Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia.
Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
J Hered. 2021 Nov 1;112(6):526-534. doi: 10.1093/jhered/esab048.
The ability to produce viable offspring without recently mating, either through sperm storage or parthenogenesis, can provide fitness advantages under a suite of challenging ecological scenarios. Using genetic analysis, we demonstrate that 3 wild-caught female Tree Skinks (Egernia striolata) reproduced in captivity with no access to males for over a year, and that this is best explained by sperm storage. To the best of our knowledge, this is the first time female sperm storage has been documented in any monogamous family-living reptile, including social Australian egerniine skinks (from the subfamily Egerniinae). Furthermore, by using paternal reconstruction of genotypes we show that captive-born offspring produced by the same females in the preceding year, presumably without sperm storage, were sired by different males. We qualitatively compared aspects of these females' mates and offspring between years. The parents of each litter were unrelated, but paternal and offspring genotypes from litters resulting from stored sperm were more heterozygous than those inferred to be from recent matings. Family-living egerniine skinks generally have low rates of multiple paternity, yet our study suggests that female sperm storage, potentially from outside social partners, offers the real possibility of benefits. Possible benefits include increasing genetic compatibility of mates and avoiding inbreeding depression via cryptic female choice. Sperm storage in Tree Skinks, a family-living lizard with a monogamous mating system, suggests that females may bet-hedge through extra-pair copulation with more heterozygous males, reinforcing the idea that females could have more control on reproductive outcomes than previously thought.
无需近期交配，通过精子储存或孤雌生殖，产生有活力的后代的能力，在一系列具有挑战性的生态情景下，可为生物适应性带来优势。通过遗传分析，我们证明了 3 只野生捕获的雌性树蜥（Egernia striolata）在没有雄性接触的情况下，在圈养中繁殖了一年多，这最好通过精子储存来解释。据我们所知，这是首次在任何单配制、群居的爬行动物中记录到雌性精子储存，包括社会性澳大利亚鳄蜥（来自鳄蜥亚科）。此外，通过使用父本基因型重建，我们表明，前一年由同一雌性产生的、可能没有精子储存的圈养后代，是由不同的雄性父亲所生。我们定性地比较了这些雌性在不同年份的配偶和后代的特征。每窝幼仔的父母都是不相关的，但来自储存精子的幼仔的父本和后代基因型比推测来自近期交配的幼仔更杂合。群居鳄蜥的多父性率通常较低，但我们的研究表明，雌性精子储存，可能来自于社交伴侣之外，为潜在的利益提供了真正的可能性。可能的好处包括增加配偶的遗传相容性，并通过隐蔽的雌性选择避免近交衰退。在具有单配制交配系统的群居蜥蜴——树蜥中存在精子储存，这表明雌性可能通过与更多杂合雄性的婚外交配来进行风险分散，这进一步证实了这样一种观点，即雌性可能比之前认为的对生殖结果拥有更多的控制权。
