Abstract
Invasive predators can exert strong selection on native populations. If selection is strong enough, populations could lose the phenotypic variation caused by adaptation to heterogeneous environments. We compare frog tadpoles prior to and 14 years following invasion by crayfish. Prior to the invasion, populations differed in their intrinsic developmental rate, with tadpoles from cold areas reaching metamorphosis sooner than those from warm areas. Following the invasion, tadpoles from invaded populations develop faster than those from non-invaded populations. This ontogenetic shift overwhelmed the intraspecific variation between populations in a few generations, to the point where invaded populations develop at a similar rate regardless of climate. Rapid development can have costs, as fast-developing froglets have a smaller body size and poorer jumping performance, but compensatory growth counteracts some costs of development acceleration. Strong selection by invasive species can disrupt local adaptations by dampening intraspecific phenotypic variation, with complex consequences on lifetime fitness.
Highlights
Invasive predators can exert strong selection on native populations
Native species often inhabit heterogeneous environments, and populations exposed to diverging selective pressures by natural gradients can show local adaptations, which allow them to cope with different environmental challenges[12]
As development time can respond to multiple selective forces with complex patterns, it is an excellent trait to evaluate the interplay between natural selective gradients and the pressure by invasive species
Summary
Invasive predators can exert strong selection on native populations. If selection is strong enough, populations could lose the phenotypic variation caused by adaptation to heterogeneous environments. Despite the growing literature on the evolutionary consequences of biological invasions, few studies have considered how selective pressures imposed by invasive species interfere with pre-existing patterns of local adaptations and environmental heterogeneity of native populations[15,16]. This is likely a result of the complexity of disentangling multiple selective forces. When reared within the same temperature conditions, individuals showed significant differences in intrinsic development time across populations, with tadpoles from the colder foothills reaching metamorphosis earlier, as expected under a pattern of counter-gradient variation[25] Such adaptive variability was recorded in 2003, immediately before the invasion by the American red swamp crayfish (Procambarus clarkii). Amphibians can show both plastic and rapid evolutionary responses to recent environmental changes that can help them to withstand these novel challenges[6,31,32]
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