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With the advent of PCR and DNA sequencing, DNA data have been widely applied to the assessment of relationships among taxa of recent origin (e.g., island endemics). Numerous recent studies have used DNA sequence data and/or cpDNA RFLPs to reconstruct phylogeny for many members of the Macaronesian flora. One such genus that has received attention recently is Tolpis (Asteraceae: Lactuceae). Sequences of the cpDNA gene ndhF provided strong support for a clade comprising species of Tolpis that are largely endemic to Macaronesia, to the exclusion of several European taxa that had previously been placed within the genus. Subsequently, cpDNA RFLP data were used to assess the biogeography and potential patterns of dispersal within the genus. However, relationships among species of Tolpis present on the Canary Islands were not well-resolved. Analyses of intersimple sequence repeat (ISSR) data were employed to assess relationships among species of Tolpis from the Canary Islands and Madeira. The five primers used across 80 individuals from 10 populations of seven species resulted in 48 bands that could be scored consistently. Neighbor-joining and parsimony analyses indicate close relationships among individuals within populations and differentiation among allopatric conspecific populations. In agreement with prior molecular results, the Canarian species form a well-supported group. Both neighbor-joining and parsimony analyses of ISSR markers resolve relationships (often with bootstrap support) among species, something that was not achieved previously. The present study demonstrates the potential of hypervariable single-locus markers for elucidating relationships in rapidly radiating lineages, many of which occur in oceanic archipelagos. |
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