Riginos C, Cunningham C W
Department of Biology, Box 90338, Duke University, Durham, NC 27708, USA.
Mol Ecol. 2005 Feb;14(2):381-400. doi: 10.1111/j.1365-294X.2004.02379.x.
Few marine hybrid zones have been studied extensively, the major exception being the hybrid zone between the mussels Mytilus edulis and Mytilus galloprovincialis in southwestern Europe. Here, we focus on two less studied hybrid zones that also involve Mytilus spp.; Mytilus edulis and Mytilus trossulus are sympatric and hybridize on both western and eastern coasts of the Atlantic Ocean. We review the dynamics of hybridization in these two hybrid zones and evaluate the role of local adaptation for maintaining species boundaries. In Scandinavia, hybridization and gene introgression is so extensive that no individuals with pure M. trossulus genotypes have been found. However, M. trossulus alleles are maintained at high frequencies in the extremely low salinity Baltic Sea for some allozyme genes. A synthesis of reciprocal transplantation experiments between different salinity regimes shows that unlinked Gpi and Pgm alleles change frequency following transplantation, such that post-transplantation allelic composition resembles native populations found in the same salinity. These experiments provide strong evidence for salinity adaptation at Gpi and Pgm (or genes linked to them). In the Canadian Maritimes, pure M. edulis and M. trossulus individuals are abundant, and limited data suggest that M. edulis predominates in low salinity and sheltered conditions, whereas M. trossulus are more abundant on the wave-exposed open coasts. We suggest that these conflicting patterns of species segregation are, in part, caused by local adaptation of Scandinavian M. trossulus to the extremely low salinity Baltic Sea environment.
很少有海洋杂交区得到广泛研究，主要的例外是欧洲西南部贻贝紫贻贝（Mytilus edulis）和地中海贻贝（Mytilus galloprovincialis）之间的杂交区。在此，我们聚焦于另外两个较少被研究的也涉及贻贝属物种的杂交区；紫贻贝和翡翠贻贝（Mytilus trossulus）在大西洋的西海岸和东海岸同域分布并杂交。我们回顾了这两个杂交区的杂交动态，并评估了局部适应在维持物种边界中的作用。在斯堪的纳维亚半岛，杂交和基因渐渗非常广泛，以至于未发现具有纯翡翠贻贝基因型的个体。然而，对于一些等位酶基因，翡翠贻贝的等位基因在盐度极低的波罗的海以高频率维持。不同盐度条件下相互移植实验的综合结果表明，不连锁的葡萄糖磷酸异构酶（Gpi）和磷酸葡萄糖变位酶（Pgm）等位基因在移植后频率发生变化，使得移植后的等位基因组成类似于在相同盐度下发现的本地种群。这些实验为Gpi和Pgm（或与其连锁的基因）的盐度适应性提供了有力证据。在加拿大沿海省份，纯紫贻贝和翡翠贻贝个体数量众多，有限的数据表明紫贻贝在低盐度和隐蔽条件下占主导，而翡翠贻贝在暴露于海浪的开阔海岸更为丰富。我们认为，这些相互矛盾的物种隔离模式部分是由斯堪的纳维亚半岛的翡翠贻贝对波罗的海极低盐度环境的局部适应所导致的。
