Variable genomic patterns of hybridization in two independent hybrid
zones of damselflies
Abstract
Hybrid zones with multiple independent contact regions between the same
species allow to determine the relative importance of intrinsic and
extrinsic factors in the evolution of hybrid zones and thus, parallelism
in hybridization outcomes. In this study, we take advantage of two
hybrid regions between the damselfly species Ischnura elegans and I.
graellsii in Spain to measure: i) the extent of parallelism across
geographic hybridization replicates, and what factors (intrinsic and
extrinsic) drive that variation; and ii) if hybridization has an impact
on the ability of species to expand their ranges. RAD sequencing was
used to generate 5,702 SNPs to quantify population diversity and
population differentiation, and a subset of 381 species-specific SNPs to
analyze genotypic composition (individual ancestry and the proportion of
individuals in different hybrid classes Our individual ancestry results
showed on-going hybridization and introgression with different
admixture-class distributions between hybrid regions and between
populations explained by i) species proportions, ii) time elapsed since
colonization, and iii) asymmetric and reinforced prezygotic barriers and
Batson Dobzhansky and Müller (BDM) hybrid incompatibilities, and
indicated a role of hybridization as a facilitator of species range
expansions. Our study highlights the value of studying complex hybrid
zones to gain insights into microevolutionary processes.