Sagehen Creek Field Station

14 Jul, 03 AM - 14 Jul, 10 AM

The primary aim of my doctoral research will be to assess the roles of genetic drift and divergent selection in engendering reproductive isolation among allopatric populations of Mimulus guttatus, a California native plant that is undergoing ecotypic differentiation in response to recent, human induced soil chemistry changes. Concurrently, I will explore to what extent this early reproductive isolation reflects intrinsic genetic incompatibilities versus maladaptation to extrinsic selection pressures. The annual/perennial M. guttatus is one of few species that have successfully invaded the soils of abandoned copper mines. Allen and Sheppard (1971) documented the presence of copper-tolerant ecotypes on several California copper mines abandoned between 125-150 years ago. This wild, possibly incipient, species is not yet fully reproductively isolated, thereby enabling identification of the forces driving the evolution of this early isolation. My approach will focus on an array of recently diverging, presently intraspecific, populations in the field. To my knowledge, M. guttatus is the only wild species for which pleiotropic effects of divergent selection pressures have been implicated as the cause of early reproductive isolation (Macnair and Christie 1983). Through a series of diallelic crossing experiments, Macnair and Christie (1983) demonstrated the presence of hybrid inviability between particular Cu-tolerant (from Copperopolis, CA) and non-tolerant individuals (Stinson Beach, CA and Cerig-y-drudion, North Wales). Their progeny analysis suggests that the genes conferring copper tolerance (one of large effect and several modifiers) are the same as (or closely linked to) a major locus causing reproductive incompatibility (RI). Furthermore, an RI allele may complement an allele at an unlinked locus to create ?hybrid? inviability in a cross between the tolerant and non-tolerant genotypes. This interpopulation variation in reproductive isolation, combined with the hypothesis that the copper tolerance gene is linked to an incompatibility locus, suggests that M. guttatus system offers a unique opportunity to address several questions about the allopatric speciation process: 1) What is the relative importance of natural selection and random forces in the evolution of reproductive isolation? and 2) To what extent does reproductive isolation reflect intrinsic genetic incompatibilities versus maladaptation to extrinsic selection pressures?

Visit #5616 @Sagehen Creek Field Station

Approved

Under Project # 4402 | Research

The evolution of reproductive isolation in Mimulus guttatus

graduate_student - University of California, Davis

Reservation Members(s)

Mia Levine Jul 14, 2004 (1 days)
Mia Levine Jul 14, 2004 (1 days)

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Day Use 2 Jul 14 (7 hours)