Frequency and distribution of haplotypes in populations of <i>Montastraea cavernosa</i> (A) and <i>Xestospongia muta</i> (B) in the wider Caribbean region.

<p>Haplotype frequencies provided as pie-chart per location, number of samples in brackets. Haplotype network of ITS (A) and I3-M11 (B), baes on all sequences collected throughout the wider Caribbean region. Size of circle reflects the number of individuals with a specific haplotype. Each line represents the genetic distance between haplotypes. Specific haplotype colors match those presented in the pie-charts. White circles (ITS) are haplotypes private to a certain location.</p

Matrix of pairwise population differentiation values (Φ_st) between populations of <i>Montastraea cavernosa</i> at Saba Bank and in the wider Caribbean and Gulf of Mexico.

<p>Significant values (p < 0.05) are provided in bold.</p

Population Genetic Structure, Abundance, and Health Status of Two Dominant Benthic Species in the Saba Bank National Park, Caribbean Netherlands: <i>Montastraea cavernosa</i> and <i>Xestospongia muta</i>

<div><p>Saba Bank, a submerged atoll in the Caribbean Sea with an area of 2,200 km², has attained international conservation status due to the rich diversity of species that reside on the bank. In order to assess the role of Saba Bank as a potential reservoir of diversity for the surrounding reefs, we examined the population genetic structure, abundance and health status of two prominent benthic species, the coral <i>Montastraea cavernosa</i> and the sponge <i>Xestospongia muta</i>. Sequence data were collected from 34 colonies of <i>M</i>. <i>cavernosa</i> (nDNA ITS1-5.8S-ITS2; 892 bp) and 68 <i>X</i>. <i>muta</i> sponges (mtDNA I3-M11 partition of COI; 544 bp) on Saba Bank and around Saba Island, and compared with published data across the wider Caribbean. Our data indicate that there is genetic connectivity between populations on Saba Bank and the nearby Saba Island as well as multiple locations in the wider Caribbean, ranging in distance from 100s–1000s km. The genetic diversity of Saba Bank populations of <i>M</i>. <i>cavernosa</i> (π = 0.055) and <i>X</i>. <i>muta</i> (π = 0.0010) was comparable to those in other regions in the western Atlantic. Densities and health status were determined along 11 transects of 50 m² along the south-eastern rim of Saba Bank. The densities of <i>M</i>. <i>cavernosa</i> (0.27 ind. m^-2, 95% CI: 0.12–0.52) were average, while the densities of <i>X</i>. <i>muta</i> (0.09 ind. m^-2, 95% CI: 0.02–0.32) were generally higher with respect to other Caribbean locations. No disease or bleaching was present in any of the specimens of the coral <i>M</i>. <i>cavernosa</i>, however, we did observe partial tissue loss (77.9% of samples) as well as overgrowth (48.1%), predominantly by cyanobacteria. In contrast, the majority of observed <i>X</i>. <i>muta</i> (83.5%) showed signs of presumed bleaching. The combined results of apparent gene flow among populations on Saba Bank and surrounding reefs, the high abundance and unique genetic diversity, indicate that Saba Bank could function as an important buffer for the region. Either as a natural source of larvae to replenish genetic diversity or as a storehouse of diversity that can be utilized if needed for restoration practices.</p></div

Main characteristics of <i>Montastraea cavernosa</i> and <i>Xestospongia muta</i> population at the 11 Saba Bank sites.

<p>All values for densities and signs of stress are based on image analysis of 50 m² transect surveys at each site and do not correspond to the samples collected for genetic analyses. (n) number of <i>M</i>. <i>cavernosa</i> and <i>X</i>. <i>muta</i>; densities per square meter; percentage of <i>M</i>. <i>cavernosa</i> colonies with tissue loss and overgrowth; and percentage of <i>X</i>. <i>muta</i> with cyclic bleaching or Sponge Orange Band Disease (SOB [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155969#pone.0155969.ref049" target="_blank">49</a>]). No disease was detected in any of the recorded <i>M</i>. <i>cavernosa</i> colonies.</p

Bleaching in Xestospongia muta.

<p>(A) Cyclic bleaching (blue arrows). (B) Close up of cyclic bleaching close up.</p

Sample locations on Saba Bank (SB01-SB11) and around Saba Island (SI01 and SI02).

<p>Included is a scheme of Saba Bank’s position with respect to nearby islands and in the wider Caribbean region (indicated by red square in overview).</p

Number of obtained sequences, number of haplotypes and genetic diversity indices for <i>Montastraea cavernosa</i> (ITS) and <i>Xestospongia muta</i> (I3-M11).

<p>Number of obtained sequences, number of haplotypes and genetic diversity indices for <i>Montastraea cavernosa</i> (ITS) and <i>Xestospongia muta</i> (I3-M11).</p