Dagmar MartinaHanzSenckenberg Biodiversity and Climate Research Centre (SBiK-F)

Dagmar MartinaHanzassociatedPartyMatthiasSchleuningCo-ownerKatrinBöhning-GaeseCo-ownerTillTöpferCo-owner2018-11-23It is not yet clear whether similar mechanisms influence the assembly of ecological communities across different continents. Here, we investigated the functional and phylogenetic diversity of bird assemblages along elevational gradients in two biogeographic regions in order to identify how these are driven by biotic factors, such as food resources and vegetation structure, and abiotic factors, such as ambient temperature and precipitation. We recorded bird species abundances on 18 and 30 plots in the Ecuadorian Andes and on Mount Kilimanjaro, respectively. We measured ten functional morphological traits, related to bird feeding and movement, and utilized bird phylogenies to compare observed values and null-model corrected effect sizes of functional and phylogenetic diversity along elevational gradients and between biogeographic regions. Furthermore, we assessed how observed values and effect sizes of functional and phylogenetic diversity were associated with the underlying gradients in available food resources, vegetation structure, temperature and precipitation. Functional and phylogenetic diversity were generally higher in species assemblages in the Ecuadorian Andes than on Mount Kilimanjaro. Both observed values and effect sizes of functional and phylogenetic diversity decreased significantly with increasing elevation in both biogeographic regions. Functional diversity consistently increased with increasing resource availability, whereas phylogenetic diversity increased with increasing vegetation heterogeneity and canopy closure in both biogeographic regions. Temperature and precipitation were not significantly associated with functional and phylogenetic diversity. Our results suggest that in both mountain systems the diversity of functional traits in bird species assemblages is the result of environmental filtering by available food resources, whereas phylogenetic diversity is primarily limited by vegetation structure. These findings suggest important differences in the main drivers of functional and phylogenetic diversity. We conclude that biotic factors might be more important for driving bird diversity patterns than abiotic factors and that a loss of resource availability and vegetation structure, e.g. through human impacts, is likely to trigger changes in community assembly on tropical mountains.afrotropicscommunity assemblyelevational gradientenvironmental filteringfood resourcesfunctional diversityfunctional traitsneotropicsphylogenetic diversityvegetation structureObtain permission from data set owner(s)Ecuadorian Andes and Mount Kilimanjaro-79.203137.3517-3.9889-3.065620152016ClassAvesMatthiasSchleuningSenckenberg Biodiversity and Climate Research Centre (SBiK-F)

Senckenberganlage 25Frankfurt am Main60325Germany

matthias.schleuning@senckenberg.de

We collected data of ten morphological traits that are functionally related to the feeding and foraging behaviour of birds (Dehling, Töpfer, et al., 2014; Moermond & Denslow, 1985; Wheelwright, 1985). Morphological trait data of the respective bird species were measured on museum specimen at Zoologisches Forschungsmuseum Alexander König (Bonn, Germany), Museum für Naturkunde (Berlin, Germany), Senckenberg Naturmuseum (Frankfurt am Main, Germany), Senckenberg Naturhistorische Sammlungen (Dresden, Germany), Statens Naturhistoriske Museum (Copenhagen, Denmark), Natural History Museum (Tring, UK), Natural History Museum (London, UK), Field Museum of Natural History (Chicago, USA), Instituto de Ciencias Naturales (Bogotá, Colombia) and Museo Ecuatoriano de Ciencias Naturales (Quito, Ecuador). Related to the feeding behaviour, we measured the bill length, maximum bill height and bill width. Bill length was defined as the distance from the commissural point of the upper and lower bill to the tip of the closed bill, the bill width was defined as the external distance between the two commissural points (Dehling, Töpfer, et al. 2014). In order to capture the flight performance, we measured the wing length, Kipp’s distance and tail length. The wing length was measured as the distance from the carpal joint to the longest primary after the “maximum chord” method, Kipp’s distance was measured as the distance from the tip of the first secondary to the tip of the longest primary in the naturally folded wing and tail length was measured from the two innermost rectrices to the tip of the longest tail feather in the naturally folded tail (Eck et al., 2011). Related to the bipedal locomotion, we measured tarsus length and the sagittal and lateral diameter of the tarsus. The tarsus length was taken from the joint between tarsus and toes to the intertarsal joint, sagittal and lateral diameter were measured at the middle of the tarsus (Eck et al., 2011). In order to account for intraspecific variation, we aimed to measure two well-preserved specimens of each sex for each bird species and then calculated a species mean (on average 3.8 individuals were measured for each of the 315 species).

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