Fine‐scale spatiotemporal patterns of genetic variation reflect budding dispersal coupled with strong natal philopatry in a cooperatively breeding mammal

Abstract

The relatedness structure of animal populations is thought to be a critically important factor underlying the evolution of mating systems and social behaviours. While previous work has shown that population structure is shaped by many biological processes, few studies have investigated how these factors vary over time. Consequently, we explored the fine-scale spatiotemporal genetic structure of an intensively studied population of cooperatively breeding banded mongooses (Mungos mungo) over a 10-year period. Overall population structure was strong (average F(ST) = 0.129) but groups with spatially overlapping territories were not more genetically similar to one another than noncontiguous groups. Instead, genetic differentiation was associated with historical group-fission (budding) events, with new groups diverging from their parent groups over time. Within groups, relatedness was high within but not between the sexes, although the latter increased over time since group formation due to group founders being replaced by philopatric young. This trend was not mirrored by a decrease in average offspring heterozygosity over time, suggesting that close inbreeding may often be avoided, even when immigration into established groups is virtually absent and opportunities for extra-group matings are rare. Fine-scale spatiotemporal population structure could have important implications in social species, where relatedness between interacting individuals is a vital component in the evolution of patterns of inbreeding avoidance, reproductive skew and kin-selected helping and harming.

Female breeding dispersal in wolverines, a solitary carnivore with high territorial fidelity

“…This could be to secure an area that can later be bequeathed to a female offspring (c.f. budding dispersal in social species; Gardner and West 2006;Nichols et al 2012). One female (F9986) maintained her expanded territory for 4 years before her adult daughter (F04189) gained possession of half the area.…”

The evolution of group dispersal with leaders and followers

“…Despite this, little is known theoretically about the evolution of dispersal involving leader-follower relationships. It is standard in mathematical models to assume that dispersal occurs independently, but in many species dispersal occurs in groups of individuals that are often but not always related, and group dispersal is frequently initiated by a subset of individuals (Schoof et al, 2009;Wikberg, 2012;Nichols et al, 2012;Yano, 2008;Berg et al, 2009;Mumme et al, 1988;Lewis et al, 2011;Andersson and Wallander, 2004). The few models that incorporate the concept of group dispersal do not examine the emergence or maintenance of this biological phenomenon, nor do they assume the presence of leader-follower relationships (Gardner and West, 2006;Gardner et al, 2009;Nakamaru et al, 2014).…”

The origins of consistent individual differences in cooperation in wild banded mongooses, Mungos mungo

“…Rather, each group generally contains a 'core' of breeding adults (one to five females and three to seven males) and a subset of younger individuals that breed occasionally (Cant, Hodge, Bell, Gilchrist, & Nichols, 2010;Nichols, Amos, et al, 2012, Nichols, Bell, Hodge, & Cant, 2012, Nichols, Jordan, Jamie, Cant, & Hoffman, 2012. Although contributions to cooperative offspring care are skewed towards younger individuals (Cant, 2003;Hodge, 2007), all individuals, including current breeders, assist in rearing communal litters (Gilchrist & Russell, 2007).…”