A comparative study of floral and electrophoretic variation with life history variation in Limnanthes alba (Limnanthaceae).

Plants derived from ten representative Limnanthes alba populations in Northern California, grown in a common environment, showed significant among-population genetic variation of certain floral and life history characters. Variation of these two sets of characters also correlated with the geographic distribution of populations, suggesting the influence either of common ancestry of neighboring populations, or of gradients of natural selection. In contrast, allozyme variation at eleven polymorphic loci showed little pattern. This suggests, if allozyme variants are assumed to accurately measure co-ancestry and each character set is assumed to give adequate and similar statistical power, that selection may have predominated over certain neutral processes during the evolution of some floral and life history characters.Life history characters, being closely tied to fitness, are particularly relevant to the postulated selection gradient. Studies of three representative populations in nature revealed significant differences in the sizes of dormant seed banks and several reproductive characters. These differences correlated with some field measures of soil and biotic variables, and were compared with certain predictions from reproductive strategy models in an attempt to identify any agents of selection. Alternative sets of life history characters were discernable corresponding to varieties identified on the basis of floral morphology, but these sets did not match those predicted the by r and k selection dichotomy; instead alternative selection regimes that may also favor some "bethedging" adaptations are postulated, although we emphasize our measures of habitat and climatic factors are too preliminary to clearly distinguish selective environmental factors.