Postglacial recolonization of eastern Blacknose Dace,Rhinichthys atratulus(Teleostei: Cyprinidae), through the gateway of New England

During the last ice age, much of North America far south as 40°N was covered by glaciers (Hewitt 2000). About 20,000 years ago, as the glaciers retreated, the hydrologic landscape changed dramatically creating waterways for fish dispersal. The number of populations responsible for recolonization and the regions from which they recolonized are unknown for many freshwater fishes living in New England and southeastern Canada. The Blacknose Dace,Rhinichthys atratulus, is one of the freshwater fish species that recolonized this region. We hypothesize that the earliest deglaciated region, modern-day Connecticut, was recolonized byR. atratulusvia a single founding event by a single population. In this paper, we test this hypothesis phylogenetically with regard to the major drainage basins within Connecticut. The mitochondrial DNA exhibits low nucleotide diversity, high haplotype diversity, and a dominant haplotype found across the state. A small percentage of individuals in the Housatonic drainage basin, however, share a haplotype with populations in New York drainage basins, a haplotype not found elsewhere in Connecticut's drainage basins. We calculated a range for the rate of divergence for NADH dehydrogenase subunit 2 (nd2) and control region (ctr) of 4.43-6.76% and 3.84-8.48% per million years (my), respectively. While this range is higher than the commonly accepted rate of 2% for mitochondrial DNA, these results join a growing list of publications finding high rates of divergence for various taxa (Peterson and Masel 2009). The data support the conclusion that Connecticut as a whole was recolonized initially by a single founding event that came from a single refugium. Subsequently, the Housatonic basin alone experienced a secondary recolonization event.     

水温变化对绥芬河滩头雅罗鱼产卵的影响

The Dace ( Leucisus brandti Dybowski) was a migration fish in Suifen river. The Dace can spawn at the water temperatures from 7℃ to 25℃. Changing of water temperature is the leading factor cause the spawning population to ovulate. However, high or low current water temperature had no obvious effectuation on ovulating behavior of Dace. The ovulation of the Dace often occurred in the evening or next morning after the water temperature rapidly in creased. The fish spawning often occurred as the water temperature decreased at first, after a period of steady low water temperature, then increased. A massive ovulating action began at the time. If the rising of water temperature happens only after a period of steady level without any decreasing of the water temperature, the change can not stimulate ovulation of the Daces. Usually, every large scale ovulate can sustain for 1 or 2 days. The peak time of ovulation often appears in 48 hours after the water temperature increases. Once the spawning population began to ovulate, their actions will be very intense, so that even catching action of human on them can not prevent the ovulation. The test of artificial induced ovulation showed that only when variation of water temperature were more than 10℃ ( increased degree+decreased degree), the Dace would ovulate. The Dace began to ovulate in 12～36 hours after the water temperature's change. The efficient time was shorter and the ovulation rate was higher the variation of water temperature were greater. At the range from 8℃ to 24℃, as high or low water temperature had no effect on the efficient time stimulating ovulate, the Dace can not ovulate out of the temperature range.     

Assessing phylogeographic variation in the Rosyside Dace (Teleostei,Leuciscidae), a widespread morphologically variable taxon

Clinostomus (Leuciscidae) is a wide-ranging freshwater fish genus that occurs throughout eastern North America and southern portions of Canada with two species currently recognized: C. elongatus and C. funduloides. A previous taxonomic study of C. funduloides recognized two subspecies (estor and funduloides) and one diagnosed, but undescribed subspecies based on morphological characteristics and geographic distribution. In this study, we used three molecular markers (cytochrome b, S7 intron 1 and growth hormone intron 4) to test the three lineage hypothesis and evaluate genetic variation of C. funduloides across the range using Bayesian inference. Our results indicate that C. funduloides is not monophyletic, as individuals of C. elongatus nest within C. funduloides in both the mtDNA and nDNA phylogenetic analyses, although the position of C. elongatus varies between data sets. In addition, some of the recovered clades are deeply divergent from one another, further supporting the distinctiveness of many of the populations. Overall, these results suggest that subspecies designations are not warranted and a taxonomic revision is needed as Clinostomus is likely more diverse than is currently recognized.     

基于线粒体Cyt b序列对新疆额尔齐斯河贝加尔雅罗鱼遗传结构的分析

采用线粒体Cyt b基因序列对额尔齐斯河流域的青河(QH,18尾)、哈巴河(HBH,21尾)、185团(185T,18尾)和乌伦古湖(WLG,20尾)4个贝加尔雅罗鱼(Leuciscus leuciscus baicalensis)群体进行了遗传结构的比较分析。在片段长度为1 109 bp的同源序列上,77尾个体共检测到54种单倍型,其中共享单倍型7个,总单倍型多样性指数(Hd)、总核苷酸多样性指数(π)和平均核苷酸差异数(K)分别为0.981 9、0.008 21和9.091,且185团群体单倍型多样性指数和核苷酸多样性指数最高、青河群体最低。4个群体间遗传距离在0.006~0.011之间,基于Kimura 2-parameter法构建的单倍型邻接关系树分为3支,群体间遗传关系和地理分布没有明显的相关性。AMOVA分析显示额尔齐斯河流域贝加尔雅罗鱼遗传差异极显著(P0.01)。青河和乌伦古湖群体基因流(Nm)远高于其他群体间,推测乌伦古河或许是二者进行基因交流的渠道。尽管单倍型核苷酸不配对分布呈双峰,但偏差平方和(Q)与粗糙指数(r)均不显著(P0.05),且Tajima′s D和Fu′s Fs检验也均显著偏离中性,结合群体呈现高单倍型多样性和低核苷酸多样性的特点,推测贝加尔雅罗鱼经历了群体扩张事件。参考已校正的鲤科鱼类Cyt b基因0.76%/Ma的进化速率,估算群体扩张的时间大约在1.97 Ma前的更新世中晚期,推测该时期阿尔泰山地区发生的冰川作用和频繁的古地震造成的地理隔离和融合可能是贝加尔雅罗鱼发生群体扩张的重要原因。