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Many fleshy-fruited plants from the Mediterranean and Macaronesian islands are dispersed through endozoochory. In mainland Mediterranean areas, reciprocal adaptations have been found between plants and animals, although evidence is scarce. On small isolated oceanic islands, such reciprocal adaptations might well be more prevalent due to intrinsic island traits. Here we evaluate the existence of selective pressures exerted by two different disperser guilds (lizards and birds) on two seed traits (seed coat thickness and seed germination pattern) of two congeneric species present on Mediterranean and Macaronesian islands. In the continental Balearic Islands, Rubia peregrina has evolved mostly with birds, although frugivorous lizards are present in some of these islands and are known to eventually consume its fruits. By contrast, R. fruticosa, endemic to the Macaronesian archipelago, has evolved mostly interacting with lizards and only recently with birds. We hypothesized that R. fruticosa would be especially adapted to saurochory, with thicker seed coats and higher germination proportion, whereas R. peregrina would be more adapted to ornithocory, with thinner seed coats and showing a lower germination percentage after being ingested by lizards. Captivity experiments of seed ingestions by natural and non-natural dispersers (i.e., frugivores that have not evolved with those plants) were conducted. Results suggest that dispersers did not exert any strong enough selective pressure to induce changes in germination patterns. We attribute this to the fact that the Rubiaceae is an ancestral family in the Mediterranean (both on continent and islands) and thus probably interacted with lizards in the past. Lastly, although we hold that the seed coat structure of R. fruticosa is probably associated with its evolutionary success after a long interaction with insular lizards, our findings support the idea that the relationship between endozoochorous plants and the guild of dispersers with whom they evolved is rather unspecific. [ABSTRACT FROM AUTHOR]

A microhistological collection and its respective key on the leaves and fleshy fruits produced by the mostly endemic trees that integrate the relict laurel forest in the Macaronesian Islands are presented. Epidermal tissues from the adaxial and abaxial surfaces of leaves and fruits of 23 species were extracted by scraping and prepared on individual microscope slides. An optical microscope with a camera lucida fixed at magnifications of ×400 was used to analyse and to draw the morphological traits of epidermal tissues to the same scale. Furthermore, quantitative data for those congeneric species were also obtained by using an image analysis program system. The results indicate that this microhistological method permits the differentiation of practically all species of trees present in the Macaronesian laurel forest. Furthermore, most species belonging to the same taxa (genus or family) show a general common pattern in the morphology of the different epidermal traits. Lastly, despite the effort that constitutes the preparation of plant microhistological collections of a determined ecosystem, it is of basic importance because it makes possible the performance of feeding ecological studies of several herbivorous and frugivorous vertebrate species. These results provide crucial information that elucidates the functioning of the food web and energetic flux dynamics of the Macaronesian laurel forest ecosystem. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 148, 409–426. [ABSTRACT FROM AUTHOR]