Intraspecific trait variation and community assembly in old-field grasslands

Trait-based approaches are increasingly used in plant community ecology, but previous research has largely ignored functional trait variation within species. Here I investigated the role of intraspecific trait variation in community assembly and responses to spatial and temporal environmental variation in old-field plant communities in the eastern United States. In the first study I analyzed spatial patterns of functional divergence in old fields in central New York on spatial scales from 1-1500 m. Results showed that spatial divergence in functional traits at the community and intraspecific levels corresponded with spatial heterogeneity in edaphic variables, consistent with predicted patterns resulting from trait-based environmental filtering. In the second study I tested for evidence of environmental filtering and niche differentiation based on trait dispersion patterns, with or without accounting for intraspecific trait variation. The tests provided evidence of strong trait-based environmental filtering and weak niche differentiation, and these patterns were strengthened by the inclusion of intraspecific trait variation, demonstrating its importance for community assembly. In the third study I examined the contributions of intraspecific variation and species turnover to community trait responses to environmental gradients across a 1200-km latitudinal extent in the eastern United States. Community trait shifts in response to broad-scale climatic variation were driven primarily by species turnover, but intraspecific variation contributed strongly to trait shifts along edaphic gradients and at fine spatial scales. Finally I investigated the role of intraspecific variation in community trait responses to experimental nutrient enrichment in old-field communities and the influence of community functional diversity and dispersal in mediating these responses. After three years, community functional responses were driven almost entirely by intraspecific trait shifts, which were strongest in communities with high initial intraspecific variation for some traits. Taken together, my results suggest that intraspecific trait variation plays a strong role in the assembly of old-field plant communities and shed light on the circumstances in which intraspecific variation is likely to be important for plant community ecology in general

Automating embedded analysis capabilities and managing software complexity in multiphysics simulation part II: application to partial differential equations

A template-based generic programming approach was presented in a previous paper that separates the development effort of programming a physical model from that of computing additional quantities, such as derivatives, needed for embedded analysis algorithms. In this paper, we describe the implementation details for using the template-based generic programming approach for simulation and analysis of partial differential equations (PDEs). We detail several of the hurdles that we have encountered, and some of the software infrastructure developed to overcome them. We end with a demonstration where we present shape optimization and uncertainty quantification results for a 3D PDE application

Set-valued State Estimation for Nonlinear Systems Using Hybrid Zonotopes

This paper proposes a method for set-valued state estimation of nonlinear, discrete-time systems. This is achieved by combining graphs of functions representing system dynamics and measurements with the hybrid zonotope set representation that can efficiently represent nonconvex and disjoint sets. Tight over-approximations of complex nonlinear functions are efficiently produced by leveraging special ordered sets and neural networks, which enable computation of set-valued state estimates that grow linearly in memory complexity with time. A numerical example demonstrates significant reduction of conservatism in the set-valued state estimates using the proposed method as compared to an idealized convex approach

Mitral valve force balance: a quantitative assessment of annular and subvalvular forces

In vitro and in vivo models were proposed to evaluate the effects of ischemic mitral regurgitation and surgical repair on the function and mechanics of the heart’s mitral valve. In specific aim 1, a novel transducer was developed to measure the radially directed forces that may act on devices implanted to the mitral annulus. In an ovine model, radial forces were found to statistically increase with left ventricular pressure and were reduced in the setting of ischemic mitral regurgitation. In specific aim 2, the suture forces required to constrain true-sized and undersized annuloplasty rings to the mitral annulus of ovine animals was evaluated. Suture forces were observed to be larger on the anterior aspect of the rings and were elevated with annular undersizing. In specific aim 3, an in vitro simulator’s ability to mimic healthy and ischemic mitral regurgitation ovine mitral valve function was evaluated. After understanding the accuracy of the model, the in vitro ischemic mitral regurgitation model was used to evaluate the progressive effects of annuloplasty on strut and intermediary chordal tethering. The generated data and knowledge will contribute to the development of more durable devices and techniques to assess the significant clinical burden known as ischemic mitral regurgitation.Ph.D

A global meta-analysis of the relative extent of intraspecific trait variation in plant communities

