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.

Laserocarpum, a new genus of Apiaceae endemic to Greece

“…The topology of molecular trees was similar to that found in previous molecular studies with the same major clades corresponding to the recognized genera of Daucinae [7,10]. Although these clades usually received high bootstrap support in all analyses, the relationships among them were often ambiguous, with BS < 50%.…”

“…The fruits of P. ramosissima are slightly dorsally compressed and have filiform secondary ribs, whereas those of Athamanta s. s. are laterally compressed and do not have any secondary ribs [12]. Within tribe Scandiceae, the presence of secondary ribs is a presumed synapomorphy for subtribes Daucinae, Torilidinae, and Artediinae [10], whereas Athamanta s. s. is placed in the subtribe Scandicinae [13]. The affinity of Portenschlagiella to subtribe Daucinae has not been inferred previously.…”

“…The fruits of P. ramosissima are covered with stellate hairs and the primary ribs are stout and prominent, whereas the secondary ribs are filiform [3]. In contrast, the fruits of L. pseudomeum are naked, with primary ribs obsolete and secondary ribs protruding into prominent wings [9,10]. Given the lack of any obvious morphological synapomorphies and a rather low molecular support for the sister-group status of these species, we see no advantage of placing them in one genus.…”

“…Recent fruit morphological and anatomical studies have demonstrated that Laserpitium s. s. is distinguished from its former congeners by a suite of characters including the shape of the endosperm in transverse section and the fruit sclerification pattern (i.e., the presence of nonelongated sclerified cells in endocarp and mesocarp tissues [10]). The fruits of L. pseudomeum are superficially similar to those of Laserpitium s. s., in having wings on both dorsal and lateral secondary ribs, but are more similar to those of Laser, in having a distinctly flattened endosperm and a nonsclerified exocarp and mesocarp, thus supporting its position inferred from molecular data [7,10]. However, preliminary molecular analyses using nuclear ribosomal DNA internal transcribed spacer (nrDNA ITS) data have identified another relative of L. pseudomeum, namely Portenschlagiella ramosissima (Port.)…”

Tracing insular woodiness in giant Daucus (s.l.) fruit fossils from the Early Pleistocene of Madeira Island (Portugal)

“…However, several lines of other evidence from mericarp evolution and size, palaeoecology and taphonomy are indicative of the establishment of insular woodiness by this early date. According to Wojewódzka & al. (2019), M. decipiens mericarp wings can be interpreted as an evolutionary reversal from ancestral Daucus spp.…”