Fifteen species in one: deciphering the Brachionus plicatilis species complex (Rotifera, Monogononta) through DNA taxonomy

Abstract

Understanding patterns and processes in biological diversity is a critical task given current and rapid environmental change. Such knowledge is even more essential when the taxa under consideration are important ecological and evolutionary models. One of these cases is the monogonont rotifer cryptic species complex Brachionus plicatilis, which is by far the most extensively studied group of rotifers, is widely used in aquaculture, and is known to host a large amount of unresolved diversity. Here we collate a dataset of previously available and newly generated sequences of COI and ITS1 for 1273 isolates of the B. plicatilis complex and apply three approaches in DNA taxonomy (i.e. ABGD, PTP, and GMYC) to identify and provide support for the existence of 15 species within the complex. We used these results to explore phylogenetic signal in morphometric and ecological traits, and to understand correlation among the traits using phylogenetic comparative models. Our results support niche conservatism for some traits (e.g. body length) and phylogenetic plasticity for others (e.g. genome size).

Empirical evidence for fast temperature-dependent body size evolution in rotifers

“…B. plicatilis was previously regarded as a cosmopolitan species of a global geographic range. Molecular techniques have shown that the former taxon B. plicatilis is actually a complex of fifteen cryptic species (Mills et al, 2017). Four species from this complex co-exist in the shallow ponds of the Mediterranean coast of Spain (Gomez et al, 1995;Ortells et al, 2003;Montero-Pau et al, 2011).…”

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

“…Here, we identified mitochondrial DNA (mtDNA) groups and compared their lorica morphology in a complementary approach as recommended by Schlick-Steiner et al (2006), Fontaneto et al (2015) and Mills et al (2016). Combining genetic information with other species-bound aspects such as species morphology and ecology or biochemistry of species habitat can result in a more robust species delimitation than when using genetic information alone (SchlickSteiner et al, 2006;Fontaneto et al, 2015;Mills et al, 2016).…”

“…Combining genetic information with other species-bound aspects such as species morphology and ecology or biochemistry of species habitat can result in a more robust species delimitation than when using genetic information alone (SchlickSteiner et al, 2006;Fontaneto et al, 2015;Mills et al, 2016). We hypothesised that K. cochlearis is a complex of putative evolutionary significant units (ESUs) and that it is possible to delimit ESUs based on lorica measurements.…”

Do genome size differences within Brachionus asplanchnoidis (Rotifera, Monogononta) cause reproductive barriers among geographic populations?

“…On the other hand, sex can be induced experimentally, which allows to cross different clones with each other (e.g., Fu et al, 1993). Initially considered a single species with geographically variable races, by use of multiple molecular markers Brachionus plicatilis Müller, 1786 was shown to be a cryptic species complex of 14-22 species (Gómez et al, 2002;Suatoni et al, 2006;Fontaneto et al, 2009;Gribble & Mark Welch, 2012;Mills et al, 2016). The species complex can be divided into three major clades (see Fig.…”