14 páginas.-- 5 figuras.-- 77 referencias.-- Additional Supporting Information may be downloaded via the online version of this article at Wiley Online Library (www.ecologyletters.com). Ecology Letters 18(12): 1406-1419 (2015) Siefert, Andrew et al..Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the total trait variation among communities on average. The relative extent of ITV tended to be greater for whole-plant (e.g. plant height) vs. organ-level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait-based community and ecosystem studies.We thank Mark Westoby, Ian Wright and three anonymous reviewers for providing valuable comments on an earlier version of the manuscript. AS was supported by the National Science Foundation Graduate Research Fellowship (DGE-1247399) and NSF grant DEB-03089. CV was supported by a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Program (DiversiTraits project, no. 221060) and by the European Research Council (ERC) Starting Grant Project ‘Ecophysiological and biophysical constraints on domestication in crop plants’ (Grant ERC-StG- 2014-639706-CONSTRAINTS). LC received funding from the European Research Council under the 7th European Community Framework Program FP7/2007-2013 Grant Agreement no. 281422 (TEEMBIO). Financial support to AF came from the Chilean Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT) project No. 1120171. FdB was supported by the Czech Science Foundation, grant P505/12/1296. LWA and BSS were supported by Discovery Grants from the Natural Science and Engineering Research Council of Canada. CS was supported by the Swiss National Science Foundation (PA00P3_136474 and PZ00P3_148261). MBC, MVC, LDSD, VDP and CRF were supported by CAPES-Brazil (grants BEX 7913/13-3 and PNPD #1454013) and CNPq-Brazil (grants 479083/2008-8, 141451/2011-4, 306573/2009-1, 303534/2012-5 and 303714/2010-7). MK received support from the JSPS as a Postdoctoral Fellow for Research Abroad. VLD was supported by Sao Paulo Research Foundation (processes: 2013/50169-1 and 2014/06453-0). DAP, SJR and NWHM were supported by the New Zealand Ministry of Business, Innovation and Employment core funding to Crown Research Institutes and the Ministry for the Environment. YLBP was supported by the project Postdoc USB (reg.no. CZ.1.07/2.3.00/30.0006) realised through EU Education for Competitiveness Operational Programme and received funding from the European Social Fund and Czech State Budget. The Forest Dynamics Plot of Yasuni National Park has been made possible through the generous support of the Pontifical Catholic University of Ecuador, the government of Ecuador, the Andrew W. Mellon Foundation, the Smithsonian Tropical Research Institute and the University of Aarhus of Denmark.Peer reviewe

Data from: The interplay among intraspecific leaf trait variation, niche breadth and species abundance along light and soil nutrient gradients

It is assumed that widespread, generalist species have high phenotypic variation, but we know little about how intraspecific trait variation (ITV) relates to species abundance and niche breadth. In the temperate rainforest of southern Chile, we hypothesized that species with wide niche breadth would exhibit 1) high among-plot ITV, 2) a strong relationship between trait values and the environment, and 3) a close fit between traits and local environment trait optima. We measured leaf functional traits (leaf area, LMA, leaf N and P concentrations) of saplings in woody species, and compared the relative abundance of each species with its niche breadth, measured as the range of light, soil N and P availability. We used the slope of the linear regression of species’ trait-environment relationships to assess the strength and direction of these relationships, and measured the degree to which species’ trait values track the environmental optimum across plots. In some cases, species having wide niche breadth had high ITV in leaf N and also matched traits (LMA and leaf P) to local optima along the light gradient; they also had high ITV in general and matched leaf P to local optima along the soil P gradient. The relationship between species with wide niche breadth and the strength of intraspecific trait-environment relationships was generally weak and varied depending on the niche dimension and trait in question. Species varied considerably in the strength of trait-environment relationships and total magnitude of ITV, and this variation was not generally strongly related to species abundances or niche breadth patterns. In conclusion, trait variation at the community level is not driven by a few abundant, widely distributed species, but depends on the aggregate trait responses of both abundant and rare species. This makes it difficult to scale individual species trait responses up to the community level

Estimating the net effect of functional traits on fitness across species and environments

Abstract Functional traits affect the demographic performance of individuals in their environment, leading to fitness differences that scale up to drive population dynamics and community assembly. Understanding the links between traits and fitness is, therefore, critical for predicting how populations and communities respond to environmental change. However, the net effects of traits on species fitness are largely unknown because we have lacked a framework for estimating fitness across multiple species and environments. We present a modelling framework that integrates trait effects on demographic performance over the life cycles of individuals to estimate the net effect of traits on species fitness. This approach involves (1) modelling trait effects on individual demographic rates (growth, survival and recruitment) as multidimensional performance surfaces that vary with individual size and environment and (2) integrating these effects into a population model to project population growth rates (i.e., fitness) as a function of traits and environment. We illustrate our approach by estimating performance surfaces and fitness landscapes for trees across a temperature gradient in the eastern United States. Functional traits (wood density, specific leaf area and maximum height) interacted with individual size and temperature to influence tree growth, survival and recruitment rates, generating demographic trade‐offs and shaping the contours of fitness landscapes. Tall tree species had high survival, growth and fitness across the temperature gradient. Wood density and specific leaf area had interactive effects on demographic performance, resulting in fitness landscapes with multiple peaks. With this approach it is now possible to empirically estimate the net effect of traits on fitness, leading to an improved understanding of the selective forces that drive community assembly and permitting generalizable predictions of population and community dynamics in changing environments

clean_nodC_field2015_OTU_seqs

OTU sequences of nodC genotypes measured on nodules from experimental plants in the field

fuc_mdn_nodC_field2015

OTU counts of nodC genotypes measured on nodules from experimental plants in the field