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1) Urbanization may lead to changes in local richness (alpha diversity) or in community composition (beta diversity), although the direction of change can be challenging to predict. For instance, introduced species may offset the loss of native specialist taxa, leading to no change in alpha diversity in urban areas, but decreased beta diversity (i.e., more homogenous community structure). Alternatively, because urban areas can have low connectivity and high environmental heterogeneity between sites, they may support distinct communities from one another over small geographic distances. 2) Wetlands and ponds provide critical ecosystem services and support diverse communities, making them important systems in which to understand consequences of urbanization. To determine how urban development shapes pond community structure, we surveyed 68 ponds around Madison, Wisconsin, USA, which were classified as urban, greenspace, or rural based on surrounding land use. We evaluated the influence of local abiotic factors, presence of nonnative fishes, and landscape characteristics on alpha diversity of aquatic plants, macroinvertebrates, and vertebrates. We also analyzed whether surrounding land cover was associated with changes in community composition and/or the presence of specific taxa. 3) We found a 23% decrease in mean richness (alpha diversity) from rural to urban pond sites, and a 15% decrease in richness from rural to urban greenspace pond sites. Among landscape factors, observed pond richness was negatively correlated with adjacent developed land and mowed lawns, as well as greater distances to other waterbodies. Among pond level factors, habitat complexity was associated with increased richness, while the presence of invasive fish was associated with decreased richness. 4) Beta diversity was relatively high for all ponds due to turnover in composition between sites. Urban ponds supported more introduced species, lacked a subset of native species found in rural ponds, and had slightly higher beta diversity than greenspace and rural ponds. 5) Synthesis and Applications: Integrating ponds into connected greenspaces comprised of native vegetation (rather than mowed grass), preventing nonnative fish introductions, and promoting habitat complexity may mitigate negative effects of urbanization on aquatic richness. The high beta diversity of distinct pond communities emphasizes their importance to biodiversity support in urban environments, despite being small in size and rarely incorporated into urban conservation planning. 

Abstract Urbanization can influence local richness (alpha diversity) and community composition (beta diversity) in numerous ways. For instance, reduced connectivity and land cover change may lead to the loss of native specialist taxa, decreasing alpha diversity. Alternatively, if urbanization facilitates nonnative species introductions and generalist taxa, alpha diversity may remain unchanged or increase, while beta diversity could decline due to the homogenization of community structure. Wetlands and ponds provide critical ecosystem services and support diverse communities, making them important systems in which to understand the consequences of urbanization. To determine how urban development shapes pond community structure, we surveyed 68 ponds around Madison, Wisconsin, USA, which were classified as urban, greenspace, or rural based on surrounding land use. We evaluated how landscape and local pond factors were correlated with the alpha diversity of aquatic plants, macroinvertebrates, and aquatic vertebrates. We also analyzed whether surrounding land use was associated with changes in community composition and the presence of specific taxa. We found a 23% decrease in mean richness (alpha diversity) from rural to urban pond sites and a 15% decrease from rural to greenspace pond sites. Among landscape factors, adjacent developed land, mowed lawn cover, and greater distances to other waterbodies were negatively correlated with observed pond richness. Among pond level factors, habitat complexity was associated with increased richness, while nonnative fishes were associated with decreased richness. Beta diversity was relatively high for all ponds due to turnover in composition between sites. Urban ponds supported more nonnative species, lacked a subset of native species found in rural ponds, and had slightly higher beta diversity than greenspace and rural ponds. Our results suggest that integrating ponds into connected greenspaces, maintaining riparian vegetation, preventing nonnative fish introductions, and promoting habitat complexity may mitigate the negative effects of urbanization on aquatic richness. While ponds are small in size and rarely incorporated into urban conservation planning, the high beta diversity of distinct pond communities emphasizes their importance for supporting urban biodiversity. 

Disease outbreaks among wildlife have surged in recent decades alongside climate change, although it remains unclear how climate change alters disease dynamics across different geographic regions. We amassed a global, spatiotemporal dataset describing parasite prevalence across 7346 wildlife populations and 2021 host-parasite combinations, compiling local weather and climate records at each location. We found that hosts from cool and warm climates experienced increased disease risk at abnormally warm and cool temperatures, respectively, as predicted by the thermal mismatch hypothesis. This effect was greatest in ectothermic hosts and similar in terrestrial and freshwater systems. Projections based on climate change models indicate that ectothermic wildlife hosts from temperate and tropical zones may experience sharp increases and moderate reductions in disease risk, respectively, though the magnitude of these changes depends on parasite identity. 

Abstract Global climate change is increasing the frequency of unpredictable weather conditions; however, it remains unclear how species‐level and geographic factors, including body size and latitude, moderate impacts of unusually warm or cool temperatures on disease. Because larger and lower‐latitude hosts generally have slower acclimation times than smaller and higher‐latitude hosts, we hypothesised that their disease susceptibility increases under ‘thermal mismatches’ or differences between baseline climate and the temperature during surveying for disease. Here, we examined how thermal mismatches interact with body size, life stage, habitat, latitude, elevation, phylogeny and International Union for Conservation of Nature (IUCN) conservation status to predict infection prevalence of the chytrid fungusBatrachochytrium dendrobatidis(Bd) in a global analysis of 32 291 amphibian hosts. As hypothesised, we found that the susceptibility of larger hosts and hosts from lower latitudes toBdwas influenced by thermal mismatches. Furthermore, hosts of conservation concern were more susceptible than others following thermal mismatches, suggesting that thermal mismatches might have contributed to recent amphibian declines. 

Abstract Complex ecological relationships, such as host–parasite interactions, are often modeled with laboratory experiments. However, some experimental laboratory conditions, such as temperature or infection dose, are regularly chosen based on convenience or convention, and it is unclear how these decisions systematically affect experimental outcomes. Here, we conducted a meta‐analysis of 58 laboratory studies that exposed amphibians to the pathogenic fungusBatrachochytrium dendrobatidis(Bd) to understand better how laboratory temperature, host life stage, infection dose, and host species affect host mortality. We found that host mortality was driven by thermal mismatches: hosts native to cooler environments experienced greater Bd‐induced mortality at relatively warm experimental temperatures and vice versa. We also found that Bd dose positively predicted Bd‐induced host mortality and that the superfamilies Bufonoidea and Hyloidea were especially susceptible to Bd. Finally, the effect of Bd on host mortality varied across host life stages, with larval amphibians experiencing lower risk of Bd‐induced mortality than adults or metamorphs. Metamorphs were especially susceptible and experienced mortality when inoculated with much smaller Bd doses than the average dose used by researchers. Our results suggest that when designing experiments on species interactions, researchers should carefully consider the experimental temperature, inoculum dose, and life stage, and taxonomy of the host species.