A biogeographical analysis of Muhlenbergia (Poaceae: Chloridoideae: Cynodonteae: Muhlenbergiinae)

Abstract

A phylogeny based on the analysis of six DNA sequence markers (ITS, ndhA intron, rpl32-trnL, rps3, rps16 intron, and rps16-trnK) is used to infer ancestral areas and divergence times, and reconstruct the biogeographical history and evolution of 150 of the 183 (82%) species of Muhlenbergia. Our results suggest that the genus originated 9.3 mya in the Sierra Madre (Occidental and Oriental) in Mexico, splitting into six lineages: M. ramulosa diverging 8.2 mya, M. subg. Muhlenbergia at 5.9 mya, M. subg. Pseudosporobolus at 5.9 mya, M. subg. Clomena at 5.4 mya, M. subg. Bealia at 4.3 mya, and M. subg. Trichochloa at 1 mya, each of these with a high probability of Sierra Madrean origin. Our results further suggest that founder-event speciation from Sierra Madre to South America occurred independently multiple times in all five subgenera during the Pleistocene and late Pliocene. One long-distance dispersal event most likely originating from Central or Eastern North America to East and Central Asia occurred 1.6-1 mya in M. subg. Muhlenbergia. In our cladogram, members of M. subg. Trichochloa show little genetic resolution, suggesting very low levels of divergence among the species, and this may be a consequence of rapid radiation.

Grasses through space and time: An overview of the biogeographical and macroevolutionary history of Poaceae

“…), Pentapogon R. Br. (at least 22 spp., Australasia, Peterson et al, 2022c), Relchela Steud. (1 sp., South America, Patagonia, sister to the rest of Echinopogoninae).…”

“…(1 sp., Argentina to Brazil, and disjunct in Chile); Chascolytrum Desv. (6 spp., all of South America, 1 reaching Central America; (Essi et al, 2017; Da Silva et al, 2020, 2022); Condilorachia (3 spp., Argentina, Brazil, and Chile; Peterson et al, 2022c), Erianthecium Parodi (1 sp., Brazil and Uruguay); Lombardochloa Roseng. & B.R.…”

“…Calothecinae Soreng (Soreng et al, 2015b) has a stem date of 12.58 Ma and contains 10 genera (Da Silva et al, 2022; Peterson et al, 2022c), with all species occurring in South America and one reaching Central America. The monograph by Matthei (1975) covered many of the genera.…”

“…In our newest analysis, Diplachne P. Beauv. (2 spp., African, Asian, and Australian) is basal to the remaining genera (Snow et al, 2018; Peterson et al, 2022b). As documented previously, Dinebra Jacq.…”

The biogeography of grasses (Poaceae)

“…Four of the manuscripts in this issue include new dated biogeographical analyses (Gallaher et al, 2022;Peterson et al, 2022b;Soreng et al, 2022a;Zhou et al, 2022); three comprise new phylogenetic analyses with subsequent taxonomic novelties (Da Silva et al, 2022;Peterson et al, 2022aPeterson et al, , 2022c, one is an ecological study investigating functional traits in a clade of savanna/wetland grasses (Arthan et al, 2022), one looked at the current distribution of the grasses over the Australian continent to determine migration directionality (Bryceson & Morgan, 2022), and one is an updated classification of the family primarily based on molecular phylogenetic studies (Soreng et al, 2022).…”