Differential Adhesion between Moving Particles as a Mechanism for the Evolution of Social Groups

Abstract

The evolutionary stability of cooperative traits, that are beneficial to other individuals but costly to their carrier, is considered possible only through the establishment of a sufficient degree of assortment between cooperators. Chimeric microbial populations, characterized by simple interactions between unrelated individuals, restrain the applicability of standard mechanisms generating such assortment, in particular when cells disperse between successive reproductive events such as happens in Dicyostelids and Myxobacteria. In this paper, we address the evolutionary dynamics of a costly trait that enhances attachment to others as well as group cohesion. By modeling cells as self-propelled particles moving on a plane according to local interaction forces and undergoing cycles of aggregation, reproduction and dispersal, we show that blind differential adhesion provides a basis for assortment in the process of group formation. When reproductive performance depends on the social context of players, evolution by natural selection can lead to the success of the social trait, and to the concomitant emergence of sizeable groups. We point out the conditions on the microscopic properties of motion and interaction that make such evolutionary outcome possible, stressing that the advent of sociality by differential adhesion is restricted to specific ecological contexts. Moreover, we show that the aggregation process naturally implies the existence of non-aggregated particles, and highlight their crucial evolutionary role despite being largely neglected in theoretical models for the evolution of sociality.

Mobility can promote the evolution of cooperation via emergent self-assortment dynamics

“…in group-level assortment of individuals based on the cohesive trait (Fig 3c), as has previously been 168 hypothesized for animal and cellular groups [35][36][37]45]. Cooperators benefit from positive assortment 169 when their cohesive tendency is higher than that of defectors (i.e.…”

“…Classical 34 theory shows that sufficiently high mobility will undercut selection for cooperation [14,33,34]. One 35 mechanism that generates spontaneous sorting of phenotypes in mobile social groups is differential 36 cohesion between cooperators and defectors [35][36][37]. However, defectors could evolve to match the 37 cohesion of cooperators, thus eliminating differential cohesion driven spatial sorting of cooperators.…”

Resolving Conflicts During the Evolutionary Transition to Multicellular Life

“…Traits that affect, for example, local adaptation, kin recognition, adhesion, speed of movement, and perception of environmental cues ensure assortment among cooperating types (Aviles 2002, Garcia & De Monte 2013, Garcia et al 2014, Guttal & Couzin 2010, Jiang et al 1998, Mehdiabadi et al 2006, Ostrowski et al 2008, van Veelen et al 2010. For instance, cell adhesion plays a central role in establishing tissuelevel functionality, cell segregation, and sorting both in cancer and during development (Friedl & Gilmour 2009, Newman 2012.…”

“…For instance, cell adhesion plays a central role in establishing tissuelevel functionality, cell segregation, and sorting both in cancer and during development (Friedl & Gilmour 2009, Newman 2012. Differential adhesion is also sufficient for coherent groups of cells to evolve (Garcia et al 2014). These and similar mechanisms may be especially important when collectives are a mixture of genotypes such as when collectives arise as a consequence of fusion.…”

The ecology and evolution of social behavior in microbes

“…Multiple mechanisms have been proposed to achieve assortment (see Nowak, 2006, for a review), such as: (i) the existence of an underlying spatial structure combined with limited dispersal, also known as population viscosity, which clusters together parents and offspring (Hamilton, 1964;Lieberman et al, 2005;Nowak and May, 1992;Nowak et al, 2010a;Pfeiffer and Bonhoeffer, 2003;Tarnita et al, 2009b;West et al, 2006); (ii) structure arising from the properties of the individuals such as adhesion, speed of movement or perception of environmental cues (Avilés, 2002;Garcia et al, 2014Garcia et al, , 2015; (iii) recognition of like or discrimination of non-like based on various cues such as kinship, phenotypic similarity, signaling or shared preferences (Antal et al, 2009;Mehdiabadi et al, 2006;Ostrowski et al, 2008;Pacheco et al, 2006;Rousset and Roze, 2007;Stefanic et al, 2015;Tarnita et al, 2009a;Traulsen and Nowak, 2007;Vos and Velicer, 2009); (iv) reciprocity, which relies on either memory or reputation to ensure that future interactions are informed by previous ones (Axelrod and Hamilton, 1981;Nowak andSigmund, 1989, 2005;Trivers, 1971); or (v) multilevel selection Wilson, 1975), which considers selective pressures both at the individual Glossary Cooperation Costly behavior that confers fitness benefits on same-species recipients. Defection (free-riding) Absence of the cooperative behavior coupled with exploitation of its benefits.…”