Evolution, 46(3), 1992, pp. 665-676
Evolution, 46(3), 1992, pp. 665-676


RAYMOND D. SEMLITSCH AND HEINZ-ULRICH REYER Institute of Zoology, University of Zörich, CH-8057 Zörich, SWITZERLAND

Abstract.ĐThe performance of three genotypes (LL, LR, RR) of tadpoles resulting from the hybrid mating system of Rana lessonae (phenotype L, genotype LL) and Rana esculenta (phenotype E, genotype LR) was determined in artificial ponds. The effects of interspecific competition and pond drying on growth, development, and survival of tadpoles were used to measure the performance of genotypes and the relative fitness of offspring. Among the three genotypes, tadpoles from the homogametic mating RR had the lowest survival, growth, and development under all environ-mental conditions. Body size of the LL and LR genotype tadpoles at metamorphosis was reduced by competition and pond drying. Days to metamorphosis were also higher for the LL and LR genotype tadpoles in competition ponds. The proportion of individuals metamorphosing of each genotype was differentially lowered by competition and pond drying. The LL genotype produced more metamorphs than the LR genotype in the constant water level ponds, but the LR genotype produced more in drying ponds. In competition ponds, the LR genotype produced more meta-morphs than the LL genotype, but the LL genotype produced more metamorphs in ponds without competition. The RR genotype produced no metamorphs in any of the experimental environments. Increased performance of LR offspring from the heterogametic mating, in harsh conditions, and reduced performance of RR offspring from the homogametic mating, even under favorable conditions, relative to the parental genotype (LL) suggests that the population dynamics of this hybridogenetic system is strongly dependent on mate choice in mixed populations and the subsequent pond environment females select for oviposition and larval development.

Key words.- Amphibian, development, growth, hybridogenetic, metamorphosis, phenotypic vari-ation, Rana esculenta complex, survival, tadpole.

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Peter Beerli, Dept. of Genetics, University of Washington, Seattle 98195, beerli@scs.fsu.edu