Commerson's dolphin population structure: evidence for female phylopatry and male dispersal

A key in species conservation is understanding the amount and distribution of genetic diversity and how environmental changes that occurred in the recent past may have influenced current patterns of population structure. Commerson's dolphin, Cephalorhynchus commersonii, has two subspecies, one of which is endemic to South America (C. commersonii commersonii) and little is known about its population genetics. Our objective was to investigate the population genetics of this subspecies throughout its distribution. Using 70 skin samples and information available in GenBank, 308 mitochondrial DNA sequences and 28 species-specific microsatellites were analyzed. The species presented low genetic diversity when compared to other dolphin species, but was consistent with other species within the genus. Strong population structure based on mitochondrial DNA was exhibited throughout its entire distribution, a pattern consistent with female philopatry. However, this pattern was not detected when using microsatellites, suggesting male-mediated gene flow. Demographic tests suggested a population expansion beginning approximately 15,000 years ago, after the Last Glacial Maximum. In a climate change scenario, we recommended considering each sampling location as an independent population management unit in order to evaluate the impact of possible environmental changes on the distribution of genetic information within the species.

Hawksbill turtle terra incognita: conservation genetics of eastern Pacific rookeries

Prior to 2008 and the discovery of several important hawksbill turtle (Eretmochelys imbricata) nesting colonies in the EP (Eastern Pacific), the species was considered virtually absent from the region. Research since that time has yielded new insights into EP hawksbills, salient among them being the use of mangrove estuaries for nesting. These recent revelations have raised interest in the genetic characterization of hawksbills in the EP, studies of which have remained lacking to date. Between 2008 and 2014, we collected tissue samples from 269 nesting hawksbills at nine rookeries across the EP and used mitochondrial DNA sequences (766 bp) to generate the first genetic characterization of rookeries in the region. Our results inform genetic diversity, population differentiation, and phylogeography of the species. Hawksbills in the EP demonstrate low genetic diversity: We identified a total of only seven haplotypes across the region, including five new and two previously identified nesting haplotypes (pooled frequencies of 58.4% and 41.6%, respectively), the former only evident in Central American rookeries. Despite low genetic diversity, we found strong stock structure between the four principal rookeries, suggesting the existence of multiple populations and warranting their recognition as distinct management units. Furthermore, haplotypes EiIP106 and EiIP108 are unique to hawksbills that nest in mangrove estuaries, a behavior found only in hawksbills along Pacific Central America. The detected genetic differentiation supports the existence of a novel mangrove estuary "reproductive ecotype" that may warrant additional conservation attention. From a phylogeographic perspective, our research indicates hawksbills colonized the EP via the Indo-Pacific, and do not represent relict populations isolated from the Atlantic by the rising of the Panama Isthmus. Low overall genetic diversity in the EP is likely the combined result of few rookeries, extremely small reproductive populations and evolutionarily recent colonization events. Additional research with larger sample sizes and variable markers will help further genetic understanding of hawksbill turtles in the EP.

The conservation status of the Galápagos marine iguanas, Amblyrhynchus cristatus: a molecular perspective

Traditionally, conservation management focuses efforts on taxonomic units. However, when the taxa used do not reflect biologically meaningful units, such methods should be reconsidered to avoid the loss of irreplaceable biodiversity. The Galápagos marine iguana (Amblyrhynchus cristatus) is listed as Vulnerable on the IUCN Red List of Threatened Species and is facing growing anthropogenic threats. Currently, management is based on a taxonomy which is questionable in the light of recent molecular data. As such, there is a danger that evolutionarily significant populations may be left vulnerable to extirpation. Herein, we apply molecular data to elucidate the population structure of this species across the Galápagos archipelago, and thus advise conservation management in the absence of a revised taxonomy. Applying a wealth of molecular data including 12 microsatellite loci and 1181 bp of the mitochondrial control region in over 1200 individuals, we delineate distinct populations and prioritize their management. Bayesian population structure analysis revealed 10 distinct population clusters, which we propose as management units (MUs). All MUs are significantly differentiated, with one unit on San Cristóbal Island being particularly distinct in terms of both microsatellite loci and mitochondrial data. Based on estimates of the genetic effective population size (Ne), we find the MUs comprised of populations occurring on Floreana, Española, Marchena, and San Cristóbal to be alarmingly small. In consideration of both Neand anthropogenic threats, we recommend that conservation practitioners focus efforts on Floreana and San Cristóbal islands, and argue that better census size estimates of populations are urgently needed.