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Plastid DNA diversity is higher in the island endemic Guadalupe cypress than in the continental Tecate cypress.

ABSTRACT: Callitropsis guadalupensis (Guadalupe cypress) is endemic to Guadalupe Island, Mexico, where it is the dominant species of the only forest. The species has suffered declining numbers following the introduction of goats to the island over 150 years ago. Callitropsis guadalupensis is closely related to Callitropsis forbesii (Tecate cypress), distributed in small isolated populations in mainland Baja California and southern California. The objective of the present study was to compare the genetic diversity of the island endemic to the continental species.We measured genetic diversity in Callitropsis guadalupensis (n =54) from Guadalupe Island and in Callitropsis forbesii (n = 100) from five populations in mainland Baja California. The plastid DNA trnS-trnG spacer and the trnL-trnF region were chosen for characterization. Thirty-four haplotypes were observed, of which six were shared between both species. One of these haplotypes was also shared with three other species, Callitropsis lusitanica, Callitropsis montana, and Callitropsis stephensonii. Haplotype diversity (h) and nucleotide diversity (?) were significantly higher for Callitropsis guadalupensis (h = 0.698, ? = 0.00071) than for Callitropsis forbesii (h = 0.337, ? = 0.00024).Callitropsis guadalupensis shows no evidence of a founder effect or of a genetic bottleneck, and can be added to a growing list of insular species with higher genetic diversity than their mainland relatives.

SUBMITTER: Rosas Escobar P

PROVIDER: S-EPMC3024418 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Plastid DNA diversity is higher in the island endemic Guadalupe cypress than in the continental Tecate cypress.

Rosas Escobar Patricia P Gernandt David S DS Piñero Daniel D Garcillán Pedro P PP

PloS one 20110120 1

<h4>Background</h4>Callitropsis guadalupensis (Guadalupe cypress) is endemic to Guadalupe Island, Mexico, where it is the dominant species of the only forest. The species has suffered declining numbers following the introduction of goats to the island over 150 years ago. Callitropsis guadalupensis is closely related to Callitropsis forbesii (Tecate cypress), distributed in small isolated populations in mainland Baja California and southern California. The objective of the present study was to co ...[more]

PMID: 21283771

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Project description:BACKGROUND:Debated aspects in speciation research concern the amount of gene flow between incipient species under secondary contact and the modes by which post-zygotic isolation accumulates. Secondary contact zones of allopatric lineages, involving varying levels of divergence, provide natural settings for comparative studies, for which the Aegean (Eastern Mediterranean) geography offers unique scenarios. In Palearctic green toads (Bufo viridis subgroup or Bufotes), Plio-Pleistocene (~?2.6 Mya) diverged species show a sharp transition without contemporary gene flow, while younger lineages, diverged in the Lower-Pleistocene (~?1.9 Mya), admix over tens of kilometers. Here, we conducted a fine-scale multilocus phylogeographic analysis of continental and insular green toads from the Aegean, where a third pair of taxa, involving Mid-Pleistocene diverged (~?1.5 Mya) mitochondrial lineages, earlier tentatively named viridis and variabilis, (co-)occurs. RESULTS:We discovered a new lineage, endemic to Naxos (Central Cyclades), while coastal islands and Crete feature weak genetic differentiation from the continent. In continental Greece, both lineages, viridis and variabilis, form a hybrid swarm, involving massive mitochondrial and nuclear admixture over hundreds of kilometers, without obvious selection against hybrids. CONCLUSIONS:The genetic signatures of insular Aegean toads appear governed by bathymetry and Quaternary sea level changes, resulting in long-term isolation (Central Cyclades: Naxos) and recent land-bridges (coastal islands). Conversely, Crete has been isolated since the end of the Messinian salinity crisis (5.3 My) and Cretan populations thus likely result from human-mediated colonization, at least since Antiquity, from Peloponnese and Anatolia. Comparisons of green toad hybrid zones support the idea that post-zygotic hybrid incompatibilities accumulate gradually over the genome. In this radiation, only one million years of divergence separate a scenario of complete reproductive isolation, from a secondary contact resulting in near panmixia.

Dataset Information

Plastid DNA diversity is higher in the island endemic Guadalupe cypress than in the continental Tecate cypress.

Publications

Plastid DNA diversity is higher in the island endemic Guadalupe cypress than in the continental Tecate cypress.

Similar Datasets

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