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Detecting functional diversity loss under directional, stabilizing, and disruptive models of nonrandom anthropogenic extinction of species
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DOI：10.1002/oik.12350.png)
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Abstract
En 中文
Humans alter extinction pressures in ways that favor some species over others, causing nonrandom loss of functional diversity. While the three classic models of natural selection within species – directional, stabilizing, and disruptive – are widely used to explain trait evolution, it remains unclear whether they can also capture human-caused nonrandom functional diversity loss among species. Here we develop a framework to test for nonrandom extinction by tracking how trait means and variances change as species with different functional traits are sequentially lost. Applying this approach to the Caribbean lizard genus Leiocephalus, which has already lost eight of its 32 species and has 10 more threatened with future extinction, we found that past extinctions were directional with respect to ecomorphological traits, as large-bodied species were disproportionately eliminated, likely due to hunting and introduced predators. In contrast, predicted-future extinctions are best explained by stabilizing processes, with species exhibiting extreme appendage morphologies most at risk and species with intermediate appendage lengths least likely to go extinct in the future, possibly because this phenotype is better adapted to the deforested habitats that dominate Caribbean islands today. Such a shift from directional to stabilizing nonrandom extinction is expected when natural extinction pressures are replaced by anthropogenic pressures that directionally shift trait distributions to new adaptive optima. By linking trait-based extinction sequences to classic evolutionary models, our approach provides a generalizable framework for detecting and comparing nonrandom extinction across traits, clades, and ecosystems.
Keywords:
adaptive landscape
Anthropocene
anthropogenic impact
body size
Caribbean
deforestation
functional diversity
hunting
introduced predators
island biogeography
land development
Leiocephalus
lizard
natural selection
nonrandom extinction
statistical methods
