COS 47-5 - Climate-mediated changes in species interactions among North American wood-warblers (Parulidae)

Background/Question/Methods

Anthropogenic climate change is causing a global redistribution of terrestrial species. The rate and magnitude of range shifts, however, will differ among taxa, resulting in novel community assemblages. Changing patterns of co-occurrence between ecologically and/or genetically similar taxa may have particularly dramatic consequences, such as competition over common resources and introgression due to hybridization. Despite the potential for these dramatic changes, few studies have estimated the effects of climate change on patterns of sympatry between organisms. As such, we examined the potential impacts of climate-mediated breeding range shifts among North American wood-warblers (Parulidae). This family of birds is especially likely to be impacted by such changes, as hybridization is very common and co-occurring species impose strong selective pressures on each other. We used publicly available species distribution model (SDM) range outputs to compare current ranges and patterns of sympatry among 47 warbler species to future ranges and sympatry under 1.5 °C, 2.0 °C, and 3.0 °C of average global warming. These SDMs incorporated current species occurrence, dispersal limitation, climate, vegetation, and land cover data to create continuous projections of suitable habitat across North America.

Results/Conclusions

Average breeding range area, range overlap among species, and number of sympatric species are all predicted to decrease significantly due to differential range shifts. These general decreases in local warbler species diversity in future warming scenarios will be accompanied and perhaps exacerbated by species turn-over. On average, each warbler species will gain sympatry with approximately one new species and lose sympatry with approximately two species. Although all but two species in our analysis are predicted to either gain or lose sympatric relationships, eastern and boreal forest species will experience the greatest impacts in terms of species turn-over or decreased range area, respectively. Despite this, lower levels of warming are predicted to result more often in significantly less change in warbler breeding ranges and patterns of co-occurrence across each region of North America examined here. Altogether, our results add to mounting evidence that species would benefit greatly from efforts to mitigate and ultimately eliminate anthropogenic greenhouse gas emissions. Policies that achieve these goals along with conservation efforts to help species adjust to the impacts of climate change will be crucial to ensuring the persistence of our ecosystems for generations to come.