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

Adam Cieplinski,Ulrike Obertegger,Thomas Weisse

doi:10.1007/s10750-016-2781-z

Adam Cieplinski, Ulrike Obertegger + Show 1 more

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https://doi.org/10.1007/s10750-016-2781-z

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Journal: Hydrobiologia	Publication Date: May 17, 2016
Citations: 43	License type: open-access

Affiliation: Fondazione Edmund Mach, Universität Innsbruck

Abstract

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.

Highlights

Biodiversity is currently under threat, and our perception of species loss is highly dependent on accurate estimates of species richness
Distances between generalised mixed Yule coalescent (GMYC) evolutionary significant units (ESUs) ranged from 9% (ESU 7 vs. 8) to 33% (ESU 8 vs. 3) with an overall average value of 21% (Table 3)
The automatic barcode gap discovery (ABGD) and the Poisson tree process model (PTP)-maximum likelihood (ML) grouped the same haplotypes in the same ESUs as GMYC (Fig. 3)

Summary

Introduction

Biodiversity is currently under threat, and our perception of species loss is highly dependent on accurate estimates of species richness. 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 (Gomez & Snell, 1996). The occurrence of cryptic species is often related to rotifer ubiquity and their wide tolerance to environmental parameters such as salinity (Ciros-Perez et al, 2001a), temperature (Gomez & Snell, 1996; Ortells et al, 2003; Papakostas et al, 2012) or total phosphorus (Obertegger et al, 2012)

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