Do functionally richer communities improve ecosystem functioning? Dung removal and secondary seed dispersal by dung beetles in the Western Palaearctic

This research has been presented at the Ecology Across Borders (EAB) 2017 conference at December 14th, 2017 in Ghent, Belgium.
The relation between biodiversity and ecosystem functioning has been intensively studied during the last two decades. Nevertheless, the diversity of functional traits is expected to have a more profound effect on ecosystem functioning as functional groups of species fulfil similar ecosystem functions. In a multi-site experiment, we tried to unravel some aspects of the relation between ecosystem functioning and the functional diversity of species assemblages. Dung beetles were used as model organism group. Due to their interaction with dung during nesting and feeding, dung beetles provide ecosystem functions such as dung removal and secondary seed dispersal. Dung beetle species were classified into functional groups according to their dung processing behaviour (dwellers, tunnelers and rollers) and size (small or large). At 17 grassland locations, different exclosure types were constructed to control the dung and seed removing activities of individual functional groups of the local dung beetle assemblage across biogeographic regions. By sampling the dung beetle community and measuring the remaining dung and seeds after the experiment, the impact of each functional group was estimated.
A clear difference in dung beetle assemblage composition was found along a north-south and east-west gradient, with higher dung beetle abundance, and species and functional group richness at lower latitudes. While northernmost sites were dominated by dwellers, a functional shift towards more tunnelers and rollers was found in the southern sites. Overall, more dung and seeds were removed in the southern sites; and, when present, tunnelers and rollers were more effective dung removers. At the northernmost sites where tunnelers were scarce or absent, dung removal was partly taken over by other soil macro-invertebrates.
The positive relation between functional group richness and dung removal rates stresses the need of functional group conservation in order to maintain the ecosystem functions of dung removal and secondary seed dispersal.

Transcript

1. Do functionally richer communities improve ecosystem functioning? Dung removal and secondary seed dispersal by dung beetles in the Western Palaearctic Tanja Milotić @tmilotic
2. Why? • Relation biodiversity – ecosystem functioning • Functional traits of species groups • Challenge in changing and disturbed environments • Functional shift in species assemblages • Artificial, closed systems vs. open field environment • Focal taxon: dung beetles (Scarabaeidae)
3. Dung beetle functional groups dwellers tunnelers rollers Bertone et al. (2006)
4. Dung beetle biogeography Hortal et al. (2011) Ecology letters low high Species diversity dwellers tunnelers rollers Functional group diversity
5. Dung beetles & ecosystem functioning Dung removal for feeding and breeding • secondary seed dispersal • nutrient cycling • bioturbation • plant growth • parasite control • reduction of methane emission
6. Research questions 1. Relation between functional group composition and biogeography? 2. Regional differences in dung removal? 3. How do individual functional groups contribute to dung removal and secondary seed dispersal? 4. What happens when functional richness is reduced?
7. Multi-site approach
8. Field experiments • Different dung types • Dung beetle sampling • Removal of dung and seeds • tunnelers: large/small • other soil macro- invertebrates: large/small • rollers: large/small • dwellers
9. Dung beetle assemblages dwellers tunnelers (small) rollers (small) tunnelers (large)
10. Dung beetle assemblages y x tP mT
11. Resource specialists & generalists
12. Dung removal
13. Effectiveness of functional groups dwellers
14. Effectiveness of functional groups small tunnelers
15. Effectiveness of functional groups large tunnelers
16. Effectiveness of functional groups small rollers
17. Effectiveness of functional groups other soil macro-invertebrates
18. Dung & seed removal p<0.05 n.s. - + - + - + - +
19. Take home message • Regional differences in dung beetle assemblages • Dung removal differs between regions • Positive relation between functional richness and dung removal rates  Conservation of functionally complete species assemblages • North-south shift in functional composition – Effects of climate change? – North: increased dung removal – South: extinction of species?
20. Thank you! Christophe Baltzinger Carsten Eichberg Amy E. Eycott Marco Heurich Jörg Müller Jorge A. Noriega Rosa Menendez Jutta Stadler Réka Ádám Tessa Bargmann Isabelle Bilger Jörn Buse Joaquin Calatayud Constantin Ciubuc Gergely Boros Marie Hauso Pierre Jay-Robert Märt Kruus Enno Merivee Geoffrey Miessen Anne Must Elham Omidzadeh Ardali Elena Preda Iraj Rahimi Dirk Rohwedder Rob Rose Eleanor M. Slade László Somay Pejman Tahmasebi Stefano Ziani Maurice Hoffmann Discover our dataset at GBIF! “Dung beetles of the Western Palaearctic” www.gbif.org @tmilotic tanja.milotic@inbo.be