Baughman Jenna T, Payton Adam C, Paasch Amber E, Fisher Kirsten M, McDaniel Stuart F
Department of Biological Sciences, California State University, 5151 State University Drive, Los Angeles, California 90032 USA
Department of Biology, University of Florida, 876 Newell Drive, Gainesville, Florida 32611 USA.
Am J Bot. 2017 May;104(5):733-742. doi: 10.3732/ajb.1700045. Epub 2017 May 10.
Natural populations of many mosses appear highly female-biased based on the presence of reproductive structures. This bias could be caused by increased male mortality, lower male growth rate, or a higher threshold for achieving sexual maturity in males. Here we test these hypotheses using samples from two populations of the Mojave Desert moss .
We used double-digest restriction-site associated DNA (RAD) sequencing to identify candidate sex-associated loci in a panel of sex-expressing plants. Next, we used putative sex-associated markers to identify the sex of individuals without sex structures.
We found a 17:1 patch-level phenotypic female to male sex ratio in the higher elevation site (Wrightwood) and no sex expression at the low elevation site (Phelan). In contrast, on the basis of genetic data, we found a 2:1 female bias at the Wrightwood site and only females at the Phelan site. The relative area occupied by male and female genets was indistinguishable, but males were less genetically diverse.
Our data suggest that both male-biased mortality and sexual dimorphism in thresholds for sex expression could explain genetic and phenotypic sex ratio biases and that phenotypic sex expression alone over-estimates the extent of actual sex ratio bias present in these two populations of .
基于生殖结构的存在，许多苔藓的自然种群似乎高度偏向雌性。这种偏向可能是由雄性死亡率增加、雄性生长速率较低或雄性达到性成熟的阈值较高引起的。在这里，我们使用来自莫哈韦沙漠两种苔藓种群的样本对这些假设进行检验。
我们使用双酶切限制性位点关联DNA（RAD）测序，在一组有性表达的植物中识别候选性别相关位点。接下来，我们使用推定的性别相关标记来识别没有性别结构的个体的性别。
我们发现在海拔较高的地点（赖特伍德），斑块水平上的表型雌雄比为17:1，而在海拔较低的地点（费兰）没有性别表达。相比之下，基于遗传数据，我们发现在赖特伍德地点存在2:1的雌性偏向，而在费兰地点只有雌性。雄性和雌性基株所占据的相对面积没有差异，但雄性的遗传多样性较低。
我们的数据表明，雄性偏向的死亡率和性别表达阈值中的性别二态性都可以解释遗传和表型性别比偏向，并且仅表型性别表达高估了这两种苔藓种群中实际存在的性别比偏向程度。
