Abstract
Microorganisms, including rotifers, are thought to be capable of long distance dispersal. Therefore, they should show little population genetic structure due to high gene flow. Nevertheless, substantial genetic structure has been reported among populations of many taxa. In rotifers, genetic studies have focused on planktonic taxa leaving sessile groups largely unexplored. Here, we used COI gene and ITS region sequences to study genetic structure and delimit cryptic species in two sessile species (Limnias melicerta [32 populations]; L. ceratophylli [21 populations]). Among populations, ITS region sequences were less variable as compared to those of the COI gene (ITS; L. melicerta: 0–3.1% and L. ceratophylli: 0–4.4%; COI; L. melicerta: 0–22.7% and L. ceratophylli: 0–21.7%). Moreover, L. melicerta and L. ceratophylli were not resolved in phylogenetic analyses based on ITS sequences. Thus, we used COI sequences for species delimitation. Bayesian Species Delimitation detected nine putative cryptic species within L. melicerta and four putative cryptic species for L. ceratophylli. The genetic distance in the COI gene was 0–15.4% within cryptic species of L. melicerta and 0.5–0.6% within cryptic species of L. ceratophylli. Among cryptic species, COI genetic distance ranged 8.1–21.9% for L. melicerta and 15.1–21.2% for L. ceratophylli. The correlation between geographic and genetic distance was weak or lacking; thus geographic isolation cannot be considered a strong driver of genetic variation. In addition, geometric morphometric analyses of trophi did not show significant variation among cryptic species. In this study we used a conservative approach for species delimitation, yet we were able to show that species diversity in these sessile rotifers is underestimated.
Highlights
Microorganisms are capable of long distance dispersal it has been suggested that they have cosmopolitan distributions with little geographic structure [1,2,3,4]
For the c oxidase subunit I (COI) gene, sequences were analyzed for 72 individuals from Limnias melicerta and 25 individuals from L. ceratophylli
Using the Bayesian Species Delimitation (BSD) delimitation method, nine putative cryptic species for L. melicerta and four putative cryptic species for L. ceratophylli were identified based on COI gene sequences
Summary
Microorganisms are capable of long distance dispersal it has been suggested that they have cosmopolitan distributions with little geographic structure [1,2,3,4]. National Institutes on Minority Health and Health Disparities (2G12MD007592) [a component of the National Institutes of Health (NIH)]. Funds from this grant were used by the authors for data collection and analysis. Sigma Xi Grants-in-Aid of Research (G2012162274 to AK). Funds from this grant were used for data collection. Dodson Research Grant from University of Texas at El Paso to AK (2014 and 2015). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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