Molecular phylogeny of Panicum s. str. (Poaceae, Panicoideae, Paniceae) and insights into its biogeography and evolution

Abstract

Panicum sensu stricto is a genus of grasses (Poaceae) with nearly, according to this study, 163 species distributed worldwide. This genus is included in the subtribe Panicinae together with Louisiella, the latter with 2 species. Panicum and subtribe Panicinae are characterized by including annual or perennial taxa with open and lax panicles, and spikelets with the lower glume reduced; all taxa also share a basic chromosome number of x = 9 and a Kranz leaf blade anatomy typical of the NAD-me subtype photosynthetic pathway. Nevertheless, the phylogenetic placements of many Panicum species, and the circumscription of the genus, remained untested. Therefore, phylogenetic analyses were conducted using sequence data from the ndhF plastid region, in an extensive worldwide sampling of Panicum and related genera, in order to infer evolutionary relationships and to provide a phylogenetic framework to review the classification of the genus. Diversification times, historical biogeography and evolutionary patterns of the life history (annual vs. perennial) in the subtribe and Panicum were also studied. Results obtained provide strong support for a monophyletic Panicum including 71 species and 7 sections, of which sections Arthragrostis and Yakirra are new in the genus; 7 new combinations are made here. Furthermore, 32 species traditionally assigned to Panicum were excluded from the genus, and discussed in other subtribes of Paniceae. Our study suggested that early diversification in subtribe Panicinae and Panicum occurred through the Early-Mid Miocene in the Neotropics, while the subsequent diversification of its sections mainly occurred in the Late Miocene-Pleistocene, involving multiple dispersals to all continents. Our analyses also showed that transition rates and changes between annual and perennial life history in Panicum were quite frequent, suggesting considerable lability of this trait. Changes of the life history, together with C4 photosynthesis, and the multiple dispersal events since the Mid Miocene, seem to have facilitated a widespread distribution of the genus. All these findings contribute to a better understanding of the systematics and evolution of Panicum.

A tale of worldwide success: Behind the scenes of Carex (Cyperaceae) biogeography and diversification

“…A, S1, S2; Data S6), consistent with a temporal lag between the origin of the group and the diversification of its main lineages. This has been also found in other groups (Dupin et al, ; Zuloaga et al, ; Huang et al, ), although extinct lineages may have dispersed earlier from E Asia as noted above.…”

“…B; Tables A, S1A). Asymmetric patterns of dispersal between different continents have been previously reported from other groups (e.g., Sanmartín et al, ; Dupin et al, ; Zuloaga et al, ). While animal and plant migration from the Late Miocene (c. 7 Mya) onwards is considered about 30% more frequent from South America to North America (Bacon et al, ), our results inferred 5–7 times as many dispersals in the opposite direction (Fig.…”

“…A, S1, S2). As in other studies (Berger et al, ; Dupin et al, ; Spalink et al, 2016a, 2016b; Zuloaga et al, ), the real importance of allopatric speciation can be masked by these facts, and thus caution should be taken in interpreting our results, that suggest within‐area speciation, but not sympatric speciation in the strict sense, as predominant in Carex . Biogeographic analyses focusing on particular clades and implementing a fine‐scale geographic division within the wide areas considered here would probably unveil a greater role of allopatric speciation processes (i.e., founder events; Spalink et al, ; Johnson et al, ).…”

Development of molecular markers for invasive alien plants in Korea: a case study of a toxic weed, Cenchrus longispinus L., based on next generation sequencing data

“…In the present study, the ML and BI analysis revealed a close relationship between Panicum incomtum, Thyridopepsis xerophila (subtribe Neurachninae), and Dichanthelium acuminatum (subtribe Dichantheliinae, Fig. 3), which was not shown in the study of Zuloaga, Salariato & Scataglini (2018). Therefore, more samples and molecular data of Panicum should be covered to clarify its relationship to other members of tribe Panicinae in further studies.…”

“…3). Zuloaga, Salariato & Scataglini (2018) provided a deeper understanding of the phylogeny of Panicum and suggested a new circumscription of Panicum , including seven sections, based on ndhF data. However, the sample of Panicum incomtum was not included in their data.…”