Infertility Center of Saint Louis, St Luke's Hospital, Saint Louis, MO 63017, USA.
Biol Lett. 2011 Apr 23;7(2):295-8. doi: 10.1098/rsbl.2010.0882. Epub 2010 Oct 27.
It has been suggested that climate change at the Cretaceous-Palaeogene (K-Pg) boundary, initiated by a bolide impact or volcanic eruptions, caused species with temperature-dependent sex determination (TSD), including dinosaurs, to go extinct because of a skewed sex ratio towards all males. To test this hypothesis, the sex-determining mechanisms (SDMs) of Cretaceous tetrapods of the Hell Creek Formation (Montana, USA) were inferred using parsimony optimizations of SDMs on a tree, including Hell Creek species and their extant relatives. Although the SDMs of non-avian dinosaurs could not be inferred, we were able to determine the SDMs of 62 species; 46 had genotypic sex determination (GSD) and 16 had TSD. The TSD hypothesis for extinctions performed poorly, predicting between 32 and 34 per cent of survivals and extinctions. Most surprisingly, of the 16 species with TSD, 14 of them survived into the Early Palaeocene. In contrast, 61 per cent of species with GSD went extinct. Possible explanations include minimal climate change at the K-Pg, or if climate change did occur, TSD species that survived had egg-laying behaviour that prevented the skewing of sex ratios, or had a sex ratio skewed towards female rather than male preponderance. Application of molecular clocks may allow the SDMs of non-avian dinosaurs to be inferred, which would be an important test of the pattern discovered here.
有人认为，白垩纪-古近纪（K-Pg）边界的气候变化，无论是由陨石撞击还是火山爆发引发的，都导致了温度依赖型性别决定（TSD）的物种灭绝，包括恐龙，因为性别比例严重偏向雄性。为了验证这一假说，我们通过对树进行简约优化来推断来自美国蒙大拿州地狱溪组（Hell Creek Formation）的白垩纪四足动物的性别决定机制（SDM），其中包括地狱溪物种及其现存的亲属。虽然无法推断非鸟类恐龙的 SDM，但我们能够确定 62 种物种的 SDM；其中 46 种具有基因型性别决定（GSD），16 种具有 TSD。性别决定机制假说对于灭绝的预测效果不佳，预测存活率和灭绝率分别为 32%和 34%。最令人惊讶的是，在 16 种具有 TSD 的物种中，有 14 种存活到了古新世早期。相比之下，61%的具有 GSD 的物种灭绝了。可能的解释包括 K-Pg 时期气候变化最小，或者如果确实发生了气候变化，幸存下来的 TSD 物种具有防止性别比例偏斜的产卵行为，或者具有偏向雌性而不是雄性优势的性别比例。应用分子钟可能允许推断非鸟类恐龙的 SDM，这将是对这里发现的模式的重要检验。
