House mouse subspecies do differ in their social structure

Abstract

It is widely acknowledged that population structure can have a substantial impact on evolutionary trajectories. In social animals, this structure is strongly influenced by relationships among the population members, so studies of differences in social structure between diverging populations or nascent species are of prime interest.Ideal models for such a study are two house mouse subspecies, Mus musculus musculus and M. m. domesticus, meeting in Europe along a secondary contact zone. Though the latter subspecies has usually been supposed to form tighter and more isolated social units than the former, the evidence is still inconclusive. Here, we carried out a series of radiofrequency identification experiments in semi-natural enclosures to gather large longitudinal data sets on individual mouse movements. The data were summarized in the form of uni-and multi-layer social networks. Within them, we could delimit and describe the social units ("modules"). While the number of estimated units was similar in both subspecies, domesticus revealed a more "modular" structure. This subspecies also showed more intramodular social interactions, higher spatial module separation, higher intramodular persistence of parent-offspring contacts, and lower multiple paternity, suggesting more effective control of dominant males over reproduction. We also demonstrate that long-lasting modules can be identified with basic reproductive units or demes. We thus provide the first robust evidence that the two subspecies differ in their social structure and dynamics of the structure formation.

Rank-dependency of major urinary protein excretion in two house mouse subspecies

“…Even though the correlation between MUP and testosterone levels was non-significant in this study, the striking similarity between the MUP and testosterone curves, including the secondary peak appearing at the same time during M. m. musculus development, suggests the existence of a general pattern associated with continuing contests over social position well beyond the onset of male-male aggression (and likely beyond 100 days of age) in this subspecies. Though the results of this study are, admittedly, based on a straightforward experimental design that differs from natural conditions, and the evidence is somewhat circumstantial, the data are fully congruent with the results of Hiadlovská et al (2015, 2021) and Mikula et al (2022), adding another facet to the overall picture of different population structures and dynamics of establishing social hierarchy in two European house mouse taxa.…”

“…Despite several decades of MUP research, most studies have been limited to inbred laboratory strains or a single mouse subspecies. However, since the two European subspecies differ significantly in MUP amount and profile (Stopková et al 2007, Hurst et al 2017) as well as testosterone and corticosterone production dynamics (Hiadlovská et al 2015, Daniszová et al 2017) and social structure and hierarchy development (Hiadlovská et al 2021, Mikula et al 2022), simultaneous studies embracing both taxa could be highly important. The compelling findings of such comparative studies consistently suggest a more rapid establishment of social hierarchy in M. m. domesticus males compared to M. m. musculus males.…”

The strength of gut microbiota transfer along social networks and genealogical lineages in the house mouse

“…Since the “modules” were identified with reproductive units (demes), it was concluded that the experimental MMD populations had more “demic” social structure than MMM. This finding was also consistent with a higher frequency of multiple paternity in the latter subspecies (Mikula et al 2022 ). This provided a unique opportunity to assess the impact of this variation on the patterns of inter-individual transmission of gut microbiota.…”

“…We compared the transmission patterns among three gut sections: the colon, the cecum, and the ileum. The mice used in this study were first generation offspring from free-living populations, possessing wild-type microbiota, and were maintained for several generations in semi-natural arena experiments that mimicked free-living populations (Bendová et al 2022 , Mikula et al 2022 ). Unlike experiments conducted in laboratory settings, the mating of mice and their social contacts were not constrained by external factors.…”

“…The absence of emigration and immigration from and into the studied population allowed detailed analyses of genetic parentage (based on microsatellite data) and social interactions (using radiofrequency identification microtransponders). In this way, the transmission of the microbiota along social networks and genealogical host lineages (Mikula et al 2022 ) could be tracked with a degree of precision and completeness that would be nearly impossible to achieve in free-living populations of this species.…”