Gonospermum

Abstract: The pollen of nine endemic taxa of the Gonospermum Less., Lugoa DC. and Tanacetum L. complex and of T. parthenium L. (introduced species from the Canary Islands) was studied using light and scanning electron microscopy with the aim of extending the knowledge of their morphology and to investigate whether pollen morphology may help clarifying the controversial taxonomy of these taxa. Twenty six populations in the Canary Islands (Spain) were studied and the following parameters were measured: polar axis (P), equatorial diameter (E), polar exine thickness (Ex1), length (L) and thickness (A) of the spines in the meridional optical section, exine thickness at the centre of the mesocolpium in the interapertural area (Ex2) and distance between spines (De) in the equatorial optical section. The studies show that the pollen of the three genera is very similar regarding shape, apertures, and ornamentation, but may be distinguished by size and exine thickness.

Abstract: The Gonosperminae (Asteraceae) are composed of three genera endemic to the Canary Islands (Gonospermum Less., and Lugoa DC.) and southern Africa (Inulanthera Kallersjo ¨), and they are considered an example of a floristic link between these two regions. Phylogenetic analyses of ITS sequences reveal that the Canarian genera are not sister to Inulanthera and do not support the monophyly of the Gonosperminae. These results, coupled with previous phylogenetic studies of other groups, suggest that many of the putative biogeographic links between Macaronesia and southeast Africa need to be evaluated by rigorous phylogenetic analyses. Inulanthera forms part of the basal southern African radiation of the Anthemideae, and therefore it is closely related to other taxa from this region. Maximum likelihood and weighted parsimony analyses support a monophyletic group in the Canary Islands, that includes Lugoa, Gonospermum, and three Tanacetum species endemic to the island of Gran Canaria. Bootstrap support for the monophyly of this Canarian group is weak, and it collapses in the strict consensus tree based on unweighted parsimony. Lugoa is nested within Gonos- permum, and both interisland colonization among the western islands of La Gomera, El Hierro, La Palma and Tenerife, and radiation on the central island of Gran Canaria have been the major patterns of species diversification for these Canarian endemics.