Insights into the phylogeny and evolutionary history of Calyceraceae

Abstract

Calyceraceae is a small family with six traditionally recognized genera and 47 species from southern South America. Most species grow along the Andes (of both Argentina and Chile) and in arid regions of the Patagonian steppe. This family belongs to the well‐supported MGCA clade within Asterales, which includes Menyanthaceae+Goodeniaceae+Calyceraceae+ Asteraceae. Calyceraceae is monophyletic and sister to Asteraceae, one of the five largest families of angiosperms. Although Calyceraceae is clearly distinct as a family, its genera are not, and taxonomic revisionary effort has confirmed the lack of sharp boundaries among genera. We performed a phylogenetic analysis of Calyceraceae with a broad taxon sampling (41 of 47 species), and with sequence data from multiple regions from the nuclear (ITS) and plastid genomes (ycg6‐psbM, psbM‐trnD, trnS‐trnG, trnH‐psbA, trnD‐trnT) using maximum parsimony and Bayesian approaches. We aimed at identifying monophylectic groups, their putative morphological synapomorphies and their geographical distribution; we also estimated divergence times and examined chromosomes numbers in an evolutionary context. We obtained well‐resolved and strongly supported phylogenies that show Calyceraceae to be divided into two major clades with geographically structured subclades within each. Our results indicate that an early split within Calyceraceae occurred about 27.4 Ma, probably related to differential changes in chromosome numbers, which allowed the two lineages to evolve in sympatry. We found that major natural subgroups diverged 15–12 Ma, following the Early‐Miocene South Andes construction stage. Finally, the diversification of the extant species is probably associated to Andean orogeny and climate changes in the last 5–4 Myr. We recovered Acicarpha as monophyletic, while the remaining traditionally recognized genera of Calyceraceae are para‐ or polyphyletic. Most species of Moschopis are included in the Glutinose group, but M. monocephala is more closely related to some Calycera species. Calycera is divided into two clades; the Calycera group and the Pilose group. All species of Nastanthus are placed in a well‐supported main group with species of Gamocarpha and Boopis. Gamocarpha could be monophyletic after exclusion of G. dentata and G. angustifolia, but is nested within Nastanthus and Boopis species. Boopis is clearly polyphyletic with its species distributed in all main groups.

Can we build it? Yes we can, but should we use it? Assessing the quality and value of a very large phylogeny of campanulid angiosperms

“…Specifically, within these clades are short branches near the tips and very long internal branches descended from the crown as well as the descended from the divergences between the major Viburnum clades. On the other extreme, we note an issue within the Nastanthus + Gamocarpha group (see Denham et al., ) of the Calyceraceae. A majority of their tip branches exceeded >20 Myr, with very short internode distances separating the divergences.…”

Evolution of flower morphology and a natural re‐arrangement of Calyceraceae

“…Calyceraceae is a small family of 46 species of non‐showy, therophytic, geophytic, and chamaephytic herbs endemic to southern South America (Zanotti & Pozner, 2008; Zavala‐Gallo, 2013; Denham & al., 2016, 2019). Erected by Richard (1820), Calyceraceae includes six genera established early in the 19th century: Calycera Cav.…”

“…Despite the evolutionary relevance of Calyceraceae as sister to Asteraceae, the evolutionary history of Calyceraceae has only recently been investigated (Denham & al., 2016, 2019). These phylogenetic analyses confirmed that most Calyceraceae genera are para‐ or polyphyletic.…”

“…Summarizing the findings of Denham & al. (2016, 2019), Calyceraceae initially diversified about 27 million years ago during the Oligocene into two main clades. These two clades (A and B) may have diverged following changes in chromosome numbers, which allowed the two lineages to evolve in sympatry.…”

“…Later, during the Miocene, five minor, geographically structured groups, informally named by Denham & al. (2016), and two isolated species evolved. Within clade A, Boopis gracilis was recovered as a well‐differentiated sister lineage to the remainder of clade A.…”