When: Thursday 13th September 2018, 13:00-14:00.
Included in meeting:
The fortnightly BRAG meeting will be held tomorrow 13th September 2018 at 1pm in room Y801. This week we will have presentations by Cath and Jess.
Title: Extreme drought alters the temporal beta diversity and functional stability of stream invertebrate communities
Catherine Leigh 1 2 , Thomas WH Aspin 3 , Thomas J Matthews 3 4 5 , Rob J Rolls 6 7 , Mark E Ledger 3
- Australian Rivers Institute, Griffith University, Nathan, QLD, Australia
- ARC Centre of Excellence for Mathematics and Statistical Frontiers, and Institute for Future Environments, Queensland University of Technology, Brisbane, QLD, Australia
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, UK
- 2CE3C – Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group, Universidade dos Açores – Depto de Ciências Agráriase Engenharia do Ambiente, Angra do Heroísmo, Açores, Portugal
- Birmingham Institute of Forest Research, University of Birmingham, Edgbaston, UK
- Institute for Applied Ecology, University of Canberra, Bruce, ACT, Australia
- School of Environment and Rural Science, University of New England, Armidale, NSW, Australia
In fresh waters, most biogeographical understanding of how extreme events such as drought modify biodiversity and ecosystem functioning derives from static, spatial comparisons of ecological communities, between intact and disturbed sites or along stress gradients. Impacts of drought on the development of ecological communities over time remain poorly resolved, with information on parallel trends in community structure and function particularly scarce. In theory, drought could progressively eliminate both species and functional traits, rendering communities increasingly taxonomically and functionally nested subsets of their pre-existing counterparts. Alternatively, drought could create new niche opportunities, producing a continuous turnover of species and traits, or simply arrest natural community development. We studied temporal changes in aquatic invertebrate community structure and function in artificial streams over two years, comparing drought (frequent drying) with control (constant flow) conditions. Temporal beta-diversity was partitioned into turnover and nestedness components, calculated using both presence-absence and abundance data, and analysed using time-lag and null modelling approaches. Community development was comparable taxonomically under control and drought conditions, driven primarily by temporal turnover of species. Under control conditions, corresponding trends in functional composition were not apparent, and species turnover was simply characterised by the progressive replacement of some species by others of equivalent abundance. By contrast, species turnover in disturbed communities was accompanied by both functional turnover and greater loss of individuals, indicating that newly colonising taxa were not equivalent, either functionally or numerically, to those they replaced. Furthermore, functional dissimilarities between timepoints were greater under drought, and more similar in magnitude to taxonomic dissimilarities, implying that drying reduced the stability and redundancy of functional attributes. Shifts to drier climate could disrupt natural evolution of stream community structure, and undermine functional stability, at local and biogeographical scales, with potentially significant consequences for ecosystem services provisioning in fresh waters.
Title: A Mixture of Objectives
Jess will talk about mixtures clustering methods, understanding the results of multidimensional clustering and presenting results convincingly.
We look forward to seeing you all there!
Trish and Farzana