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Phillips KF, Martin KR, Stahelin GD, Savage AE, Mansfield KL. Genetic variation among sea turtle life stages and species suggests connectivity among ocean basins. Ecol Evol 2022; 12:e9426. [PMID: 36329816 PMCID: PMC9618668 DOI: 10.1002/ece3.9426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 09/21/2022] [Accepted: 09/26/2022] [Indexed: 11/06/2022] Open
Abstract
Regional genetic differentiation of mitochondrial lineages occurs in migratory species with natal philopatry such as sea turtles. However, early juvenile dispersal represents a key opportunity for gene flow and colonization of new regions through founder events, making it an important yet under-studied life stage. To assess connectivity among sea turtle life stages and ocean basins, we sequenced mitochondrial DNA (mtDNA) fragments from 35 juveniles sampled in the Gulf of Mexico from the rarely observed dispersal stage across three species: green turtles (Chelonia mydas; n = 30), hawksbills (Eretmochelys imbricata; n = 3), and loggerheads (Caretta caretta; n = 2). We estimated green turtle rookery contributions using a many-to-many Bayesian mixed stock analysis that incorporated dispersal probabilities based on rookery size and transport via ocean currents. We assembled a gene tree including 709 distinct mtDNA control region haplotypes from the literature for all seven extant sea turtle species to assess gaps in life-stage data across ocean basins, as well as contextualize the lineages we sampled from dispersing juveniles. Our results indicate a high likelihood that green turtles sampled in the Gulf of Mexico originated from rookeries along the coast of Mexico, with smaller contributions from Costa Rica and Suriname. The gene tree analysis yielded species-level relationships consistent with those presented previously, while intra-species relationships between lineages and ocean basins differed, particularly within loggerhead and green turtle clades. Our results highlight the lack of genetic data from juvenile sea turtles, especially the early dispersal stage, and the potential for these data to answer broader questions of connectivity and diversification across species and lineages.
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Affiliation(s)
| | | | | | - Anna E. Savage
- Department of BiologyUniversity of Central FloridaOrlandoFloridaUSA
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van de Geer CH, Bourjea J, Broderick AC, Dalleau M, Fernandes RS, Harris LR, Inteca GE, Kiponda FK, Louro CMM, Mortimer JA, Msangameno D, Mwasi LD, Nel R, Okemwa GM, Olendo M, Pereira MAM, Rees AF, Silva I, Singh S, West L, Williams JL, Godley BJ. Marine turtles of the African east coast: current knowledge and priorities for conservation and research. ENDANGER SPECIES RES 2022. [DOI: 10.3354/esr01180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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The population genomic structure of green turtles (Chelonia mydas) suggests a warm-water corridor for tropical marine fauna between the Atlantic and Indian oceans during the last interglacial. Heredity (Edinb) 2021; 127:510-521. [PMID: 34635850 PMCID: PMC8626443 DOI: 10.1038/s41437-021-00475-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 09/21/2021] [Accepted: 09/21/2021] [Indexed: 01/01/2023] Open
Abstract
The occasional westward transport of warm water of the Agulhas Current, "Agulhas leakage", around southern Africa has been suggested to facilitate tropical marine connectivity between the Atlantic and Indian oceans, but the "Agulhas leakage" hypothesis does not explain the signatures of eastward gene flow observed in many tropical marine fauna. We investigated an alternative hypothesis: the establishment of a warm-water corridor during comparatively warm interglacial periods. The "warm-water corridor" hypothesis was investigated by studying the population genomic structure of Atlantic and Southwest Indian Ocean green turtles (N = 27) using 12,035 genome-wide single nucleotide polymorphisms (SNPs) obtained via ddRAD sequencing. Model-based and multivariate clustering suggested a hierarchical population structure with two main Atlantic and Southwest Indian Ocean clusters, and a Caribbean and East Atlantic sub-cluster nested within the Atlantic cluster. Coalescent-based model selection supported a model where Southwest Indian Ocean and Caribbean populations diverged from the East Atlantic population during the transition from the last interglacial period (130-115 thousand years ago; kya) to the last glacial period (115-90 kya). The onset of the last glaciation appeared to isolate Atlantic and Southwest Indian Ocean green turtles into three refugia, which subsequently came into secondary contact in the Caribbean and Southwest Indian Ocean when global temperatures increased after the Last Glacial Maximum. Our findings support the establishment of a warm-water corridor facilitating tropical marine connectivity between the Atlantic and Southwest Indian Ocean during warm interglacials.
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Liu J, Lindstrom AJ, Chen YS, Nathan R, Gong X. Congruence between ocean-dispersal modelling and phylogeography explains recent evolutionary history of Cycas species with buoyant seeds. THE NEW PHYTOLOGIST 2021; 232:1863-1875. [PMID: 34342898 DOI: 10.1111/nph.17663] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 07/29/2021] [Indexed: 05/25/2023]
Abstract
Ocean currents play a significant role in driving the long-distance dispersal (LDD), spatial distribution and phylogeographic patterns of many organisms. Integrating phylogeographic analyses and mechanistic ocean current modelling can provide novel insights into the evolutionary history of terrestrial littoral species but has been rarely applied in this context. We focused on a group of Cycas that have buoyant seeds and occupy coastal habitats. By integrating evidence from mechanistic simulations and whole plastomic data, we examined the role of ocean circulation in shaping the phylogeography of these Cycas species. Plastomes of the studied Cycas species showed extreme conservatism, following a post-Pleistocene divergence. Phylogenies revealed three subclades, corresponding to the Pacific Ocean, Sunda Shelf and Indian Ocean. The ocean modelling results indicate that hotspots of seed stranding coincide well with the contemporary distribution of the Cycas species and that drifting trajectories from the three subclades are largely confined to separate regions. These findings suggest that ocean current systems, by driving long-distance dispersal, have shaped the distribution and phylogeography for Cycas with buoyant seeds. This study highlights how the combination of genomic data and ocean drift modelling can help explain phylogeographic patterns and diversity in terrestrial littoral ecosystems.
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Affiliation(s)
- Jian Liu
- CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, 650201, China
- Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
| | - Anders J Lindstrom
- Global Biodiversity Conservancy, 144/124 Moo3, Soi Bua Thong, Bangsalae, Sattahip, Chonburi, 20250, Thailand
| | - Yong-Sheng Chen
- Institute of Ecology and Key Laboratory for Earth Surface Processes of the Ministry of Education, College of Urban and Environmental Sciences, Peking University, Beijing, 100871, China
| | - Ran Nathan
- Movement Ecology Laboratory, Department of Ecology, Evolution and Behavior, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel
| | - Xun Gong
- CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, 650201, China
- Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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