Homotypic assortative mating is consistent across temporal scales in the spider Mecynogea lemniscata (Araneidae)

Identifying patterns of size-assortative mating (SAM) indicates the direction of genetic changes in a population. A reliable method for estimating it in a population is to measure mate assortments within and between breeding seasons¸ as well as describing size variation of males and females between temporal scales to avoid Simpson’s paradox. We assessed sexual size dimorphism, the effects of ontogeny, size differences within each sex, the consistency of SAM within and between seasons, and male mate choice in the spider Mecynogea lemniscata . We collected mating pairs in a Eucalyptus plantation across two breeding seasons and in four periods of the second season. We measured body mass and carapace width of spiders. Males matured earlier than females and guarded subadult partners. Although adults were larger and heavier than subadults, ontogeny did not affect SAM. Females were generally heavier than males in the second season but not in first, but mate assortments were random based on body mass in both seasons. Females showed a smaller carapace width in the first season and a larger one than males in the second season. Despite varying size differences between seasons, SAM remained homotypic based on carapace width across seasons and within the second season. Hence, homotypic SAM was consistent across different temporal scales. Male mate choice was not affected by female size. Unlike other species, temporal variation in the size of M. lemniscata spiders did not disrupt SAM, indicating that a consistent SAM can influence evolutionary changes in body size in this population. • A reliable method for estimating size-assortative mating (SAM) is to measure it at different temporal scales. • SAM remained homotypic based on carapace width across seasons and within the second season. • Females were larger than males, except in the first season based on mass. • Male mate choice was not affected by female size.