Data from: Genetic distinction between contiguous urban and rural multimammate mice in Tanzania despite gene flow

Special conditions are required for genetic differentiation to arise at a
local geographical scale in the face of gene flow. The Natal multimammate
mouse, Mastomys natalensis, is the most widely distributed and abundant
rodent in sub-Saharan Africa. A notorious agricultural pest and a natural
host for many zoonotic diseases, it can live in close proximity to man,
and appears to compete with other rodents for the synanthropic niche. We
surveyed its population genetic structure across a 180 km transect in
central Tanzania along which the landscape varied between agricultural
land in a rural setting and natural woody vegetation, rivers, roads and a
city. We sampled M. natalensis across 10 localities, and genotyped 15
microsatellite loci from 515 individuals. Hierarchical STRUCTURE analyses
show a K-invariant pattern distinguishing Morogoro suburbs (located in the
centre of the transect) from nine surrounding rural localities. Landscape
connectivity analyses in Circuitscape and comparison of rainfall patterns
suggest that neither geographical isolation nor natural breeding
asynchrony could explain the genetic differentiation of the urban
population. Using the Isolation-with-Migration model implemented in IMa2
we inferred that a split between suburban and rural populations would have
occurred recently (<150 years ago) with higher urban effective
population density consistent with an urban-source to rural-sink of
effective migration. The observed genetic differentiation of urban
multimammate mice is striking given the uninterrupted distribution of the
animal throughout the landscape and the high estimates of effective
migration (2NeM = 3.0 and 29.7), suggesting a strong selection gradient
across the urban boundary.