QUANTITATIVE VARIATION, HERITABILITY, AND TRAIT CORRELATIONS FOR ULTRAVIOLET FLORAL TRAITS IN ARGENTINA ANSERINA (ROSACEAE): IMPLICATIONS FOR FLORAL EVOLUTION

摘要

Premise of research. Variation in flower color in the human-visible spectrum is well studied but less understood for ultraviolet (UV) floral traits despite their ubiquity and importance in mediating plant-insect interactions. Describing the extent of quantitative phenotypic variation and determining the heritability of UV pattern are crucial for understanding the evolution of flower color. Finally, selection on vegetative biochemical properties can indirectly influence flower color evolution, and thus, establishing correlation between biochemistry and color pattern will inform whether indirect selection could act on flower color patterns. Methodology. We characterize phenotypic variation for the proportion of petal area that absorbs UV (UV proportion) in 13 populations representing two taxa in the Argentina anserina aggregate. We estimate broad-sense heritability and genetic correlations for UV proportion, floral spectral qualities measured at the base and apex of petals (UV reflectance, UV chroma, brightness, green chroma), and the concentration of foliar UV-absorbing compounds. Pivotal results. We found substantial quantitative variation for UV proportion in the field (0.34-0.99) and UV proportion was heritable in both taxa (H~2 ≥ 0.85). In one taxa, heritabilities for quantitative measures of petal color were low but significant. Petal color at the petal base and apex were independent in one taxon but positively correlated in the other. UV proportion was not correlated with foliar UV-absorbing compound concentration in either taxa. Conclusions. Variation and heritability of UV proportion suggest that it could respond to selection. Within-petal spatial correlations for color in one taxon but not the other shows that, for species with patterned petals, color of distinct petal regions may evolve independently in some taxa but be constrained in others. The decoupling of UV proportion from vegetative biochemistry in this system implies that indirect selection on UV pattern through selection on vegetative organs is unlikely.