Hidden diversity in plain sight: four new species of Nemesia (Araneae: Mygalomorphae) from the Córdoba Province of Spain

Posted by
  Hidden diversity in plain sight: four new species of Nemesia (Araneae: Mygalomorphae) from the Córdoba Province of Spain Abstract A taxonomic revision of the species of Nemesia Audouin, 1826, distributed in the vicinity of Córdoba City, southern Spain, is presented. Four new species are described: Nemesia morana sp. nov. (female), N. kodama sp. nov. (male and female), N. rosae sp. nov. (male and female), and N. tamajoni sp. nov. (male and female). These species are distinguished by distinct morphological characters, including the shape of the spermathecae, palpal bulbs, and spinnerets, as well as by burrow architecture. Fieldwork was conducted across two of the three major habitat types in the region—the humid, forested mountains of Sierra Morena and the croplands and riparian forests of the Guadalquivir Valley—while the third, the “campiña”, which is mainly composed of agricultural landscapes, remains poorly explored. Sampling methods included pitfall trapping and the direct e...

Extreme sexual size dimorphism correlates with proxies of postcopulatory sexual selection across selected Dolomedes fishing spiders

Posted by

 


Extreme sexual size dimorphism correlates with proxies of postcopulatory sexual selection across selected Dolomedes fishing spiders

Abstract

Sexual size dimorphism (SSD) and mating system diversity are key factors shaping reproductive evolution, yet their relationships with post-mating sexual selection remain incompletely understood. Here, we use a comparative framework across multiple species of Dolomedes fishing spiders to examine how mating systems, sperm production strategies, and proxies of postcopulatory selection relate to SSD. We quantified testes size and spermatogenesis in three closely related species— D. tenebrosus, D. okefinokensis, and D. scriptus —that differ in mating system and SSD. Dolomedes tenebrosus, a monogynous species with extreme female-biased SSD (eSSD) and male self-sacrifice, showed evidence of termination of spermatogenesis at maturity, indicating a terminal investment strategy. Dolomedes okefinokensis exhibited a similar pattern, suggesting convergent evolution toward monogyny. In contrast, D. scriptus, with moderate SSD and a polygynous system, maintained continuous spermatogenesis, consistent with repeated mating opportunities. Expanding to 13 Dolomedes species, we found a strong positive association between eSSD, monogyny, and spermatogenesis termination, alongside increased spermophor volume in eSSD species. These findings suggest that eSSD is associated with both a terminal male reproductive strategy and intensified investment in sperm transfer structures. Together, our results highlight an integrated evolutionary link between sexual size dimorphism, mating system, and male reproductive investment across Dolomedes spiders.

Linde, M., Donke, E., Schwartz, S. K., Hebets, E., & Michalik, P. Extreme sexual size dimorphism correlates with proxies of postcopulatory sexual selection across selected Dolomedes fishing spiders. Evolution. https://doi.org/10.1093/evolut/qpag041