143 Views 50 Downloads
An increasing volume of empirical studies demonstrated that hybridization
between distant lineages may have promoted speciation in various taxa.
However, the timing, extent, and direction of introgressive hybridization
remain unknown in many cases. Here, we report a possible case in which
repeated hybridization promoted divergence of Oryzias ricefishes
(Adrianichthyidae) on Sulawesi, an island of Wallacea.
Four Oryzias species are endemic to the Malili Lake system in central
Sulawesi, which is composed of five tectonic lakes; of these, one lake is
inhabited by two species. Morphological and population genomic analyses of
genome-wide single-nucleotide polymorphisms revealed that these two
sympatric species are phylogenetically sister to but substantially
reproductively isolated from each other. Analyses of admixture and
comparison of demographic models revealed that the two sympatric species
experienced several substantial introgressions from outgroup populations
that probably occurred soon after they had secondary contact with each
other in the lake. However, the ratio of migrants from the outgroups was
estimated to be different between the two species, which is consistent
with the hypothesis that these introgressions aided their divergence or
prevented them from forming a hybrid swarm. Repeated lake fragmentations
and fusions may have promoted diversification of this freshwater fish
species complex that is endemic to this ancient lake system.
143 views reported since publication in 2021.