Reproductive isolation and morphological divergence between cryptic lineages of the copepod Acartia tonsa in Chesapeake Bay

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 597:99-113 (2018) - DOI: https://doi.org/10.3354/meps12569 Reproductive isolation and morphological divergence between cryptic lineages of the copepod Acartia tonsa in Chesapeake Bay L. V. Plough*, C. Fitzgerald, A. Plummer, J. J. Pierson Horn Point Laboratory, University of Maryland Center for Environmental Science, Cambridge, MD 21613, USA *Corresponding author: lplough@umces.edu ABSTRACT: Recent advances in molecular technologies have revealed cryptic species across many marine zooplankton taxa. However, the patterns and drivers of cryptic divergence are complex, and few studies have examined reproductive status among lineages through crosses. In this study, we performed pair crosses within and between 2 deeply divergent (cryptic) lineages (named 'fresh' [F] and 'salt' [S]) of the estuarine copepod Acartia tonsa from upper Chesapeake Bay, USA, to examine egg production and hatching rate. We also examined differences in morphology (prosome length) and chemical composition of the 2 lineages. Crossing experiments revealed that egg production did not differ among cross types but hatching rate was significantly lower for the between-lineage crosses (mean hatching rate of 0.02 for F×S vs. 0.46 and 0.52 for F×F and S×S, respectively). The nearly complete lack of nauplii production for between-lineage crosses suggests strong reproductive isolation, which supports previous molecular data. Significant differences between the lineages in size (F lineage is 13-14% shorter) and chemical composition (F lineages have 70% less carbon per copepod) may indicate pre-zygotic barriers to reproduction (e.g. morphological or gametic incompatibility). Overall, based on the crossing, morphological, and chemical data reported here, and synthesizing previous biological data on the F and S lineages, we suggest that these cryptic lineages are likely to be separate, reproductively isolated species. Further work examining how divergent lineages of A. tonsa respond to environmental change and how they differ in their quality as prey items will be important for understanding trophic dynamics in estuarine environments like Chesapeake Bay. KEY WORDS: Cryptic species · Zooplankton · Reproduction · Copepod · Food web Full text in pdf format Supplementary material PreviousNextCite this article as: Plough LV, Fitzgerald C, Plummer A, Pierson JJ (2018) Reproductive isolation and morphological divergence between cryptic lineages of the copepod Acartia tonsa in Chesapeake Bay. Mar Ecol Prog Ser 597:99-113. https://doi.org/10.3354/meps12569 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 597. Online publication date: June 11, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.