Botanical Journal of the Linnean Society, 2007, 154, 187–204. With 4 figures © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154, 187–204 187 CANARY ISLAND CONVOLVULUS HYBRIDS M. A. CARINE ET AL. *Corresponding author. E-mail: m.carine@nhm.ac.uk Molecular and morphological evidence for hybridization between endemic Canary Island Convolvulus MARK A. CARINE 1 *, LAVINIA ROBBA 1 , ROBERT LITTLE 1 , STEVE RUSSELL 1 and ARNOLDO SANTOS GUERRA 2 1 Department of Botany, The Natural History Museum, Cromwell Road, London SW7 5BD, UK 2 Jardín de Aclimatación de La Orotava (ICIA), Calle Retama Num. 2, E-38400, Puerto de la Cruz, Tenerife, Canary Islands, Spain Received August 2006; accepted for publication February 2007 Morphological data and molecular data from the chloroplast trnH-psbA region and nuclear ribosomal ITS region are used to test the hypothesis that the problematic Canary Island endemic Convolvulus floridus var. virgatus is a hybrid between the endemic species C. floridus and C. scoparius. Analysis of mean leaf length and width of 58 individuals indicates that accessions referable to C. floridus var. virgatus are intermediate between the parental taxa in leaf dimensions. Direct sequencing of the ITS region of C. scoparius and C. floridus revealed two species-specific ribotypes distinguished by 10 base differences. Examination of ITS chromatograms for putative hybrids revealed poly- morphisms at those sites that are diagnostic between species in all except one putative hybrid. Morphological intermediacy and ITS additivity therefore support the hybrid status of C. floridus var. virgatus. An analysis of intraindividual ITS variation confirmed the co-occurrence of both parental ribotypes in putative hybrids and dem- onstrated that some hybrid individuals contained chimaeric ITS types. It is proposed that chimaeric ITS types are the result of recombination following backcrossing. Sequencing of the trnH-psbA region revealed four haplotypes. Three were, for the most part, confined to C. floridus and putative hybrids although one C. scoparius accession was also found to share this haplotype. The remaining haploype was only found in C. scoparius and putative hybrid acces- sions. Patterns of haplotype distribution between parental and hybrid accessions suggest multiple, bidirectional hybridization events between C. floridus and C. scoparius. The nomenclature of the hybrid is discussed and the nec- essary new name C. × despreauxii is proposed. © 2007 The Linnean Society of London, Botanical Journal of the Lin- nean Society, 2007, 154, 187–204. ADDITIONAL KEYWORDS: hybrid – ITS evolution – trnH–psbA. INTRODUCTION The generation of novel, and potentially advanta- geous, combinations of traits through hybridization is thought to play an important role in the adaptive radi- ation of groups into new environments such as those encountered on oceanic islands (see Seehausen, 2004 for a review) although there is only limited empirical evidence to support this (e.g. Rieseberg et al., 2003). In the Canary Islands, hybrids have been recorded in a diverse range of endemic groups including Euphorbia (Euphorbiaceae; Molero & Rovira, 2005), the Sonchus alliance (Asteraceae; Sventenius, 1960), Argyranthe- mum (Borgen, 1976; Humphries, 1976; Brochmann, Borgen & Stabbetorp, 2000; Borgen, Leitch & Santos Guerra, 2003), Echium (Boraginaceae; Bramwell, 1973), Aeonium alliance (Crassulaceae; Santos Guerra, 1983; Bañares Baudet, 1986), Bystropogon (Lamiaceae; La Serna, 1984), Micromeria (Pérez de Paz, 1978) and Sideritis (Lamiaceae; Pérez de Paz & Negrín Sosa, 1992), Adenocarpus (Fabaceae, Lems, 1958), and the Bencomia alliance (Rosaceae; Santos Guerra, 1983). Whilst many such hybrids are associ- ated with disturbed habitats and appear to be unsta- ble, indicating a recent origin (Humphries, 1979; Borgen et al., 2003), incongruent nuclear and chloro- plast phylogenies suggest that ancestral hybridization has played a role in the radiation of Macaronesian plant groups (e.g. Mort et al., 2002). Furthermore, morphological, karyological and molecular data Downloaded from https://academic.oup.com/botlinnean/article/154/2/187/2544421 by guest on 01 July 2023