GENOTYPIC AND ENVIRONMENTAL COMPONENTS OF VARIATION IN GROWTH AND REPRODUCTION OF FISH HEMICLONES ( POECILIOPSIS : POECILIIDAE)

Abstract

The frozen-niche-variation model was proposed to account for the coexistence of genetically related clones in naturally occurring unisexual populations. This model is based on two assumptions: 1) ecologically different clones have multiple independent origins from sexual ancestors; and 2) the population of sexual ancestors contains genetic variability for ecologically relevant traits. To test these assumptions, we produced 14 new "hemiclones" (nonrecombining haploid genotypes) of fish (Poeciliopsis: Poeciliidae). Our ability to synthesize many new hemiclones demonstrates the feasibility of multiple independent origins of nonrecombining genotypes. A substantial proportion (10-50%) of the phenotypic variation among hemiclones in size at birth, juvenile growth rate, and fecundity had a genetic basis. Thus, we conclude that multiple origins can give rise to an assemblage of genetically distinct hemiclones, each with a unique combination of life-history traits. Additionally, a comparative analysis of two natural hemiclones revealed that the synthetic strains represent a broad field of variation from which natural hemiclones can be selected.

Variations on maternal-embryonic relationship in two natural and six laboratory made hybrids of Poeciliopsis monacha-lucida (Pisces, Cyprinodontiformes)

“…The same pattern had been observed for MLVII and MLVIII and in the most of the laboratory made hybrids for life-history traits, genital pigmentation, maternal cannibalism, innate avoidance of filial cannibalism, aggressiveness, and feeding behavior (Wetherington et al, 1989;Weeks et al, 1993;Lima, 1998). The present results suggested that the unusual reproductive mode of P. monacha expressed by the strains MLVII and MLVIII cannot be evolved subsequent to their origins as hybrids because of similar patterns were observed among most of the unselected laboratory made hybrids.…”

“…The variation of maternal-embryonic relationship was higher among unselected laboratory made hybrids than between MLVII and MLVIII. This pattern of phenotype variation was also observed for others morphological, physiological, and behavioral traits (Wetherington et al, 1987;Wetherington et al, 1989;Lima, 1998). Foundresses from Río Mayo (like E) usually produced a more diversity of hybrids' phenotypes than foudresses from Río del Fuerte (A and B).…”

“…The laboratory made hybrids produced by Wetherington et al (1987) represent new and unselected strains that have been used to analyze several traits to test model that attempt to explain the source and the mechanisms responsible for the hybrid diversities observed in Mexico. Natural and laboratory made hybrids exhibit variation in life-history, morphology, and behavioral traits (Wetherington et al, 1987;Wetherington et al, 1989;Weeks et al, 1993;Lima, 1998). However the reproductive strategies of these hybrids remain to analyze.…”

DIFFERENTIAL SURVIVAL OF SEXUAL AND ASEXUAL POECILIOPSIS DURING ENVIRONMENTAL STRESS

“…In nature, the habitat preferences and differential growth rates of these fish may also complement survival differences. Experimental studies revealed that growth rates and behavior of Poeciliopsis clones have a strong genetic basis (Wetherington et al 1989b;Lima and Vrijenhoek 1996).…”

Feeding behavior in sexual and clonal strains of Poeciliopsis

“…The key premises of the model (e.g., multiple origins and frozen phenotypic differences among clones) have been tested and verified in controlled laboratory studies (Wetherington et al 1987(Wetherington et al , 1989. Despite their potential twofold reproductive advantage, sexual and asexual strains of Poeciliopsis coexist as mixed reproductive complexes in the desert streams of northwestern Mexico.…”