Genetic differentiation and phylogeography of rotifer Polyarthra
dolichoptera and P. vulgaris complexes between Southern China and
eastern North America: high intercontinental differences
AbstractGenetic differentiations and phylogeographical patterns of small
organisms may be shaped by spatial isolation, environmental gradients
and gene flow. However, knowledge about genetic differentiation of
rotifers on intercontinental gradient is still limited. Polyarthra
dolichoptera and P. vulgaris are cosmopolitan rotifers and tolerant to
environmental changes, offering an excellent model to address the
research gap. Here, we investigated the populations in Southern China
and eastern North America, and evaluated the phylogeographical patterns
from their geographical range sizes, geographic-genetic distance
relationships and their response to spatial-environmental factors. Using
mitichondrial cytochrome c oxidase subunit I gene as the DNA marker, we
analyzed a total of 170 individuals. At least 24 putative cryptic
species, including 20 of P. dolichoptera and 4 of P. vulgaris were
detected based on three delimitation methods. Our results showed that
some cryptic species were widely distributed but most of them were
limited to single areas. The divergence of P. dolichoptera and P.
vulgaris complexes indicated that gene flow between continents was
limited while that within each continent was stronger. Furthermore, on
the intercontinental scale spatial distance had a stronger influence
than physicochemical variables on the genetic differentiations of P.
dolichoptera and P. vulgaris complexes. However, the relationship
between genetic distance and geographic distance was not continuously
linear and the P. dolichoptera data best fitted the power-law model.
This might be due to the effects of habitat heterogeneity, long-distance
colonization and oceanographic barriers. Outliers above the correlation
line between geographic distance and genetic distance suggest a
significant dispersal barrier on large geographic scales studies.