Chromosome polymorphisms affecting recombination and exophenotypic traits in Leptysma argentina (Orthoptera): A populational survey
Leptysma argentina is polymorphic for a centric fusion between pairs 3 and 6 of the basic complement, for interstitial (Si) and proximal (Sp) supernumerary segments in the smallest member of the complement, and for a B-chromosome. Fusion 3/6 is associated with several effects that would lead to a dr...
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| Formato: | JOUR |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_0018067X_v62_n3_p289_Colombo |
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| Sumario: | Leptysma argentina is polymorphic for a centric fusion between pairs 3 and 6 of the basic complement, for interstitial (Si) and proximal (Sp) supernumerary segments in the smallest member of the complement, and for a B-chromosome. Fusion 3/6 is associated with several effects that would lead to a drastic reduction of recombination (Colombo 1987, 1988). Nine populations from the Argentine provinces of Buenos Aires, Entre Ríos and Santa Fe were analysed for total (T), proximal (P), interstitial (I) and distal (D) chiasma frequencies, and for the morphometrical characters tegmina length, total length, femur length, tibia length, thorax length and thorax height. There was a strong negative correlation of T, P and I frequencies, and a significant positive correlation of D, with fusion 3/6 frequency. Fusion carriers were significantly bigger than basic homozygotes, leading to highly significant correlations of all morphometrical variables with fusion frequency. The frequencies of the fusion, segment Si and the B-chromosome follow a geographical pattern. The uneven distribution of the fusion is explained by effects on several exo- and endophenotypic traits. The nonrandom distribution of the B-chromosome is attributed to differential tolerance under differing chromosomal, genetical and/or ecological environments. No significant effects were detected for segments but Si is geographically widespread, arguing against its neutrality, while the low frequency and even frequency distribution of Sp suggests maintenance by mutation. © 1989, The Genetical Society of Great Britain. |
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