Genetic variation and clonal differentiation in the Daphnia population of the Greifensee, a pre-alpine Swiss lake
Genetic variation and clonal differentiation in the Daphnia population of the Greifensee, a pre-alpine Swiss lake
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瑞士阿尔卑斯山前湖泊格赖芬湖水蚤种群的遗传变异和克隆分化
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发表时间：
2000
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通讯作者：
Hans Rudolf Bürgi
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作者：
P. Spaak;L. Eggenschwiler;Hans Rudolf Bürgi
种间杂交是水蚤种群中的一种常见现象（ScHWE：--IK & SPAAK 1997）。在一些欧洲国家，来自D. galeata复合体已经被确定（例如德国、瑞典、荷兰、捷克共和国、波兰、法国和英国），在其中几个中杂种是最常见的分类群（WOLF 1987，SPAAK 1996）。然而，在这些国家中，杂交水蚤只在有限数量的湖泊中被描述过。一个重要的原因是很难区分paremal种和杂交种的基础上形态特征（FLOGNER 1993）。WOLF & MORT（1986）指出，Got等位酶可用于区分D.盔状复合体自rhen以来，许多研究人员使用这种相对简单的方法来识别和定量他们系统中的杂交水蚤。最近，GmBLER（1997）表明Got在所有情况下都不是一个好的标记位点。Got-F等位基因虽然是D. galeata，在D.来自德国南部湖泊的透明藻克隆。但Got-5等位基因（WoLF & MoRT（1986）描述为D. hyalína，也是D.产于德国南部的透明玻璃。GrEGLER（1997）建议使用等位酶Ao，因为D. ga/eata复合体（如D. galeata、毛萼藓D. cucullata和D. hyalina）对于一个或多个独特等位基因是固定的。使使用标记基因座区分亲本物种和杂种变得复杂的另一个因素是回交的产生。最近的研究（SPAAK 1996，ScHWENK 1997）表明，渐渗是在D.盔状花序种复合体。然而，这些回交不能仅用一个物种特异性位点来鉴定，因为这些回交中的50%具有亲本基因型之一。在瑞士阿尔卑斯山北方的大湖中，D. galeata复合体（BüRGI et al. 1985）。很可能这些湖里也有杂交种。本研究的目的是描述这些湖泊之一（格赖芬湖）的水蚤种群的遗传组成。我们推测，在这个湖，其中D。galeata和D. hyalina（BüRGI et al.1985），杂交D. galeata x D.玻璃体也会出现。通过使用两个物种特异性的遗传标记，（Got和Ao），我们检查是否回交发生，并在什么速度。最后，我们测试了水蚤种群的遗传组成是否与沉积物上方的其他水柱不同，以测试是否发生基因型特异性迁移模式。
Interspecific hybridization is a common phenomenon in Daphnia populations (ScHWE:--IK & SPAAK 1997). In several European coumries, populations from the D. galeata complex have been idemified (e.g. Germany, Sweden, The Netherlands, Czech Republic, Poland, France and England), in several of which hybrids are the most common taxa (WOLF 1987, SPAAK 1996). However, hybrid daphnids have been described only for a limited number of lakes in each of these countries. An important reason for this is the difficult distinction between paremal species and hybrids based on morphological characters (FLOGNER 1993). WOLF & MORT (1986) showed that the allozyme Got could be used to distinguish between the hybrids and parental species of the D. galeata complex. Since rhen, many researchers have used this relatively easy method to idemifY and quantifY hybrid daphnids in their system. Recently, GmBLER (1997) showed that Got is nor a good marker locus in all cases. The Got-F allele, which was rhoughr to be unique for D. galeata, was also found in D. hyalina clones from lakes in southern Germany. But the Got-5 allele, which was described by WoLF & MoRT (1986) as unique to D. hyalína, was also unique for D. hyalina in southern Germany. GrEGLER (1997) suggested to use the allozyme Ao because all three species in the D. ga/eata complex (e.g. D. galeata, D. cucullata and D. hyalina) are fixed for o ne or more unique alleles. Another factor complicating the use of marker loci to distinguish between parental species and hybrids is the production of backcrosses. Recent studies (SPAAK 1996, ScHWENK 1997) showed that introgression is an important process within rhe D. galeata species complex. However, these backcrosses cannot be identified with only one species-specific locus, since 50% of these backcrosses have one of the parental genotypes. In the large lakes o n the northern side o f the Swiss Alps, all three parental taxa of the D. galeata complex are present (BüRGI et al. 1985). Most likely there are also hybrids in these lakes. The aim of the present study is to describe the genetic composition of the Daphnia population for one of these lakes (Greifensee). We hypothesise that in this lake, in which D. galeata and D. hyalina were described (BüRGI et al. 1985), the hybrid D. galeata x D. hyalina also occurs. By using two species-specific genetic markers, (Got and Ao) we examine whether backcrossing occurs and at what rate. Lastly, we tested if the genetic composition of the Daphnia population was different just above the sediment compared to the rest of the water column, to test i f genotype specific migration patterns take place.