Data from: The consequences of an introgression event

The spread of adaptive alleles is fundamental to evolution, and in theory,
this process is well‐understood. However, only rarely can we follow this
process—whether it originates from the spread of a new mutation, or by
introgression from another population. In this issue of Molecular Ecology,
Hanemaaijer et al. (2018) report on a 25‐year long study of the mosquitoes
Anopheles gambiae (Figure 1) and Anopheles coluzzi in Mali, based on
genotypes at 15 single‐nucleotide polymorphism (SNP). The species are
usually reproductively isolated from each other, but in 2002 and 2006,
bursts of hybridization were observed, when F1 hybrids became abundant.
Alleles backcrossed from A. gambiae into A. coluzzi, but after the first
event, these declined over the following years. In contrast, after 2006,
an insecticide resistance allele that had established in A. gambiae spread
into A. coluzzi, and rose to high frequency there, over 6 years (~75
generations). Whole genome sequences of 74 individuals showed that A.
gambiae SNP from across the genome had become common in the A. coluzzi
population, but that most of these were clustered in 34 genes around the
resistance locus. A new set of SNP from 25 of these genes were assayed
over time; over the 4 years since near‐fixation of the resistance allele;
some remained common, whereas others declined. What do these patterns tell
us about this introgression event?