Phylogenetic analyses of DNA sequences with chromosomal and morphological data confirm and refine sectional and series classification within Melampodium (Asteraceae, Millerieae)

Abstract

The genus Melampodium consists of 40 species distributed throughout Mexico and Central America with extensions into the southwestern United States and Colombia and Brasil of South America. The genus reflects broad chromosomal evolution involving dysploidy and polyploidy withn = 9, 10, 11, 12, 14, 18, 20, 23, 24, 27, 28, 30, and 33 having been documented (x = 9, 10, 11, 12, and 14). The most recent classification of the genus, based primarily on morphology and chromosome num bers, recognized six taxonomic sections: Alcina, Bibractiaria, Melampodium, Rhizomaria, Serratura, and Zarabellia. Section Melampodium, which contains 22 species, was divided into five series: Cupulata, Leucantha, Longipila, Melampodium, and Sericea. This hypothesis had been tested by previous morphological phenetic and cladistic analyses, and several problem areas had been highlighted, especially involving section Alcina, but no modifications to the classification have been made. Recent molecular studies utilizing nrITS, 5S rDNA spacer and low‐copy nuclear PgiC gene, plus plastid matK and psbA‐trnH regions allow the classificatory hypothesis to be tested more precisely. Congruence between ITS and matK phylogenies for all species reveals sections Bibractiaria, Rhizomaria, and Serratura to be holophyletic. The largest section Melampodium is holophyletic with both plastid markers, but M. longipilum is shown as an outlier (tying to sect. Rhizomaria) in all nuclear marker phylogenies (ITS, PgiC and 5S rDNA spacer). Section Zarabellia appears holophyletic in matK but biphyletic with ITS, suggesting recogni tion of two distinct series. Section Alcina is the most problematic, being triphyletic in ITS and matK, and with the species not connecting to the same relatives. These insights recommend recognition of three sections from within section Alcina, one hous ing M. nutans (Nutantia Stuessy, sect. nov.) another M. glabrum (Glabrata Stuessy, sect. nov.) and a third M. perfoliatum (sect. Alcina (Cav.) DC.). These may represent ancient independent lines that have diverged from original x = 11 ancestors. Within section Melampodium, 5S rDNA NTS, PgiC and psbA‐trnH, in addition to ITS and matK, provide insights on relationships among taxonomic series. Series Leucantha and Longipila are holophyletic, and series Cupulata nearly so, with M. glabribracteatum deserving treatment in a series of its own. The most complex relationships are between series Melampodium, Cupulata, and Sericea, the latter comprising five exclusively polyploid taxa (4x and 6x). Molecular and cytogenetic data reveal allopolyploid origins for all of these polyploids, in some cases involving hybridization between the two series Cupulata and Melampodium / Sericea, such as with M. mayfieldii and M. longicorne, which exacerbates taxonomic circumscription.

Differential Genome Size and Repetitive DNA Evolution in Diploid Species of Melampodium sect. Melampodium (Asteraceae)

“…All species have had their karyotypes established including localization of 5S and 35S rDNA loci and genome sizes measured (Weiss-Schneeweiss et al, 2009. Although all diploid species have the same chromosome number, they exhibit approximately 4.5-fold variation in genome size (0.49 pg-2.27 pg/1C) and are classified into five phylogenetically distinct series (Stuessy et al, 2011).…”

“…Melampodium. Material for M. sinuatum was not available, and the isolated phylogenetic position of Melampodium longipilum (series Longipila) relative to the other species of section Melampodium inferred using nuclear markers (Blöch et al, 2009;Stuessy et al, 2011;McCann et al, 2018) precluded it from analyses. The main goal of this study is to elucidate patterns of genome size change along the phylogeny of the group through an investigation of repetitive DNA evolution.…”

Diversidad y distribución de los endemismos de Asteraceae (Compositae) en la Flora del Ecuador

“…Las filogenias moleculares realizadas por Blöch et al (2009) y Stuessy et al (2011) muestran que el género Lecocarpus está incluido dentro de la variación del género Melampodium L. (parafilético), cuyo origen pudo ocurrir a partir de la rápida divergencia de poblaciones ancestrales de Acanthospermum a consecuencia de las condiciones ambientales imperantes en las islas (Stuessy et al, 2014).…”

“…Los géneros Chrysanthellum Pers. (n = 8; Turner, 1988), Darwiniothamnus (n = 9; Crawford et al, 2009), Lecocarpus (2n = 2x = 22; Blöch et al, 2009;Crawford et al, 2009;Stuessy et al, 2011), y Trigonopterum (2n = 2x = 28; Eliasson, 1984) son diploides, mientras que Scalesia (n = 34; Ono, 1967;Crawford et al, 2009), Jaegeria gracilis Hook. f. (2n = 4x = 36; Torres, 1968), y Pectis subsquarrosa (2n = 6x = 72; Keil, 1977) son poliploides; probablemente deriven de especies ancestrales también poliploides.…”

The importance of comprehensive phylogenetic (evolutionary) classification—a response to Schmidt‐Lebuhn's commentary on paraphyletic taxa

“…For more detailed theoretical considerations, the reader is referred to Stuessy (), Brummitt (), Hörandl (), and Hörandl and Stuessy (); for case studies of evolutionary classification, see Carpenter (), Stuessy et al. (), and Hörandl and Emadzade (). A forthcoming series dealing with paraphyly in classification will present theoretical and empirical papers from the species to the family level (in press: Brummitt, ; Ehrendorfer et al, ; George, ; Hörandl, ; Lokchart et al, 2013; Stuessy and Hörandl, ; Stuessy et al., ; Zander, ).…”