Rapid temporal succession identified by COI of the rotifer Brachionus calyciflorus Pallas in Xihai Pond, Beijing, China, inn relation to ecological traits

摘要

We investigated clone succession and genetic variation of the rotifer Brachionus calyciflorus, in Xihai Pond, Beijing, China, using partial sequence of the COI gene (543 bp). We sampled the rotifer population once per week for 4 weeks in the autumn of 2004, when the water temperature decreased from 27 to 17°C and algal density, correspondingly, from 5.50 × 106 to 3.14 × 106 cells·mL−1. In total of 96 samples, 15 haplotypes were identified, among which 2 distinct lineages (Lineages A and B) were revealed by phylogenetic analysis. Sequence divergence was 12.1% between the two lineages, resembling that of sibling species. The two lineages showed short-term overlap as well as displacement. In the “population” of Lineage A, different responses to environmental variation were observed in the three clades with average sequence divergence ranging from 5.2 to 7.6%. To further investigate the forces shaping the varying pattern of different haplotype clones within the “population” of Lineage A, we selected four frequently collected haplotypes and compared their growth parameters at different algal food (Chlorella pyrenoidosa) concentrations (1 × 106, 6 × 106 and 12 × 106 cells·mL−1) at 25°C or at different temperatures (15, 25 and 35°C) with algal density of 6 × 106 cells·mL−1, respectively. Data derived from life-table demography indicated that the four haplotypes had different reactions to relevant ecological parameters. BC1 clones revealed the highest frequencies, which could be explained by prolific population growth and the build-up of a large resting propagule bank. BC10 and BC11 clones, in contrast to BC1 and BC9 clones, showed no obvious responses to the environmental variations when algal density decreased below 6 × 106 cells·mL−1 or temperature decreased below 25°C.