Evolutionary shifts in fruit dispersal syndromes in Apiaceae tribe Scandiceae

Abstract

Apiaceae tribe Scandiceae includes species with diverse fruits that depending upon their morphology are dispersed by gravity, carried away by wind, or transported attached to animal fur or feathers. This diversity is particularly evident in Scandiceae subtribe Daucinae, a group encompassing species with wings or spines developing on fruit secondary ribs. In this paper, we explore fruit evolution in 86 representatives of Scandiceae and outgroups to assess adaptive shifts related to the evolutionary switch between anemochory and epizoochory and to identify possible dispersal syndromes, i.e., patterns of covariation of morphological and life-history traits that are associated with a particular vector. We also assess the phylogenetic signal in fruit traits. Principal component analysis of 16 quantitative fruit characters and of plant height did not clearly separate species having different dispersal strategies as estimated based on fruit appendages. Only presumed anemochory was weakly associated with plant height and the flattening of mericarps with their accompanying anatomical changes. We conclude that in Scandiceae, there are no distinct dispersal syndromes, but a continuum of fruit morphologies relying on different dispersal vectors. Phylogenetic mapping of ten discrete fruit characters on trees inferred by nrDNA ITS and cpDNA sequence data revealed that all are homoplastic and of limited use for the delimitation of genera. Spines evolved from wings developing on secondary ribs. We hypothesize that spines cannot form on primary ribs because these contain vascular bundles that may constrain such a transformation. We describe a new subtribe for Artedia and propose three new combinations in Daucus.