Natural and Experimental Hybridization in Armeria (Plumbaginaceae): Armeria salmantica

Abstract

An experimental crossing program was carried out to investigate the presumed hybrid origin of Armeria salmantica, a local endemic species from a single mountain range in western Spain. Fruit set and pollen stainability data in artificial hybrids between the two putative parents, A. transmontana and A. bigerrensis, demonstrate that internal interspecific barriers are weak. The F1 hybrids exhibit an average pollen stainability of 89.8%, which minimizes the need for a restoration of pollen viability through backcrossing. No evidence of male sterility in artificial hybrids was found. A morphometric analysis of 146 specimens belonging to parental species, artificial hybrids (F1, B1, B2), and wild putative hybrids showed that (1) morphological characters have a strong genetic basis and thus may be good markers to identify hybrids and to track introgression in the genus Armeria; (2) artificial backcrossing produces variation in morphometric characters that conforms in both trend and magnitude to what is commonly attributed in the wild to introgression; and (3) the results of a multivariate morphometric study are congruent with a hybrid origin of A. salmantica, although not conclusive as to its parentage or to the degree of introgression that might have occurred.