CONCLUSION
Overall, we found that the
response of Hawaiian native tree diversity to precipitation varies
across different aged islands on the archipelago. Specifically, we found
that all facets of tree diversity strongly responded to precipitation on
the older island compared to the younger islands, affecting both local
diversity and the turnover of species across habitats with different
levels of precipitation. Our
findings suggest that macroevolution influences how patterns of
diversity respond to the environment, where evolutionary time is needed
for new colonizers to arrive or resident species to sort and specialize
into different environments. Additional factors that vary greatly across
the islands, such as soil diversity and island topography that were not
tested here, may also play a role. Finally, we find that the
introduction of alien species modifies the precipitation-diversity
relationship of native island floras. This indicates that the ongoing
invasion of the Hawaiian islands will fundamentally reshape the local
biodiversity patterns of trees and the ecosystem services this
biodiversity offers.