Influence of mating system and variable selection on adaptive variation within and across species of cannibalistic black widow spiders

点击翻译按钮获取中文摘要

My research examines how social and environmental conditions affect the evolution of male reproductive traits. I propose field and laboratory studies of variation in male size, development time, and mating strategies in three closely related species of cannibalistic black widow spiders. The extreme mating system of two of these species (Redbacks and Brown Widows) involves self-sacrifice by males to their cannibalistic mates. This severely restricts male mating opportunities. Thus male fitness depends on the ability to compete successfully under a limited range of conditions experienced soon after maturity. I predict that males of these species will use cues of small-scale fluctuations in competitive challenges to adjust development of adult traits to forms that are optimal for the local environment (= developmental plasticity). In contrast, males of the third species (Western Black Widows) mate with multiple females over a longer period, and are likely to encounter a range of micro-habitat challenges. I predict these males will adopt traits that perform well on average across the most commonly encountered conditions, but will not be optimal under any one condition. My work will examine this idea by measuring spatial and temporal variation in selection pressures across local and broad geographic scales, and fitness effects of variable adult traits across widely separated populations in each species. I will answer two main questions. (1) How is fitness affected by variable selection on mating strategies, development time, and body size traits within the context of each species' mating system? and (2) Does selection for developmental plasticity in sexually-selected traits depend on mating system? Studies proposed here will shed light on causes of adaptive variation between species of black widow spiders-a group that is notable for its extreme mating systems and broad species distributions. More generally, this work will make significant contributions to our understanding of the how different levels of environmental variability affect adaptive variation within and across populations.