Population Structure of the Red Macroalga Botryocladia occidentalis (Børgesen) Kylin (Rhodymeniaceae, Rhodymeniales) in the Gulf of Mexico Before the Deepwater Horizon Oil Spill (original) (raw)
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PloS one, 2015
Describing patterns of connectivity among populations of species with widespread distributions is particularly important in understanding the ecology and evolution of marine species. In this study, we examined patterns of population differentiation, migration, and historical population dynamics using microsatellite and mitochondrial loci to test whether populations of the epinephelid fish, Gag, Mycteroperca microlepis, an important fishery species, are genetically connected across the Gulf of Mexico and if so, whether that connectivity is attributable to either contemporary or historical processes. Populations of Gag on the Campeche Bank and the West Florida Shelf show significant, but low magnitude, differentiation. Time since divergence/expansion estimates associated with historical population dynamics indicate that any population or spatial expansions indicated by population genetics would have likely occurred in the late Pleistocene. Using coalescent-based approaches, we find that the best model for explaining observed spatial patterns of contemporary genetic variation is one of asymmetric gene flow, with movement from Campeche Bank to the West Florida Shelf. Both estimated migration rates and ecological data support the hypothesis that Gag populations throughout the Gulf of Mexico are connected via present day larval dispersal. Demonstrating this greatly expanded scale of connectivity for Gag highlights the influence of "ghost" populations (sensu Beerli) on genetic patterns and presents a critical consideration for both fisheries management and conservation of this and other species with similar genetic patterns.
Diversity, 2019
Stochastic events can have catastrophic effects on island populations through a series of genetic stressors from reduced population size. We investigated five populations of red mangrove (Rhizophora mangle) from St. John, USVI, an UNESCO Biosphere Reserve, which were impacted by Hurricane Hugo in 1989. Our goal was to determine diversity and to ascertain potential population bottlenecks two decades after the event. With the lowest observed heterozygosity, highest inbreeding coefficient, and evidence of a major bottleneck, our results demonstrated that the Great Lameshur mangroves, devastated by Hurricane Hugo, were the least diverse stand of trees. The other four populations from St. John manifested diversity reflecting the vegetation patterns of “fringing” mangrove or “developed forest” characteristics. The two fringing mangrove populations (Hurricane Hole and New Found Bay) evinced low observed heterozygosity and high inbreeding coefficients, while the fully forested sites showed ...
Continental Shelf Research, 2011
The sinking of the tanker Prestige in November 2002 off the coast of Galicia resulted in the release of about 60,000 tons of heavy oil. The oil-spill provoked a serious environmental impact in Spanish and French coasts, which biological consequences are still being assessed. In this study we address the temporal dynamics of genetic diversity in some mussel populations impacted by the oil-spill. Changes in genetic diversity can be measured in natural populations provided that serial samples are available from before (year 2000) and after (years 2003, 2005) the oil-spill. Analyses of seven microsatellites indicate a weak but significant increase of genetic variation after the spill. This phenomenon is interpreted herein in terms of a balance between a enhanced genome mutability on microsatellite variation and a low genetic drift due to toxicants and asphyxia although other stochastic phenomena cannot be ruled out. Per locus annotation showed that in spite of the allelic changes observed in the period 2000–2005, the final size of most allelic series remained quite alike to those of year 2000. Present genetic data suggest that the genotoxic impact of the Prestige spill did not compromise the genetic diversity of studied mussel populations, at least regarding the genetic markers analysed.
Journal of Biogeography, 2019
Aim: Historical and geological events can impact the genetic structure of species, producing signatures that vary among taxa and among gene pools within taxa. Such signatures can also be affected by local geography and tolerance to environmental conditions. However, disentangling the different drivers of population structure is often difficult. In an attempt to do so, we surveyed two independent gene pools of the same species that followed similar paths of post-glacial colonization across contrasting landscapes and environmental conditions. We aimed to determine how these differences have affected the post-glacial population dynamics of each gene pool. Location: The Pacific and Atlantic coasts of Mexico. Taxon: Black mangrove (Avicennia germinans; Avicenniaceae). Methods: Using microsatellite variation, we estimated the divergence time of black mangrove populations through approximated Bayesian computation and implemented a comparative approach to evaluate different demographic hypotheses within and between coasts. Results: The Pacific and Atlantic gene pools diverged long after the rise of the Central American Isthmus (Mid-Pleistocene), although occasional transisthmian gene exchanges were also inferred. Both coasts showed the characteristic isolation by distance (IBD) pattern expected for expanding gene pools. However, populations from the Atlantic coast were more genetically diverse and admixed than those from the Pacific basin. Both our migration models and the climate data gathered suggested a more ancient establishment and/or more stable conditions for black mangrove on the Atlantic coast. Main conclusions: The Atlantic basin likely bore more favourable climate conditions than the Pacific, allowing for the survival of A. germinans during the Last Glacial Maximum in situ. Populations from the northern Pacific coast became established after the Holocene warming, leading to contrasting genetic patterns between the two gene pools. Nevertheless, the action of environmental factors in determining the contemporary distribution of genetic variation in A. germinans cannot be discarded.
