Edwards Amy M, Cameron Elissa Z, Deakin Janine E, Ezaz Tariq, Pereira Jorge C, Ferguson-Smith Malcolm A, Robert Kylie A
Department of Ecology, Environment and Evolution, School of Life Sciences La Trobe University Melbourne Victoria Australia.
School of Biological Sciences University of Canterbury Christchurch New Zealand.
Ecol Evol. 2019 Apr 5;9(8):4340-4348. doi: 10.1002/ece3.4813. eCollection 2019 Apr.
Sex ratio biases are often inconsistent, both among and within species and populations. While some of these inconsistencies may be due to experimental design, much of the variation remains inexplicable. Recent research suggests that an exclusive focus on mothers may account for some of the inconsistency, with an increasing number of studies showing variation in sperm sex ratios and seminal fluids. Using fluorescent in-situ hybridization, we show a significant population-level Y-chromosome bias in the spermatozoa of wild tammar wallabies, but with significant intraindividual variation between males. We also show a population-level birth sex ratio trend in the same direction toward male offspring, but a weaning sex ratio that is significantly female-biased, indicating that males are disproportionately lost during lactation. We hypothesize that sexual conflict between parents may cause mothers to adjust offspring sex ratios after birth, through abandonment of male pouch young and reactivation of diapaused embryos. Further research is required in a captive, controlled setting to understand what is driving and mechanistically controlling sperm sex ratio and offspring sex ratio biases and to understand the sexually antagonistic relationship between mothers and fathers over offspring sex. These results extend beyond sex allocation, as they question studies of population processes that assume equal input of sex chromosomes from fathers, and will also assist with future reproduction studies for management and conservation of marsupials.
性别比例偏差往往并不一致，在物种和种群之间以及种群内部均是如此。虽然其中一些不一致可能归因于实验设计，但许多变异仍无法解释。最近的研究表明，仅关注母亲可能是造成某些不一致的原因之一，越来越多的研究显示精子性别比例和精液存在差异。通过荧光原位杂交，我们发现野生帚尾袋貂的精子在种群水平上存在显著的Y染色体偏差，但雄性个体之间存在显著的个体内差异。我们还发现，在同一方向上，种群水平的出生性别比例趋势偏向雄性后代，但断奶时的性别比例显著偏向雌性，这表明雄性在哺乳期间不成比例地死亡。我们推测，父母之间的性冲突可能会导致母亲在出生后通过抛弃雄性育儿袋幼崽和重新激活滞育胚胎来调整后代的性别比例。需要在圈养、可控的环境中进行进一步研究，以了解驱动和机械控制精子性别比例及后代性别比例偏差的因素，以及理解母亲和父亲在后代性别方面的性拮抗关系。这些结果不仅超出了性别分配的范畴，因为它们对那些假设父亲的性染色体输入相等的种群过程研究提出了质疑，还将有助于未来有袋类动物管理和保护的繁殖研究。
