ISTA Purity Seminar 15. June 2009 Zürich TlTools for seed identifi cati on species classification and nomenclature by Norbert Leist and Andrea Jonitz Prof. Dr. Norbert Leist Dr. Andrea Jonitz Brahmsstr.25 LTZ Augustenberg 76669 Bad Schönborn Neßlerstr.23 Germany 76227 Karlsruhe
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[email protected] Aquilegia vulgaris, Variation Variation • Variation is everywhere in biological systems. Natural variation at the population level is usualy not continuous, but occurs in discrete units or taxa. Easily the most important taxonomic level is the species because it is often the smallest clearly recognizable and discrete set of populations. • Understanding how species form and how to recognize them have been major challenges to systematists. The variation in one population becomes interrupted, the way to a split into two species strong hairy nearly glabrous Variation on species • Sources of variation: MttiMutation Recombination Independent assortment of the chromosomes Random genetic drift Selection Conservation of species characteristics avoiding gene flow Isolating barriers: temporal (seasonal, diurnal) habitat (wet, dry; calceous, silicious) floral (structural, behavioral eg. adaptations for pollinators) reproductive mode (self fertilisation, agamospery) incompatibility (pollen, seeds) hybrid inviability hybrid floral isolation hybrid sterility hybrid break down Iris germanica Iris sibirica Isolation by habitat Definition of „species“ is not easy A species is the smallest aggregation of populations