Systematics And Phytogeography Of Temperate And Alpine Poales S.l. From Northern Pakistan

Zahid, Ullah (2014) Systematics And Phytogeography Of Temperate And Alpine Poales S.l. From Northern Pakistan. Doctoral thesis, Quaid-i-Azam University, Islamabad.

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The monocot order Poales is one of the largest (ca. 20,000 species), and economically and ecologically most important group of flowering plants. Exploring this important component of the biodiversity is of paramount significance in conservation of species and developing climate change models.Northern Pakistan occupies a unique biogeographic position at the summit of the planet’s three highest mountain ranges i-e Himalaya, Hindukush and Karakurum).These ranges contain the hot spots of floral and faunal diversity with high proportions of endemic and rare species. Poales is represented by three families Poaceae (grasses), Cyperaceae (sedges) and Juncaceae (rushes) in Northern temperate and alpine regions of Pakistan.This dissertation is based on a multidisciplinary approach, incorporating morphological systematics, palynology, phytogeography and molecular phylogeny, with each aspect being constituted into a separate chapter.The first chapter gives a comprehensive overview of different aspects of Poales.The taxonomic treatment of taxa based on morphological markers constitutes the second chapter.The studies revealed 112 species belonging to 30 genera in three families of the order Poales. Juncaceae is represented by single genus Juncus with four species, Cyperaceae by five genera and 27 species, and Poaceae being the dominant family with 25 genera and 81 species. Carex and Poa are the largest genera having 21 and 16 species respectively. Other notable genera are Elymus (10 species), Bromus (7 species), Calamagrostis (6 species), Agrostis and Festuca (5 species each).Morphological features have proved to be the most important at all levels of taxonomic hierarchy.All sort of morphological variations were studied in detail and original observations were supplemented and compared with published literature.Keys for identification and field photographs are provided for each species.Different morphological features showed different extent of utilization; in vegetative characters, features of rhizome, stolons, ligule and leaf size and leaf indumentum were found more useful than others. But in over all comparison floral characters like size, shape, texture, veins, indumentum and awns of glumes, paleas, lemmas and spikelets are important in Poaceae.In Carex the minor details of fruit (achene) and the surrounding peryginea, along with shape and size of the male and female glumes, and the nature and relative length of the bracts subtending the spikelets were found to be of pivotal value in separating closely related species.The morphological markers have resulted in recognition of a new species Elymus swatianus.This species has been described from Swat district (Hindukush region).This taxon is closely related in appearance and qualitative features to E. semicostatus but markedly different in quantitative features. In E. swatianus, the spikes are 4-13 cm, spikelets are 10-16 mm, upper glume is 9-12 mm and lemmas are 7-11 mm. In Elymus semicostatus the spikes are 8-30 cm, spikelets 20-30 mm, upper glume 11-18 mm and lemmas are 12-14 mm long.The third chapter is comprised of Palynological studies.The pollen morphological features were sampled from 87 species representing 28 genera, including 57 species of Poaceae, 28 Cyperaceae and two Juncaceae. Microscopic features revealed that pollen grains in Poaceae are stenopalynous, monoporate rarely diporate, subspheroidal to oblate spheroidal to sub oblate, circular, operculate, non-operculate and annulate. Pollen features are not consistent with generic and tribal delimitation. However shows some consistency at the specific level.In Cyperaceae the pollens are obovoidal or triangular to apple shaped, having a single aperture or 4-aperturate to polyporate.The length of polar axis and thickness of exine were found as useful diagnostic features. Pollen features are relatively constant in sedges and correspond to subgeneric delimitation in Carex. Phytogeography represents the fourth chapter of the thesis.The analysis including 117 species in 29 genera of Poales of Northern Pakistan shows twelve different phytogeographic elements. The highest percentage of species (30%) belongs to the western Himalayan floristic region (near endemics), with cosmopolitan elements (19%), Central Asian elements (17%) and Eurasian elements (12%) being the other significant elements. The proportion of Endemic species (8%) is less apparent, while the rest of the seven categories are poorly represented.The Two Way Cluster Analysis (TWCA) divided the sixteen districts into two major groups, and four subgroups based on environmental gradient of altitude, latitude, longitude.TWCA classified the species into seven clusters based on presence/absence data and elevation from mean sea level. Species in each cluster can be attributed to similar habitat conditions and altitudinal ranges. Hence it is clear that climatic characters associated with each category control the species distribution pattern. The fifth chapter is dedicated to molecular phylogeny of Northern Pakistan’s Poales using a regional approach. Phylogenetic relationship has been investigated among 68 species in 15 genera of Poaceae, Cyperaceae and Juncaceae, based on the plastid matK gene.The phylogenetic trees inferred from both Maximum parsimony and Maximum likelihood analyses are in congruence with most studies carried out at global scale. In both the MP and ML analyses Cyperaceae and Juncaceae form a clade with 100% bootstrap support. Both these families also form monophyletic assemblages with 100% BS.However the species of Poaceae form a polytomy.In the genus Carex, matK was successful in dividing the genus into three sub-genera corresponding to the morphological classification.Kobresia laxa appear as sister to Carex, however K. shoenoides is nested within the unispicate sub-genus Primocarex. In Poaceae all the tribes are resolved with medium to strong bootstrap values.The analysis shows that Poaceae members are grouped into Poeae/Aveneae and Bromeae/Triticeae complexes. In both these complexes all genera form monophyletic clades with strong support.The overall results follow the traditional tribal and generic classification based on morphological features.It is concluded that multidisciplinary approach gives more clear and authentic picture of relationship and circumscription of taxa. In several cases infraspecific variations were observed and I believe more intense studies focusing on individual taxon may produce new subspecies, varieties or may be regarded as new species.There is need of further studies, as in many groups taxonomic revision is required.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Northern, Systematics, Alpine, Poales, Temperate, Phytogeography
Subjects: S Agriculture > SB Plant culture
Depositing User: Muhammad Khan Khan
Date Deposited: 03 Oct 2016 06:23
Last Modified: 03 Oct 2016 06:23

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