Is morphology supporting a monophyletic Proustia Lag., (Nassauvieae, Asteraceae)?

Abstract

Proustia is an Andean genus traditionally considered to have three species and ten infraspecific taxa, which has often been placed in tribes other than Nassauvieae mainly because of its distinctive style features. Currently, each of the three species of Proustia is included in its own section denoting a consistent morphological variability within the genus. The heterogeneity among Proustia species mainly relies on habit, spiny structures arrangement, capitula arrangement, and pappus features. On the contrary, the forms or varieties within each species are apparently more homogeneous. The phylogenetic analysis performed here is based on morphological features and includes all the species, and all but two varieties and forms of Proustia. We test the boundaries of Proustia and the hypothesis that morphological discontinuities in the genus are phylogenetically uninformative. A total of 26 taxa and 29 morphological, anatomical, and palynological characters were studied. A maximum parsimony analysis yield six most parsimonious trees that showed almost identical topologies. Our results do not support the current generic concept of Proustia. Independently, each species of Proustia was monophyletic when taxa at sub-specific level were considered. Proustia pyrifolia was retrieved sister to the genus Berylsimpsonia although this clade did not obtain significant support. The spiny structures usually referred to as diagnostic for Proustia are not homologous for the genus. Characteristics of habit, spiny structures, secondary inflorescences and pappus support clades representing each species of Proustia, which may in turn, represent different genera.

Phylogenetic relationships and generic reassessment of Proustia and allies (Compositae: Nassauvieae)

“…However, we failed to find this type of corolla. Drawn by Gisela Sancho. Version of Record 1974; Sancho & al., 2014), dorsally covered by collecting hairs on the distal half (vs. usually apically truncate style branches with an apical tuft of collecting hairs in most Nassauvieae). In addition, the corollas of Proustia are sometimes deeply 5-lobed ( Fig.…”

“…Intergeneric relationships of Proustia are no less problematic. Lophopappus Rusby, an Andean genus of five species (Katinas & al., 2013) has been closely related to Proustia, mainly by sharing style, corolla, and pollen features (Crisci, 1974;Tellería & al., 2003;Katinas & al., 2013;Sancho & al., 2014). Figures 1A-P and U-Y show some of their distinctive features.…”

“…Although it only includes three species (Fabris, 1968;Sancho & al., 2014) (Table 1), Proustia shows a highly variable morphology, and this variation led Fabris (1968) to recognize several forms under each species. Besides, recent morphological phylogenetic analyses have challenged its monophyly (Sancho & al., 2014). If Proustia is confirmed as non-monophyletic, the systematic and evolutionary significance of its unusual morphological characters mentioned above would need to be re-evaluated within Nassauvieae.…”

“…A non-monophyletic Proustia could explain its variable morphology despite the low number of species (Sancho & al., 2014). Indeed, homology of some of the traditional diagnostic features of Proustia is under debate.…”

“…Indeed, homology of some of the traditional diagnostic features of Proustia is under debate. Sancho & al. (2014) indicated that the spiny structures usually referred to as diagnostic of Proustia are not homologous and probably adaptations to particular habitats.…”