Grosberg Richard K, Levitan Don R, Cameron Brenda B
Center for Population Biology, University of California, Davis, California, 95616.
Department of Biological Sciences, Florida State University, Tallahassee, Florida, 32306-2043.
Evolution. 1996 Dec;50(6):2221-2240. doi: 10.1111/j.1558-5646.1996.tb03612.x.
Many sedentary, clonal marine invertebrates compete intensively with conspecifics for habitable space. Allorecognition systems mediate the nature and outcome of these intraspecific competitive interactions, such that the initiation of agonistic behavior and the potential for intergenotypic fusion depend strongly on the relatedness of the contestants. The dependence of these behaviors on relatedness, along with the extraordinary precision with which self can be discriminated from nonself, suggest that allorecognition systems are highly polymorphic genetically. However, allotypic specificity of this sort could be produced by any number of genetic scenarios, ranging from relatively few loci with abundant allelic variation to numerous loci with relatively few alleles per locus. At this point, virtually nothing is known of the formal genetics of allorecognition in marine invertebrates; consequently, the evolutionary dynamics of such systems remain poorly understood. In this paper, we characterize the formal genetics of allorecognition in the marine hydrozoan Hydractinia symbiolongicarpus. Hydractinia symbiolongicarpus colonizes gastropod shells occupied by hermit crabs. When two or more individuals grow into contact, one of three outcomes ensues: fusion (compatibility), transitory fusion (a temporary state of compatibility), and rejection (incompatibility, often accompanied by the production of agonistic structures termed hyperplastic stolons). Observed patterns of compatibility between unrelated, half-sib pairs, and full-sib pairs show that unrelated and half-sib pairs under laboratory culture have a very low probability of being fusible, whereas full sibs have a roughly 30% rate of fusion in experimental pairings. The genetic simulations indicate that roughly five loci, with 5-7 alleles per locus, confer specificity in this species. In ecological terms, the reproductive ecology of H. symbiolongicarpus should promote the cosettlement of kin, some of which should be full sibs, and some half sibs. Thus, there is potential for kin selection to play a major role in the evolution of the H. symbiolongicarpus allorecognition system. In genetic terms, this system conforms to theoretical predictions for a recognition system selected to distinguish among classes of kin, in addition to self from nonself.
许多 sedentary、克隆性的海洋无脊椎动物会与同种个体激烈竞争可居住空间。异体识别系统介导这些种内竞争相互作用的性质和结果，因此，攻击行为的引发以及基因型间融合的可能性在很大程度上取决于竞争者之间的亲缘关系。这些行为对亲缘关系的依赖性，以及能够极其精确地区分自我与非自我的能力，表明异体识别系统在基因上具有高度多态性。然而，这种异型特异性可以由多种遗传情况产生，从具有丰富等位基因变异的相对较少的基因座到每个基因座具有相对较少等位基因的众多基因座。目前，对于海洋无脊椎动物异体识别的形式遗传学几乎一无所知；因此，此类系统的进化动态仍然知之甚少。在本文中，我们描述了海洋水螅虫 Hydractinia symbiolongicarpus 异体识别的形式遗传学。Hydractinia symbiolongicarpus 会在寄居蟹占据的腹足纲贝壳上定殖。当两个或更多个体生长到相互接触时，会出现三种结果之一：融合（相容性）、短暂融合（一种暂时的相容状态）和排斥（不相容，通常伴随着产生被称为增生性茎的攻击结构）。观察到的无亲缘关系个体、半同胞对和全同胞对之间的相容模式表明，在实验室培养条件下，无亲缘关系个体和半同胞对融合的概率非常低，而全同胞在实验配对中的融合率约为 30%。遗传模拟表明，该物种中大约五个基因座，每个基因座有 5 - 7 个等位基因，赋予了特异性。从生态学角度来看，Hydractinia symbiolongicarpus 的生殖生态应该会促进亲属的共同定殖，其中一些应该是全同胞，一些是半同胞。因此，亲缘选择有可能在 Hydractinia symbiolongicarpus 的异体识别系统进化中发挥重要作用。从遗传学角度来看，这个系统符合理论预测，即一个被选择用于区分亲属类别以及自我与非自我的识别系统。 （注：原文中“sedentary”可能有误，推测为“sedentary”的错误拼写，正确的可能是“sedentary”，但未找到确切含义，暂保留原文形式。）
