OUTCROSSING IN NATURAL POPULATIONS. V. ANALYSIS OF OUTCROSSING, INBREEDING, AND SELECTION IN CLARKIA EXILIS AND CLARKIA TEMBLORIENSIS.

Abstract

Earlier papers in this series (Vasek, 1964b, 1965, 1967, 1968) have been concerned with the estimation of outcrossing for the purpose of comparing the breeding systems of closely related Clarkia species. Outcrossing estimates have been obtained for three populations of Clarkia exilis and one population of Clarkia unguiculata. The latter species has an outcrossing frequency of essentially 100%, an estimate in accord with expectations based on its long styled, protandrous flowers. Clarkia exilis has received greater emphasis because the first estimates of about 44% were higher than expected on the basis of its short styled, synandrogynous flower structure, and because several fairly large populations with suitable markers were known and accessible. A continuing search for suitable markers in large populations of the other species in the section has not been particularly successful. However, markers have been located and studied in several relatively small populations of C. tembloriensis and in two additional populations of C. exilis. These studies permit an initial estimate of the breeding system of C. tembloriensis, a comparison of small populations with large populations of C. exilis, and an assessment of whether a reasonable outcrossing estimate is possible from a small population or whether a large population is necessary. The same studies also permit an evaluation of inbreeding in these populations and an evaluation of selection by comparing gametic with sporophytic gene frequencies. The purpose of this paper is to summarize and evaluate these parameters.