The effective number of species ( We used simulations of five stream macroinvertebrate assemblages and spatially extensive field data of stream fishes and mussels to show (a) how different Values of The amount of variation in
Univariate and multivariate methods are commonly used to explore the spatial and temporal dynamics of ecological communities, but each has limitations, including oversimplification or abstraction of communities. Rank abundance curves (RACs) potentially integrate these existing methodologies by detailing species‐level community changes. Here, we had three goals: first, to simplify analysis of community dynamics by developing a coordinated set of R functions, and second, to demystify the relationships among univariate, multivariate, and
- NSF-PAR ID:
- 10460563
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 10
- Issue:
- 10
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Weighting effective number of species measures by abundance weakens detection of diversity responsesmore » « less
Abstract ENS ) has been proposed as a robust measure of species diversity that overcomes several limitations in terms of both diversity indices and species richness (SR). However, it is not yet clear ifENS improves interpretation and comparison of biodiversity monitoring data, and ultimately resource management decisions.ENS formulations respond to stress and (b) how diversity–environment relationships change with values ofq , which weightENS measures by species abundances.ENS derived from whole simulated assemblages with all species weighted equally (true SR) steadily decreased as stress increased, andENS ‐stress relationships became weaker and more different among assemblages with increased weighting.ENS across the fish and mussel assemblages that was associated with environmental gradients decreased with increasingq .Synthesis and applications . Species diversity is valued by many human societies, which often have policies designed to protect and restore it. Natural resources managers and policy makers may use species richness and diversity indices to describe the status of ecological communities. However, these traditional diversity measures are known subject to limitations that hinder their interpretation and comparability. The effective number of species (ENS ) was proposed to overcome the limitations. Unfortunately, our analyses show thatENS does not improve interpretability of how species diversity responds to either stress or natural environmental gradients. Moreover, incorporating the relative abundance of individuals in different species (evenness) into diversity measures as implemented inENS can actually weaken detection of diversity responses. Natural resources managers and policy makers therefore need to be cautious when interpreting diversity measures, includingENS , whose values are jointly influenced by richness and evenness. We suggest that both researchers and practitioners measure and report three aspects of diversity (species richness, evenness, and composition) separately when assessing and monitoring the diversity of ecological communities. -
more » « less
Abstract During the 1980s, the North Sea plankton community underwent a well‐documented ecosystem regime shift, including both spatial changes (northward species range shifts) and temporal changes (increases in the total abundances of warmer water species). This regime shift has been attributed to climate change. Plankton provide a link between climate and higher trophic‐level organisms, which can forage on large spatial and temporal scales. It is therefore important to understand not only whether climate change affects purely spatial or temporal aspects of plankton dynamics, but also whether it affects spatiotemporal aspects such as metapopulation synchrony. If plankton synchrony is altered, higher trophic‐level feeding patterns may be modified. A second motivation for investigating changes in synchrony is that the possibility of such alterations has been examined for few organisms, in spite of the fact that synchrony is ubiquitous and of major importance in ecology. This study uses correlation coefficients and spectral analysis to investigate whether synchrony changed between the periods 1959–1980 and 1989–2010. Twenty‐three plankton taxa, sea surface temperature (
SST ), and wind speed were examined. Results revealed that synchrony inSST and plankton was altered. Changes were idiosyncratic, and were not explained by changes in abundance. Changes in the synchrony ofCalanus helgolandicus andPara‐pseudocalanus spp appeared to be driven by changes inSST synchrony. This study is one of few to document alterations of synchrony and climate‐change impacts on synchrony. We discuss why climate‐change impacts on synchrony may well be more common and consequential than previously recognized. -
more » « less
Abstract The leaf economic spectrum is a widely studied axis of plant trait variability that defines a trade‐off between leaf longevity and productivity. While this has been investigated at the global scale, where it is robust, and at local scales, where deviations from it are common, it has received less attention at the intermediate scale of plant functional types (
