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)