Leaving a solitary life behind: Evolutionary processes leading to sociality in animals
von Lluis Socias Martínez
Datum der mündl. Prüfung:2019-12-13
Erschienen:2020-02-25
Betreuer:Prof. Dr. Peter M. Kappeler
Gutachter:Dr. Oliver Schülke
Gutachter:Dr. Markus Port
Gutachter:Dr. Sven Bradler
Gutachter:Prof. Dr. Julia Fischer
Gutachter:Prof. Dr. Jutta Schneider
Dateien
Name:PhD_Thesis_Socias-Martinez_2019_bm.pdf
Size:8.43Mb
Format:PDF
Description:PhD thesis manuscript
Zusammenfassung
Englisch
The evolution of stable animal groups is a major transition in evolution entailing changes in population structure and emerging properties due to the selective pressures associated with social interactions. Sociality is based on cooperation, an evolutionary puzzle in Darwinian theory that is grounded on competition for limited resources. In the first chapter, we challenge the importance of kin selection (i.e. nepotism) to explain the appearance of animal groups, which is the current paradigm. This theory suggests that genetic similarity is needed to reduce competition between individuals allowing cooperation to be selected. We propose an alternative framework that takes into account the numerous and diverse ways in which parental care may have catalyzed the evolution of group living. We emphasize the importance of coevolutionary processes between parasites and predators with parental investment strategies long before transitions to sociality may occur. Building on empirical and theoretical evidence from a wide range of taxa, including vertebrates and invertebrates, we suggest that direct fitness benefits arising from selective pressures associated with parental care evolution are the force behind the appearance of animal groups. Under this framework, kin-selection is rather an enhancer or even a by-product derived from evolutionary processes related to parental care and not the main prerequisite for cooperation to evolve. In the second chapter, we focus on studying facultatively social species to understand the processes that lead a solitary species to become group-living. In this sense, we describe the social system of a facultatively social primate with communal breeding, Microcebus murinus, using data on more than 200 individuals from a wild population. By studying sleeping site sharing in this solitary foraging species, we aim to characterize the social flexibility both at the species as well as at the individual levels. We find evidence for social flexibility in philopatric females and dispersing males. Moreover, contrary to previous findings, we show a higher capacity for sociality and social flexibility in males. Thus, our results suggest that female communal breeding may not be the only force driving sociality in this species, criticizing the framework exposed in chapter 1; and that unrelated males may be as prone as related females to form social groups, which suggests that kin-selection is also unable to explain the evolution of mouse lemurs’ social systems. While in the first two chapters, we discussed transitions to sociality from an adaptationist perspective, in Chapter 3.1, we examine the possibility that sociality in Microcebus murinus may be a passive result of heterogeneous distribution of food resources and sleeping sites. We find no evidence for an effect of food resource availability or nesting limitation on individual social strategies. Thus, intrinsic benefits associated with sleeping together and sharing a home range with others may be at play in this species. In chapter 3.2, we develop the method used in chapter 3.1 to assess the reliability of information gathered per individual to construct home ranges using Michaelis-Menten modeling. We believe this might be a potentially useful tool for studies in the wild where scarcity of data as well as between-individual variation in the amount of data collected may hamper movement ecology analyses. We end by emphasizing that social evolution is a manifold process that embeds and intertwines several layers of life complexity, resisting attempts for unitary explanations of its origins.
Keywords: Evolution animal sociality; Behavior; Kin selection; Parental care; Microcebus murinus; Home range; Michaelis-Menten modeling