Karyological evolution and molecular phylogeny in Macaronesian dendroid spurges (Euphorbia subsect. Pachycladae)
2002
Molero Briones, Julián | Garnatje, Teresa | Rovira, Ana | Garcia-Jacas, Núria | Susanna de la Serna, Alfonso
Euphorbia subsect. Pachycladae is a taxon of primarily Macaronesian distribution, defined by morphological and biogeographical criteria. On the basis of morphological data, it is a heterogeneous group within which at least three complexes of species can be distinguished. To ascertain whether it is a natural group and discover its phylogenetic relations, we performed a cladistic analysis of the sequences of ribosomal nuclear DNA and a karyological study. The results of the two studies are concordant and show that the sub-section is polyphyletic and includes three different groups. The first monophyletic group is made up of the Macaronesian endemics E. atropurpurea complex and E. lamarckii complex, which form a polytomy with E. dendroides as the basal species. The lauroid species E. longifolia and E. stygiana represent the second monophyletic group, which derive from Mediterranean forms of E. sect. Helioscopia Dumort. Both species are paleopolyploid (2n=44) with highly symmetrical karyotypes. Finally, E. balsamifera, with a Canarian, African and Arabian distribution, remains isolated in a basal position. Its karyotype, with 2n=20 chromosomes, differs from the Macaronesian model and displays analogies with African cactiform spurges. On the basis of the results, some hypotheses are formulated about speciation processes in the three groups.
Show more [+] Less [-]This study was funded by projects DIGCYT-PB87/10008 and PB97/1134 of the Spanish Ministry of Education and Science and by grant 1999SGR 00332 for Consolidated Research Groups form the Catalan autonomous government (Generalitat de Catalunya).
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