Fractions with too much friction; Genome-wide SNPs in the spiny lobster
Panulirus homarus reveal a hybrid origin for the subspecies
Abstract
Evolutionary divergence and speciation often occur at a slower rate in
the marine realm due to the higher potential for long-distance
reproductive interaction through larval dispersal. One common
evolutionary pattern in the Indo-Pacific, is divergence of populations
and species at the peripheries of widely-distributed organisms. However,
the evolutionary and demographic histories of such divergence are yet to
be well understood. Here we address these issues by coupling genome-wide
SNP data with mitochondrial DNA sequences to test the patterns of
genetic divergence and possible secondary contact among geographically
distant populations of the highly valuable spiny lobster Panulirus
homarus species complex, distributed widely through the Indo-Pacific,
from South Africa to the Marquesas Islands. After stringent filtering,
2020 SNPs were used for population genetic and demographic analyses,
revealing strong regional structure (FST = 0.148, P<0001),
superficially in accordance with previous analyses. However, detailed
demographic analyses supported a much more complex evolutionary history
of these populations, including a hybrid origin of a North-West Indian
Ocean (NWIO) population, which has previously been discriminated
morphologically, but not genetically. The best-supported demographic
models suggested that the current genetic relationships among
populations were due to a complex series of past divergences followed by
asymmetric migration in more recent times. Overall, this study suggests
that alternating periods of marine divergence and gene flow have driven
the current genetic patterns observed in this lobster and may help
explain the observed wider patterns of marine species diversity in the
Indo-Pacific.