Interspecific and intergeneric hybridization in South American Rhamnaceae-Colletieae

Abstract

In Gondwanic Discaria, phenotypically intermediate individuals exist between Discaria chacaye (G. Don) Tortosa and Discaria articulata (Phil.) Miers, and between D. chacaye and related Ochetophila trinervis (Gillies ex Hook. & Arn.) Poepp. ex Miers. We studied phenology, pollinators, parental crossability, morphological features, and variation patterns on neutral markers. Intermediates occur wherever parental taxa are sympatric or in close proximity. Flowering was synchronous in D. chacaye and D. articulata for 2 weeks. They also shared three to six pollinator species (depending on site). O. trinervis, which flowered later, occasionally overlapped with D. articulata, with which it shared two pollinators. Germinable seeds were obtained from hand pollinations only from crosses with D. articulata as paternal parent and D. chacaye as maternal parent. Sequencing of chloroplast DNA revealed only two haplotypes. One occurred in D. articulata, D. chacaye, and their intermediates, and the other in O. trinervis and its intermediate with D. chacaye. Only pure parentals had diagnostic alleles by isozymes, whereas intermediates mainly showed those of D. chacaye. Our results confirm intrageneric hybridization between D. chacaye and D. articulata, and intergeneric hybridization between D. chacaye and related O. trinervis.