Percorrer por autor "Scharff, Nikolaj"
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- Ant Diversity Declines with Increasing Elevation along the Udzungwa Mountains, TanzaniaPublication . Kunene, Caroline; Foord, Stefan H.; Scharff, Nikolaj; Pape, Thomas; Malumbres-Olarte, Jagoba; Munyai, Thinandavha C.Biodiversity patterns along elevational gradients are generally characterised by monotonic decreases or mid-elevational peaks in species richness, while elevational zones may be characterised by distinct assemblages, or higher zones may be subsets of lowland assemblages. Elevational gradients in diversity have been less studied in the Afrotropical region. This study documents ant diversity patterns in three forest types associated with the tropical mountains of Udzungwa; we hypothesise that: (1) ant diversity and activity will show a monotonic decrease from mid-elevation with increasing elevation and (2) that forests associated with different elevations will have a distinct ant assemblage. Pitfall traps were deployed at three targeted elevations (650–800, 800–1400, and 1400–1500 m a.s.l.). Ant species richness declined with increasing elevation from 650 m a.s.l. and formed three elevational assemblages with lower elevation forests having almost twice as many species as sub-montane forests and three times as many as that of the montane forests. In contrast, overall ant activity peaked at 800–1400 m a.s.l. The ant assemblages associated with the lower elevation forest were very distinct, while assemblages associated with the sub-montane and montane forests shared species. Our study reveals valuable and relevant information for biodiversity monitoring and conservation planning as the species associated with each forest type may be used as indicator species for assessing biodiversity responses to climate change and anthropogenic activities on these mountains.
- Within-Habitat β Diversity Increases With Elevation in Tropical Forest Spider AssemblagesPublication . Malumbres-Olarte, Jagoba; Crespo, Luís Carlos; Cardoso, Pedro; Laizzer, Richard; Mwakisoma, Aloyce; Rigal, François; Szűts, Tomás; Pape, Thomas; Scharff, NikolajABSTRACT: While between-habitat comparisons are commonplace in ecology, we know very little about the changes among species assemblages within habitats. Here we aimed to examine within-habitat processes in spider assemblages across three elevations in tropical forests, using a design tailored both geographically and methodologically for this purpose. We hypothesised greater within-habitat βTD (caused by lower connectivity), decreasing body sizes (because of lower temperatures) and less frequent ballooning (due to greater isolation) with increasing elevation. We collected spiders at five within-habitat (horizontal) distances at each elevation in the Udzungwa Mountains, Tanzania, applying standardised protocols. We assessed differences among assemblages using taxonomic and functional β-diversity measures and their components. We applied PerMANOVAs to test for different β between elevations, PERMDISP to evaluate within-habitat variability, exponential and power-law models to examine within-habitat distance-decay, and community weighted values of traits to capture functional patterns for each trait. As predicted, within-habitat βTD was greater at higher elevations, with stronger distance-decay relationships (taxonomic and functional). Also, as predicted, high elevation assemblages appeared to show smaller body sizes and lower ballooning frequency. Our results demonstrate the uniqueness of mountain assemblages and that the Udzungwa Mountains, as well as other mountainous areas, should receive increasing conservation attention, as they provide unmissable opportunities to conserve, through small additions or connections, countless small-range or habitat-restricted endemic species.