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Van Steenberge M, Raeymaekers JAM, Hablützel PI, Vanhove MPM, Koblmüller S, Snoeks J. Delineating species along shifting shorelines: Tropheus (Teleostei, Cichlidae) from the southern subbasin of Lake Tanganyika. Front Zool 2018; 15:42. [PMID: 30459820 PMCID: PMC6234679 DOI: 10.1186/s12983-018-0287-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2018] [Accepted: 10/14/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Species delineation is particularly challenging in taxa with substantial intra-specific variation. In systematic studies of fishes, meristics and linear measurements that describe shape are often used to delineate species. Yet, little is known about the taxonomic value of these two types of morphological characteristics. Here, we used Tropheus (Teleostei, Cichlidae) from the southern subbasin of Lake Tanganyika to test which of these types of characters best matched genetic lineages that could represent species in this group of stenotypic rock-dwelling cichlids. We further investigated intra-population variation in morphology. By linking this to a proxy of a population's age, we could assess the evolutionary stability of different kinds of morphological markers. RESULTS Morphological data was collected from 570 specimens originating from 86 localities. An AFLP approach revealed the presence of five lineages in the southern subbasin: T. moorii, T. brichardi, T. sp. 'maculatus', T. sp. 'Mpimbwe' and T. sp. 'red', which we consider to represent distinct species. Although both types of morphological data supported this classification, a comparison of PST-values that describe inter-population morphological differentiation, revealed a better correspondence between the taxon delineation based on AFLP data and the patterns revealed by an analysis of meristics than between the AFLP-based taxon delineation and the patterns revealed by an analysis of shape. However, classifying southern populations of Tropheus was inherently difficult as they contained a large amount of clinal variation, both in genetic and in morphological data, and both within and among species. A scenario is put forward to explain the current-day distribution of the species and colour varieties and the observed clinal variation across the subbasin's shoreline. Additionally, we observed that variation in shape was larger in populations from shallow shores whereas populations from steep shores were more variable in meristics. This difference is explained in terms of the different timescales at which small and large scale lake level fluctuations affected populations of littoral cichlids at steep and shallow shores. CONCLUSIONS Our results showed meristics to be more evolutionary stable, and of higher taxonomic value for species delimitation in Tropheus, than linear measurements that describe shape. These results should be taken into account when interpreting morphological differences between populations of highly stenotypic species, such as littoral cichlids from the Great East African Lakes.
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Affiliation(s)
- Maarten Van Steenberge
- Vertebrates Section, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium
- Operational Directorate Taxonomy and Phylogeny, Royal Belgian Institute for Natural Sciences, Vautierstraat 29, 1000 Brussels, Belgium
- Institute of Biology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | | | - Pascal István Hablützel
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium
- Flanders Marine Institute (VLIZ), Wandelaarkaai 7, 8400 Oostende, Belgium
| | - Maarten Pieterjan Maria Vanhove
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
- Centre for Environmental Sciences, Research Group Zoology: Biodiversity & Toxicology, Hasselt University, Agoralaan Gebouw D, B-3590 Diepenbeek, Belgium
- Zoology Unit, Finnish Museum of Natural History, University of Helsinki, P.O.Box 17, FI-00014 Helsinki, Finland
| | - Stephan Koblmüller
- Institute of Biology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | - Jos Snoeks
- Vertebrates Section, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium
- Laboratory of Biodiversity and Evolutionary Genomics, University of Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium
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Grummer JA, Morando MM, Avila LJ, Sites JW, Leaché AD. Phylogenomic evidence for a recent and rapid radiation of lizards in the Patagonian Liolaemus fitzingerii species group. Mol Phylogenet Evol 2018; 125:243-254. [DOI: 10.1016/j.ympev.2018.03.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 02/07/2018] [Accepted: 03/15/2018] [Indexed: 10/17/2022]
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Sefc KM, Mattersdorfer K, Ziegelbecker A, Neuhüttler N, Steiner O, Goessler W, Koblmüller S. Shifting barriers and phenotypic diversification by hybridisation. Ecol Lett 2017; 20:651-662. [PMID: 28384842 PMCID: PMC6555762 DOI: 10.1111/ele.12766] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 03/06/2017] [Indexed: 01/30/2023]
Abstract
The establishment of hybrid taxa relies on reproductive isolation from the parental forms, typically achieved by ecological differentiation. Here, we present an alternative mechanism, in which shifts in the strength and location of dispersal barriers facilitate diversification by hybridisation. Our case study concerns the highly diverse, stenotopic rock-dwelling cichlids of the African Great Lakes, many of which display geographic colour pattern variation. The littoral habitat of these fish has repeatedly been restructured in the course of ancient lake level fluctuations. Genetic data and an experimental cross support the hybrid origin of a distinct yellow-coloured variant of Tropheus moorii from ancient admixture between two allopatric, red and bluish variants. Deficient assortative mating preferences imply that reproductive isolation continues to be contingent on geographic separation. Linking paleolimnological data with the establishment of the hybrid variant, we sketch a selectively neutral diversification process governed solely by rearrangements of dispersal barriers.
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Affiliation(s)
- Kristina M. Sefc
- Institute of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | - Karin Mattersdorfer
- Institute of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | | | - Nina Neuhüttler
- Institute of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | - Oliver Steiner
- Institute of Chemistry - Analytical Chemistry, University of Graz, Universitätsplatz 1, 8010 Graz, Austria
| | - Walter Goessler
- Institute of Chemistry - Analytical Chemistry, University of Graz, Universitätsplatz 1, 8010 Graz, Austria
| | - Stephan Koblmüller
- Institute of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
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