ABSTRACT
Aim Studying the
interaction between macroevolutionary and ecological factors is critical
for understanding the principles of diversity regulation, as well as for
predicting the effects of human activities. Here, we use the Hawaiian
archipelago as a testbed to examine the interaction between island age
and strong climatic factors (i.e., precipitation) on patterns of native
and non-native tree taxonomic, functional and phylogenetic diversity.
Location The islands of Hawai’i, Maui Nui, and O’ahu in the
Hawaiian archipelago
Major Taxa studied Trees
Time period 2003-2021
Methods We estimated patterns of tree species diversity from
375 forest plots spread across three islands that ranged from
~0.5-3 million years old, each encompassing a large
precipitation gradient. We included data on species traits and
phylogenies, as well as their abundances, so that we could calculate
multiple facets of diversity (taxonomic, functional and phylogenetic)
and with different weightings for common versus rare species (i.e., the
Hill number continuum). We used general linear models to investigate the
interaction between island age and precipitation, and examined species
compositional turnover along the precipitation gradient. We compared
results between plots that were less and more heavily invaded by
non-native species to discern how the patterns were altered.
Results We found a strong positive relationship between
precipitation and each facet of diversity on the oldest island (O’ahu),
but no such relationship on the two younger islands (islands in the Maui
Nui complex and Hawai’i). We also found high species turnover between
drier and wetter environments, and thus higher ecological
specialization, only on the oldest island. When we included highly
invaded plots, precipitation had a larger effect on diversity and
turnover on the younger islands.
Main Conclusions Our results demonstrate that macroevolutionary
and ecological processes interactively shape tree species diversity, but
that biological invasions are degrading these signatures.
KEYWORDS : Alien species, alpha diversity, beta diversity,
oceanic islands, Hawaiian forest, precipitation.