An analysis of five enzyme‐gene loci in four etheostomid species (Percidae: Pices) in an area of possible introgression

Incongruence between recognized taxonomy and phylogenetic relationships between two species from a diverse clade (Percidae: Etheostomatinae) of stream fishes was found in a mitochondrial (mt) DNA gene tree. Two darters in subgenus Oligocephalus, Etheostoma uniporum current darter and Etheostoma caeruleum rainbow darter were sampled throughout their sympatric distribution in the Ozark Highlands of the central United States. Sequences from cytochrome (cyt) b and the first intron of the nuclear marker S7 were analysed separately using maximum parsimony and Bayesian methods. Cyt b recovered both species as polyphyletic; E. uniporum haplotypes were interspersed within E. caeruleum. However, both species were monophyletic and non-sister taxa based on S7. The cyt b gene tree pattern is caused by introgressive hybridization resulting in the mtDNA replacement of E. uniporum haplotypes by those of E. caeruleum. Some E. uniporum haplotypes are shared with geographically proximate E. caeruleum, and this is consistent with recent hybridization, while other E. uniporum haplotypes indicate historical sorting of introgressed lineages. The mechanism of introgression is likely asymmetric sneaking behaviour by male E. uniporum, a mating tactic observed in related species. MtDNA replacement may have occurred in E. uniporum due to drift fixation in a historically small female effective population. Additional evidence for darter hybridization will likely be discovered in future molecular genetic surveys of the nearly 200 species in eastern North America.

Section: Introductionmentioning

confidence: 98%

History repeated: recent and historical mitochondrial introgression between the current darter Etheostoma uniporum and rainbow darter Etheostoma caeruleum (Teleostei: Percidae)

Ray¹,

Lang²,

Wood³

et al. 2008

“…In tribute to their quality, only two published cases could be found where biochemical results contradict the conclusions drawn on the basis of morphological analyses. In Etheostomid (Percidae) species populations (Martin & Richmond, 1973;McLeod et al, 1980), morphologically intermediate individuals have not proven to be hybrids even though the species involved hybridize freely in the laboratory. Also, allozyme data were able to disallow the hybrid origin of the cyprinid species Rhinichfhys bowersi (Goldsborough & Clark) from R. micropogan and R. cataructae (Valenciennes) (Goodfellow et af., 1984).…”

Section: Hybridizationmentioning

confidence: 99%

Introgressive hybridization in fishes: the biochemical evidence

Verspoor

Hammart²

1991

131

Biochemical methods can detect variation at individual genetic loci, making possible the direct assessment of natural hybridization and introgression between fish populations. Protein electrophoresis has been used to confirm and extend knowledge of many situations where species hybrids have been detected by morphological analyses. New cases of natural hybridization, including some at the subspecies level, have also been identified. Biochemical studies have provided the first conclusive evidence of natural post F, hybrids and of introgression between fish taxa. The strongest cases for introgression have used a combined analysis of nuclear protein genes and taxaspecific maternally inherited mitochondrial DNA variation. Information on the significance of introgression as a source of gene flow between taxa, particularly below the species level where sympatric subspecies and sibling species are involved, should expand in the future as the numbers and types of nuclear and mitochondrial DNA loci which can be assayed for variation increase.The full importance of introgressive hybridization in speciation may then be understood.

“…471 trutta L.) and the Atlantic salmon (S. salur L.) in which the F, hybrids morphologically resemble one of the parents. An electrophoretic study of enzymes has been used to show that presumed hybrids between Etheostoma species are most probably not genetic hybrids (Martin & Richmond, 1973).…”

Section: Introductionmentioning

confidence: 99%

Electrophoretic identification of roach (Rutilus rutilus L.), rudd (Scardinim erythrophthalmus L.), bream (Abramis brama L.) and their natural hybrids

Brassington

Ferguson

1976

Electrophoretic identification of roach (Rutilus rutilus L.), rudd (Scardinius e r~t h r~~h~~u l m u s L.), bream (Abramis brama L.) and their natural hybrids Roach, rudd, bream and their natural hybrids of 2cm standard length or larger can be definitively identified by their enzyme electrophoretic patterns. Zymograms of lactate dehydrogenase and esterases as produced by vertical starch gel electrophoretic analysis of whole fry or adult eye extracts are the most useful in this respect. The lactate dehydrogenase isozymes, containing B sub-units, migrate more anodally in rudd and bream than in roach. Due to the tetrameric structure of lactate dehydrogenase, in hybrid rudd x roach and roachxbream, eleven isozymes can be observed as compared with six in the parental patterns. Esterases show unique patterns for all species and hybrids. With the exception of one fraction in rudd x bream, the esterase patterns of hybrids show summations of the parent a1 phenotypes. PLATE I . Esterase zyrnograms of eye extracts separated by vertical starch gel electrophoresis. Sample identification as in Fig. I , The top of the photograph is the anodal end.