|dc.description.abstract||Berberis L. contains more than 500 species, is the largest genus in the Berberidaceae,
and is now recognised to comprise Berberis s.s. with simple leaves and compoundleaved
species formally ascribed to Mahonia. Because of its sheer size, much basic
taxonomy is required in Berberis, and this thesis provides a taxonomic revision for the
species found in Nepal, which includes a key, full descriptions, illustrations, phenology,
notes on ecology, distinguishing features and distribution maps. Twenty one species are
recognised in Nepal, of which two, B. karnaliensis and B. pendryi, are newly described.
Nine taxa are lectotypified during this study.
Berberis has a mainly Northern Hemisphere distribution, with its main centre of
distribution in the Sino-Himalaya. Berberis s.s. extends into South America where it has
a secondary centre of diversity. There have been few phylogenetic studies of Berberis,
and previous studies were inadequate because they did not use outgroups to root their
phylogenies. This thesis provides parsimony and Bayesian analyses of chloroplast ndhF
data of 64 accessions of 59 Berberis taxa, rooted using multiple outgroups including
Ranzania, the putative sister group of Berberis. The results support the monophyly of
Berberis s.l, but compound-leaved Berberis are shown to be paraphyletic. Berberis
higginsae, a member of section Horridae, is sister to all other taxa sampled. The ndhF
phylogeny, dated using a fossil calibration, indicates the North American origin of
compound-leaved Berberis, and the origin of the simple-leaved South American lineages in long distance dispersal events from Eurasia.
ITS sequences of 97 accessions of 79 species of Berberis are studied to investigate the
origin and diversification of simple-leaved Berberis in Nepal. The Nepalese species are
shown to have multiple origins from at least four different colonisations and have
subsequently speciated in situ. The diversification of some groups appears to have been
triggered by the active uplift phase of the Himalaya during the Miocene. The tendency
of phylogenetically close Nepalese species to grow in similar ecological conditions
indicates that phylogenetic niche conservatism is evident in Nepalese Berberis species.
Chromosome counts for nine taxa of Nepalese simple-leaved Berberis are obtained, of
which five taxa are counted for the first time. All the taxa examined are diploids with
2n=28, suggesting that the polyploidy is not an important factor in the diversification of
Berberis in Nepal.||en