Ecological speciation in a cyclic parthenogen: Sexual capability of experimental hybrids between Daphnia pulex and Daphnia pulicaria
Ecological speciation in a cyclic parthenogen: Sexual capability of experimental hybrids between Daphnia pulex and Daphnia pulicaria
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DOI：
10.4319/lo.2009.54.2.0492
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发表时间：
2009-03-01
影响因子：
4.5
通讯作者：
Dudycha, Jeffry L.
中科院分区：
文献类型：
--
作者：
Heier, Christopher R.;Dudycha, Jeffry L.
蚤状蚤（Daphnia pulex）和蚤状蚤（Daphnia pulicaria）是广泛分布于北美淡水的周期性孤雌生殖甲壳动物。D. pulex和D.在野外，蚤状蚤属是很常见的，种群遗传分析表明，它们总是专性无性繁殖。在这项研究中，我们的特征性的三个方面（性卵生产，男性生产，有性后代生产）的生活史在实验繁殖的杂交，以确定生殖隔离的程度。与自然杂交形成鲜明对比的是，在我们培育的53个F-1杂交种中，没有一个是专性无性的。无论是男性生产还是有性产卵都不受杂交限制。我们的杂交试验表明，产生或回交F-1代没有什么困难。此外，我们还能成功地将F（1）杂交产生F-2后代。我们没有发现证据表明，这些类群是生殖不兼容，尽管其他报告的明显适应性遗传分歧。我们的结论是D. pulex和D.蚤状菌属是由于生态分离，而不是遗传不亲和。根据我们的研究结果和发表的数据，这些类群的植物地理学和育种系统，无论是由于杂交不育，也没有直接遗传的性别限制减数分裂抑制基因似乎提供了一个令人满意的解释无性的野生杂交种。我们提出了另一种假设，其中一个亲本类群入侵人口的其他，由此产生的F-1杂交回减数分裂抑制因子的载体，并由此产生的后代，高健身无性克隆最终取代其余的人口。
Daphnia pulex and Daphnia pulicaria are cyclically parthenogenetic crustaceans that are distributed widely in North American freshwaters. Hybrids of D. pulex and D. pulicaria are common in the wild, where population genetic analyses have indicated that they are invariably obligately asexual. In this study, we characterize three sexual aspects (sexual egg production, male production, and sexual offspring production) of life history in experimentally bred hybrids to determine the degree of reproductive isolation. In striking contrast to natural hybrids, out of the 53 F-1 hybrids we bred, none were obligately asexual. Neither male production nor sexual egg production was limited by hybridization. Our experimental crosses showed that there was little difficulty in generating or backcrossing the F-1 generation. In addition, we were able to intercross F(1)s successfully to produce F-2 progeny. We found no evidence that these taxa are reproductively incompatible, despite other reports of apparent adaptive genetic divergence. We conclude that reproductive isolation between D. pulex and D. pulicaria is due to ecological separation, not genetic incompatibility. In light of our results and published data on the biogeography and breeding system of these taxa, neither sterility due to hybridization nor direct inheritance of a sex-limited meiosis suppressor appears to provide a satisfactory explanation for the asexuality of wild hybrids. We propose an alternate hypothesis in which one parental taxon invades a population of the other, the resulting F-1 hybrids cross back to a carrier of a meiosis suppressor, and out of the resulting progeny, a high-fitness asexual clone eventually displaces the rest of the population.