative contributions of climatic stability (i.e., lower past climatic‐change velocity) and topographic heterogeneity, this study highlights the complex dynamics shaping biodiversity in tropical mountains and calls for further integrative approaches to understand species diversification in the face of climatic and geological change.

Biogeographical reconstructions of the Indo-Australian Archipelago (IAA) have suggested a recent spread across the Sunda and Sahul shelves of lineages with diverse origins, which appears to be congruent with a geological history of recent tectonic uplift in the region. However, this scenario is challenged by new geological evidence suggesting that the Sunda shelf was never submerged prior to the Pliocene, casting doubt on the interpretation of recent uplift and the correspondence of evidence from biogeography and geology. A mismatch between geological and biogeographical data may occur if analyses ignore the dynamics of extinct lineages, because this may add uncertainty to the timing and origin of clades in biogeographical reconstructions. We revisit the historical biogeography of multiple IAA taxa and explicitly allow for the possibility of lineage extinction. In contrast to models assuming zero extinction, we find that all of these clades, including plants, invertebrates and vertebrates, have a common and widespread geographic origin, and each has spread and colonized the region much earlier than previously thought. The results for the eight clades re-examined in this article suggest that they diversified and spread during the early Eocene, which helps to unify the geological and biological histories of IAA.

To understand how ectotherms will respond to warming temperatures, we require information on thermal habitat quality at spatial resolutions and extents relevant to the organism. Measuring thermal habitat quality is either limited to small spatial extents, such as with ground‐based 3D operative temperature (T_e) replicas, representing the temperature of the animal at equilibrium with its environment, or is based on microclimate derived from physical models that use land cover variables and downscale coarse climate data. We draw on aspects of both these approaches and test the ability of unoccupied aerial vehicle (UAV) data (optical RGB) to predict fine‐scale heterogeneity in sub‐canopy lizard (Anolis bicaorum) T_e in tropical forest using random forest models. Anolis bicaorum is an endemic, critically endangered, species, facing significant threats of habitat loss and degradation, and work was conducted as part of a larger project. Our findings indicate that a model incorporating solely air temperature, measured at the centre of the 20 × 20 m plot, and ground‐based leaf area index (LAI) measurements, measured at directly above the 3D replica, predicted T_e well. However, a model with air temperature and UAV‐derived canopy metrics performed slightly better with the added advantage of enabling the mapping of T_e with continuous spatial extent at high spatial resolutions, across the whole of the UAV orthomosaic, allowing us to capture and map T_e across the whole of the survey plot, rather than purely at 3D replica locations. Our work provides a feasible workflow to map sub‐canopy lizard T_e in tropical environments at spatial scales relevant to the organism, and across continuous areas. This can be applied to other species and can represent species within the same community that have evolved a similar thermal niche. Such methods will be imperative in risk modelling of such species to anthropogenic land cover and climate change.

Understanding how temperature determines the distribution of life is necessary to assess species’ sensitivities to contemporary climate change. Here, we test the importance of temperature in limiting the geographic ranges of ectotherms by comparing the temperatures and areas that species occupy to the temperatures and areas species could potentially occupy on the basis of their physiological thermal tolerances. We find that marine species across all latitudes and terrestrial species from the tropics occupy temperatures that closely match their thermal tolerances. However, terrestrial species from temperate and polar latitudes are absent from warm, thermally tolerable areas that they could potentially occupy beyond their equatorward range limits, indicating that extreme temperature is often not the factor limiting their distributions at lower latitudes. This matches predictions from the hypothesis that adaptation to cold environments that facilitates survival in temperate and polar regions is associated with a performance trade-off that reduces species’ abilities to contend in the tropics, possibly due to biotic exclusion. Our findings predict more direct responses to climate warming of marine ranges and cool range edges of terrestrial species.

