Data from: Invasion facilitates hybridization with introgression in the Rattus rattus species complex

Biological invasions result in novel species interactions, which can have
significant evolutionary impacts on both native and invading taxa. One
evolutionary concern with invasions is hybridization among lineages that
were previously isolated, but make secondary contact in their invaded
range(s). Black rats, consisting of several morphologically very similar
but genetically distinct taxa that collectively have invaded six
continents, are arguably the most successful mammalian invaders on the
planet. We used mitochondrial cytochrome b sequences, two nuclear gene
sequences (Atp5a1 and DHFR), and nine microsatellite loci to examine the
distribution of three invasive black rat lineages (R. tanezumi, R. rattus
I, and R. rattus IV) in the U.S. and Asia, and determine the extent of
hybridization among these taxa. Our analyses revealed two mitochondrial
lineages that have spread to multiple continents, including a previously
undiscovered population of R. tanezumi in the southeastern U.S., whereas
the third lineage (R. rattus IV) appears to be confined to Southeast Asia.
Analyses of nuclear DNA (both sequences and microsatellites) suggested
significant hybridization is occurring among R. tanezumi and R. rattus I
in the U.S., and also suggest hybridization between R. tanezumi and R.
rattus IV in Asia, although further sampling of the latter species pair in
Asia is required. Furthermore, microsatellite analyses suggest
unidirectional introgression from both R. rattus I and R. rattus IV into
R. tanezumi. Within the U.S., introgression appears to be occurring to
such a pronounced extent that we were unable to detect any nuclear genetic
signal for R. tanezumi, and a similar pattern was detected in Asia.