Molecular phylogenetics of Alternanthera (Gomphrenoideae, Amaranthaceae): resolving a complex taxonomic history caused by different interpretations of morphological characters in a lineage with C4 and C3-C4 intermediate species

Abstract

Alternanthera (Amaranthaceae) is a diverse genus (80–200 species) largely restricted to the American Tropics. With Pedersenia and Tidestromia, it makes up the ‘Alternantheroid clade’ in Gomphrenoideae. Parsimony and Bayesian analyses of nucleotide sequences of nuclear (ITS) and plastid (rpl16, trnL‐F) and morphological characters identify that the capitate stigma of Alternanthera is a synapomorpy within the Alternantheroids. Within Alternanthera, two major clades were resolved, both of which were marked by otherwise homoplasious characters of the gynoecium: Clade A [99% jackknife (JK); 1.0 posterior probability (PP)] with nine species and Clade B (60% JK; 0.98 PP) with 22 species. Four subclades (B1–B4), strongly supported statistically, were identified in Clade B. Previous subgeneric classifications of Alternanthera appear artificial in light of our new molecular phylogenetic analyses. Most major lineages are congruently resolved by nuclear and plastid data but some incongruence between the nrITS and plastid phylogenetic trees suggests hybridization may have played a role in the rampant speciation in Alternanthera. Whereas C4 photosynthesis appears to have evolved in a single clade, the position of A. littoralis var. maritima (C3) in this clade may be explained by hybrid speciation rather than a reversal from C4 to C3. All C3–C4 intermediates belong to a different clade that also contains C3 species, but species limits, including the widely studied A. tenella, are unclear. The clade including A. tenella and A. halimifolia contains most of the species endemic to the Galápagos whereas A. nesiotes, also endemic to the islands, is nested among widespread American taxa. This suggests that the Galápagos radiation of Alternanthera may have arisen from at least two independent colonization events followed by a subsequent radiation in the former lineage. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 493–517.

Pollen characters and DNA sequence data converge on a monophyletic genus Iresine (Amaranthaceae, Caryophyllales) and help to elucidate its species diversity

“…Nevertheless, the very high number of small membrane bodies (state 3) is unique to the metareticulate pollen of Alternanthera (Fig. 10), and was also reported for many other species of this monophyletic genus (Sánchez-del Pino & al., 2012, 2016. In the case of both characters 14 and 15, the vast majority of species in the Iresine clade display one state, which consequently is reconstructed as ancestral state (Fig.…”

Lectotypification of Linnaean names in the genus Achyranthes (Amaranthaceae)

“…2 here) as the lectotype of the name A. repens. According to the wide discussion by Melville (1958) and the agreement by recent authors (e.g., Sánchez-del Pino & al., 2012), the current name for A. repens is Alternanthera pungens Kunth. Fig.…”

Taxonomic revision of the genus Alternanthera (Amaranthaceae) in Italy

“…The epithet "achyranth." was treated as "achyranthoides" by Hiern (1900, p. 896) and as "achyranthes" by Christensen (1922, p. 13) and Sánchez-del Pino et al (2012). Forsskål seems to have used stops rather indiscriminately at the end of epithets, sometimes indicating an abbreviation and sometimes not.…”

“…is a Neotropical genus of 80 -200 species with main center of diversity in South America (Mears 1977;Robertson 1981;Eliasson 1988Eliasson , 2004Pedersen 1997Pedersen , 2000Sánchez-del Pino et al 2012). Few taxa are native to Africa, Asia, and Australia (Robertson 1981), while some are introduced in central-northern America and Europe (e.g., Clemants 2003;Iamonico et al 2010;Iamonico & Sánchez-del Pino 2012) and colonize mainly wetlands and water bodies, that are one of the most vulnerable and threatened ecosystems in the world (Ervin et al 2006;Iberite et al 2011;Azzella et al 2013;Brundu et al 2013;Gomarasca et al 2013;Liendo et al 2013).…”