Geographic distributions of mangrove gastropods

Knowledge of the biogeography of marine taxa has lagged significantly
behind terrestrial ecosystems. A hotspot of marine biodiversity associated
with coral reefs is known in the Coral Triangle of the Indo-West Pacific,
but until now there was little data with which to evaluate broad patterns
of species richness in the coastal fauna of ecosystems other than coral
reefs. This data is critically needed for fauna with low functional
redundancy like that of mangroves, that are vulnerable to habitat loss and
rising sea levels. Here we show that the diversity of mangrove fauna is
characterized by two distinct hotspots in the Indo-West Pacific,
associated with two habitat types: fringe mangroves in the Coral Triangle,
and riverine mangroves in the Strait of Malacca, between the west coast of
Peninsular Malaysia and Sumatra. This finding, based on a family of slugs
of which the systematics has been completely revised, illustrates an
unexpected biogeographic pattern that emerged only after this taxon was
studied intensively. Most organisms that live in the mangrove forests of
Southeast Asia remain poorly known both taxonomically and ecologically,
and the hotspot of diversity of onchidiid slugs in the riverine mangroves
of the Strait of Malacca indicates that further biodiversity studies are
needed to support effective conservation of mangrove biodiversity.