Type of Document	Thesis
Author	Easton, Erin Elizabeth
URN	etd-04132009-221412
Title	On Species Boundaries in Zausodes-complex Species
Degree	Master of Arts
Department	Oceanography, Department of
Advisory Committee	Advisor Name Title David Thistle Committee Chair Amy Baco-Tayor Committee Member Joel Kostka Committee Member
Keywords	Species Boundary Copepoda Harpacticoida Zausodes Cytochrome b 18 S rRNA Gene Gene Sequencing
Date of Defense	2009-02-26
Availability	unrestricted
Abstract Prior to 1999, the harpacticoid copepod species Zausodes arenicolus had been considered to be very useful for ecological studies because its unusual shape made it easy to recognize. Bouck et al.’s (1999) taxonomic revision based on an evaluation of the morphology of specimens from the northern Gulf of Mexico near the Florida State University Coastal and Marine Laboratory split Z. arenicolus into three species, some of which co-occur. If Bouck et al. are correct, then the previous ecological results would be suspect, and Z. arenicolus would be much less useful in ecological work. It is therefore important to evaluate the validity of the species’ boundaries they erected. Because convergent evolution and morphological stasis are known in harpacticoid copepods, morphologically based approaches such as those of Bouck et al. may not be sufficient. I decided to use gene-sequencing methods instead, but I saved voucher material from each specimen so I could search for new morphological characters if the initial morphological identifications and those indicated by gene sequences did not agree. A 393-base-pair region of the mitochondrial cytochrome b gene and a 478-base-pair region of the 18S rRNA gene were separately analyzed from individual Zausodes-complex specimens found at five sites within 30 km of the Florida State University Coastal and Marine Laboratory. Zausodes septimus individuals formed a single cytochrome b gene-sequence clade, whereas Z. arenicolus individuals formed five clades. The uncorrected genetic divergences among these clades were ten times greater than the divergences within them, a degree of differences that suggests that each clade is a different species. The 18S rDNA results support those from cytochrome b. Subsequent analysis of the vouchers revealed morphological differences that will allow two of the Z. arenicolus clades to be described as new species. Further analysis may reveal morphological differentiation among the other three clades. In sum, Bouck et al. (1999) perceived some but not all of the species present.
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