“…Introgression has resulted in the fixation of heterospecific mitochondrial haplotypes in both the strawberry darter Etheostoma fragi Distler 1968 and in E. uniporum . In the case of E. uniporum , the heterospecific alleles originated from E. caeruleum , though conversely the E. caeruleum clade shows no evidence of introgression from the E. spectabile clade (Ray et al, ; Bossu & Near, ).The recent formation of a hybrid swarm between E. spectabile and the redbelly darter Etheostoma radiosum (Hubbs & Black 1941) sub‐species cyanorum in the Blue River may illustrate the initial process of sympatric interaction and introgression in darters, as the species had previously been largely separated by a dam (Branson & Campbell, ; Echelle et al, ). On the other hand, introgression does not follow inevitably from darter hybridization; hybrids between the logperch Percina caprodes (Rafinesque 1818) and the blackside darter Percina maculata (Girard 1859) are well‐reported (Keck & Near, ), yet there is no evidence of introgression between the two lineages (Near, ; Near & Bernard, ).…”