Devlin, Donna

In Palm Beach County, S. terebrans burrows into grounded roots and
trunks of R. mangle causing collapse. This is contrary to previous studies
suggesting this species burrows only into free-hanging roots. Nutrients and C.
virginica cover may affect S. terebrans abundance and distribution. Surveys
show burrowing significantly varies among sites, but not between free-hanging
and grounded roots. Nutrients vary by site, but neither N nor P was correlated
with burrowing. Nutrient treated roots showed no colonization pattern associated
with N or P. Lignin varied among sites, but didn’t affect burrowing. Finally, C.
virginica limited colonization in the portion of R. mangle tissue it covered. The
location of C. virginica on the seaward/landward side was not predictive of
burrowing. R. mangle height and leaves were not negatively affected by cover
treatment or burrowing. Results highlight the need for additional research to
determine the influence of environmental factors on this species interaction.

The hermit crab Clibanarius vittatus kills Melongena corona solely to
acquire a better fitting shell. This finding is contrary to previous studies, which
found that hermit crabs of other species cannot kill gastropods or, in most
instances, remove freshly dead gastropods from their shells. This interaction
cannot be classified as predation because Melongena tissue was never
consumed. Clibanarius killed Melongena only when by doing so they could trade
up to a better fitting shell. It cannot be classified as competition because there is
no opportunity for Melongena to gain from the interaction. Therefore the term
“lethal eviction” is hereby proposed for this interaction. The ability to kill a
gastropod to obtain a superior shell gives Clibanarius vittatus an evolutionary
advantage over other hermit crab species. It is not known if the outcome of this
interaction is widespread where both species occur or if it is confined to the
study area.

The Last Glacial Maximum (LGM) was a period of massive range contraction for
numerous taxa, including the water-dispersed mangrove species, Rhizophora mangle L.
Following the LGM, R. mangle expanded poleward via propagule transport by ocean
currents. In this study, we use microsatellite loci to characterize the genetic structure of
nine R. mangle populations and compare potential expansion pathways that resulted in
the colonization of the Florida peninsula and Caribbean islands. Results show
comparatively greater genetic connectivity between the Caribbean mainland and Florida,
a similar pattern between West Africa and Caribbean islands, and substantial admixture
on the island of San Salvador, the Bahamas. We conclude that Florida and Caribbean
island R. mangle populations were likely recolonized via different expansion pathways.
Estimates of recent migration rates are low and populations are structured into three
regions (Caribbean mainland, Caribbean islands, Florida). These findings provide insight
for future management and conservation initiatives.