In the midst of global biodiversity loss and rising disease incidence in wildlife, there has been growing interest in the role of infectious disease in species extinction. At local scales infectious disease is a common driver of population declines but globally it is an infrequent driver of species extinction and endangerment. For those unfortunate species threatened by disease questions remain, including when, along the pathway to extinction, do pathogens become a threat? We used the 2011 IUCN Red List, focusing on amphibians, birds, and mammals to test the null hypothesis that the proportion of species threatened by disease is the same in each status category (least concern to extinct). Overall, we found that pathogens appear to increase in importance as species move towards extinction though this varies with host taxonomy. We compare this finding to other threats (e.g. land-use change and invasive species) and discuss the role of potential ecological and artifactual drivers. Furthermore, we identify what other threats most frequently co-occur with infectious disease to examine the specific role of disease in driving extinction. We determined that infectious disease is rarely the sole driver of extinction and that being affected by other threats increases the odds of infectious disease co-occurring as a driver of extinction. Ultimately, our conclusions echo previous calls for baseline data on the presence of pathogens in species when they show the first signs of extinction risk and arguably before.
Differences between native and exotic species in competitive ability and susceptibility to herbivores are hypothesized to facilitate coexistence. However, little fieldwork has been conducted to determine whether these differences are present in invaded communities. Here, we experimentally examined whether asymmetries exist between native and exotic plants in a community invaded for over 200 years and whether removing competitors or herbivores influences coexistence. We found that natives and exotics exhibit pronounced asymmetries, as exotics are competitively superior to natives, but are more significantly impacted by herbivores. We also found that herbivore removal mediated the outcome of competitive interactions and altered patterns of dominance across our field sites. Collectively, these findings suggest that asymmetric biotic interactions between native and exotic plants can help to facilitate coexistence in invaded communities.
Climate change is shifting the phenology of many species throughout the world. While the interspecific consequences of these phenological shifts have been well documented, the intraspecific shifts and their resultant evolutionary consequences remain relatively unexplored. Here, we present a conceptual framework and overview of how phenological shifts within species can drive evolutionary change. We suggest that because the impacts of climate change are likely to vary across the range of a species and differentially impact individuals, phenological shifts may often be highly variable both within and among populations. Together these changes have the potential to alter existing patterns of gene flow and influence evolutionary trajectories by increasing phenological isolation and connectivity. Recent research examining the response of species to contemporary climate change suggests that both phenological isolation and connectivity may be likely responses to future climate change. However, recent studies also show mixed results on whether adaptive responses to climate change are likely to occur, as some populations have already shown adaptive responses to changing climate, while others have not despite fitness costs. While predicting the exact consequences of intraspecific phenological shifts may be difficult, identifying the evolutionary implications of these shifts will allow a better understanding of the effects of future climate change on species persistence and adaptation.
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