High diversity in Keratella cochlearis (Rotifera, Monogononta): morphological and genetic evidence

Hydrobiologia, May 2016

Rotifers are ubiquitous freshwater animals for which many complexes of cryptic species (i.e. distinct species that are morphologically difficult to distinguish) are described. Keratella cochlearis occurs globally and shows a wide phenotypic diversity indicating the potential presence of a species complex. We sampled lakes of the Trentino-South Tyrol region (Italy) and investigated mitochondrial genetic diversity in K. cochlearis in relation to detailed lorica measurements. We sequenced the mitochondrial cytochrome c oxidase subunit I and used the generalised mixed Yule coalescent approach, Poisson tree process model and automatic barcode gap discovery to delimit mitochondrial groups, associated with putative evolutionary significant units (ESUs). Based on 248 sequences, eight putative ESUs were indicated that could only partially be delimited by lorica morphology. Specifically, several morphological characteristics (i.e. spinelets, bended median ridge, and posterior spine) were found in specimens of different putative ESUs, and thus, these characters seem to be of poor discriminatory value. Furthermore, different putative ESUs of K. cochlearis were found in the same lake. We conclude that the high mitochondrial genetic diversity may be linked to tolerance of K. cochlearis to varying environmental conditions.

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High diversity in Keratella cochlearis (Rotifera, Monogononta): morphological and genetic evidence

High diversity in Keratella cochlearis (Rotifera, Monogononta): morphological and genetic evidence Adam Cieplinski . Thomas Weisse . Ulrike Obertegger 0 1 2 GMYC PTP Lauterborn 0 1 2 Lorica 0 1 2 0 A. Cieplinski T. Weisse Research Institute for Limnology, University of Innsbruck , Mondseestraße 9, 5310 Mondsee , Austria 1 A. Cieplinski (&) U. Obertegger Department of Sustainable Agro-ecosystems and Bioresources, Research and Innovation Centre, Fondazione Edmund Mach (FEM) , Via E. Mach 1, 38010 San Michele all'Adige, TN , Italy 2 Guest editors: M. Devetter , D. Fontaneto, C. D. Jersabek , D. B. Mark Welch, L. May & E. J. Walsh / Evolving rotifers , evolving science Rotifers are ubiquitous freshwater animals for which many complexes of cryptic species (i.e. distinct species that are morphologically difficult to distinguish) are described. Keratella cochlearis occurs globally and shows a wide phenotypic diversity indicating the potential presence of a species complex. We sampled lakes of the Trentino-South Tyrol region (Italy) and investigated mitochondrial genetic diversity in K. cochlearis in relation to detailed lorica measurements. We sequenced the mitochondrial cytochrome c oxidase subunit I and used the generalised mixed Yule coalescent approach, Poisson tree process model and automatic barcode gap discovery to delimit mitochondrial groups, associated with putative evolutionary significant units (ESUs). Based on 248 sequences, eight putative ESUs were indicated that could only partially be delimited by lorica morphology. Specifically, several morphological characteristics (i.e. spinelets, bended median ridge, and posterior spine) were found in specimens of different putative ESUs, and thus, these characters seem to be of poor discriminatory value. Furthermore, different putative ESUs of K. cochlearis were found in the same lake. We conclude that the high mitochondrial genetic diversity may be linked to tolerance of K. cochlearis to varying environmental conditions. Rotifera measurements; NMDS Introduction Biodiversity is currently under threat, and our perception of species loss is highly dependent on accurate estimates of species richness. However, estimates of species richness are often impaired by the occurrence of cryptic species (i.e. species that are impossible or difficult to distinguish based on their morphology) in diverse groups such as protists (Foissner, 2006) , ants (Fournier et al., 2012) , harvestmen (Arthofer et al., 2013) , and rotifers (Go´ mez & Snell, 1996) . Understanding how and why species occur is one of the fundamental aspects in ecology (Gaston, 2000) . Evidence on cryptic species diversity in rotifers, subclass Monogononta, is growing and challenges our understanding of rotifer biodiversity. In monogonont rotifers, cryptic species complexes have been described for species such as Brachionus plicatilis (Go´mez & Serra, 1995; Go´ mez & Snell, 1996; Go´mez et al., 2002) , B. calyciflorus (Schro¨der & Walsh, 2007; Xi et al., 2011) , Epiphanes senta (Gilbert & Walsh, 2005), Lecane spp. (Garc´ıa-Morales & El´ıas-Gutie´rrez, 2013) , Polyarthra dolichoptera (Obertegger et al., 2014) , Synchaeta spp. (Obertegger et al., 2012) , and Testudinella clypeata (Leasi et al., 2013) . The occurrence of cryptic species is often related to rotifer ubiquity and their wide tolerance to environmental parameters such as salinity (Ciros-Pe´rez et al., 2001a) , temperature (Go´ mez & Snell, 1996; Ortells et al., 2003; Papakostas et al., 2012) or total phosphorus (Obertegger et al., 2012). Keratella cochlearis Gosse, 1851 can be found in most freshwater lakes and ponds all over the world (Green, 1987) . In fact, the whole genus Keratella is considered eurytopic and cosmopolitan (Segers & De Smet, 2008) , and this makes the genus a good candidate for investigating the occurrence of cryptic species. Lauterborn (1900) described several morphotypes in K. cochlearis, and his detailed descriptions and drawings were the basis for following taxonomic work (e.g. Ahlstrom, 1943; RuttnerKolisko, 1974; Koste, 1978) . The morphotypes described by Lauterborn (1900) encompass three series (macracantha–typica–tecta, hispida, and irregularis) and the group of robusta. These morphological varieties of K. cochlearis are different with respect to lorica length (LL), spine length, presence of spinelets on the lorica, and the course of the median ridge. Here, we give an overview of the Lauterborn (1900) series and a German to English translation of Lauterborn’s (1900) descriptions. In the macracantha–typica–tecta series (Lauterborn’s 1900, Figs. 1–10) , the posterior spine is as long as the lorica or even longer, and the basis of the spine is so wide that it is difficult to decide where the spine begins and the lorica ends. The areolation is present on half of the spine, and only the distal part is smooth and pointed. In lateral view, the spine points to left or right, and this i (...truncated)


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Adam Cieplinski, Thomas Weisse, Ulrike Obertegger. High diversity in Keratella cochlearis (Rotifera, Monogononta): morphological and genetic evidence, Hydrobiologia, 2017, pp. 145-159, Volume 796, Issue 1, DOI: 10.1007/s10750-016-2781-z