Testing Morphological Relationships Between Female and Male Copulatory Structures in Bats

Area of Science:

• Comparative anatomy
• Evolutionary biology
• Mammalian reproductive morphology

Background:

• Female reproductive tracts perform multiple functions, including mating, health maintenance, and parturition.
• Female copulatory morphology is crucial but understudied, despite diverse vaginal anatomy suggesting sexual selection.
• Bat (Chiroptera) reproductive morphology offers a model for studying coevolution due to diverse male and female anatomy.

Purpose of the Study:

• To investigate the coevolution of female vaginal thickness and collagen density with male penile morphology in bats (Chiroptera).
• To test hypotheses linking vaginal traits to penile spines and baculum presence/width.
• To understand the role of phylogenetic history in observed morphological patterns.

Main Methods:

• Comparative histological analysis of vaginal tissues from 24 bat species (suborder Yangochiroptera).
• Examination of corresponding male penis anatomy, including spines and baculum.
• Phylogenetic comparative methods to assess evolutionary correlations.

Main Results:

• Evidence supports coevolution between female vaginal thickness and the presence of penile spines.
• No significant covariation was found between vaginal thickness and baculum presence or width.
• Female vaginal collagen density did not show a significant correlation with male penile features.

Conclusions:

• Female vaginal thickness is influenced by male penile spine morphology, indicating sexual selection.
• Collagen density appears less directly linked to male penile traits in this bat group.
• The study underscores the importance of intersexual interactions in shaping reproductive structures and their evolutionary trajectories.