Natural hybridization in Cardamine (Brassicaceae) in the Pyrenees: evidence from morphological and molecular data

Abstract

While researching Cardamine (Brassicaceae) in the Pyrenees, putative hybrid plants were found at two natural sites. Pollen grain viability, AFLP, and multivariate morphometric analyses were performed in order to assess the plants' presumed hybrid origin, establishing that natural hybridization between the diploids C. crassifolia and C. amara ssp. pyrenaea had occurred. A new diploid nothospecies, C. xenriquei (2n = 2x = 16), is described. Examination of 18 morphological characters showed the intermediacy of the hybrid between the parental taxa in most characters. AFLP analyses of C. amara ssp. amara, ssp. austriaca, ssp. olotensis and C. raphanifolia, demonstrated the close position of the hybrid to C. crassifolia, and revealed that the highest number of markers were shared with the parents. Polymorphism found in the AFLP pattern of the hybrid suggested recurrent origin, segregation and/or backcrosses, although, assessment of pollen viability indicated high male sterility. The hybridization event reported here represents the second documented case between the C. pratensis group and C. amara. An account of the nomenclature of C. crassifolia is also presented, including lectotypification of relevant names. (C) 2002 The Linnean Society of London.