Differential allocation in a gift-giving spider: males adjust their reproductive investment in response to female condition.

• Autor(a) principal: Brenes, Diego Esteban Solano
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/41/41134/tde-13092021-193011/
• topic: Body condition; Condição corporal; Copulatory courtship; Cortejo copulatório; Cortejo pré-copulatório; Escolha masculina de parceiras; Esforço de acasalamento; Esforço parental; Male cryptic selection; Male mate selection; Mating effort; Parental effort; Precopulatory courtship; Seleção críptica masculina; Sperm transfer; Transferência de esperma

When males are selective, they can either reject low-quality females or adjust their reproductive investment in response to traits that indicate female quality (e.g., body size or condition). According to the differential allocation hypothesis, males increase their reproductive investment when paired with high-quality females (positive differential allocation) or increase their reproductive investment when paired with low-quality females (negative differential allocation). This hypothesis has been proposed for monogamous species with biparental care, and most empirical studies focus on birds. Here we used the polygamous spider Paratrechalea ornata, in which males offer prey wrapped in silk as nuptial gifts, to test whether males adjust their reproductive investment in gift size, pre-copulatory and copulatory courtship intensity, and sperm transfer in response to female body condition. We found that males exposed to females in good body condition added more flies to the gift, stimulated these females more intensively with abdominal touches during pre-copulatory courtship, and had longer pedipalp insertions than males exposed to females in poor body condition. Female condition affected neither silk investment in nuptial gift wrapping nor the quantity of sperm transferred by males. Finally, females in good body condition laid more eggs and oviposited faster after copulation than females in poor body condition. We provide experimental evidence that males of a gift-giving spider exhibit positive differential allocation in three key aspects of their reproductive investment: the size of the nutritious gift, pre-copulatory courtship intensity, and duration of pedipalp insertions, which is regarded as a form of genital courtship by males in spiders. This positive differential allocation is likely associated with the benefits of copulating with females in good body condition. These females are more fecund and oviposit faster after copulation than females in poor body condition, which under natural field conditions probably reduce the risk of multiple matings and thus the level of sperm competition faced by the males. As a final remark, our findings indicate that the hypothesis of differential allocation also applies to species with a scramble competition mating system, in which males heavily invest in nuptial gift construction, but not in parental care