The so-called primitive genera of Genisteae (Fabaceae): systematic and phyletic considerations based on karyological data

Authors: CUSMA-VELARI, TIZIANA; FEOLI-CHIAPELLA, LAURA

Source: Botanical Journal of the Linnean Society, Volume 160, Number 2, June 2009 , pp. 232-248(17)

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Abstract:

A karyological analysis of the so-called primitive genera of Genisteae has shown that they have a relatively homogeneous chromosome complement: all species tend to have a somatic chromosome number 2n = 48, which can increase to 2n = 52, presumably as a result of hyperaneuploidy. Karyological data suggest that Argyrocytisus, Cytisophyllum and Petteria may be considered as distinct genera rather than being assigned to Cytisus, with 2n = 52 for the first of these and 2n = 50 for the other two genera. They may be interpreted as relict monotypic genera as a result of the presence of a stabilized aneuploidy. Karyological characters exclude a recent origin of Genisteae from Thermopsideae. On the contrary, they are consistent with the hypothesis that Genisteae and Thermopsideae are independently derived from a basic papilionoid stock, of which present day Sophoreae are the remainder. At least two lines would lead from Sophoreae to the taxa of the `genistoid alliance', one to Thermopsideae and the other `podalyrioid alliances' (Podalyrieae and Mirbelieae), with the prevailing basic number of x = 9, and the other to Genisteae, with a basic number of x = 12 persisting in some present day genera, including Cytisus s.l. From this lineage, a wide range of secondary basic numbers has been formed, mostly by descending aneuploidy. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160, 232-248.

Keywords: aneuploidy; Argyrocytisus; Cytisophyllum; Hesperolaburnum; Laburnum; Petteria; Podocytisus; polyploidy

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1095-8339.2009.00859.x

Publication date: 2009-06-01