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

Abstract

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