Maria AlejandraMaglianesiBiodiversity and Climate Research Centre (BiK-F) & Senckenberg Gesellschaft fuer Naturforschung

MatthiasSchleuningBiodiversity and Climate Research Centre (BiK-F) & Senckenberg Gesellschaft fuer Naturforschung

B.BluthgenKatrinBoehning-GaeseBiodiversity and Climate Research Centre (BiK-F) & Senckenberg Gesellschaft fuer Naturforschung

2015-03-27Understanding causes of variation in multispecies assemblages along spatial environmental gradients is a long-standing research topic in ecology and biogeography. Ecological networks comprising interacting species of plants and pollinators are particularly suitable for testing effects of environmental gradients on the functional structure and specialization in multispecies assemblages. In this study, we investigated patterns in functional assemblage structure and specialization of hummingbirds at the individual and species level along a tropical elevational gradient. We mist-netted hummingbirds at three elevations in Costa Rica in seven temporally distinct sampling periods and used the pollen carried by hummingbird individuals to construct plant-hummingbird networks at each elevation. We measured four functional traits of hummingbird species and quantified different metrics of functional community structure. We tested the effect of elevation on functional metrics of hummingbird assemblages and specialization within the networks, employing the variability across sampling periods and hummingbird species to compare the respective metrics among elevations. Hummingbird species and individuals were more specialized at low and mid elevations than at the highest elevation. This pattern corresponded to a more even and over-dispersed assemblage structure at the lower elevations throughout the year and suggests a high level of floral resource partitioning in functionally diversified communities. In contrast, an uneven and clustered functional structure of the highland assemblage across all sampling periods suggests that this assemblage was structured by environmental filtering and by niche expansion of hummingbird individuals and species at this elevation. We conclude that high degrees of specialization on specific floral resources might be crucial for the coexistence of hummingbird species in diversified lowland communities. Spatial variation in animal resource use may be a crucial driver of spatial patterns in the functional structure of diversified species assemblages also in other types of ecological networks.biotic interactionscommunity structurecosta ricaelevationelevational gradientfunctional diversityhummingbirdsmutualistic networkspollen loadspollinationspecializationtraitstropical forestObtain permission from data set owner(s)The study was conducted at La Selva Biological Station located in the lowlands of northeastern Costa Rica (10 deg 26 min N, 84 deg 01 min W) and adjacent Braulio Carrillo National Park. This study region constitutes a corridor of continuous forest from sea level at La Selva Biological Station (LS) to elevations higher than 2,900 m a.s.l. at the Braulio Carrillo National Park. Our study sites were located at three different elevations: low (50 m) in LS, mid (1,000 m) and high elevation (2,000 m) in the park. According to Holdridge's (1967) life zone classification, forests represented at those three elevations are tropical wet, pre-montane and lower montane wet forest. All sites were located in old-growth forest. Canopy heights were approximately 35 m at LS, 30 m at 1,000 m, and 20 m at 2,000 m (Hartshorn and Peralta 1988). Mean annual temperature ranges from 25 deg C at LS to 14 deg C in the highlands, while mean annual precipitation ranges from 4,300 mm in the lowlands to 2,200 mm in the highlands (Blake and Loiselle 2000). The dry season lasts from January to April and the wettest months are July and October-November.-84.0167-84.016710.433310.43332011-05-012012-04-30TrochilidaeHummingbird speciesKatrinBoehning-GaeseBiodiversity and Climate Research Centre (BiK-F) & Senckenberg Gesellschaft fuer Naturforschung

katrin.boehning-gaese@senckenberg.deMaria AlejandraMaglianesiBiodiversity and Climate Research Centre (BiK-F) & Senckenberg Gesellschaft fuer Naturforschung

MatthiasSchleuningBiodiversity and Climate Research Centre (BiK-F) & Senckenberg Gesellschaft fuer Naturforschung

B.Bluthgen

During the year of sampling, we repeatedly collected data on abundances and functional traits of hummingbirds. We also sampled pollen loads carried by hummingbirds to determine plant-hummingbird interactions. Hummingbird abundances and functional traits were collected during seven sampling periods of approximately 10 d each. Repeated sampling periods were separated by at least one month. Pollen loads were analysed for a subset of four periods covering both the wet and the dry season, that is, we identified pollen samples from plant species that bloomed at different times of the year.

attached_fileNot authorized to access resourceOtherattached_fileNot authorized to access resourceOtherattached_fileNot authorized to access resourceOther timeseries We conducted the study from May 2011 to April 2012, covering an entire study year and focused on the understory hummingbirds and their foraging plants. During the year of sampling, we repeatedly collected data on abundances and functional traits of hummingbirds. We also sampled pollen loads carried by hummingbirds to determine plant–hummingbird interactions. Hummingbird abundances and functional traits were collected during seven sampling periods of approximately 10 days each. Repeated sampling periods were separated by at least one month. Pollen loads were analysed for a subset of four periods covering both the wet and the dry season, that is, we identified pollen samples from plant species that bloomed at different times of the year. monthly