COS 105-10
Are endemics different? Testing an endemic syndrome hypothesis
Linking evolutionary history to contemporary ecological interactions is a burgeoning field that is bringing with it many new insights into the relationship between biodiversity, species interactions, and ecosystem function. Species ranges have been shifting since the Pleistocene, whereby fragmentation, isolation, and the subsequent reduction in gene flow have resulted in local adaptation of novel genotypes and the repeated evolution of endemic species. While there is a wide body of literature focused on understanding endemic species, very few studies empirically test whether or not the evolution of endemics results in unique function or ecological differences relative to their widespread congeners. Using a model island flora, here we ask: Are endemic species functionally and ecologically different than non-endemics? We used a common garden with 15 Eucalyptus species (9 endemic, 6 non-endemic) to test the hypothesis that functional plant traits and associated patterns of herbivory of endemic species differ from those traits in closely related widespread species.
Results/Conclusions
In comparison to their widespread congeners, endemic species have unique suites of functional plant traits that have extended effects across trophic levels. We found that specific leaf area, internode length, and leaf thickness varied significantly between endemic and non-endemic Eucalyptus species. Additionally, we found that endemics experienced less herbivory than non-endemics; indicating that the functional plant traits associated with the endemic species reflect a poorer quality resource for herbivores. Our results suggest that while endemics occupy many diverse habitats, convergent evolution among endemic species has potentially resulted in an endemic syndrome of traits. Furthermore, our results have important implications for biodiversity, as we show that the loss of an endemic species is greater than species loss, as it also represents the loss of novel ecological interactions. Moreover, our results provide a testable hypothesis for endemic syndromes that is worthy of future attention across plant systems.