Regional management units for marine turtles: a novel framework for prioritizing conservation and research across multiple scales

Abstract

Background: Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques--including site-based monitoring, genetic analyses, mark-recapture studies and telemetry--can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges.

Methodology/principal findings: To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine- to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally.

Conclusions/significance: The RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework--including maps and supporting metadata--will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.

Figure 1. Multi-scale Regional Management Units for loggerhead turtles Caretta caretta.

Individual maps are presented for A) global nesting sites and in-water distributions (global distributions for each species represented by hatching); B) mitochondrial (mtDNA) genetic stocks; C) nuclear genetic (nDNA) stocks; and D) Regional Management Units (shown with nesting sites). Nesting sites that were unquantified or have no count values reported since 2000 are represented by black squares, whereas nesting sites for which count data are available are represented by a colored circle. For genetic stock maps (Figs. 1B and C), each symbol represents a different site that was sampled for genetic analyses, while each color represents a distinct genetic stock. Putative RMUs (see text for description) are noted by asterisks in the figure legends, and are colorless. Data shown are contained in metadata tables (Appendix S2).

Figure 2. Multi-scale Regional Management Units for green turtles Chelonia mydas.

Individual maps are presented for A) global nesting sites and in-water distributions (global distributions for each species represented by hatching); B) mitochondrial (mtDNA) genetic stocks; C) nuclear genetic (nDNA) stocks; and D) Regional Management Units (shown with nesting sites). Nesting sites that were unquantified or have no count values reported since 2000 are represented by black squares, whereas nesting sites for which count data are available are represented by a colored circle. For genetic stock maps (Figs. 2B and C), each symbol represents a different site that was sampled for genetic analyses, while each color represents a distinct genetic stock. Data shown are contained in metadata tables (Appendix S2).

Figure 3. Multi-scale Regional Management Units for leatherback turtles Dermochelys coriacea.

Individual maps are presented for A) global nesting sites and in-water distributions (global distributions for each species represented by hatching); B) mitochondrial (mtDNA) genetic stocks; C) nuclear genetic (nDNA) stocks; and D) Regional Management Units (shown with nesting sites). Nesting sites that were unquantified or have no count values reported since 2000 are represented by black squares, whereas nesting sites for which count data are available are represented by a colored circle. For genetic stock maps (Figs. 3B and C), each symbol represents a different site that was sampled for genetic analyses, while each color represents a distinct genetic stock. Data shown are contained in metadata tables (Appendix S2).

Figure 4. Multi-scale Regional Management Units for hawksbill turtles Eretmochelys imbricata.

Individual maps are presented for A) global nesting sites and in-water distributions (global distributions for each species represented by hatching); B) mitochondrial (mtDNA) genetic stocks; C) nuclear genetic (nDNA) stocks; and D) Regional Management Units (shown with nesting sites). Nesting sites that were unquantified or have no count values reported since 2000 are represented by black squares, whereas nesting sites for which count data are available are represented by a colored circle. For genetic stock maps (Figs. 4B and C), each symbol represents a different site that was sampled for genetic analyses, while each color represents a distinct genetic stock. Putative RMUs (see text for description) are noted by asterisks in the figure legends, and are colorless. Data shown are contained in metadata tables (Appendix S2).

Figure 5. Multi-scale Regional Management Units for olive ridley turtles Lepidochelys olivacea.

Individual maps are presented for A) global nesting sites and in-water distributions (global distributions for each species represented by hatching); B) mitochondrial (mtDNA) genetic stocks; C) nuclear genetic (nDNA) stocks; and D) Regional Management Units (shown with nesting sites). Nesting sites that were unquantified or have no count values reported since 2000 are represented by black squares, whereas nesting sites for which count data are available are represented by a colored circle. For genetic stock maps (Figs. 5B and C), each symbol represents a different site that was sampled for genetic analyses, while each color represents a distinct genetic stock. Putative RMUs (see text for description) are noted by asterisks in the figure legends, and are colorless. Data shown are contained in metadata tables (Appendix S2).

Figure 6. Multi-scale Regional Management Units for Kemp's ridley turtles Lepidochelys kempii.

Individual maps are presented for A) global nesting sites and in-water distributions (global distributions for each species represented by hatching); and D) Regional Management Units (shown with nesting sites). Nesting sites that were unquantified or have no count values reported since 2000 are represented by black squares, whereas nesting sites for which count data are available are represented by a colored circle. Putative RMUs (see text for description) are noted by asterisks in the figure legends, and are colorless. Note: There are no genetics maps (Panels B or C) for L. kempii because all individuals are presumed to belong to same stock and RMU. Data shown are contained in metadata tables (Appendix S2).

Figure 7. Multi-scale Regional Management Units for flatback turtles Natator depressus.

Individual maps are presented for A) global nesting sites and in-water distributions (global distributions for each species represented by hatching); B) mitochondrial (mtDNA) genetic stocks; and D) Regional Management Units (shown with nesting sites). Nesting sites that were unquantified or have no count values reported since 2000 are represented by black squares, whereas nesting sites for which count data are available are represented by a colored circle. For genetic stock maps (Fig. 7B), each symbol represents a different site that was sampled for genetic analyses, while each color represents a distinct genetic stock. Note: There is no map for N. depressus nDNA stocks (panel C, due to lack of available data). Data shown are contained in metadata tables (Appendix S2).