Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037, USA.
Syst Biol. 2023 Jun 16;72(2):264-274. doi: 10.1093/sysbio/syac057.
Although the diversity, beauty, and intricacy of sexually selected courtship displays command the attention of evolutionists, the longevity of these traits in deep time is poorly understood. Population-based theory suggests sexual selection could either lower or raise extinction risk, resulting in high or low persistence of lineages with sexually selected traits. Furthermore, empirical studies that directly estimate the longevity of sexually selected traits are uncommon. Sexually selected signals-including bioluminescent courtship-originated multiple times during evolution, allowing the empirical study of their longevity after careful phylogenetic and divergence time analyses. Here, we estimate the first transcriptome-based molecular phylogeny and divergence times of Cypridinidae. We report extreme longevity of bioluminescent courtship, a trait important in mate choice and probably under sexual selection. Our relaxed-clock estimates of divergence times coupled with stochastic character mapping show luminous courtship evolved only once in Cypridinidae-in a Sub-Tribe, we name Luxorina-at least 151 millions of years ago from cypridinid ancestors that used bioluminescence only in antipredator displays, defining a Tribe we name Luminini. This time-calibrated molecular phylogeny of cypridinids will serve as a foundation for integrative and comparative studies on the biochemistry, molecular evolution, courtship, diversification, and ecology of cypridinid bioluminescence. The persistence of luminous courtship for hundreds of millions of years suggests that sexual selection did not cause a rapid loss of associated traits, and that rates of speciation within the group exceeded extinction risk, which may contribute to the persistence of a diverse clade of signaling species. [Ancestral state reconstruction; Biodiversity; co-option; divergence time estimates; macroevolution; Ostracoda; phylogenomics; sexual selection.].
尽管性选择求偶展示的多样性、美丽和复杂性吸引了进化生物学家的注意，但这些特征在深层时间中的持久性却知之甚少。基于种群的理论表明，性选择既可以降低也可以提高灭绝风险，从而导致具有性选择特征的谱系的高或低持续性。此外，直接估计性选择特征持久性的实证研究并不常见。性选择信号——包括生物发光求偶——在进化过程中多次出现，这使得在经过仔细的系统发育和分化时间分析后，可以对其持久性进行实证研究。在这里，我们估计了 Cypridinidae 的第一个基于转录组的分子系统发育和分化时间。我们报告了生物发光求偶的极端持久性，这是一个在配偶选择中很重要的特征，可能受到性选择的影响。我们的松弛时钟估计的分化时间加上随机特征映射表明，发光求偶在 Cypridinidae 中只进化了一次——在一个我们命名为 Luxorina 的亚部落中——至少在 1.51 亿年前，从只在防御捕食者时使用生物发光的 Cypridinidae 祖先进化而来，定义了一个我们命名为 Luminini 的部落。这个经过时间校准的 Cypridinidae 分子系统发育将成为 Cypridinidae 生物发光的生物化学、分子进化、求偶、多样化和生态学的综合和比较研究的基础。发光求偶持续数亿年表明，性选择并没有导致相关特征的快速丧失，而且该群体内的物种形成速度超过了灭绝风险，这可能有助于信号物种的多样化分支的持续存在。[祖先状态重建；生物多样性；共适应；分化时间估计；宏观进化；介形纲；系统基因组学；性选择。]
