RESUMEN
Theory predicts that sexual selection can promote the evolution of reproductive isolation and speciation. Those cases in which sexual selection has led to speciation should be characterized by significant differentiation in male display traits and correlated female preferences in the absence of post-zygotic isolation, accompanied by little genetic or other morphological differentiation. Previous evidence indicates that a cluster of populations of the guppy (Poecilia reticulata Peters) from Cumana, Venezuela, the 'Cumana guppy', differs significantly in female preferences from a nearby guppy population (A. Lindholm & F. Breden, Am. Nat., 160: 2002, S214). Here, we further document sexual isolation between these populations. In addition, these populations exhibit significant divergence in male display traits correlated to differences in between-population mating success, little mitochondrial genetic differentiation, and we find no evidence for genetic incompatibility between a Cumana population and several geographically isolated populations. These results suggest that divergent sexual selection has contributed to differentiation of the Cumana guppy, and this may be the first example of incipient speciation in the guppy.
Asunto(s)
Variación Genética , Poecilia/anatomía & histología , Poecilia/fisiología , Reproducción/fisiología , Selección Genética , Caracteres Sexuales , Conducta Sexual Animal/fisiología , Animales , Secuencia de Bases , Pesos y Medidas Corporales , Análisis por Conglomerados , ADN Mitocondrial/genética , Demografía , Femenino , Geografía , Guyana , Masculino , Datos de Secuencia Molecular , Filogenia , Pigmentación/fisiología , Poecilia/genética , Análisis de Secuencia de ADN , Especificidad de la Especie , Suriname , Trinidad y Tobago , VenezuelaRESUMEN
The standard slipped-strand mispairing (SSM) model for the formation of variable number tandem repeats (VNTRs) proposes that a few tandem repeats, produced by chance mutations, provide the "raw material" for VNTR expansion. However, this model is unlikely to explain the formation of VNTRs with long motifs (e.g., minisatellites), because the likelihood of a tandem repeat forming by chance decreases rapidly as the length of the repeat motif increases. Phylogenetic reconstruction of the birth of a mitochondrial (mt) DNA minisatellite in guppies suggests that VNTRs with long motifs can form as a consequence of SSM at noncontiguous repeats. VNTRs formed in this manner have motifs longer than the noncontiguous repeat originally formed by chance and are flanked by one unit of the original, noncontiguous repeat. SSM at noncontiguous repeats can therefore explain the birth of VNTRs with long motifs and the "imperfect" or "short direct" repeats frequently observed adjacent to both mtDNA and nuclear VNTRs.
Asunto(s)
Disparidad de Par Base/genética , Repeticiones de Minisatélite/genética , Mitocondrias/genética , Modelos Genéticos , Poecilia/genética , Animales , Secuencia de Bases , ADN Mitocondrial/análisis , ADN Mitocondrial/genética , Genética de Población , Datos de Secuencia Molecular , Mutación , Filogenia , Análisis de Secuencia de ADN , Trinidad y TobagoRESUMEN
The standard slipped-strand mispairing (SSM) model for the formation of variable number tandem repeats (VNTRs) proposes that a few tandem repeats, produced by chance mutations, provide the "raw material" for VNTR expansion. However, this model is unlikely to explain the formation of VNTRs with long motifs (e.g., minisatellites), because the likelihood of a tandem repeat forming by chance decreases rapidly as the length of the repeat motif increases. Phylogenetic reconstruction of the birth of a mitochondrial (mt) DNA minisatellite in guppies suggests that VNTRs with long motifs can form as a consequence of SSM at noncontiguous repeats. VNTRs formed in this manner have motifs longer than the noncontiguous repeat originally formed by chance and are flanked by one unit of the original, noncontiguous repeat. SSM at noncontiguous repeats can therefore explain the birth of VNTRs with long motifs and the "imperfect" or "short direct" repeats frequently observed adjacent to both mtDNA and nuclear VNTRs.