Emasculation in orb web spiders has been a poorly understood phenomenon of sexual mutilation that has sometimes been assumed to represent maladaptive strategies. By reviewing all evidence including our original research from the past years, we showed that the eunuch phenomenon is adaptive. Namely, males engage in genital mutilation in order to become more agile and aggressive in fighting their rivals. Through emasculation, the males even secure remote copulation. These behaviours have co-evolved with extreme sexual size dimorphism as a response to sexual conflict.
COBISS.SI-ID: 37090861
Many organisms are sexually dimorphic, reflecting sex-specific selection pressures. But although sexual dimorphism may consist of different variables from size to shape and physiology, most research emphasizes a single aspect of sexual dimorphism, notably size. We dissected sexual dimorphism in spiders at two phylogenetic hierarchical levels. At the species level, we employed comparative phylogenetic tests to explore the association between sexual shape dimorphism (SShD) and sexual size dimorphism (SSD) in the orbweb clade Argiopinae. At the genus level, we then explored such patterns on a phylogeny of orb weavers (Araneoidea). While in argiopines we detected no clear association between SShD and SSD, we detected a significant correlation in all orb weavers at the genus level. The shape and the size components of sexual dimorphism may thus respond independently to selection pressures, but at certain phylogenetic levels SSD may be a prerequisite for SShD.
COBISS.SI-ID: 38237485
Bark spiders (genus Caerostris) are important models in biomaterial research due to the remarkable biomechanical properties of the silk of C. darwini and its gigantic web. They also exhibit female gigantism and are promising candidates for coevolutionary research on sexual size dimorphism. However, Caerostris spiders are taxonomically understudied and the lack of a phylogeny impedes evolutionary research. With the first species-level phylogeny of Caerostris, we provided the first step towards understanding of the evolution of the toughest biological material. Our phylogenetic and morphological research allowed description of six new species, highlighting the undescribed diversity in this genus.
COBISS.SI-ID: 39077421