The social microbiome: gut microbiome diversity and abundance are negatively associated with sociality in a wild mammal

Abstract

The gut microbiome has a well-documented relationship with host fitness. Greater microbial diversity and abundance of specific microbes have been associated with improved fitness outcomes. Intestinal microbes also may be associated with patterns of social behaviour. However, these associations have been largely studied in captive animal models; we know less about microbiome composition as a potential driver of individual social behaviour and position in the wild. We used linear mixed models to quantify the relationship between fecal microbial composition, diversity and social network traits in a wild population of yellow-bellied marmots ( Marmota flaviventer ). We focused our analyses on microbes previously linked to sociability and neurobehavioural alterations in captive rodents, primates and humans. Using 5 years of data, we found microbial diversity (Shannon–Wiener and Faith's phylogenetic diversity) has a modest yet statistically significant negative relationship with the number of social interactions an individual engaged in. We also found a negative relationship between Streptococcus spp. relative abundance and two social network measures (clustering coefficient and embeddedness) that quantify an individual's position relative to others in their social group. These findings highlight a potentially consequential relationship between microbial composition and social behaviour in a wild social mammal.

Social control is associated with increased reproductive skew in a wild mammal

“…Using SOCPROG (v. 2.9 [42]), we determined annual simple-ratio pairwise association indices for adult females based on this space-use overlap [43]. We used these indices in the random walk community detection algorithm Map Equation to identify social group membership [44][45][46][47].…”

Zebrafish (Danio rerio) behavioral phenotypes not underscored by different gut microbiota

“…In contrast, significant differences in caecal microbiomes were determined between selectively bred resilient (high litter size) and non-resilient (low litter size) rabbit lines (Casto-Rebollo et al, 2023) and dogs from well-established aggressive, phobic, or standard lines (Mondo et al, 2020). However, some evidence indicates that this can depend on whether a particular animal exists in social groups or is solitary (Pfau et al, 2023). We argue in this work that investigating the gut-brain axis and its impacts more definitively on animal behavior broadly requires the use of selectively bred lines with already established behavioral phenotypes (empirically underscored by differing neurophysiological mechanisms) rather than the use of “atypical” behaviors following treatment conditions.…”