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CARYOLOGIA Vol.

59, no. 3: 277-283,

2006 Chromosomal differentiation of Solanum vespertilio and S. lidii (Solanaceae), rare, endemic species of the Canary Islands (Spain) Chiarini1 Franco, Gabriel Bernardello1,* , Gregory Anderson2 and Arnoldo Santos Guerra3

1 Instituto Multidisciplinario de Biolog? ?a Vegetal (CONICET-Universidad Nacional de Co ?rdoba), Casilla de Correo 495,

5000 Co ?rdoba, Argentina.

2 Department of Ecology and Evolutionary Biology, The University of Connecticut, Storrs, CT 06269-3043, U.S.A.

3 Jard? ?n de Aclimatacio ?n La Orotava, Puerto de La Cruz, Tenerife, Spain. Abstract ― A morphometric karyotype analysis was performed on the two Solanum subgenus Leptostemonum spe- cies of the Canary Islands (S. lidii and S. vespertilio) to understand patterns of chromosome differentiation, taxo- nomic relationships and evolutionary implications. The somatic chromosome number, 2n = 24, was documented for both species, supporting the basic chromosome number of Solanum (x = 12). For S. vespertilio, our data confirm a previous report based on meiotic counts, while the chromosome number of S. lidii is reported for the first time. Chromosomes are very small: for S. vespertilio the average chromosome length was 1.5 ± 0.3 ?m and the haploid karyotype length 18.4 ± 3.6 ?m, and for S. lidii 1.3 ± 0.09 ?m and 15.85 ± 1.0 ?m, respectively. These sizes are among the smallest for Solanum. Both species have symmetrical karyotypes with the same formula:

8 m pairs +

4 sm pairs. However, in addition to the length differences between the species, the only chromosome pair with a satellite on the short arm is different: it is found on chromosome pair #2 in S. lidii and on a slightly shorter chromosome, pair # 4, in S. vespertilio. Satellites were visualized in almost 100% of the cells of both species. Our karyotype data thus imply that these island species are closely related, and likely evolved in situ on the islands, via sympatric or sequential spe- ciation (S. vespertilioi is the more likely most derived member of the pair). In addition, although both species show a number of derived reproductive traits, like heterandry, zygomorphy, and andromonoecy, they retain the presump- tively more generalized symmetrical karyotypes. Key words: Canary Islands, cytotaxonomy, karyotype evolution, Solanaceae, Solanum, speciation, subgenus Lepto- stemonum. INTRODUCTION Around 40% of the vascular plant species of the Canary Islands flora are endemic (Santos 2001). The Solanaceae is not common on islands in general, nor is it in the Canaries where it is rep- resented by only four species (Bramwell and Bramwell 2001). However, all four species are endemic. One is in Withania (W. aristata (Aiton) Pers.) and three are in Solanum, the latter consti- tuting one of the largest genera of angiosperms, and elsewhere represented by several species of economic, pharmaceutical, or ornamental value (Heiser 1987;

Hunziker 2001). The three Sola- num species are S. nava Webb. and Berthel. (previously in the genus Normania;

Bohs and Ol- mstead 2001), S. lidii Sunding, and S. vespertilio Aiton. The latter two are a closely related species pair placed in subgenus Leptostemonum (Dunal) Bitter (Whalen 1984;

Bohs et al., unpubl.). This subgenus is considered to be a monophyletic group, likely of ancient origin, conclusions most recently supported by chloroplast DNA restric- tion site, chloroplast ndhF and nuclear ITS DNA sequence analyses (Olmstead and Palmer 1997;

Bohs and Olmstead 1999;

2001). These two Ca- narian species are particularly notable because of the presence of highly zygomorphic flowers with unequal anthers (i.e. heterandry) and andromon- oecy (Whalen 1984;