Invasive species are a major threat to modern ecosystems and cause billions of dollars in economic damage annually. As global climate shifts, both native and invasive species are experiencing novel conditions that alter impact geographic spread, survival, and ecological interactions of populations. The long-term impacts of species invasions and potential feedback loops with climate change are difficult to assess on ecological timescales available to biologists, but the fossil record provides analogues that allow investigation of the long-term impacts of species invasions. Notably, most ancient species invasions are related to intervals of climatic or environmental change, so fossil analogs of modern invasive species have the potential to provide insight about the interaction of invasive species and climate change in substantive ways.
This talk with review the long-term impacts of invasive species by focusing on a series of case studies the fossil record. Two shallow marine examples: the Late Ordovician Richmondian Invasion (~446 million years ago) and Late Devonian Biodiversity Crisis (~375 million years ago) and one terrestrial example: the Great American Biotic Interchange (~3 million years ago) will be examined with respect to extinction, speciation, niche evolution, and ecosystem restructuring.
Results/Conclusions
Ancient invasive species were characterized by broad ecological tolerances, broad geographic ranges, and higher-than-average survival potential through intervals of environmental change. Among native species, narrowly-adapted species were more likely to become extinct, while more broadly-adapted species persisted through the invasion interval by modifying aspects of their ecological niche via niche evolution. In addition, formation of new species practically stopped during the invasion intervals due to reduced opportunities for geographic isolation and speciation. The results of these impacts produced post-invasion biotas with less diversity, greater biotic homogenization between regions, and a lack of new species forming.
Thus, in modern ecosystems it could be expected that widespread establishment of invasive species will depress speciation rather than lead to long-term biodiversity accumulation. Most introduced species are accommodated within their new environments by employing ecological fitting within sloppy fitness space rather than by exhibiting adaptive change that could results in speciation events. In the absence of successful speciation events, habitat loss and climate change will likely combine with species invasions to exacerbate biodiversity loss. Conservation efforts to eradicate invasive species may help mitigate these outcomes in the current biodiversity crisis.