Alfredo Valido

Frugivory and seed dispersal by the lizard Gallotia galloti (Lacertidae) in a xeric habitat of the Canary Islands

The relationship between an endemic lizard (Gallotia galloti) and plants with fleshy fruits was examined in a xeric habitat on the island of Tenerife, Canary Islands. An analysis of 441 droppinps collected in May 1991, showed that fruits are an important item in the diet of this omnivorous lizard; 92% and 56% of droppinps contained fruits from two different areas. Fruits of seven plant species were found in the droppinps: Rubia fruticosa, Neochamaelea pulverulenta, Withania aristata, Lycium intricatum, Atriplex semibaccata, Opuntia dillenii and Scilla cf. haemorrhoidalis. The number of fruit species consumed at each area by G. galloti was related to their availability. Seed viability did not differ between control seeds and seeds from the droppings, except for N. pulverulenta and L. intricatum, where viability was higher in control seeds

Native birds and insects, and introduced honey bees visiting Echium wildpretii (Boraginaceae) in the Canary Islands

In this paper, we report observations of flower visitors of the endemic Echium wildpretii in Tenerife, Canary Islands. This plant inhabits the high altitudinal sub-alpine zone, which is characterized by a harsh climate, low species diversity and a short growing season. Echium wildpretii is a monocarpic perennial, producing a 2–3 m column-shaped, red-flowered, nectar-rich inflorescence. Although these floral traits have previously been suggested as being typical of ornithophilous flowers, this is the first study reporting observations of native birds (Phylloscopus collybita and Serinus canarius) in addition to insects visiting the flowers for nectar. The purposes of this study were firstly to investigate levels of visitation by native birds, native insects, and introduced honey bees. Secondly, we studied the influence of floral display (plant height and number of flowers), nearest neighbours (distance and size) and local vegetation structure on visitation rate. Finally, we discuss the evolution of ornithophily in an otherwise entomophilous plant lineage. We found that the level of bird visitation was relatively high early in the flowering season, but decreased in mid/late season, while the opposite pattern was found for introduced honey bees. For native insects, the frequency of visits was similar in early and late season. Bird visits were correlated with floral display. In the early season, visitation rates of honey bees and the two most common native bee species were correlated with size of the plant or its nearest neighbours, consistent with preference patterns for larger resource patches. Since only insects visit the flowers of other species in the Echium clade, E. wildpretii appears to have evolved from a truly insect-pollinated lineage.

Fleshy Fruits in the Diet of Canarian Lizards Gallotia galloti (Lacertidae) in a Xeric Habitat of the Island of Tenerife

Abstract We analyzed the frugivorous diet of the lizard Gallotia galloti, a Canary Island endemic, in relation to season and fruit availability in a xeric habitat from Tenerife. Gallotia galloti was omnivorous throughout the year (including >59% of plant material by volume in fecal pellets); only in the winter months (December and January) did invertebrates dominate the diet (>73% in volume). The most remarkable aspect of the diet was the high level of consumption of fleshy fruits, showing pronounced seasonal variation (from 30% in January to 95% in April in frequency of occurrence). Variation in fleshy fruit consumption was associated with seasonal patterns of fruits availability. A total of 4710 seeds were found in 1120 droppings analyzed during the entire year corresponding the majority to Rubia fruticosa and Plocama pendula (Rubiaceae). The extensive consumption of fleshy fruits during seven months of the year (>50% by volume) suggests G. galloti is an important seed disperser in the Canary Islands. These results contrast with the majority of continental lacertids that are insectivorous.

Morphological evolution and changes in foraging behaviour of island and mainland populations of Blue Tit (Parus caeruleus) - a test of convergence and ecomorphological hypotheses

SummaryWe study the leg morphology and feeding postures of two subspecies of the Blue Tit (Parus caeruleus; Tenerife island and the Iberian Peninsula) and the Coal Tit (Parus ater; Iberian Peninsula). We search for evidence supporting the hypothesis of convergent evolution in morphological and ecological traits and we discuss the role of ecomorphological hypotheses as predictors of foraging differences at the intraspecific level. To overcome the problems introduced by environmental characteristics not related to locomotion and competition, we make observations under controlled situations to manage food quality and food access. We determine that the island Blue Tit has a longer tarsometatarsus, larger foot span and a more proximal insertion of the tibialis cranialis muscle (flexor of the tarsometatarsus) than the mainland Blue Tit. These morphological differences are consistent with the more frequent use of hanging and clinging ‘head-up’ postures by the Iberian Blue Tit. Several ecomorphological hypotheses obtained at the interspecific level with other taxa, have proved to be of high predictive value for explaining ecological differences considering morphological evolution. The Tenerife Blue Tit and the Iberian Coal Tit clearly show close convergence in both feeding postures and leg structure, although some differences in morphology were found between these two species. Convergence in foraging methods between the island Blue Tit and the mainland Coal Tit can be explained without considering current interspecific competition as a determinant of niche space.

Frugivory and factors influencing visitation by birds at "Balo" (Plocama pendula Ait., Rubiaceae) plants in the Canary Islands

We thank many friends for helping us during the fieldwork and laboratory analysis but we would specially like to mention L. Hernandez and M. Gonzalez, P. Jordano offered valuable advice during the planning of this study, as well as during data analysis and interpretation. R. Sallabanks, P. Joprdano, D. Levey, J. Lovett-Doust, and an anonymous referee revised the manuscript and gave very valuable suggestions. Meterorological data were provided by Instituto Nacional de Meteorologia (Canarias Occidentales). We are also grateful to J. Vega for permission to work on Teno bajo. Part of this investigation was supported by the Direccion General de Universidades e Investigacion del Gobierno de Canarias, grant 93/150.