Molecular systematics of the Mexican tussilaginioid genera (Asteraceae: Senecioneae)
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The Mexican tussilaginioid group consists of 13 diverse genera of sunflowers (Asteraceae: Senecioneae) distributed from the USA to Panama, with most species occurring in montane regions from Central Mexico to Guatemala. Presently, 140 species in 13 genera are recognized with many of these species considered to be endemic to threatened pine-oak forest or cloud forest ecosystems. Sixty-two species within the study group were included in a combined phylogenetic analysis of two regions of the nuclear ribosomal repeat, the internal and external transcribed spacers. Fifty-two of these taxa were analyzed in a phylogenetic framework for the first time. The results from the combined nrDNA analysis (62 species in 12 genera in the combined analysis) strongly support the monophyly of the Mexican tussilaginioid group, however, the topology and hypothesis testing using constraint models indicate that the genera Pittocaulon, Psacaliopsis, and Roldana are not monophyletic. Telanthophora s.s. is monophyletic, although this genus is nested within Roldana s.s. Endemism is abundant among the clade with over half of the species restricted to relatively small geographic areas. Moreover, most members of the group (ca. 120 species, or 87%) are present in montane regions under immense pressure from human land use practices at or above 1500 meters in Mexico and Guatemala. Two of the genera from my study group, Pippenalia and Psacaliopsis were taxonomically assessed based on their morphological characters and the nrDNA results. A single species, Psacaliopsis purpusii, remains in the genus, while Pippenalia delphinifolia, Psacaliopsis macdonaldii, and P. pudica are transferred to Psacalium. Funstonia gen. nov. is here erected a new genus encompassing a single species with two varieties. Chloroplast genomes of Arnoglossum atriplicifolium, Roldana aschenborniana, R. barba-johannis, and Telanthophora grandifolia were sequenced with next generation sequencing in order to identify regions of variation and to compare the assemblies produced via de novo and reference-based methods. The reference-based assemblies were more complete than the de novo assemblies, and therefore the former sequences were utilized for phylogenetic analyses.