Selection Of Genetic Diversity Research Articles

Male flat lizards prefer females with novel scents

In lizards, pheromonal cues are important for mate recognition and are expected to diverge during the speciation process. We tested for divergence in pheromonal mate and species recognition between male flat lizards (Platysaurus broadleyi) belonging to the same population, a different population, and a sister species. Males were given a choice between two refuges, an odourless control and one of the following: a conspecific female from the same population (sympatric), a conspecific female from a distant population (allopatric), and a female from their sister species (heterospecific), P. capensis. Males chose refuges treated with the scent of a heterospecific over an odourless control refuge but showed no preference for refuges that were scented with female conspecific (allopatric or sympatric) cues over the control. These results were consistent in the breeding and non-breeding seasons. In a second experiment males were offered a choice of female scents between sympatric and allopatric conspecifics; an allopatric conspecific and a heterospecific; and a sympatric conspecific and a heterospecific. Males showed a trend of preferring heterospecific over conspecific refuges and allopatric over sympatric conspecific-scented refuges, but these results were not significant at alpha <0.05. Contrary to our original expectations, these experiments do not provide any evidence for a pheromonal pre-mating isolation mechanism within this species complex. However, our results suggest a preference for novel female scents by males, consistent with selection for genetic diversity.

Male flat lizards prefer females with novel scents

In lizards, pheromonal cues are important for mate recognition and are expected to diverge during the speciation process. We tested for divergence in pheromonal mate and species recognition between male flat lizards (Platysaurus broadleyi) belonging to the same population, a different population, and a sister species. Males were given a choice between two refuges, an odourless control and one of the following: a conspecific female from the same population (sympatric), a conspecific female from a distant population (allopatric), and a female from their sister species (heterospecific), P. capensis. Males chose refuges treated with the scent of a heterospecific over an odourless control refuge but showed no preference for refuges that were scented with female conspecific (allopatric or sympatric) cues over the control. These results were consistent in the breeding and non-breeding seasons. In a second experiment males were offered a choice of female scents between sympatric and allopatric conspecifics; an allopatric conspecific and a heterospecific; and a sympatric conspecific and a heterospecific. Males showed a trend of preferring heterospecific over conspecific refuges and allopatric over sympatric conspecific-scented refuges, but these results were not significant at alpha <0.05. Contrary to our original expectations, these experiments do not provide any evidence for a pheromonal pre-mating isolation mechanism within this species complex. However, our results suggest a preference for novel female scents by males, consistent with selection for genetic diversity.

Cloning and sequence analysis of 14 DRB alleles of the bovine major histocompatibility complex by using the polymerase chain reaction

The genetic diversity in the first domain exon of a bovine class II DRB gene was investigated by PCR amplification and DNA sequencing. Genomic DNA samples representing 14 different class II haplotypes, defined by RFLP analysis, were used. The analysis revealed an extensive polymorphism and 14 alleles at a single locus, designated DRB3, were identified. Multiple amino acid substitutions were found in all pairwise comparisons of alleles; 5 to 21 substitutions in the 83 positions compared. The genetic diversity at the amino acid level found in cattle matches the one previously found in the DRB1 locus in man. The significantly higher frequency of replacement substitutions compared with the frequency of silent substitutions provides strong evidence that there is selection for genetic diversity in the bovine DRB3 first domain exon. A comparison of the DRB polymorphism in man and cattle reveals a striking similarity as regards the location of polymorphic positions in the DRB molecule and the degree of polymorphism at polymorphic positions. The majority of polymorphic positions in both species are found in the proposed antigen recognition site of the class II molecule. In addition, there are eight positions which are polymorphic in both species but have not been assigned to the antigen recognition site. The possible functional significance of the polymorphism of these latter positions is discussed.