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The systematics of indigenous species of Hieracium Asteraceae in British Columbia Guppy, Geraldine Anne Allen

Abstract

Hieracium L., a large and taxonomically complex genus in the family Asteraceae, is represented in British Columbia by seven species. The present study was undertaken in order to gain insight into the relationships between these species. Data was gathered from various sources. Patterns of morphological variation were studied, as well as the type of reproduction in each taxon and its ability to hybridize with other taxa. Chromosome number, karyotype, and meiotic behaviour were also investigated. Five of the species were examined chemically and their flavonoids identified. The species of Hieracium in British Columbia fall into two groups. The subgenus Euhieracium (a predominantly European group) contains one species, Hieracium umbellatum, which is triploid, apomictic and morphologically variable. The other six species belong to the subgenus Stenotheca (a mainly New World group). Within the subgenus they form three clusters of one or more species each, all of which are diploid and sexually reproducing. The clusters are morphologically and chemically distinct from one another, and differ in reproductive strategy. However, they have very similar chromosomes and are interfertile. The hybrids between species of different clusters, though they have lowered pollen viability, are all meiotically regular (indicating close relationships between the parents). Within the clusters the species intergrade morphologically and reproductively, and are chemically similar (with the exception of Hieracium triste and H. gracile, which differ chemically). A synopsis of the seven Hieracium species is given.

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