Cryptic molecular diversity in the morphologically variable rotiferan Brachionus quadridentatus (Rotifera: Monogononta)

Abstract

Brachionus quadridentatus is a morphologically variable species distributed worldwide. Its taxonomy is confusing due the numerous infrasubspecific variants described in the taxon. Here we explore genetic diversity of certain B. quadridentatus populations, using sequences of COI mtDNA and 18S rDNA genes. With traditional morphology (taxonomic keys), the specimens identified fell into three recognized variants: B. quadridentatus quadridentatus, B. quadridentatus f. brevispinus and B. quadridentatus f. cluniorbicularis. The coalescent species delimitation analysis highly supports the presence of at least three putative species within B. quadridentatus complex in agreement with the phylogenetic result and GMYC analysis with the 18S gene. Nevertheless, the morphological and mitochondrial information show that the variation within each of the three putative species is much more extensive, finding seven monophyletic and highly divergent genetic groups (>10%) that have congruence with the morphotypes found in this study and ABGD analysis, which display clear morphological differences mainly in the diagnostic characters.

Patterns of Rotifer Diversity in the Chihuahuan Desert

“…Our analyses also show that rotifer assemblages are correlated with distance at smaller spatial scales but are more homogenous at the regional level (Table 4). Other papers have reported similar patterns in multiple studies analyzing species assemblages or populations of a single species [147,160,[163][164][165][166][167]. Thus, our results seem to support the Baas Becking Principle-"Everything is everywhere, but, the environment selects"-the ubiquity hypothesis [168].…”

The gems of the Middle-East: Unveiling the biodiversity of Monogonont rotifers in temporary waterbodies of Israel

“…Among the most highly represented species in the 26 temporary ponds were Hexarthra mira , Polyarthra vulgaris and Brachionus quandridentatus . These species comprise species-complexes (García-Morales & Domínguez-Domínguez, 2019; Moreno et al, 2017; Zhang et al, 2021) which suggests that their widespread distribution among different climatic regions may be attributed to the presence of different cryptic entities with distinct ecological requirements. This phenomenon has been previously observed in other rotifer taxa such as Brachionus plicatilis and Brachionus calyciflorus , which were once thought to have a ubiquitous distribution, but were later found to be species complexes with relatively restricted ecological niches (Gabaldón et al, 2017; Zhang et al, 2018; Walczyńska et al, 2023).…”

Uncovering Hidden Diversity: Three New Species of the Keratella Genus (Rotifera, Monogononta, Brachionidae) of High Altitude Water Systems from Central Mexico

“…In fact, the discordance observed here is similar to the latter species, where ITS1 did not split the species as COI. Mitonuclear discrepancies were attributed to processes such as hybridization, incomplete lineage sorting and horizontal gene transfer [7,49]. Nevertheless, other factors as concerted evolution of the ribosomal nuclear markers can be considered to explain the incongruence between the mitochondrial and nuclear phylogenies [52].…”

“…However, it is an important water body due that harbors some native fish species, for example, Chirostoma compressum de Buen, 1940; C. jordani Woolman, 1894 and Xenotoca variata (Bean, 1887) [67], and recently a copepod species Mastigodiaptomus patzcuarensis was found here [68]. Recently, another cryptic species belonging to the Brachionus quadridentatus species complex was found in this lagoon [7].…”

“…They play an essential role in aquatic food webs by transferring energy to higher trophic levels [4,5]. Rotifera harbors a high level of cryptic diversity [6], and this hidden diversity is expected due to the small size of rotifers, the scarcity of rotifer taxonomists that can identify them reliably, the lack of taxonomically relevant morphological features, little or no morphological variation between species, as well as the high level of phenotypic plasticity present in several species [2,7]. Cryptic species complexes have been described for taxa such as Brachionus plicatilis (Müller, 1786) [8,9], B. calyciflorus Pallas, 1766 [10], Epiphanes senta (Müller, 1773) [11], Polyarthra dolichoptera (Idelson, 1925) [12], Keratella cochlearis (Gosse, 1851) [13,14], Limnias melicerta (Weisse, 1848) Diversity 2021, 13, 676 2 of 21 and L. ceratophylli (Schrank, 1803) [15], and other such as Platyias quadricornis (Ehrenberg, 1832) and Testudinella patina (Hermann, 1783) [6].…”