MaximilianVollstädtSenckenberg Biodiversity and Climate Research Centre (SBiK-F)

MaximilianVollstädtassociatedPartyKatrinBöhning-GaeseCo-ownerMatthiasSchleuningCo-owner2018-04-20Aim: Climate change and an increase in human disturbance are major drivers of global biodiversity loss. Yet it is not clear to what extent their effects on animal communities are direct or indirectly mediated by changes in biotic factors, such as plant diversity. Here, we disentangle the direct and indirect effects of climate, human disturbance, vegetation structure and plant functional traits on the functional diversity of avian frugivore communities across a large environmental gradient. Location: Mount Kilimanjaro. Time period: Sampling between November 2013 and October 2015. Major taxa studied: Fleshy-fruited plants, frugivorous birds. Methods: We sampled plant and bird communities along an elevational and a human disturbance gradient and measured corresponding morphological traits of plants and birds to calculate indices of functional identity and functional diversity of plant and bird communities. We used structural equation models to disentangle direct and indirect effects of all variables on functional identity and diversity of frugivorous bird communities. Results: Both functional identity and diversity of frugivorous bird communities were consistently related to the functional identity and diversity of plant communities. Climate had almost exclusively indirect effects on functional identity and diversity of bird communities mediated through effects on plant functional identity and diversity. In contrast, human disturbance also had direct negative effects on bird diversity. Main conclusions: We show that plant functional identity and diversity are the most important drivers of functional identity and diversity of frugivorous birds. Although effects of climate on bird communities are almost exclusively mediated indirectly through plant communities, human disturbance resulted in a direct reduction of bird diversity. The high degree of trait matching between interdependent trophic levels over a large environmental gradient demonstrates the importance of biotic drivers for animal communities and shows that biodiversity models need to consider such bottom-up effects in future conditions. bottom-up effectselevational gradientfrugivorous birdsfruiting plantskilimanjaroland-use gradientstructural equation modelsObtain permission from data set owner(s)Southern slope of Mt. Kilimanjaro, Tanzania37.037.7167-2.75-3.41672013-11-052015-10-20MatthiasSchleuningSenckenberg Biodiversity and Climate Research Centre (SBiK-F)

Senckenberganlage 25Frankfurt am MainHesse60325Germany

matthias.schleuning@senckenberg.de

On 50 study plots of 30 x 100m in size, distributed over 10 habitat types on an elevational gradient of 2000 m, we observed plant and bird interactions. We identified the interacting species and took morphological measurements corresponding to functional traits, which are essential for seed dispersal interactions between plants and birds. For plants we measured the following four traits: crop mass, plant height, (maximum) fruit diameter and fruit length (peduncle to tip). Crop mass was calculated as the number of fruit per plant multiplied with the mean fruit weight (± 0.01 g). Plant height was measured with a laser range finder (± 0.9 m) for very tall plants and with measuring tape for small plant (≤ 2m), respectively. Fruit size (diameter and length) were measured with a sliding caliper (± 0.01 mm). For birds we measured the following four corresponding traits in museum collections (Natural History Museum, Berlin; Museo Ecuatoriano de Ciencias Naturales, Quito; Zoological Research Museum Alexander Koenig, Bonn; Zoological Museum of Denmark at the University of Copenhagen): body mass, Kipp’s index, bill height and bill length. Body mass was compiled from literature (Dunning, J. B. (2007). CRC handbook of avian body masses (2nd ed.). Boca Raton, FL: Taylor and Francis). Kipp’s index calculated Kipp’s index as the ratio between Kipp’s distance (distance between tip of the first secondary and tip of the longest primary of the folded wing) and wing length. Wing measures were taking with wing rulers (± 0.01 mm). Bill measurements were taken with sliding calipers (± 0.01 mm).

attached_fileNot authorized to access resourceOther timeseries yearly Study plots were sampled during the dry seasons of Mt. Kilimanjaro