How can we increase our capacity to predict ecosystem responses to environmental change?

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Published on March 5, 2014

Author: tanogutierrezcanovas

Source: slideshare.net

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Chronic stress modifies the structure and function of ecosystems through different processes. Despite that some convergent responses have been found, as changes in community composition and a reduction in diversity, there is unclear how this may affect to the processes explaining changes in beta diversity and ecosystem features. In my research, I used stream macroinvertebrates to explore these questions, as they offer interesting properties to test ecological hypotheses. As these organisms respond to marked environmental habitats, we use natural and anthropogenic stress gradients to see if the degree in which the regional pool of species is adapted to a type of stress, may cause patterns that help to predict responses to ongoing global change. In a first work, I found that natural and anthropogenic stressors reduced species richness and generate contrasting patterns in beta diversity that arise through different mechanisms. While species turnover along natural stress gradients, nested subset of species developed over anthropogenic stress gradients. In a second work, we estimate some functional diversity measures from a multidimensional space composed of axes that represented the variation in biological traits of the aquatic community. Functional measures consisted of mean taxon functional richness (functional variability at taxon level), functional similarity (the percentage of niche overlap between taxon pairs), functional richness (functional variability at community level), functional dispersion (mean departure from community centroid) and functional redundancy (sum of overlapping areas between species pairs). We found similar functional responses to natural and anthropogenic stress, where mean taxon niche and functional similarity augmented with increased stress, while functional richness, dispersion and redundancy decreased when stress intensity augmented. The reduction in functional richness arose from the development of nested subsets of community traits along stress gradient. The results of these studies may have strong conservation implications and may help to predict the ecosystem responses to global change and to elucidate how organisms colonized and evolved in stressful habitats.

How can we increase our capacity to predict ecosystem responses to environmental change? Cayetano Gutiérrez-Cánovas; David SánchezFernández; Núria Bonada; Ian P. Vaughan; Steve J. Ormerod; Andrés Millán & Josefa Velasco

Odum (1985) Environmental Habitat filtering: change Response traits Community structure Community compositio n Diversity Ecosystem functioning Effect traits Ecosystem goods and services Beta-diversity gradients Regional diversity Population dynamics Community and ecosystem ecology: biodiversity-function relationship

Big challenge: Predicting the consequences of environmental change • Are there predictable patterns in response to chronic stress at ecosystem scale? • How habitat filtering modifies beta-diversity? • How habitat filtering shapes functional ecosystem features? • Can we get any insights from naturally stressed ecosystems?

How habitat filtering modifies betadiversity? GUTIÉRREZ-CÁNOVAS, C.; MILLÁN, A; VELASCO, J.; VAUGHAN, I.P. & ORMEROD, S.J. 2013. Contrasting effects of natural and anthropogenic stressors on beta-diversity in river organisms. Global Ecology and Biogeography 22(7): 796-805.

Expected responses to increased stress (a) (b) NATURAL STRESS ANTHROPOGENIC STRESS Richness response species richness species richness Richness response stress intensity Assemblage response Assemblage response Site 1 1 2 3 4 Site 3 Site 4 Site 1 1 2 3 4 5 6 7 Site 2 1 2 3 Site 3 1 2 8 9 10 Site 4 1 stresss Site 2 stress intensity

100 65 55 50 45 35 Richness Salinity 150 Altitude P<0.001; R2=0.92 1000 2000 3000 P<0.001; R2=0.93 4000 4 6 8 10 12 m a.s.l. ln-Conductivity (mS cm-1) Acidity Metals 150 25 100 30 50 -7.0 -6.5 -6.0 pH -5.5 50 P<0.001; R2=0.91 15 20 40 30 Richness 35 60 40 200 Land use P<0.001; R2=0.64 -7 -6 -5 -4 -3 -2 -1 -1 ln-Copper concentration (mg L ) P<0.001; R2=0.83 0.0 0.4 0.8 1.2 arcsin-sqrt-Land use intensity (%)

Nestedness 0.25 0.30 2.5 3.5 0.4 0.0 2.5 0.5 2.0 3.5 0.0 1.0 2.0 3.0 Land use Environmental distance 2.5 0.5 2.0 3.5 0.0 1.0 2.0 3.0 0.0 0.55 3.0 0.25 1.5 1.5 0.0 0.0 0.3 0.5 0.2 0.8 0.4 0.0 0.5 0.30 Acidity Metals 0.0 1.0 2.0 3.0 2.5 0.4 2.0 1.5 0.00 0.5 0.05 0.4 0.5 1.5 0.4 2.5 0.30 1.5 0.5 Salinity 0.2 0.9 1.5 0.00 0.5 1.0 2.5 0.1 Dissimilarity 0.5 Dissimilarity 1.5 0.4 Dissimilarity 0.5 Dissimilarity Turnover Altitude 0.05 0.4 0.1 Dissimilarity b-diversity 0.0 1.5 3.0 Environmental distance 0.0 1.5 3.0 Environmental distance

How habitat filtering shapes functional ecosystem features? GUTIÉRREZ-CÁNOVAS, C.; SÁNCHEZ-FERNÁNDEZ, D.; VELASCO, J.; MILLÁN, A. & BONADA, N. Similar functional diversity trends in response to natural and anthropogenic stressors.

