Gene linkage, ontogeny of gene expression, and reproductive isolation in Pomoxis annularis, P. nigromaculatus, and their hybrids
Epifanio, John Michael
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Permalink
https://hdl.handle.net/2142/20707
Description
Title
Gene linkage, ontogeny of gene expression, and reproductive isolation in Pomoxis annularis, P. nigromaculatus, and their hybrids
Author(s)
Epifanio, John Michael
Issue Date
1992
Doctoral Committee Chair(s)
Philipp, David P.
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Genetics
Biology, Zoology
Language
eng
Abstract
Three studies were conducted to investigate gene linkage, ontogeny of gene expression, and reproductive isolation in pure species crappies and their interspecific hybrids. In the first study, the potential linkage relationships of ten enzyme-coding loci were determined from backcross and F$\sb2$ hybrid crosses. The results indicated that eight of the loci segregated independently. Two loci, FH-1* and PGM-1*, co-jointly segregated over all crosses. The coefficient of recombination, r, between these loci was 0.136 $\pm$ 0.017 for the backcrosses and ranged from 0.046 $\pm$ 0.028 to 0.175 $\pm$ 0.058 among the F$\sb2$ hybrids. These results were consistent with an hypothesis of linkage group conservation among teleost fishes.
In the second study both crappie species and their reciprocal F$\sb1$ hybrids were used to investigate the ontogenetic regulation of gene expression. We observed that the relative rates of morphological development were similar between maternal half-sibling sets and to rates of other centrarchid species. The time of initiation for 15 of 39 enzyme-encoding loci surveyed during embryogenesis could be unambiguously established. These loci demonstrated considerable temporal variability in expression and disturbances in normal ontogeny of interspecific hybrids. Such variability in expression suggests that some gene regulating elements have diverged since the two species shared a common ancestral genome. In addition, GPI-B* exhibited a phenomenon not previously reported for that locus in centrarchids; the activity of the black crappie allele was consistently lower than the activity level of the white crappie allele.
In the third study, five kinds of experimental crosses were created over six years to investigate reproductive isolation between the crappie species. Mature adults with known heritage and genotype at four unlinked enzyme-encoding loci were introduced into ponds for reproduction the following year. Progeny data from these ponds indicated that crappie can successfully hybridize in both reciprocal directions, that second and third generation hybrids are viable, and that the pure species mate assortatively (positive). The segregation of breeding types suggests that premating isolating mechanism may be more important in these species than postmating mechanisms for maintaining the integrity of their gene pools.
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