The evolution from females to hermaphrodites results in a sexual conflict over mating in androdioecious nematode worms and clam shrimp
The evolution from females to hermaphrodites results in a sexual conflict over mating in androdioecious nematode worms and clam shrimp
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DOI：
10.1111/j.1420-9101.2009.01919.x
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发表时间：
2010-03-01
影响因子：
2.1
通讯作者：
Chasnov, J. R.
中科院分区：
文献类型：
--
作者：
Chasnov, J. R.
线虫秀丽隐杆线虫和蛤虾Eulimnadia texana是两种研究比较充分的雌雄异株物种，大多数是自体雌雄同体，很少有雄性。为了理解雄配子体的进化过程，本文建立了一个简单的两步进化数学模型，描述了雄配子体从雌雄同体到自花雌雄同体的进化过程。首先，如果生殖保证的好处超过成本，突变的女性能够兼性自花受精的频率增加。第二，如果自交后代的适合度超过异交后代适合度的一半，雌雄同体就成为专性的自花受精者。遗传因素对C。elegans和E.得克萨斯州的研究表明，男性可能会作为祖先的男性-女性物种的后代而存在。这些模型结合广泛的文献综述表明，在这些雌雄异株的物种交配的性冲突：选择有利于雌雄同体的自我和男性的异交。然而，雌雄同体和雄性的选择强度是不同的。不能进行异交的雄性会遭受基因死亡。雌雄同体可能永远不会遇到罕见的雄性，而那些遇到并进行异交的雄性只会产生繁殖力较低的后代。这种不对称的性冲突导致了进化上的对峙：罕见的，但持久的雄性偶尔会使常见的，但不情愿的雌雄同体受精。这种对峙的结果可能是雄异株交配系统的寿命增加。
The nematode worm Caenorhabditis elegans and the clam shrimp Eulimnadia texana are two well-studied androdioecious species consisting mostly of self-fertilizing hermaphrodites and few males. To understand how androdioecy can evolve, a simple two-step mathematical model of the evolutionary pathway from a male-female species to a selfing-hermaphrodite species is constructed. First, the frequency of mutant females capable of facultative self-fertilization increases if the benefits of reproductive assurance exceed the cost. Second, hermaphrodites become obligate self-fertilizers if the fitness of selfed offspring exceeds one-half the fitness of outcrossed offspring. Genetic considerations specific to C. elegans and E. texana show that males may endure as descendants of the ancestral male-female species. These models combined with an extensive literature review suggest a sexual conflict over mating in these androdioecious species: selection favours hermaphrodites that self and males that outcross. The strength of selection on hermaphrodites and males differs, however. Males that fail to outcross suffer a genetic death. Hermaphrodites may never encounter a rare male, and those that do and outcross only bear less fecund offspring. This asymmetric sexual conflict results in an evolutionary stand-off: rare, but persistent males occasionally fertilize common, but reluctant hermaphrodites. A consequence of this stand-off may be an increase in the longevity of the androdioecious mating system.