• Predicting ecosystem responses to environmental change is one of the most challenging tasks for scientists • Historical stress set predictable conditions: adaptation • Novel stressors may be entirely new: exaptation? • Some traits arose in response to historical stress may provide tolerance to modern stressors • Some traits allow tolerating stress other are sensitive. • Common patterns of functional response may be expectable for a subset of traits

Why using a trait-based niche? • Advantages: –Mechanistic relationship with environment: ecosystem response and functioning –Lower biogeographical influence –Better across-taxon comparability –Development of adequate databases and statistical techniques

Objective We compared trends of functional diversity change of stream insects along stress gradients with contrasting historical persistence (i.e. natural and anthropogenic stresses) to look for general patterns in response to stress. Niche features: a. Mean taxon functional richness (tFRic) b. Functional similarity (FSim) c. Functional richness (FRic) d. Functional dispersion (FDis) e. Functional redundancy (FR)

Expected responses to increased stress (b) Functional similarity stress intensity (d) Functional richness Functional dispersion (c) stress intensity stress intensity (e) stress intensity Functional redundancy Mean taxon functional richness (a) stress intensity

Mean Taxon functional richness (tRic) Taxon 1 Taxon 2 Taxon 3 Taxon 4 Taxon 5 Taxon 6 a b c d f n å area i tRic = i=a n e

Functional similarity (FSim) Taxon 1 Taxon 2 Taxon 3 Taxon 4 Taxon 5 Taxon 6 a ab bc b c cd n FSim = 2 å areai i=ab n å area i i=a d

Functional richness (FRic) Taxon 1 Taxon 2 Taxon 3 Taxon 4 Taxon 5 Taxon 6 Area filled by the convex hull

Taxon 1 Taxon 2 Taxon 3 Taxon 4 Taxon 5 Taxon 6 Functional dispersion (FDis) 2 2 dist = ( x - xc ) + ( y - yc ) n FDis = å dist i=a n i

Functional redundancy (FR) Taxon 1 Taxon 2 Taxon 3 Taxon 4 Taxon 5 Taxon 6 a b c n FR = å areai i=a

6 8 10 12 0.0 88 4 3.5 6 10 10 12 12 P<0.001; R2=0.13 P<0.001; R2=0.65 66 88 0.0 0.0 1 4 -0.5 7 -2.0 1 4 7 -2.0 -0.5 log(FR) log(FSim) 1.5 2.0 2 4 3.5 6 P<0.001; R2=0.35 66 10 10 12 12 0.5 0.5 1.0 1.0 1.5 1.5 1.0 1.0 1.5 1.5 P<0.001; R2=0.19 0.0 0.0 0.5 0.5 5 5 15 arcsin-sqrt(Land-use intensity) 15 log(Conductivity) FRic 1.0 Land use 2.0 2 FDis tFRic Salinity 0.5 6 8 10 12 0.0 0.5 1.0 1.5

6 8 10 12 0.0 15 12 P<0.001; R2=0.36 0.0 0.5 1.0 1.5 12 1.0 1.5 1.0 1.5 P<0.001; R2=0.41 0.0 0.5 4 4 7 10 7 8 2.0 P<0.001; R2=0.69 6 P<0.001; R2=0.16 6 8 1 1 1.5 3.5 10 3.5 2.0 FDis 8 5 P<0.001; R2=0.72 6 log(FR) 1.0 Land use 15 5 FRic Salinity 0.5 10 log(Conductivity) 12 P<0.001; R2=0.23 0.0 0.5 arcsin-sqrt(Land-use intensity)

Null models

Conclusions 1. Natural and anthropogenic stressors generate contrasting patterns in beta diversity that arise through different mechanisms. 2. However, functional diversity components responded similarly to both types of stress 3. Four out the five niche features and nestedness showed non-random responses when compare with null models, for both datasets 4. These insights may help to predict the consequences of global change 5. Useful to elucidate the historical colonization of stressful habitats 6. Important conservation implications may emerge from these results

Thanks for your attention! Thanks to the members of the Ecología Acuática research group that contributed to collect and identify the samples and the authors who provided raw data in their publications, making possible to gather the databases employed in these studies. More info: @tano_gc and www.um.es/ecoaqua

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