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首页> 外文期刊>Journal of Molluscan Studies >MULTILOCUS ALLOZYME HETEROZYGOTE DEFICIENCIES IN CREPIDULA ONYX: GEOGRAPHIC AND TEMPORAL PATTERNS AMONG ADULT SNAILS IN MISSION BAY, CALIFORNIA
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MULTILOCUS ALLOZYME HETEROZYGOTE DEFICIENCIES IN CREPIDULA ONYX: GEOGRAPHIC AND TEMPORAL PATTERNS AMONG ADULT SNAILS IN MISSION BAY, CALIFORNIA

机译：REP蛇玛瑙中的多位异体酶杂合子缺陷：加利福尼亚州MISSION BAY的成年幼鸟之间的地理和时间格局

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Although the phenomenon of multilocus heterozygote deficiencies in numerous taxonomically diverse molluscs has been studied for over 30 years it has resisted general explanation. Here we describe a case in Crepidula onyx Sowerby, a common protandrousslipper limpet on the Pacific coast of southern California. Spatial and temporal differentiation at 16 polymorphic allozyme loci were examined in samples of adult snails from three or four seasons and six localities in Mission Bay, San Diego. The populations were highly polymorphic (proportion of polymorphic loci PL = 0.65-0.69; mean individual het-erozygosity H_o = 0.13-0.29) and although there were slightly more changes in allele frequency between autumn and winter than between winter and spring, statistically significant spatial and temporal change or patterning was not detected. If the larvae are passive dispersers the lack of population structure is attributable to the fact that during any three-week period that they are in the plankton, the waters of Mission Bay are completely mixed by tidal currents. In marked contrast, statistically significant heterozygote deficiencies were found in all samples (locality and season) and subsamples (males and females). At each locality and season, deficiencieswere as pronounced in males as in females. Furthermore, at each locality, there was no increase in level of multilocus deficiency between males in one season and females in a subsequent season. We conclude that the heterozygotes had been lost in the larval planktonic stage or at the time of metamorphosis and settlement. Several hypotheses to explain the heterozygote deficiencies in adults are discussed: inbreeding, self-fertilization, presence of null alleles, allele scoring bias, aneuploidy, parentalimprinting, spatial and temporal Wahlund effects, age-effects, and direct natural selection on the marker loci. Although we can reject some of these hypotheses, others like inbreeding, require testing with markers with greater statistical power. Wahlundeffects due to inadvertent mixing of two cryptic species and/or micro-spatial population genetic structuring due to reproductive asynchronies appear unlikely causes. Natural selection against heterozygotes in the larval phase of life may account for theobservations, but selection does not appear to operate directly on any of the individual loci studied. An hypothesis is offered to explain the general selection against heterozygotes during the pelagic larval stage, and for the reverse during the sessileadult stage. Selection coefficients would, however, have to be unusually high and we conclude that we are unable satisfactorily to explain our observations.
机译：尽管已经研究了许多生物分类学多样的软体动物中的多基因座杂合子缺陷现象，但已有30多年的历史了，但这种现象一直没有得到普遍的解释。在这里，我们描述了Crepidula Cre玛瑙Sowerby的一例，这是南加州太平洋沿岸的普通长鳍sl。在圣地亚哥米申湾的三个或四个季节和六个地区的成年蜗牛样本中检查了16个多态同工酶基因座的时空分化。种群高度多态（多态位点PL的比例= 0.65-0.69;平均个体杂合子H_o = 0.13-0.29），尽管秋冬之间的等位基因频率变化比冬春之间的频率稍多，但具有统计学意义并且未检测到时间变化或模式。如果幼虫是被动扩散器，则缺乏种群结构是由于以下事实：在浮游生物中的任何三周期间，米申湾的水域都被潮流完全混合。与之形成鲜明对比的是，在所有样本（地区和季节）和子样本（雄性和雌性）中发现了统计学上显着的杂合子缺陷。在每个地方和每个季节，男性和女性的缺损都明显。此外，在每个地方，一个季节的雄性和随后一个季节的雌性之间的多位点缺乏水平没有增加。我们得出的结论是，杂合子在幼体浮游阶段或在变态和沉降时已经丢失。讨论了几种解释成人杂合子缺陷的假说：近亲繁殖，自我受精，无效等位基因的存在，等位基因评分偏差，非整倍性，亲代印迹，时空Wahlund效应，年龄效应以及对标记基因座的直接自然选择。尽管我们可以拒绝其中一些假设，但近亲繁殖等其他假设则需要使用具有更高统计功效的标记进行测试。由于两种隐性物种的无意混合和/或由于生殖异步引起的微空间种群遗传结构的瓦赫伦缺陷似乎是不太可能的原因。在生命的幼虫期对杂合子的自然选择可能是观察的原因，但选择似乎并不直接作用于所研究的任何单个基因座。提供了一个假说来解释在上层幼体阶段对杂合子的一般选择，而在芝麻阶段则相反。但是，选择系数必须非常高，我们得出的结论是，我们无法令人满意地解释我们的观察结果。

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