PubMed · 2026-06-27
Two closely related flies that form galls on rubber rabbitbrush evolved into separate species surprisingly fast — in under 110,000 years — because each became so genetically locked to its specific host plant variety that it can't survive on the other's plant.
The two fly species diverged into reproductively isolated species in only 72,000–110,000 years, an unusually rapid rate of speciation.
Purebred flies and even first- and second-generation hybrids failed to successfully induce galls on the alternate host plant variety, demonstrating near-complete 'immigrant inviability'.
Genomic analysis showed high genetic differentiation (FST) and low gene flow between the two species despite living in the same geographic area, confirming that host-plant specialization alone drove their separation.
