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The effects of functional response and host abundance fluctuations on genetic rescue in parasitoids with single‐locus sex determination
Ecology and Evolution ( IF 2.3 ) Pub Date : 2020-10-14 , DOI: 10.1002/ece3.6889
Etsuko Nonaka 1, 2 , Veijo Kaitala 3
Affiliation  

Many parasitoids have single‐locus complementary sex determination (sl‐CSD), which produces sterile or inviable males when homozygous at the sex determining locus. A previous study theoretically showed that small populations have elevated risks of extinction due to the positive feedback between inbreeding and small population size, referred to as the diploid male vortex. A few modeling studies have suggested that the diploid male vortex may not be as common because balancing selection at sex determining loci tends to maintain high allelic diversity in spatially structured populations. However, the generality of the conclusion is yet uncertain, as they were drawn either from models developed for particular systems or from a general‐purpose competition model. To attest the conclusion, we study several well‐studied host–parasitoid models that incorporate functional response specifying the number of attacked hosts given a host density and derive the conditions for a diploid male vortex in a single population. Then, we develop spatially structured individual‐based versions of the models to include female behavior, diploid male fertility, and temporal fluctuations. The results show that producing a handful of successful offspring per female parasitoid could enable parasitoid persistence when a typical number of CSD alleles are present. The effect of functional response depends on the levels of fluctuations in host abundance, and inviable or partially fertile diploid males and a small increase in dispersal can alleviate the risk of a diploid male vortex. Our work supports the generality of effective genetic rescue in spatially connected parasitoid populations with sl‐CSD. However, under more variable climate, the efficacy of the CSD mechanism may substantially decline.

中文翻译:


功能反应和宿主丰度波动对单基因座性别决定寄生蜂遗传拯救的影响



许多寄生蜂具有单基因座互补性别决定(sl-CSD),当性别决定基因座纯合时,它会产生不育或无法存活的雄性。先前的一项研究从理论上表明,由于近亲繁殖和小种群规模之间的正反馈(称为二倍体雄性漩涡),小种群灭绝的风险较高。一些模型研究表明,二倍体雄性涡旋可能并不常见,因为性别决定位点的平衡选择往往会在空间结构群体中保持较高的等位基因多样性。然而,结论的普遍性尚不确定,因为它们要么是从为特定系统开发的模型中得出的,要么是从通用竞争模型中得出的。为了证明这一结论,我们研究了几种经过充分研究的寄主-寄生蜂模型,这些模型结合了功能反应,指定了给定寄主密度的受攻击寄主的数量,并推导了单个种群中二倍体雄性涡旋的条件。然后,我们开发了基于空间结构的个体版本的模型,包括女性行为、二倍体男性生育力和时间波动。结果表明,当存在典型数量的 CSD 等位基因时,每个雌性寄生蜂产生少数成功的后代可以使寄生蜂持续存在。功能反应的效果取决于宿主丰度的波动水平,不能存活或部分可育的二倍体雄性以及扩散的小幅增加可以减轻二倍体雄性涡流的风险。我们的工作支持在具有 sl-CSD 的空间连接寄生蜂种群中进行有效遗传拯救的普遍性。然而,在更加多变的气候下,CSD机制的有效性可能会大幅下降。
更新日期:2020-12-03
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