Aim: Oceanic islands possess unique floras with high proportions of endemic species. Island floras are expected to be severely affected by changing climatic conditions as species on islands have limited distribution ranges and small population sizes and face the constraints of insularity to track their climatic niches. We aimed to assess how ongoing climate change affects the range sizes of oceanic island plants, identifying species of particular conservation concern.Location: Canary Islands, Spain.Methods: We combined species occurrence data from single‐island endemic, archipelago endemic and nonendemic native plant species of the Canary Islands with data on current and future climatic conditions. Bayesian Additive Regression Trees were used to assess the effect of climate change on species distributions; 71% (n = 502 species) of the native Canary Island species had models deemed good enough. To further assess how climate change affects plant functional strategies, we collected data on woodiness and succulence.Results: Single‐island endemic species were projected to lose a greater proportion of their climatically suitable area (x ̃ = −0.36) than archipelago endemics (x ̃ = −0.28) or nonendemic native species (x ̃ = −0.26), especially on Lanzarote and Fuerteventura, which are expected to experience less annual precipitation in the future. Moreover, herbaceous single‐island endemics were projected to gain less and lose more climatically suitable area than insular woody single‐island endemics. By contrast, we found that succulent single‐island endemics and nonendemic natives gain more and lose less climatically suitable area.Main Conclusions: While all native species are of conservation importance, we emphasise single‐island endemic species not characterised by functional strategies associated with water use efficiency. Our results are particularly critical for other oceanic island floras that are not constituted by such a vast diversity of insular woody species as the Canary Islands.

Recent work has shown that evaluating functional trait distinctiveness, the average trait distance of a species to other species in a community offers promising insights into biodiversity dynamics and ecosystem functioning. However, the ecological mechanisms underlying the emergence and persistence of functionally distinct species are poorly understood. Here, we address the issue by considering a heterogeneous fitness landscape whereby functional dimensions encompass peaks representing trait combinations yielding positive population growth rates in a community. We identify four ecological cases contributing to the emergence and persistence of functionally distinct species. First, environmental heterogeneity or alternative phenotypic designs can drive positive population growth of functionally distinct species. Second, sink populations with negative population growth can deviate from local fitness peaks and be functionally distinct. Third, species found at the margin of the fitness landscape can persist but be functionally distinct. Fourth, biotic interactions (positive or negative) can dynamically alter the fitness landscape. We offer examples of these four cases and guidelines to distinguish between them. In addition to these deterministic processes, we explore how stochastic dispersal limitation can yield functional distinctiveness. Our framework offers a novel perspective on the relationship between fitness landscape heterogeneity and the functional composition of ecological assemblages.

The distribution and transmission ofYersinia pestis, the bacterial agent of plague, responds dynamically to climate, both within wildlife reservoirs and human populations. The exact mechanisms mediating plague's response to climate are still poorly understood, particularly across large environmentally heterogeneous regions encompassing several reservoir species. A heterogeneous response to precipitation was observed in plague intensity across northern and southern China during the Third Pandemic. This has been attributed to the response of reservoir species in each region. We use environmental niche modelling and hindcasting methods to test the response of a broad range of reservoir species to precipitation. We find little support for the hypothesis that the response of reservoir species to precipitation mediated the impact of precipitation on plague intensity. We instead observed that precipitation variables were of limited importance in defining species niches and rarely showed the expected response to precipitation across northern and southern China. These findings do not suggest that precipitation–reservoir species dynamics never influence plague intensity but that instead, the response of reservoir species to precipitation across a single biome cannot be assumed and that limited numbers of reservoir species may have a disproportional impact upon plague intensity.

Understanding how temperature determines the distribution of life is necessary to assess species’ sensitivities to contemporary climate change. Here we test the importance of temperature in limiting geographic ranges of ectotherms by comparing temperatures across occupied ranges to those species could potentially occupy based on their physiological thermal tolerances. Whereas marine and tropical terrestrial species occupy temperatures that closely match their thermal tolerances, high-latitude terrestrial species under-occupy warm temperatures and are absent from thermally tolerable areas towards the equator. This suggests that on land, temperature less often limits the equatorward range edge of temperate species, supporting the hypothesis that their historic expansion ‘out of the tropics’ was associated with tropical biotic exclusion. Our findings predict more direct responses to climate warming of marine ranges and cool range edges of terrestrial species.

Current models of island biogeography treat endemic and non‐endemic species as if they were functionally equivalent, focussing primarily on species richness. Thus, the functional composition of island biotas in relation to island biogeographical variables remains largely unknown. Using plant trait data (plant height, leaf area and flower length) for 895 native species in the Canary Islands, we related functional trait distinctiveness and climate rarity for endemic and non‐endemic species and island ages. Endemics showed a link to climatically rare conditions that is consistent with island geological change through time. However, functional trait distinctiveness did not differ between endemics and non‐endemics and remained constant with island age. Thus, there is no obvious link between trait distinctiveness and occupancy of rare climates, at least for the traits measured here, suggesting that treating endemic and non‐endemic species as functionally equivalent in island biogeography is not fundamentally wrong.