Consequences of finger coral declines for coral specialists versus
generalists
Theory predicts that extinction debt should vary depending on the degree
of habitat specificity of associated species (Kuussaari et al. 2009,
Hylander & Ehrlén 2013, Watts et al. 2020) with generalists
characterized as having broad habitat requirements and specialists
“largely dependent on one particular habitat type” (Watts et al.
2020). Specialists with low dispersal should have relatively short
duration extinction debt, while generalists with high dispersal would
have the longest extinction debt, as they could utilize other habitats
after a disturbance. Of the Pocillopora associated community of
fishes and mobile macroinvertebrates, we have sufficient information on
small-scale (within-habitat) distribution to estimate that at least six
species can be considered largely dependent on the Pocilloporahabitat. These include three species of Trapezia crabs which are
known obligate Pocillopora mutualists (Glynn 1976, Hickman &
Zimmerman 2000), the spider crab Telephyrs cristolipes described
as inhabiting finger corals in Hickman & Zimmerman (2000), the
corallivorous gastropod Babelomurex hindsii , and the coral
hawkfish Cirrhitichthys oxycephalus, which is frequently observed
in finger corals and among black corals in the Galapagos (J. Witman,
pers. obs.). As in most communities of mobile species such as birds
(Watts et al. 2020), insects (Hanski & Ovaskainen 2002), and reef
fishes (Kritzer & Sale 2006), the community of fishes and
macroinvertebrates associated with live and dead finger corals
represents a mix of habitat and food specialists and generalists. Future
research to identify habitat specialist species on Galápagos reefs is
needed to understand those species most vulnerable to habitat loss and
to overall biodiversity loss following future temperature stress from
climate oscillations.