Trophic strategies of Yellow-legged Gull <i>Larus michahellis</i> on oceanic islands surrounded by deep waters

<p><b>Capsule:</b> The diet of Yellow-legged Gulls <i>Larus michahellis</i> on an oceanic island, surrounded by deep waters without a wide shelf, was mainly composed of terrestrial invertebrates.</p> <p><b>Aims:</b> To study the trophic ecology of Yellow-legged Gulls on an island surrounded by deep waters, to quantify the importance of terrestrial prey items and their availability, and to evaluate the relative importance of nutritional values of terrestrial and marine resources.</p> <p><b>Methods:</b> Diet was monitored for one year. We assessed the relative contribution of the main prey items and their macronutrients through the study of pellets and faeces.</p> <p><b>Results:</b> Terrestrial invertebrates were the most frequently consumed prey items (frequency of occurrence (FO) 67%), followed by marine fish (Osteichthyes FO 33%). Coleoptera and Orthoptera were the most consumed terrestrial invertebrates and provided a high nutritional value. The rate of consumption of terrestrial invertebrates varied in synchrony with the breeding season, being higher in spring, indicating their potential importance for reproduction.</p> <p><b>Conclusion:</b> It is unusual that terrestrial invertebrates constitute a large proportion of the diet of large gulls, but they seemed to cover their trophic energy requirements during the reproductive period.</p

Metrics used to infer inter-island colonization success of animal and plant species within the Galápagos, Azores and Canary Islands.

<p>¹ Number of current islands colonized by each species based on chorological data; (number of archipelago largest islands)</p><p>² Number of haplotypes obtained from mitochondria (animals) and plastid (plants) DNA sequences in each study</p><p>³ Number of haplotypes obtained in each study multiplied by the number of all largest islands-1</p><p>⁴ Inter-island colonization events based on distribution of each haplotype, i.e. each colonization event is inferred by haplotype sharing on two or more islands</p><p>⁵ Ratio expressing multiple colonization events, that ranges between 1 (all islands colonized by all the haplotypes) and 0 (no inter-island colonization).</p><p>* <i>Olea europaea</i> subsp. <i>guanchica</i> is distributed across the seven Canary Islands. However, the three eastern-most islands show evidence for hybridization with the olive tree. This made the authors use only material from the four western-most islands.</p><p>Metrics used to infer inter-island colonization success of animal and plant species within the Galápagos, Azores and Canary Islands.</p

Patterns of colonization of animal groups (species, genera) across the 12 Galápagos largest islands.

<p>Patterns of colonization of animal groups (species, genera) across the 12 Galápagos largest islands.</p

Phylogeographic reconstruction of <i>Xylocopa darwini</i>.

<p>Maximum clade credibility tree summarized from the geospatial Bayesian analysis of mtDNA (<i>COII</i> sequences) of 118 individuals. Pie charts represent posterior probability distributions of the ancestral range at well-supported nodes of interest. Coloured squares represent the sample’s island of origin. Haplotype relatedness is also shown in the well-supported clades. Colonization routes supported by a BF >3 are shown on the map. The colour of each route represents its relative support, with more intense purple lines indicating stronger support.</p

Distribution of genetic diversity (mitochondrial <i>cytochrome oxidase II</i> (<i>COII</i>) sequences) of <i>Xylocopa darwini</i> across the Galápagos Islands.

<p>(A) Distribution of mitochondrial haplotypes within populations (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0120597#pone.0120597.s003" target="_blank">S1 Table</a>). (B) Distribution of haplotypes across islands. (C) Statistical parsimony network of haplotypes; lines represent single nucleotide substitutions, and dots indicate missing haplotypes (extinct or not found). Circle sizes are proportional to the number of sequences obtained for each haplotype.</p