No abstract

The male-polymorphic poeciliid fish, Limia perugiae, a small teleostean endemic to the southeast of the Caribbean island Hispañola, consists of three male size morphs with uniform females. Large males differentiate at a size varying between 25 and 38 mm; intermediate males, between 21 and 25 mm. Under competition, large males exhibit an elaborate courtship display, whereas small males show only a sneak-chase behavior. Intermediate males adapt their tactics to the respective competitors. However, all male morphs can switch from courtship display to sneak-chase behavior. In large mating groups with four males of different size and five or six virgin females, large dominant alpha-males as well as small subordinate delta-males did not produce any offspring. Unexpectedly, all progeny were sired exclusively by the intermediate subordinate beta- and gamma-males. Breeding experiments with the three male morphs can best be explained by a model of Y-linked genes for small and large size which are both suspended by the activity of an autosomal recessive repressor responsible for the development of intermediate males. The dominant allele of the recessive repressor, in either its homoorits heterozygous state, activates the Y-chromosomal genes for large or small size, respectively. Accordingly, intermediate males may produce male offspring of all size classes, depending on the presence of either the Y-linked gene or the autosomal repressor.

No abstract

Hierarchical structures among male individuals in a population are frequently reflected in differences in aggressive and reproductive behavior and access to the females. In general, social dominance requires large investments, which in turn then may have to be compensated for by high reproductive success. However, this hypothesis has so far only been sufficiently tested in small mating groups (one or two males with one or two females) due to the difficulties of determining paternity by conventional methods. DNA fmgerprinting overcomes these problems by offering the possibility to determine genetic relationships and mating patterns within larger groups

Hereditary changes in the shape of the vertebral column in Lebistes reticulatus appeared after ancestral irradiation of immature germ cells with 500 or 1000 R of X-rays. Although the mutant to wild-type ratios in the F2 generation after outcrossing fitted a digenic and a trigenic segregation ratio, respectively, the quantitative characters in question are assumed to be caused by recessive mutations of polygenes which are highly mutable.