COVARIATION AMONG FLORAL TRAITS IN SPERGULARIA-MARINA (CARYOPHYLLACEAE) - GEOGRAPHIC AND TEMPORAL VARIATION IN PHENOTYPIC AND AMONG-FAMILY CORRELATIONS

Strong covariation among traits suggests the presence of constraints o n their independent evolution due to pleiotropy, to linkage, or to sel ective forces that maintain particular trait combinations. We examined floral trait covariation among individuals, among maternal families w ithin and across populations, and over time, in greenhouse-raised plan ts of the autogamous Spergularia marina. We had three aims. First, sin ce the phenotype of traits expressed by modular organs often changes a s individuals age, estimates of the degree of genetic covariation betw een such traits may also change over time. To seek evidence for this, we measured weekly (for five weeks) an array of floral traits among pl ants representing similar to 10 maternal families from each of four po pulations. The statistical significance of the phenotypic and among-fa mily correlations among traits changed over time. Second, we compared populations with respect to trait covariation to determine whether pop ulations or traits appear to be evolving independently of one another. Differences observed among populations suggest that they have diverge d genetically. Third, we sought correlations that might reflect constr aints on the independent evolution of floral traits. Investment in ant her and ovule production per flower vary independently among maternal families; there was no evidence for a ''trade-off'' between male and f emale investment. We propose that in autogamous taxa one should not fi nd a negative correlation between pollen and ovule production per flow er, as such taxa cannot evolve sexual specialization and should be und er strong selection to maintain an efficient pollen:ovule ratio, preve nting the evolution of male-biased or female-biased genotypes. We foun d that other pairs of floral traits, however, expressed highly signifi cant correlation coefficients, suggesting the presence of some evoluti onary constraints, at least within some populations, although their st rength depended on exactly when flowers were sampled.