Ecological correlates of chiasma frequency and recombination index of plants

Abstract

This paper tests four theories of the maintenance of genetic recombination using published chiasma frequencies of 194 plant species representing 15 families of angiosperms. The theories are that recombination is favoured by environmental unpredictability, by fluctuating selection, by mutational load or by sib-competition. The level of genetic recombination was approximated by recombination index and by the number of excess chiasmata. Both measures were higher in animaldispersed than in other species and increased as dispersal distance decreased. This association was found at all taxonomic levels. Chiasma frequency was not associated with life span of the species. Recombination index was lower in perennial than in annual species, but the reverse trend was observed among genera. Number of chiasmata per bivalent tended to decrease as the number of chromosomes increased, but this association was statistically insignificant at all taxonomic levels. No association was found between number of chiasmata per cell and nuclear DNA content.These patterns did not support the theories that environmental unpredictability or fluctuating selection due to parasite pressure favour recombination, and they offered only very little support for the theory that recombination is favoured so that mutational load can be decreased. The only theory that was consistent with the observed data is the sib-competition theory, which suggests that genetic recombination is maintained so that the intensity of competition with sibs is reduced.

Meiotic behavior of wild Caricaceae species potentially suitable for papaya improvement

“…Dasmaceno Junior et al (2010) reported similar RI values to those found in this study for C. papaya and V. monoecious (26.0 and 25.8 respectively). These values can be considered satisfactory, based on a review of the RI of 194 species of 46 genera and 15 angiosperm families, with values ranging from 6.56 to 75.2, with a mean of 26.9 (Koella 1993).…”

Recombination Difference between Sexes: A Role for Haploid Selection

“…Finding a pattern consistent with this general population genetic prediction is, of course, not firm evidence that male-female dimorphism in haploid selection is the evolutionary force generating heterochiasmy. Other correlates of selfing rates might have to be closely examined [23]. However, we consider this explanation the most parsimonious so far.…”

The contribution of recombination to heterozygosity differs among plant evolutionary lineages and life-forms

“…However, particular issues related to the selective or stochastic forces that shape independently each particular species might tend to blur these predictions. Indeed, different ecological and selective patterns might result in altered levels of recombination [6-8]. For example, domesticated plants tend to have higher rates of recombination than their wild ancestors or relatives [7].…”