Data from: Male-mimicking females increase male-male interactions, and decrease male survival and condition in a female-polymorphic damselfly

Biologists are still discovering diverse and powerful ways sexual conflicts shape biodiversity. The present study examines how the proportion of females in a population that exhibit male mimicry, a mating resistance trait, influences conspecific males’ behavior, condition and survival. Like most female-polymorphic damselflies, Ischnura ramburii harbors both “andromorph” females, which closely resemble males, and sexually dimorphic “gynomorph” counterparts. There is evidence that male mimicry helps andromorphs evade detection and harassment, but males can also learn to target locally prevalent morph(s) via prior mate encounters. I hypothesized that the presence of male mimics could therefore predispose males to mate recognition errors, and thereby increase rates of costly male-male interactions. Consistent with this hypothesis, male-male interaction rates were highest in mesocosms containing more andromorph (vs. gynomorph) females. Males in andromorph-biased mesocosms also had lower final body mass and higher mortality than males assigned to gynomorph-majority treatments. Male survival and body mass were each negatively affect by mesocosm density, and mortality data revealed a marginally significant interaction between andromorph frequency and population density. These findings suggest that, under sufficiently crowded conditions, female mating resistance traits such as male mimicry could have pronounced indirect effects on male behavior, condition, and survival.生物学家仍在不断揭示性冲突塑造生物多样性的多样且强效的作用机制。本研究探讨了种群中表现出雄性拟态（male mimicry，一种交配抗性性状）的雌性比例，如何影响同种雄性（conspecific males）的行为、身体状态与存活情况。与多数雌性多态（female-polymorphic）的豆娘类群一样，伊斯娜拉蟌（Ischnura ramburii）同时存在与雄性形态高度相似的雄态雌性（andromorph），以及具有典型性二态特征的雌态雌性（gynomorph）。已有研究表明，雄性拟态可帮助雄态雌性规避雄性的探测与骚扰，但雄性也可通过此前的交配经历，学会优先寻找当地占优势的雌性形态。据此本研究提出假说：雄性拟态个体的存在，会使雄性更易出现交配识别错误，进而提升代价高昂的雄雄互作发生率。与该假说一致，在雄态雌性占比更高的中型生态箱（mesocosm）中，雄雄互作发生率最高。相较于雌态雌性占多数的实验组，雄态雌性占比偏高的中型生态箱中的雄性，最终体质量更低、死亡率更高。雄性存活率与体质量均随中型生态箱的种群密度升高而下降；死亡率数据还显示，雄态雌性频率与种群密度之间存在边际显著的交互效应。上述研究结果表明，在种群足够拥挤的条件下，雄性拟态这类雌性交配抗性性状，可对雄性的行为、身体状态与存活产生显著的间接影响。