Barn swallow demographic inference using approximate Bayesian computation and whole genome data shows signal for founder event during the Holocene. Molecular Ecology
23-04-2019 09:56
Accounting for historical demographic features is vital for many types of evolutionary
inferences, including the estimation of divergence times between closely related
populations. In barn swallow, Hirundo rustica, inferring historical population sizes
and subspecies divergence times can shed light on the recent co‐evolution of this
species with humans. Pairwise sequentially Markovian coalescent uncovered population
growth beginning on the order of one million years ago—which may reflect the
radiation of the broader Hirundo genus—and a more recent population decline.
Additionally, we used approximate Bayesian computation to evaluate hypotheses
about recent timescale barn swallow demography, including population growth due
to human commensalism, and a potential founder event associated with the onset
of nesting on human structures. We found signal for a bottleneck event approximately
7,700 years ago, near the time that humans began building substantial structures,
although there was considerable uncertainty associated with this estimate.
Subspecies differentiation and subsequent growth occurred after the bottleneck in
the best‐supported model, an order of magnitude more recently than previous estimates
in this system. We also compared results obtained from whole‐genome
sequencing versus reduced representation sequencing, finding many similar results
despite substantial allelic dropout in the reduced representation data, which may
have affected estimates of some parameters. This study presents the first genetic
evidence of a potential barn swallow founder effect and subspecies divergence
coinciding with the Holocene, which is an important step in analysing the biogeographical
history of a well‐known human commensal species.