Data from: Range‐wide population genetic structure of the Caribbean marine angiosperm Thalassia testudinum

Many marine species have widespread geographic ranges derived from their
evolutionary and ecological history particularly their modes of dispersal.
Seagrass (marine angiosperm) species have ranges that are unusually
widespread, which is not unexpected following recent reviews of
reproductive strategies demonstrating the potential for long distance
dispersal combined with longevity through clonality. An exemplar of these
dual biological features is turtlegrass (Thalassia testudinum) which is an
ecologically important species throughout the tropical Atlantic region.
Turtlegrass has been documented to have long distance dispersal via
floating fruits and also extreme clonality and longevity. We hypothesise
that across its range, Thalassia testudinum will have very limited
regional population structure due to these characteristics and under
typical models of population structure would expect to detect high levels
of genetic connectivity. There are very few studies of range-wide genetic
connectivity documented for seagrasses or other sessile marine species.
This study presents a population genetic data set that represents a
geographic area exceeding 14,000 km2. Population genetic diversity was
evaluated from 32 Thalassia testudinum populations sampled across the
Caribbean and Gulf of Mexico. Genotypes were based on nine microsatellites
and haplotypes were based on chloroplast DNA sequences. Very limited
phylogeographic signal from cpDNA reduced the potential comparative
analyses possible. Multiple analytical clustering approaches on population
genetic data revealed two significant genetic partitions: 1) The
Caribbean, and 2) The Gulf of Mexico. Genetic diversity was high (HE =
0.641) and Isolation by Distance was significant, gene flow and migration
estimates across the entire range were however modest, we suggest that the
frequency of successful recruitment across the range is uncommon.
Thalassia testudinum maintains genetic diversity across its entire
distribution range. The genetic split may be explained by genetic drift
during recolonsation from refugia following relatively recent reduction in
available habitat such as the last glacial maxima.