Natural Interspecific Hybridization in Gunnera (Gunneraceae) of the Juan Fernandez Islands, Chile

Abstract

Natural interspecific hybridization between Gunnera bracteata and G. peltata (Gunneraceae) in the Juan Fernandez Islands, Chile, is analyzed morphologically and chemically. Parental types from isolated populations were compared with parents and intermediates occurring together in Quebrada Villagra on Masatierra. Two transects were made in that area, one in a relatively undisturbed site, and another along a disturbed path. Hybrid indexes and distance diagrams were used to analyze morphological relationships, and leafflavonoids revealed chemical affinities. Minor flavonoid divergence between parental species precluded detailed analysis of dynamics of hybridization. Morphological analysis revealed intermediacy in both transects,with intergradation back toward both parents. It is suggested that introgressive hybridization is occurring in Quebrada Villagra between these two wind-pollinated species, with more hybridization taking place in disturbed regions. Reduction in surface area and changes in the ecology of Masatierra during the past four million years may have brought the two species into closer contact and aided hybridization.