Invertebrate Systematics Invertebrate Systematics Society
Systematics, phylogeny and biogeography
RESEARCH ARTICLE

Species boundaries in Zausodes-complex species (Copepoda : Harpacticoida : Harpacticidae) from the north-eastern Gulf of Mexico

Erin E. Easton A C , David Thistle A and Trisha Spears B
+ Author Affiliations
- Author Affiliations

A Department of Oceanography, Florida State University, Tallahassee, Florida 32306-4320, USA.

B Department of Biological Science, Florida State University, Tallahassee, Florida 32306-4295, USA.

C Corresponding author. Email: eee04c@fsu.edu

Invertebrate Systematics 24(3) 258-270 https://doi.org/10.1071/IS09038
Submitted: 29 September 2009  Accepted: 17 June 2010   Published: 30 August 2010

Abstract

Before 1999, the harpacticoid copepod species Zausodes arenicolus Wilson, 1932 was the subject of several ecological studies. Based on morphological evaluations of specimens from the north-eastern Gulf of Mexico, Bouck et al.’s (1999) taxonomic revision revealed three new species within what had been Z. arenicolus, making the ecological results suspect. Because harpacticoid copepods show convergent evolution and morphological stasis, Bouck et al.’s morphologically based approach may not have been sufficient. We have therefore re-evaluated their results using a combination of gene-sequencing and morphological methods. Partial mitochondrial cytochrome b (cytb) and 18S rRNA gene regions from individual Zausodes specimens found at five sites in the north-eastern Gulf of Mexico were separately analysed. Individuals of Zausodes septimus Lang, 1965 formed a single cytb gene-sequence clade, whereas Z. arenicolus individuals formed five. The uncorrected genetic divergences among these clades were 10 times those within them, providing evidence that each clade could be assigned to a different species. The 18S rDNA results support those from cytb. Subsequent morphological analysis revealed differences that will allow two clades of Z. arenicolus to be described as new species. Bouck et al. (1999) revealed some but not all of the species present.

Additional keywords: 18S rDNA, cytb, molecular systematics.


Acknowledgments

K. Chodyla, C. Lichkay, L. Sedlacek, T. Troutman, and M. Volkenandt helped in the laboratory. S. Bourgoin, S. Lambert, P. Lazerevich, J. Valdez, S. White, FSUCML boat operations, and members of the FSU Academic Diving Program and the FSU Red Tide Monitoring Project helped with specimen collection. Specimens used for project design were provided by J. Baguley, R. Burton, J. Fleeger, and J. Reid. S. Miller at the FSU Sequencing Facility performed all sequencing reactions. FSU High-Performance Computing supported several of the software packages we used. This manuscript was improved by comments by A. Baco, S. Bode, S. Bourgoin, V. Cruz, E. Darrow, J. Kostka, M. Rohal, A. B. Thistle, and two anonymous reviewers. The Department of Energy, Office of Biological and Environmental Research, supported this research (award numbers DE-FG02–05ER64070 and DE-FG03–01ER63065), as did the USA Department of Energy, Fossil Energy Group (award DE-FC26–00NT40929). We are grateful for this kind help.


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