Data_Sheet_1_Possible differences in effects on ejaculate morphology between shape and size components of the intromittent membranous part of insect male genitalia: Phylogenetic comparative analyses in Carabidae.zip

Male genitalia exhibit extreme morphological diversity among animals, but its diversification mechanism has not been fully elucidated. In insects, the intromittent membranous part has been barely studied. This study performed phylogenetic comparative analysis to examine the morphological associations between the intromittent membranous part (endophallus) and ejaculate characteristics in two Carabidae taxa with different endophallus diversification patterns (genus Amara and tribe Pterostichini). Endophallus morphology was analyzed using geometric morphometrics, whereby effects of shape and size components can be evaluated separately. In both taxa, no morphological associations were found between spermatophore and endophallus traits, but an association was detected between conjugated sperm length and endophallus shape. Considering the available information regarding functional morphology, the association between conjugated sperm length and endophallus shape may indicate a physical interaction between conjugated sperm and the endophallus through the spermatophore. The similarity of results between the two taxa implies functional equivalence among different endophallus types. Concerning individual sperm, several results were detected, but functional interpretation was difficult. Overall, these results imply that shape and size have different effects on ejaculate morphology, with a larger effect of shape than size. This pattern is consistent with previous results for non-intromittent and intromittent sclerotized parts, and the diversification mechanism of the intromittent membranous part may be similar to those of non-intromittent and intromittent sclerotized parts.

动物雄性生殖器的形态多样性在动物界中极为显著，但其分化机制尚未完全阐明。在昆虫类群中，插入式膜质生殖结构的相关研究仍较为匮乏。本研究开展系统发育比较分析，针对两类具有不同内阳茎（endophallus）分化模式的步甲科（Carabidae）类群——洼胸步甲属（Amara）与广肩步甲族（Pterostichini），探究其插入式膜质部分与射精特征间的形态关联。本研究采用几何形态测量学（geometric morphometrics）方法分析内阳茎形态，该技术可分别评估形状与大小组分的独立影响。在两类类群中，均未发现精荚（spermatophore）性状与内阳茎性状间存在形态关联，但检测到共轭精子长度与内阳茎形状间存在显著关联。结合现有功能形态学研究证据，共轭精子长度与内阳茎形状间的关联或暗示共轭精子可通过精荚与内阳茎发生物理相互作用。两类类群的研究结果具有相似性，提示不同内阳茎类型间存在功能等效性。针对单个精子的多项分析结果虽有检出，但难以进行有效的功能阐释。总体而言，上述结果表明，形状与大小对射精特征具有不同影响，其中形状的影响效应显著大于大小。该模式与此前针对非插入式、插入式骨化结构的研究结果一致，提示插入式膜质结构的分化机制或与非插入式及插入式骨化结构的分化机制相似。