Spatial patterns of genetic differentiation in Brachionus calyciflorus species complex collected from East China in summer

Abstract

In this study, the mtDNA COI genes of 124 individuals in Brachionus calyciflorus complex were sequenced and analyzed. Overall, 84 mtDNA haplotypes were defined, and were split into three clades by the phylogenetic trees. The divergences of COI gene sequence among the three clades ranged from 11.4 to 22.5%, indicating the occurrence of three cryptic species (cryptic species 1, cryptic species 2, and cryptic species 3). Within cryptic species 3, a remarkable degree of differentiation (F st = 0.0947) might be attributable to habitat fragmentation, restricted gene flow, and founder effect, most probably together with local adaptation. The more shared haplotypes were observed, and a non-significant correlation existed between geographic and genetic distance, suggesting that some ancestral haplotypes might be involved in a past range expansion, and as founders give a similar distribution pattern among geographic populations. The networks were also in agreement with the pattern of genetic differentiation in B. calyciflorus species complex revealed by molecular phylogeny. The nested clade analysis suggested a slight geographic structure in the network I, network II, and the highest nesting clade levels within the network III. Under the possible effect of the Younger Dryas Event, the three cryptic species might have survived in multiple relict refugia throughout the south of China. The co-occurrence of cryptic species 2 and 3 might be found in Guangzhou and Hainan due to the possible interference of the barrier and contiguous range expansion. After the Younger Dryas Event, cryptic species 3 with high colonization ability might have arrived and colonized whole habitats at first, and reduce effective gene flow among cryptic species, thus effectively increasing persistence of founder events. Cryptic species 2 might, respectively, have expanded their ranges into Wuhu and Nanjing regions only because of the probable barrier of the Yangtze River, its weak colonization abilities and the 'priority effects' of cryptic species 3. Cryptic species 1 distributed exclusively in Danzhou probably failed to expand its ranges into mainland China because of small population size, weaker dispersal capacity, and the barrier of the Qiongzhou Strait.

Genetic differentiation and phylogeographical structure of the Brachionus calyciflorus complex in eastern China

“…2007). Similarly, in an earlier study, we also found a remarkable genetic differentiation in space in the rotifer B. calyciflorus (Xiang et al. 2010).…”

Coal fly ash effluent affects the distributions of Brachionus calyciflorus sibling species

“…It is known that COI sequence divergences ranged from 7.2% to 26.8% and from 22.8% to 25.6% among B. calyciflorus and B. plicatilis sibling species, respectively (Derry et al, 2003;Gilbert and Walsh, 2005;Li et al, 2008;Xiang et al, 2010Xiang et al, , 2011. In this study, COI sequence divergence ranged from 11.8% to 17.8% between the two clades, indicating that they are two sibling species of the B. calyciflorus complex.…”

“…Due to their cosmopolitan distribution, shorter generation time, smaller body size (about 150 μm), rapid frequency of reproduction, professional endorsement of toxicological evaluations and feasibility of cultures in the laboratory, rotifers, especially Brachionus calyciflorus and Brachionus plicatilis, are frequently used for aquatic ecotoxicology (Snell and Janssen, 1995). In the past two decades, accumulating evidence has shown that many rotifer species, such as B. plicatilis and B. calyciflorus, traditionally categorized as cosmopolitan, are now recognized as cryptic species complexes (e.g., Ciros-Pérez et al, 2001;Derry et al, 2003;Gilbert and Walsh, 2005;Gómez et al, 1995Gómez et al, , 2002aGómez et al, , 2002bLi et al, 2008;Xiang et al, 2010). Toxicity tests have shown that four sibling species in B. plicatilis species complex displayed different sensitivities to Corexit 9500A s , propylene glycol and Macondo oil (Rico-Martínez et al, 2013), but the differences in the sensitivities in life table demographic parameters between sibling species in B. plicatilis or B. calyciflorus species complex to fly ash effluent remains unknown.…”

Differences in life history characteristics between two sibling species inBrachionus calycifloruscomplex from tropical shallow lakes

“…In the past two decades, facilitated through technical advances such as PCR and direct DNA sequencing, many phylogenetic, phylogeographic and population genetic studies discovered many cryptic lineages, which were genetically divergent, but morphologically similar (Pfenninger and Schwenk, 2007). Cryptic species are distributed among major metazoan taxa including rotifers such as Brachionus plicatilis, Keratella cochlearis, Brachionus calyciflorus, Epiphanes senta, Rotaria rotatoria and some categories of Adineta Go´mez and Snell, 1996; Ciros-Pe´rez et al, 2001a; Go´mez et al, 2002;Derry et al, 2003;Gilbert and Walsh, 2005;Cheng et al, 2008;Li et al, 2008;Fontaneto et al, 2009Fontaneto et al, , 2011Li et al, 2010;Xiang et al, 2010Xiang et al, , 2011aXiang et al, , 2011b. The research of cryptic species, especially rotifer cryptic species, not only are needed for studying species diversity, but also help us understand the mechanisms of species coexistence, niche differentiation and speciation.…”