AB 1:33-43 (2007)  -  DOI: https://doi.org/10.3354/ab00002

Genetic diversity of the pelagic harpacticoid copepod Macrosetella gracilis on colonies of the cyanobacterium Trichodesmium spp.

Renate Eberl1,2,*, Sarah Cohen1, Frank Cipriano3, Edward J. Carpenter1

1Romberg Tiburon Center for Environmental Studies, Department of Biology, San Francisco State University, 3152 Paradise Drive, California 94920-1205, USA
2University of California Davis, Department of Ecology and Evolution, One Shields Avenue, Davis, California 95616-8507, USA
3Conservation Genetics Lab, Department of Biology, San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132, USA

ABSTRACT: The harpacticoid copepod Macrosetella gracilis uses colonies of the nitrogen-fixing cyanobacterium Trichodesmium spp. as a floating substrate and nursery. This association enables the copepod to lead a pelagic existence. Molecular and morphological data both indicate that M. gracilis is maintained as a single, circumglobal species across the tropical and subtropical Atlantic and Pacific. Mitochondrial DNA sequence data from cytochrome c oxidase subunit I (COI) showed moderate to high levels of diversity and limited phylogeographic structure in M. gracilis. Thirty-six different haplotypes were found among the 149 M. gracilis individuals sequenced; 4 haplotypes were shared between the Atlantic and Pacific. Samples from Japan showed the highest haplotypic and nucleotide diversity levels, suggesting that the Indo-West Pacific may be the center of diversity for M. gracilis. Wide distribution and large population size in M. gracilis may limit divergence through increased gene flow or slowing of the loss of ancestral diversity through lineage sorting. The pelagic existence of M. gracilis has led to less phylogenetic structuring than found in other species of harpacticoid copepods, illustrating the evolutionary significance of specialization on a floating substrate in this copepod.


KEY WORDS: Macrosetella · Pelagic copepod · Harpacticoidea · Holopelagic life history · Trichodesmium · Rafting · Cytochrome c oxidase subunit I · COI · Genetic diversity


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Cite this article as: Eberl R, Cohen S, Cipriano F, Carpenter EJ (2007) Genetic diversity of the pelagic harpacticoid copepod Macrosetella gracilis on colonies of the cyanobacterium Trichodesmium spp.. Aquat Biol 1:33-43. https://doi.org/10.3354/ab00002

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