Abstract：
Inbreeding and outbreeding depression are dynamic forms of selection critical to mating system evolution and the efficacy of conservation biology. Most evidence on how the relative severity and timing of these forces are shaped is confined to self-fertilization, distant outcrossing, and intermediate \'optimal outcrossing\' in hermaphrodites. We tested the notion that closed population demographics may reduce and delay the costs of inbreeding relative to distant outbreeding in an intertidal copepod with separate sexes and a biphasic larval / post-metamorphic life-history (Tigriopus californicus). At three lifecycle stages (fecundity, metamorphosis, and post-metamorphosis), we quantified the effects of inbreeding and outbreeding in crosses with varying degrees of recent common ancestry. Although inbreeding and outbreeding depression have distinct genetic mechanisms, both manifested the same stage-specific consequences for fitness. Inbreeding and outbreeding depression were not apparent for fecundity, post-metamorphic survival, sex ratio, or the ability to acquire mates, but inbreeding between full siblings and outbreeding between interpopulation hybrids reduced the fraction of offspring that completed metamorphosis by 32% and 47%, respectively. On average, the effects of inbreeding on metamorphic rate were weaker and nearly twice as variable among families than those of outbreeding, suggesting genetic load was less pervasive than the incompatibilities accrued between divergent populations. Overall, our results indicate the transition from larval to juvenile life stages is markedly susceptible to both inbreeding and outbreeding depression in T. californicus. We suggest stage-specific selection acting concurrently with the timing of metamorphosis may be an instrumental factor shaping reproductive optima in species with complex life-histories.
摘要：
近交和近交凹陷是对交配系统进化和保护生物学功效至关重要的动态选择形式。关于这些力量的相对严重程度和时间如何形成的大多数证据仅限于自我受精，遥远的穿越，和雌雄同体中的“最佳异交”。我们测试了这样一种观念，即封闭的种群人口统计学可以降低和延迟近亲繁殖的成本，相对于具有不同性别和双相幼虫/变态后生活史的潮间带co足动物（Tigriopuscalifornicus）的远亲繁殖。在三个生命周期阶段(繁殖力，变态,和后变态)，我们量化了近亲繁殖和近亲繁殖在不同程度的近亲繁殖中的影响。尽管近亲繁殖和近亲繁殖抑郁症具有不同的遗传机制，两者都表现出相同的特定阶段的健身后果。近交和近交的繁殖力不明显，变质后的生存，性别比例,或者获得配偶的能力，但是完整兄弟姐妹之间的近亲繁殖和种群间杂种之间的近亲繁殖将完成变态的后代比例降低了32％和47％，分别。平均而言,近亲繁殖对变质率的影响较弱，家庭间的变化比近亲繁殖的近两倍，表明遗传负荷比不同种群之间产生的不相容性更不普遍。总的来说,我们的结果表明，从幼虫到幼年生命阶段的过渡明显容易受到T.californicus近亲繁殖和近亲繁殖抑郁症的影响。我们建议，特定阶段的选择与变态的时间同时发生，可能是影响具有复杂生活史的物种生殖最佳的重要因素。
