Seed shape supports phylogenetic relationships and adaptive radiation in the genus Pinguicula (Lentibulariaceae)

Abstract

Recent phylogenetic analyses call into question the morphology-based classification of Pinguicula. Although considerable floral morphological diversity among taxa in the genus is present within a geographical region, the phylogenetic analyses suggest that in many cases the taxa in any such region form a monophyletic group. Floral morphology may well have masked phylogenetic relationships and further evidence is required to clarify the issue. In this study, seed shape and size in Pinguicula from Mexico and higher latitudes of the Northern Hemisphere (Northern) belonging to subgenera Isoloba and Pinguicula, a total of 38 taxa, were compared. Results showed that the seed of Mexican taxa was significantly narrower than that of the Northern taxa. The study suggests that the morphology-based subgeneric division was not supported by statistical analyses of seed characters, whereas the geographical division was supported. The Northern and Mexican taxa can, therefore, be separated by their seed shape and size, and consequently the adaptive radiation inferred by the phylogenetic analyses was strongly supported by seed shape, in addition to life-form and basic chromosome number. The shape of seed remains similar within a lineage in each region with relation to the evolutionary history of the genus.