Peripheral budding following range expansion explains diversity and distribution of one‐sided Livebearing fish

Peripheral budding occurs when populations diverge from a widespread
parental population and speciate along its periphery, facilitated by the
interaction of ecological and geographic barriers. This phenomenon results
in species that contrast in range size and ecological tolerance and can
lead to confounding phylogenies. Here we examine patterns of peripheral
budding in the Jenynsia lineata species complex using a genomic approach
via RAD sequences. The J. lineata species complex is a group of
live‐bearing fish in South America that shows signals of peripheral
budding through asymmetric range sizes, J. lineata being widespread, and
with a confounding and unresolved phylogeny. Our goal was to adequately
classify the J. lineata species complex, delimit species within the
complex via multiple approaches, and identify signals of introgression to
better understand the underlying evolutionary patterns. We collected 85
samples from the species complex for DNA extraction and performed RAD
sequencing to generate genome‐wide molecular markers for phylogenetic
analyses. We found evidence of six distinct genetic groups within the
complex and delimited at least five species, with a new species of
Jenynsia in Northern Argentina along the periphery of J. lineata. Jenynsia
lineata was recovered as the most recently diverged species in our
phylogeny. This placement, along with observed patterns of introgression
between species, suggests peripheral budding to have facilitated
speciation in the J. lineata species complex, following a range expansion
of a parental J. lineata. Our results show genomic patterns associated
with peripheral budding and support the utility of using peripheral
budding to better understand confounding phylogenetic patterns.