Hybridisierung und Retikulation als "driving forces" in der Evolution der Gräser aus den temperaten Regionen der Erde (Gräser-Unterfamilie Pooideae)?
Zusammenfassung der Projektergebnisse
Grasses (Poaceae) rank among the largest families of angiosperms and comprise about 660 genera and 10.000 species. They have worldwide distribution and are dominant in many landscapes. An estimated 20% of the land surface is occupied by grasslands. Due to their outstanding economic and ecological significance, grasses have long been investigated by different biological and agricultural sciences, including several genome sequencing projects. Evolution and phylogeny of the family have been intensively studied during the past 30 years by molecular tools in sets of selected representative genera and with focus on sequences of the plastid genome. One of the largest lineages is the subfamily Pooideae, a characteristic group of the northern hemisphere with outliers in the tropics and the southern hemisphere. Our survey of the molecular differentiation of Pooideae in a larger framework of the whole family and even in order Poales encompassed most of its genera. It was based on plastid and nuclear DNA sequence markers including coding and non-coding singlecopy genes, which were investigated in an almost overlapping set of taxa, provided a robust and well-resolved topology for most regions of the phylogenetic trees. Some major polytomies remained and should be resolved in future studies. Notably, the plastid and nuclear DNA trees agree in wide portions and show congruent branching patterns, making it likely that they reflect the actual phylogenetic relationships of the taxa in these tree portions. Several conflicts between the trees, however, occur in sometimes larger stretches of the trees and is interpreted to be indicative of past hybridization. Some new taxonomic groups with hybrid background were identified. Major reticulation processes were analyzed. Well-identifiable hybrid origins, which partly encompass lineages with several genera, were repeatedly found but may be even more frequent if denser sampling of taxa will be implemented and tree resolution will be improved by further investigations. Our analyses revealed deep phylogenetic incongruences in our study groups, pointing to hybridization events in their early evolution. Patterns of cytonuclear discordance are therefore encountered on different taxonomic levels ranging from shallow to deep phylogenetic levels and must be regarded as an important and recurrent evolutionary incident in Poaceae. The likely hybrid character of many taxa and lineages offers a detailed hypothesis for evolutionary relationships within Pooidae than can be tested in future studies employing larger sets of nuclear and organellar DNA markers. Moreover, the morphological differentiation can be analyzed using the new phylogenetic framework. From the current data it is obvious that there is a high degree of homoplasy in many morphological characters. Particularly, the strong variation in spikelet and floret characters of Pooideae relates to a high degree of selective pressure acting on these structures. It can be supposed that the variety of dispersal mechanisms caused by spikelet structures are one of the important evolutionary factors that enabled these grasses to colonize successfully almost any habitat type in the temperate and cold zones of the world.
Projektbezogene Publikationen (Auswahl)
-
(2011): Duthieeae, a new tribe of grasses (Poaceae) identified among the early diverging lineages of subfamily Pooideae: molecular phylogenetics, morphological delineation, cytogenetics, and biogeography. — Systematics and Biodiversity 9(1): 27–44
Schneider, J., Winterfeld, G., Hoffmann, M.H., Röser, M.
-
(2012): Polyphyly of the grass tribe Hainardieae (Poaceae: Pooideae): identification of its different lineages based on molecular phylogenetics, including morphological and cytogenetic characteristics. — Organisms, Diversity and Evolution 12: 113– 132
Schneider, J., Winterfeld, G., Röser, M.
-
(2012): Stipa (Poaceae) and allies in the Old World: Molecular phylogenetics realigns genus circumscription and gives evidence on the origin of American and Australian lineages. — Plant Systematics and Evolution 298(2): 351–367
Hamasha, H.R., von Hagen, K. B., Röser, M.
-
(2014): Phylogenetic relationships in the grass family (Poaceae) based on the nuclear single copy locus topoisomerase 6 compared to chloroplast DNA. — Systematics and Biodiversity 12(1): 111–124
Blaner, A., Schneider, J., Röser, M.
-
(2014): Polyploid evolution, intercontinental biogeographical relationships and morphology of the recently described African oat genus Trisetopsis (Poaceae). — Taxon 63: 773–788
Wölk, A., Röser, M.
-
(2015): A multi-locus analysis of phylogenetic relationships within grass subfamily Pooideae (Poaceae) inferred from sequences of nuclear single copy gene regions compared with plastid DNA. — Molecular Phylogenetics and Evolution 87: 14–27
Hochbach, A., Schneider, J., Röser, M.
-
(2015): Genome evolution in a Mediterranean species complex: phylogeny and cytogenetics of Helictotrichon (Poaceae) allopolyploids based on nuclear DNA sequences (rDNA, topoisomerase gene) and FISH. — Systematics and Biodiversity 13: 326–345
Wölk, A., Winterfeld, G., Röser, M.
-
(2016): Genome evolution in alpine oat-like grasses through homoploid hybridization and polyploidy. — AoB PLANTS 8: plw039
Winterfeld, G., Wölk, A., Röser, M.
-
(2017): Hybridization and long-distance colonization in oat-like grasses of South and East Asia, including an amended circumscription of Helictotrichon and the description of the new genus Tzveleviochloa (Poaceae). — Taxon 66: 20–43
Wölk, A., Röser, M.
-
(2018): Nuclear genes, matK and the phylogeny of the Poales. — Taxon 67: 521–536
Hochbach, A., Linder, H.P., Röser, M.
-
(2020): Phylogeny, morphology and the role of hybridization as driving force of evolution in grass tribes Aveneae and Poeae (Poaceae). — Taxon 69(2): 234–277
Tkach, N., Schneider, J., Döring, E., Wölk, A., Hochbach, A., Nissen, J., Winterfeld, G., Meyer, S., Gabriel, J., Hoffmann, M.H., Röser, M.
-
(2021): Molecular phylogenetics and micromorphology of Australasian Stipeae (Poaceae), and the interrelation of whole-genome duplication and evolutionary radiations in this grass tribe. — Frontiers in Plant Science 11: 630788
Tkach, N., Nobis, M., Schneider, J., Becher, H., Winterfeld, G., Barkworth, M.E., Jacobs, S.W.L., Röser, M.
