To mate, or not to mate: the evolution of reproductive diapause facilitates insect radiation into African savannahs in the Late Miocene

1. Many tropical environments experience cyclical seasonal changes, frequently with pronounced wet and dry seasons, leading to a highly uneven temporal distribution of resources. Short-lived animals inhabiting such environments often show season-specific adaptations to cope with alternating selection pressures. 2. African Bicyclus butterflies show strong seasonal polyphenism in a suite of phenotypic and life-history traits, and their adults are thought to undergo reproductive diapause associated with the lack of available larval host plants during the dry season. 3. Using three years of longitudinal field data for three species in Malawi, dissections demonstrated that one forest species reproduces continuously whereas two savannah species undergo reproductive diapause in the dry season, either with or without pre-diapause mating. Using additional data from field-collected and museum samples, we then documented the same three mating strategies for a further 37 species. 4. Phylogenetic an...1. 多数热带环境存在周期性季节更迭，往往伴随干湿两季的鲜明交替，致使资源的时间分布极不均衡。栖息于这类环境中的短寿命动物，通常演化出季节特异性适应策略，以应对交替出现的选择压力。 2. 非洲眼蝶属（Bicyclus）昆虫在一系列表型与生活史性状上呈现显著的季节多型现象（seasonal polyphenism），学界普遍认为其成虫会在旱季进入生殖滞育（reproductive diapause），以应对幼虫寄主植物匮乏的环境。 3. 研究团队基于马拉维境内3个物种的3年纵向野外调查数据（longitudinal field data），经解剖分析结果显示：一种森林栖息种类可持续繁殖，而两种稀树草原栖息种类则会在旱季进入生殖滞育，且滞育前的交配行为存在有、无两种模式。随后结合野外采集与博物馆馆藏样本的补充数据，团队又在另外37个物种中验证了这3种交配策略。 4. 系统发育（phylogenetic）分析……