Data from: A complex evolutionary history in a remote archipelago: phylogeography and morphometrics of the Hawaiian endemic Ligia isopods

Compared to the striking diversification and levels of endemism observed
in many terrestrial groups within the Hawaiian Archipelago, marine
invertebrates exhibit remarkably lower rates of endemism and
diversification. Supralittoral invertebrates restricted to specific
coastal patchy habitats, however, have the potential for high levels of
allopatric diversification. This is the case of Ligia isopods endemic to
the Hawaiian Archipelago, which most likely arose from a rocky
supralittoral ancestor that colonized the archipelago via rafting, and
diversified into rocky supralittoral and inland lineages. A previous study
on populations of this isopod from Oʻahu and Kauaʻi revealed high levels
of allopatric differentiation, and suggested inter-island historical
dispersal events have been rare. To gain a better understanding on the
diversity and evolution of this group, we expanded prior phylogeographic
work by incorporating populations from unsampled main Hawaiian Islands
(Maui, Molokaʻi, Lanaʻi, and Hawaiʻi), increasing the number of gene
markers (four mitochondrial and two nuclear genes), and conducting Maximum
likelihood and Bayesian phylogenetic analyses. Our study revealed new
lineages and expanded the distribution range of several lineages. The
phylogeographic patterns of Ligia in the study area are complex, with
Hawaiʻi, Oʻahu, and the Maui-Nui islands sharing major lineages, implying
multiple inter-island historical dispersal events. In contrast, the oldest
and most geographically distant of the major islands (Kauaʻi) shares no
lineages with the other islands. Our results did not support the monophyly
of all the supralittoral lineages (currently grouped into L. hawaiensis),
or the monophyly of the terrestrial lineages (currently grouped into L.
perkinsi), implying more than one evolutionary transition between coastal
and inland forms. Geometric-morphometric analyses of three supralittoral
clades revealed significant body shape differences among them. A taxonomic
revision of Hawaiian Ligia is warranted. Our results are relevant for the
protection of biodiversity found in an environment subject to high
pressure from disturbances.