PLoS ONE, 2012
The 3,000 oil/gas structures currently deployed in the northern Gulf of Mexico (GOM) provide hard substratum for marine organisms in a region where such has been rare since the Holocene. The major exception to this are the Flower Garden Banks (FGB). Corals are known to have colonized oil/gas platforms around the FGB, facilitating biogeographic expansion. We ask the question, what are the patterns of genetic affinity in these coral populations. We sampled coral tissue from populations of two species occurring on oil and gas platforms: Madracis decactis (hermatype) and Tubastraea coccinea (invasive ahermatype). We sampled 28 platforms along four transects from 20 km offshore to the continental shelf edge off 1) Matagorda Island, TX; 2) Lake Sabine, TX; 3) Terrebonne Bay, LA; and 4) Mobile, AL. The entire population of M. decactis was sampled between depths of 5 m and 37 m. T. coccinea populations were sub-sampled. Genetic variation was assessed using the PCR-based Amplified Fragment Length Polymorphisms (AFLPs). Data were analyzed via AFLPOP and STRUCTURE. Genetic connectivity among M. decactis platform populations was highest near the FGB and decreased to the east. Connectivity increased again in the eastern sector, indicating isolation between the populations from different sides of the Mississippi River (Transects 3 and 4). A point-drop in genetic affinity (relatedness) at the shelf edge south of Terrebonne Bay, LA indicated a population differing from all others in the northern GOM. Genetic affinities among T. coccinea were highest in the west and decreased to the east. Very low genetic affinities off Mobile, AL indicated a dramatic difference between those populations and those west of the Mississippi River, apparently a formidable barrier to larval dispersal.
Coral Reefs, 2014
Elkhorn coral, Acropora palmata, relies heavily on clonal propagation and often displays low genotypic (clonal) diversity. Populations in the Florida Keys experienced rapid declines in tissue cover between 2004 and 2006, largely due to hurricanes and disease, but remained stable from 2006 to 2010. All elkhorn colonies in 150 m 2 permanent study plots were genotyped in 2006 (n = 15 plots) and 2010 (n = 24 plots), and plots sampled in both years were examined for changes in allelic and genotypic diversity during this period of stable ecological abundance. Overall, genetic diversity of Florida plots was low and declined further over the 4-yr period; seven of the 36 original genets and two of 67 alleles (among five microsatellite loci) were lost completely from the sampled population, and an additional 15 alleles were lost from individual reefs. In 2010, Florida plots (*19 colonies) contained an average of 2.2 ± 1.38 (mean ± SD) genets with a significant negative correlation between colony abundance and genotypic diversity. When scaled to total tissue abundance, genotypic diversity is even lower, with 43 % of genets below the size of sexual maturity. We examined the hypothesized positive relationship of local genotypic diversity with ecological performance measures. In Florida plots (n = 15), genotypic diversity was not significantly correlated with tissue loss associated with chronic predation, nor with acute disease and storm-fragmentation events, though this relationship may be obscured by the low range of observed diversity and potential confounding with abundance. When more diverse plots in Curaçao (n = 9) were examined, genotypic diversity was not significantly correlated with resistance during an acute storm disturbance or rate of recovery following disturbance. Cryptic loss of genetic diversity occurred in the apparently stable Florida population and confirms that stable or even increasing abundance does not necessarily indicate genetic stability.
Tropical Conservation Science
Antillean manatees (Trichechus manatus manatus), a subspecies of the West Indian manatee, is listed as endangered species in the Red List of Threatened Species of the International Union for Conservation of Nature. The aims of this research were to survey on the possible regional genetic structure in the southern Gulf of Mexico and to compare genetic status of a landlocked population in Laguna de las Ilusiones (IL) with individuals from localities with no barriers to displacement and breed (open population [OP]). We analyzed 45 manatee skin samples collected from different locations in Tabasco (n ¼ 38, including 19 from IL), Veracruz (n ¼ 3), Campeche (n ¼ 2), and Chiapas (n ¼ 2). The genomic DNA was isolated and PCR amplifications were performed for each sample using 28 microsatellite loci, previously designed for West Indian manatees and described as polymorphic for this species. Two clusters (k ¼ 2) were identified by STRUCTURE. The analysis of both a priori populations (IL and OP) indicate that the global values of F ST and R ST (F ST ¼0.049, R ST ¼0.077) were significant. The H E for IL was 0.38 AE 0.03 and for OP was 0.49 AE 0.01. The average number of alleles N A for IL was 2.21 AE 0.09 and for OP was 2.32 AE 0.09. The overall inbreeding coefficient was F IS ¼À0.013 for analyzed populations. Genetic diversity was low. The IL population had slightly lower genetic diversity compared with OP, which could be explained by isolation of that small group, so conservation plans for IL should be considered as priority.