Taxonomic, cytogenetic and breeding relationships of Festuca rubra sensu lato.
thesisposted on 2015-11-19, 09:10 authored by Abdul-Karim Khudiyer Abbas. Al-Bermani
Work involving morphological, anatomical, ecological, distributional, cytological and hybridization studies has been carried out on F. rubra s.l. and has led to a reclassification of this complex group. Two subgroups, F. rubra subgroup and F. trichophylla subgroup, have been recognized. In the latter subgroup, FT pseudotrichophylla, F. cyrnea, F. paucispicula and F. rubra var. iberica are scarcely distinct from each other, and they are treated as synonyms of trichophylla. F. rubra ssp. asperifolia was found to be closer to F. trichophylla than to F. rubra, so it is treated as a subspecies of F. trichophylla. In the former subgroup, F. nigrescens, F. richardsonii, F. rivularis and F. diffusa cannot be satisfactorily separated from F. rubra at species level, and are therefore treated as subspecies commutata, arctica, rivularis and megastachys respectively, along with the type subspecies and three others (litoralis, scotica and juncea). F. rubra sspp. megastachys and multiflora (together treated as F. diffusa in Flora Europaea) cannot be maintained as separate entities and are treated under the former (earlier) subspecies name. Similarly F. rubra ssp. pruinosa and F. rubra ssp. juncea have been amalgamated under the latter name. F. junci folia and F_ rubra ssp. arenaria cannot be kept separate even as subspecies, yet they are distinct from F. rubra at species level and are treated under the earlier species name F. arenaria. F. rubra ssp. scotica is recognised as a new taxon. Over 30000 intra- and inter-specific crosses within F. rubra s.l. and between F. rubra s.l. and F. ovina s.l. were carried out. The results show that within F. rubra s.l. crosses were relatively easily achieved, and that the crossability in general is positively correlated with the ploidy level of the female parent. Crosses with F. ovina s.l. were most successful between hexaploid taxa; diploid taxa were more successful as female than as male parents. Natural hybridization was shown to occur in some cases, but seems to be very rare. The inheritance of morphological and anatomical characters is presented. The course of meiosis, including an analysis of chromosome configuration of the parents and their hybrids, suggests that hexaploid, octoploid and decaploid taxa of F. rubra s.l. are segmental alloploids with a multivalent suppressor system, since both homogenetic and heterogenetic pairing commonly occurs The evolution of F. rubra s.l. and the mode of allopatric speciation are discussed.
Date of award1991-01-01
Awarding institutionUniversity of Leicester