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Camila Pavón-Peláez, Vinicius S. R. Diniz, Williams Paredes-Munguía, Renato A. Teixeira, Luiz E. Costa-Schmidt, Adalberto J. Santos, Bruno A. Buzatto, and Maria J. Albo: Read the article
The nuptial gift-giving spider exhibits a fascinating courtship behavior: males present silk-wrapped bundles to females to secure mating opportunities. The contents of these bundles remain a mystery to the female until after she accepts the male’s advances. Upon unwrapping the gift, the female may discover either a nutritious prey item or a worthless object. The gift quality can directly influence the outcome—females often allow extended copulation to males offering valuable gifts but may terminate mating attempts if presented with a deceptive, “worthless” bundle. This costly trait, tied to male reproductive success, is closely linked to ecological factors like temperature and precipitation that affect prey availability and males’ ability to produce gifts. But, what happens to the selection pressures on such traits under increasing environmental variability, where survival becomes more difficult? In this study, Pavón-Peláez et al. investigate how fluctuating environmental conditions impact this sexually selected trait across diverse habitats in South America.
The authors studied variations in temperature and precipitation across six populations of the gift-giving spider, Paratrechalea ornata, distributed along a latitudinal gradient from South Uruguay to north Santa Catarina, Brazil. These spiders inhabit rocky areas near water bodies, relying on local insects for food and nuptial gifts. Field observations revealed that populations experiencing high precipitation variability also had significantly higher frequencies of males presenting worthless gifts to females. Additionally, one population under these conditions exhibited smaller male body sizes, indicating potential fitness costs associated with fluctuating environments.
The authors hypothesized that the prevalence of worthless gifts in some populations could result from weakened sexual selection driven by limited mate choice. When prey becomes scarce due to environmental instability, most males fail to procure high-quality gifts, forcing females to accept mates offering worthless gifts. Over time, this may lead to reduced female preference for nutritive gifts. To test this, the researchers conducted laboratory experiments, providing courting males from each population with either a nutritious prey item or a worthless item, and observed subsequent mating behavior based on gift type. Their findings showed that males offering nutritious gifts achieved longer mating durations in populations with low frequencies of worthless gifts. However, in populations where worthless gifts were common, males offering such gifts achieved longer mating times, indicating a reduction in female preference for nutritious gifts. This suggests that erratic climatic conditions, such as increased precipitation variability, can weaken sexual selection by constraining female choice.
Ratna Karatgi is a PhD candidate in the Fuller lab at the University of Illinois Urbana Champaign. Her research explores color polymorphism and phenotypic plasticity in bluefin killifish, aiming to uncover the environmental and genetic mechanisms that sustain trait variation. She is deeply committed to science outreach, striving to make science accessible and engaging for the public.
