Lee Hyuk Je, Boulding Elizabeth G
Department of Integrative Biology, University of Guelph, ON, Canada.
Mol Ecol. 2009 May;18(10):2165-84. doi: 10.1111/j.1365-294X.2009.04169.x. Epub 2009 Apr 1.
We investigated the effect of development mode on the spatial and temporal population genetic structure of four littorinid gastropod species. Snails were collected from the same three sites on the west coast of Vancouver Island, Canada in 1997 and again in 2007. DNA sequences were obtained for one mitochondrial gene, cytochrome b (Cyt b), and for up to two nuclear genes, heat shock cognate 70 (HSC70) and aminopeptidase N intron (APN54). We found that the mean level of genetic diversity and long-term effective population sizes (N(e)) were significantly greater for two species, Littorina scutulata and L. plena, that had a planktotrophic larval stage than for two species, Littorina sitkana and L. subrotundata, that laid benthic egg masses which hatched directly into crawl-away juveniles. Predictably, two poorly dispersing species, L. sitkana and L. subrotundata, showed significant spatial genetic structure at an 11- to 65-km geographical scale that was not observed in the two planktotrophic species. Conversely, the two planktotrophic species had more temporal genetic structure over a 10-year interval than did the two direct-developing species and showed highly significant temporal structure for spatially pooled samples. The greater temporal genetic variation of the two planktotrophic species may have been caused by their high fecundity, high larval dispersal, and low but spatially correlated early survivorship. The sweepstakes-like reproductive success of the planktotrophic species could allow a few related females to populate hundreds of kilometres of coastline and may explain their substantially larger temporal genetic variance but lower spatial genetic variance relative to the direct-developing species.
我们研究了发育模式对四种滨螺科腹足类物种的时空种群遗传结构的影响。1997年和2007年，从加拿大温哥华岛西海岸的相同三个地点采集了蜗牛样本。获得了一个线粒体基因细胞色素b（Cyt b）以及多达两个核基因热休克同源蛋白70（HSC70）和氨肽酶N内含子（APN54）的DNA序列。我们发现，具有浮游性幼虫阶段的两种滨螺，即粗糙滨螺（Littorina scutulata）和丰满滨螺（L. plena），其遗传多样性平均水平和长期有效种群大小（N(e)）显著高于另外两种滨螺，即产底栖卵块并直接孵化出可爬行幼体的锡特卡滨螺（Littorina sitkana）和近圆滨螺（L. subrotundata）。不出所料，两种扩散能力较差的滨螺，即锡特卡滨螺和近圆滨螺，在11至65公里的地理尺度上表现出显著的空间遗传结构，而在两种具有浮游性幼虫阶段的滨螺中未观察到这种结构。相反，在10年的时间间隔内，两种具有浮游性幼虫阶段的滨螺比两种直接发育的滨螺具有更多的时间遗传结构，并且对于空间合并样本表现出高度显著的时间结构。两种具有浮游性幼虫阶段的滨螺更大的时间遗传变异可能是由它们的高繁殖力、高幼虫扩散能力以及低但空间相关的早期存活率造成的。具有浮游性幼虫阶段的滨螺类似抽奖式的繁殖成功可能使少数相关雌性个体在数百公里的海岸线上定居，这可能解释了它们相对于直接发育的物种在时间遗传方差上大得多但空间遗传方差较低的原因。
