Long-Term Coexistence of Rotifer Cryptic Species

Abstract

Despite their high morphological similarity, cryptic species often coexist in aquatic habitats presenting a challenge in the framework of niche differentiation theory and coexistence mechanisms. Here we use a rotifer species complex inhabiting highly unpredictable and fluctuating salt lakes to gain insights into the mechanisms involved in stable coexistence in cryptic species. We combined molecular barcoding surveys of planktonic populations and paleogenetic analysis of diapausing eggs to reconstruct the current and historical coexistence dynamics of two highly morphologically similar rotifer species, B. plicatilis and B. manjavacas. In addition, we carried out laboratory experiments using clones isolated from eight lakes where both species coexist to explore their clonal growth responses to salinity, a challenging, highly variable and unpredictable condition in Mediterranean salt lakes. We show that both species have co-occurred in a stable way in one lake, with population fluctuations in which no species was permanently excluded. The seasonal occurrence patterns of the plankton in two lakes agree with laboratory experiments showing that both species differ in their optimal salinity. These results suggest that stable species coexistence is mediated by differential responses to salinity and its fluctuating regime. We discuss the role of fluctuating salinity and a persistent diapausing egg banks as a mechanism for species coexistence in accordance with the ‘storage effect’.

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

“…Our second aim is to present a study of the evolutionary relationships among the species in the complex for a comparative analysis exploring the phylogenetic signal of biological traits and correlations among species-specific traits of the different species. The B. plicatilis species complex is by far the most extensively studied group of rotifers, and these animals have been used to investigate a wide variety of phenomena including ecological interactions (CirosPérez et al, 2001b(CirosPérez et al, , 2004(CirosPérez et al, , 2015Montero-Pau et al, 2011;Gabaldon et al, 2015), toxicology (Serrano et al, 1986;Snell & Persoone, 1989;Dahms et al, 2011), osmoregulation (Lowe et al, 2005), local adaptation (Campillo et al, 2009;Alcántara-Rodrí-guez et al, 2012), the evolution of sex , phylogeography Mills et al, 2007), ageing (Snell et al, 2015), and evolutionary processes (Stelzer et al, 2011;Fontaneto et al, 2012;Tang et al, 2014a). In addition, due to the ease and low cost of producing highly dense cultures of these rotifers, members of this species complex have been widely used in aquaculture as a source of live feed for larval crustaceans and fishes (Fukusho, 1983;Watanabe et al, 1983;Lubzens & Zmora, 2003).…”

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

“…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). Recently, three of them, B. plicatilis sensu stricto Müller, 1786, B. ibericus Ciros-Pérez, Serra, 2001 andB.…”

Temperature and salinity induce differential responses in life histories of cryptic nematode species

“…Hypotheses about ecological niche differentiation between cryptic species are usually based on often limited information about geographical distributions (Ortells et al, 2003;Rissler and Apodaca, 2007). Abiotic niche differentiation has already been invoked as a likely explanation for the coexistence of cryptic species in e.g., rotifers, sea urchins and nematodes (Montero-Pau et al, 2011;Ortells et al, 2003;Palumbi and Metz, 1991;Van Campenhout et al, 2014).…”