Macroevolutionary trends and diversification dynamics in Atripliceae (Amaranthaceae s.l., Chenopodioideae): a first approach.

BACKGROUND AND AIMS: Atripliceae evolved and diversified by dispersals and radiations across continents in both hemispheres, colonizing similar semi-arid, saline-alkaline environments throughout the world. Meanwhile, its species developed different life forms, photosynthetic pathways, mono- or dioecy, and different morphological features in flowers, fruiting bracteoles and seeds. In this study, we introduce a first approach to the macroevolutionary patterns and diversification dynamics of the Atripliceae to understand how time, traits, speciation, extinction and new habitats influenced the evolution of this lineage. METHODS: We performed molecular phylogenetic analyses and clade age estimation of Atripliceae to apply time-, trait- and geographic-dependent diversification analyses and ancestral state reconstructions to explore diversification patterns within the tribe. KEY RESULTS: Opposite diversification dynamics within the two major clades of Atripliceae, the Archiatriplex and Atriplex clades, could explain the unbalanced species richness between them; we found low mean speciation rates in the Archiatriplex clade and one shift to higher speciation rates placed in the branch of the Atriplex core. This acceleration in diversification seems to have started before the transition between C3 and C4 metabolism and before the arrival of Atriplex in the Americas, and matches the Mid-Miocene Climatic Optimum. Besides, the American species of Atriplex exhibit slightly higher net diversification rates than the Australian and Eurasian ones. While time seems not to be associated with diversification, traits such as life form, photosynthetic pathway and plant sex may have played roles as diversification drivers. CONCLUSIONS: Traits more than time played a key role in Atripliceae diversification, and we could speculate that climate changes could have triggered speciation. The extreme arid or saline environments where Atripliceae species prevail may explain its particular evolutionary trends and trait correlations compared with other angiosperms and highlight the importance of conservation efforts needed to preserve them as genetic resources to deal with climatic changes.

Using integrative taxonomy and multispecies coalescent models for phylogeny reconstruction and species delimitation within the "Nastanthus-Gamocarpha" clade (Calyceraceae).

The Calyceraceae (47 spp.) is a small family of plants that is sister to the Asteraceae (∼ 25,000 spp.), one of the largest families of angiosperms. Most members of Calyceraceae are endemic to the Andes and Patagonia, representing an excellent model within which to study diversification patterns in these regions. The single phylogenetic study of Calyceraceae conducted to date revealed that the boundaries of most genera and several species of this family require further analyses, especially the "Nastanthus-Gamocarpha" clade. In this study, we reconstructed the phylogeny of the "Nastanthus-Gamocarpha" clade using multispecies coalescent models under BPP and StarBeast2 programs, sampling 63 individuals from 13 of the 14 species recognized to date. We then used this phylogenetic framework to delimit species using BFD and the A11 method implemented in BPP. Species limits suggested through a coalescent approach were then re-evaluated in the light of morphology, geography, and phenology. Coalescent-based methods indicated that most putative lineages could be recognized as distinct species. Morphological, geographical, ecological, and phenological data further supported species delimitation. Necessary taxonomic changes are proposed. Namely, the paraphyletic Nastanthus is synonymized under Gamocarpha, while five species of Boopis are transferred into Gamocarpha. We used an integrative taxonomic approach to recognize 13 species and one subspecies within the newly circumscribed genus Gamocarpha.