Cryptic invasion of a parasitic copepod: Compromised identification when morphologically similar invaders co-occur in invaded ecosystems
Goedknegt, M.A.; Thieltges, D.W.; van der Meer, J.; Wegner, K.M.; Luttikhuizen, P.C. (2018). Cryptic invasion of a parasitic copepod: Compromised identification when morphologically similar invaders co-occur in invaded ecosystems. PLoS One 13(3): e0193354. https://doi.org/10.1371/journal.pone.0193354 In: PLoS One. Public Library of Science: San Francisco. ISSN 1932-6203; e-ISSN 1932-6203, more |   |
| Authors | | Top | - Goedknegt, M.A., more
- Thieltges, D.W., more
- van der Meer, J., more
| - Wegner, K.M.
- Luttikhuizen, P.C., more
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| Abstract | Despite their frequent occurrence and strong impacts on native biota, biological invasionscan long remain undetected. One reason for this is that an invasive species can be morphologicallysimilar to either native species or introduced species previously established in thesame region, and thus be subject to mistaken identification. One recent case involves congenericinvasive parasites, copepods that now infect bivalve hosts along European Atlanticcoasts, after having been introduced independently first from the Mediterranean Sea (Mytilicolaintestinalis Steuer, 1902) and later from Japan (Mytilicola orientalis Mori, 1935). Atleast one report on M. intestinalis may have actually concerned M. orientalis, and M. orientalisthus qualifies as a ªcryptic invaderº. Because these two parasitic copepods are morphologicallysimilar, knowledge about their distribution, impact and interactions dependscrucially on reliable species identification. In this study, we evaluated the reliability of morphologicalidentification of these two species in parts of their invasive range in Europe(Dutch Delta and Wadden Sea) in comparison with molecular methods of well-establishedaccuracy based on COI gene sequences and ITS1 restriction fragment length polymorphism.Based on seven easily measured or scored macro-morphological variables thatwere recorded for 182 individual copepods isolated from blue mussels (Mytilus edulis Linnaeus,1758), principal component analysis showed two relatively distinct but overlappingmorphological species groups for females, but no clear separation in males. Discriminantfunction analysis showed that the females can be discriminated reasonably well based onsome of the morphological characteristics (identification error rate of 7%) while males cannot(error rate of 25%). The direction of the dorsolateral thoracic protuberances was identifiedas the most important trait for species discrimination, but among the morphologicalfeatures checked, none could flawlessly discriminate between both species. We recommendthe use of molecular techniques in future studies of invasive Mytilicola to reliably discriminatebetween the species. The morphological similarity of these two invaders suggestsa more general problem of cryptic invasions and compromised identification of parasites in invaded ecosystems. This problem should be borne in mind whenever invasive parasitesare investigated. |
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