PFT s). We investigated whether global leaf economic relationships are also present within the scale of plant functional types (PFT s) commonly used by Earth System models, and the extent to which this global‐PFT hierarchy can be used to constrain trait estimates. We developed a hierarchical multivariate Bayesian model that assumes separate means and covariance structures within and acrossPFT s and fit this model to seven leaf traits from theTRY database related to leaf longevity, morphology, biochemistry, and photosynthetic metabolism. Although patterns of trait covariation were generally consistent with the leaf economic spectrum, we found three approximate tiers to this consistency. Relationships among morphological and biochemical traits (specific leaf area [SLA ], N, P) were the most robust within and acrossPFT s, suggesting that covariation in these traits is driven by universal leaf construction trade‐offs and stoichiometry. Relationships among metabolic traits (dark respiration [R d], maximum RuBisCo carboxylation rate [V c,max], maximum electron transport rate [J max]) were slightly less consistent, reflecting in part their much sparser sampling (especially for high‐latitudePFT s), but also pointing to more flexible plasticity in plant metabolistm. Finally, relationships involving leaf lifespan were the least consistent, indicating that leaf economic relationships related to leaf lifespan are dominated by across‐PFT differences and that within‐PFT variation in leaf lifespan is more complex and idiosyncratic. Across all traits, this covariance was an important source of information, as evidenced by the improved imputation accuracy and reduced predictive uncertainty in multivariate models compared to univariate models. Ultimately, our study reaffirms the value of studying not just individual traits but the multivariate trait space and the utility of hierarchical modeling for studying the scale dependence of trait relationships. -
more » « less
Abstract The study of diversity has become increasingly sophisticated, including the use of measures of phylogenetic diversity.
We calculate the spatial variation in species richness, taxonomic beta diversity, and alpha and beta phylogenetic diversity (
PD α andPD β , respectively) of Atlantic Forest harvestman communities using a data set containing 556 species from 68 sites, distributed in 12 Brazilian states.We compare the congruence of phylogenetic and taxonomic diversity patterns, and also compare
PD α with null model expectations, to check for phylogenetic clustering or overdispersion in communities.Species richness and
PD α are correlated, peaking in southern and south‐eastern coastal sites and decreasing towards the interior and towards the north‐east.PD α in north‐eastern sites was higher than expected, while a clustered phylogenetic pattern characterised most other sites.Communities in the southern and south‐eastern regions were dominated by species from the large family Gonyleptidae, presenting a high richness and a low
PD α . As the dominance of Gonyleptidae decreased towards the north, where local communities have fewer species, but a higherPD α , they contain representatives of other families. The beta diversity was more sensitive to the compositional changes involving closely related Gonyleptidae species, whilePD β is more influenced by deeper phylogenetic compositional changes, between more distant lineages.Phylogenetic diversity may be of special importance to assess the conservation value of distantly related lineages. These species‐poor groups are less likely to influence taxonomic‐based diversity analyses, but their importance for conservation arises from their phylogenetic distinctiveness, captured by
PD α andPD β measures. -
more » « less
Abstract Succession theory predicts altered sensitivity of ecosystem functions to disturbance (i.e., climate change) due to the temporal shift in plant community composition. However, empirical evidence in global change experiments is lacking to support this prediction. Here, we present findings from an 8‐year long‐term global change experiment with warming and altered precipitation manipulation (double and halved amount). First, we observed a temporal shift in species composition over 8 years, resulting in a transition from an annual C3‐dominant plant community to a perennial C4‐dominant plant community. This successional transition was independent of any experimental treatments. During the successional transition, the response of aboveground net primary productivity (
ANPP ) to precipitation addition magnified from neutral to +45.3%, while the response to halved precipitation attenuated substantially from −17.6% to neutral. However, warming did not affectANPP in either state. The findings further reveal that the time‐dependent climate sensitivity may be regulated by successional change in species composition, highlighting the importance of vegetation dynamics in regulating the response of ecosystem productivity to precipitation change.
