Abstract
Biologists typically distinguish species by how they look. However, with the development of DNA-based techniques to identify species, they found that genetically-different species may look remarkably similar. Biologists called these called cryptic species. Cryptic species pose several consequences to our understanding of what is a species, but also represent challenges to non-fundamental fields of science such as medicine (e.g. the Anopheles gambiae mosquito, the vector for malaria, is a complex of cryptic species and not every species transmits malaria). My thesis focused on the Stygocapitella subterranea ghost-worm since this species was first described as cosmopolitan (living all over the world) but unable to disperse easily, however, another possibility was that it comprised multiple species. I found: 1) 8 new Stygocapitella species to science; 2) some of which are undistinguishable. 3) some indistinguishable species have diverged more than 100 million years ago; 4) nearly all new species are confined to a single coastline. These results contribute to our understanding of how cryptic species evolve in terms of their morphology (shape), and how they disperse. Importantly, they reveal that cryptic species may interfere with our understanding of the natural world.
List of papers
Paper 1. T. H. Struck, J. L. Feder, M. Bendiksby, S. Birkeland, J. Cerca, V. I. Gusarov, S. Kistenich, et al. 2018. Finding evolutionary processes hidden in cryptic species. Trends in Ecology & Evolution: 3, 33: 153–163. doi: 10.1016/j.tree.2017.11.007. The paper is included in the thesis. Also available at: https://doi.org/10.1016/j.tree.2017.11.007 |
Paper 2. J. Cerca, G. Purschke, and T. H. Struck. 2018. Marine connectivity dynamics: clarifying cosmopolitan distributions of marine interstitial invertebrates and the meiofauna paradox. Marine Biology 165: 123. doi: 10.1007/s00227-018-3383-2. The paper is included in the thesis. Also available at: https://doi.org/10.1007/s00227-018-3383-2 |
Paper 3. J. Cerca, C. Meyer, D. Stateczny, D. Siemon, J. Wegbrod, G. Purschke, D. Dimitrov, and T. H. Struck. Deceleration of morphological evolution in a cryptic species complex and its links to paleontological stasis. Evolution, 74: 116-131. doi: 10.1111/evo.13884 The paper is included in the thesis. Also available in DUO: http://urn.nb.no/URN:NBN:no-78461 |
Paper 4. J. Cerca, C. Meyer, G. Purschke, and T. H. Struck. Delimitation of cryptic species drastically reduces the geographical of marine interstitial ghost-worms (Stygocapitella; Annelida, Sedentaria). Molecular Phylogenetics and Evolution, vol.143, February 2020, 106663. doi: 10.1016/j.ympev.2019.106663. The paper is included in the thesis. Also available in DUO: http://urn.nb.no/URN:NBN:no-78227 |
Paper 5. J. Cerca, M. Ravinet, M. Nowak, T. H. Struck. Big data in biodiversity: genome-level data (ddRADseq) suggests a complex evolutionary history in a morphologically similar cryptic species complex, which is not revealed by few molecular markers. To be published. The paper is not available in DUO awaiting publishing. |