Hawksbill turtle terra incognita: conservation genetics of eastern Pacific rookeries

Abstract

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.

Living on the Edge: Hawksbill turtle nesting and conservation along the Eastern Pacific Rim

“…Hawksbills also occasionally nest on the beach of Puerto Lopez, where the government is currently building a cement boardwalk along most of the beach and the impacts the boardwalk may have on hawksbill nesting remain unknown. It is important to point out that recent genetic research has identified Machalilla as a distinct management unit (MU) from MUs located in Central America (n = 3; Gaos et al, 2016). Coupled with apparent differences in size (CCL) and nesting season (Table 2 and Fig.…”

Advances in the Application of Genetics in Marine Turtle Biology and Conservation

“…Perhaps the most important advances to this field have been made through expanded sample collections that provide key insights informing designation of units to conserve on a global scale, such as Evolutionary Significant Units (ESUs), Distinct Population Segments (DPSs), and Regional Management Units (RMUs; see Box 2, Table 1 for definitions and applications of conservation units). As sample coverage continues to improve for all species in parallel with better analytical tools, marine turtle studies continue to explore questions of past glacial refuges (e.g., Hamabata et al, 2013;Naro-Maciel et al, 2014a), colonization routes (Dutton et al, 2014a;Shamblin et al, 2014;Gaos et al, 2016), and multiple colonization events that create such complexity in marine turtle phylogeographic patterns (e.g., Dethmers et al, 2006;Vargas et al, 2016). The field of marine turtle phylogeography will undoubtedly continue to advance in coming years with the development of genomic approaches and novel analytical tools.…”

“…• How isolated or connected are rookeries from one another through the exchange of nesting females? Population structure analyses of nesting females across regions of interest (mtDNA haplotypes and/or fine-scale nuclear markers a ) Examples since comprehensive review in Jensen et al (2013a) include: Dutton et al (2014b), Shamblin et al (2014), Vargas et al (2016), Gaos et al (2016), and Matsuzawa et al (2016) • How does male-mediated gene flow influence population structure among rookeries? Population structure analyses, various methods including: sampling nesting females, hatchlings and/or males in-water at breeding grounds (fine-scale nuclear markers; mtDNA haplotypes under specific circumstances b ) Wallace et al (2010b); references for information specific to each species is listed within the table.…”

“…Demographically independent populations (DIPs) are characterized by a low level of differentiation that is harder to detect with mtDNA markers , and failure to detect demographic independence when it exists may lead to inappropriate management policy (Taylor and Dizon, 1999). In marine turtles, there are recently published genetic studies that have not yet been incorporated into conservation unit delineations (e.g., Gaos et al, 2016). As these are integrated, further sampling gaps are resolved, and the application of finer-resolution markers increases, the number of MUs and DIPs will likely continue to increase in coming years for several species.…”

Unexpected patterns of global population structure in melon-headed whales Peponocephala electra

“…Fontaine et al 2007, Martien et al 2014, Viricel & Rosel 2014, Gaos et al 2016. Many potential drivers of population structure within the marine realm have been identified, including resource and habitat specialization, physiographic and oceanographic barriers, and social organizations that limit gene flow between groups.…”