In search of the first caregiver: the evolution of parental care in Opiliones

• Grant number: 23/17863-3
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: June 03, 2024
• End date: June 02, 2025
• Field of knowledge: Biological Sciences - Zoology - Animal Behavior
• Principal Investigator: Glauco Machado
• Grantee: Laís Aline Grossel
• Supervisor: James Gilbert
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: University of Hull, England
• Associated to the scholarship: 22/07338-6 - Paternal care and sexual selection in harvestmen from the Atlantic Forest, BP.DR

Abstract

Considering that parental care evolves to increase the survival of offspring, the question arises: which sex should be the responsible for this task? Several theoretical models have been proposed to explain the observed patterns of caregivers, including differences in gamete investment between sexes, modes of fertilization, uncertainty of the male paternity, and even female preferences. Vertebrates groups have been extensively studied and can help us to investigate the plausibility of these models. Meanwhile, invertebrates, due to their diverse species with parental behaviors, can offer additional insights. Among arthropods, Opiliones is a particularly interesting group, as it exhibits at least nine cases of independent evolution of paternal care, ten cases of independent evolution of maternal care, and even biparental care. Therefore, our goal is to trace these back to the common ancestor and to test two hypotheses regarding the evolution of paternal care: i) male care emerged from no care (overlapping broods hypothesis); or ii) male care emerged via a female or biparental intermediate (enhanced fecundity hypothesis). We will employ phylogenetic comparative methods. Using BayesTraits we will build four evolutionary models that investigate the transitions between the different caring states. To account for potential uncertainty arising from phylogenetic relationships among species, we will fit the models using two different phylogenetic tree structures for Opiliones: i) resolving the polytomies; ii. generating random trees with possible resolutions for the polytomies. The results of this study will shed light to the evolution of parental care in Opiliones and provide valuable into the evolution of paternal care, the rarest form of caregiving observed among animals.