353 research outputs found
Fire exclusion and climate change interact to affect long-term changes in the functional composition of plant communities
© 2017 John Wiley & Sons Ltd Aim: Plant functional traits allow us to mechanistically link changes in species composition to changes in ecosystem functions. Understanding how and why changes occur in functional composition of plant communities can thus help us better conserve and restore biodiversity. We aim to examine long-term effects of fire exclusion and climate change on the functional composition of fire-maintained pine barrens in central Wisconsin. Location: Central Wisconsin, USA. Methods: Using a database that included vegetation data of surveys (1958) and resurveys (2012) of 30 sites, we quantified functional composition (α and β functional diversity, community-weighted means) of each site at both time periods. We then applied linear regression and linear mixed models to study effects of fire exclusion and climate change on changes in functional composition. Results: We observed shifts towards larger specific leaf area, greater seed mass and other traits related to shade tolerance. These communities thus appear to be undergoing ecological succession, favouring plant adaptions to better harvest light and carbon in darker, warmer and wetter habitats. Functional alpha diversity increased, while functional beta diversity decreased even after controlling for changes in taxonomic diversity. Fire exclusion and climate change both contributed to these increases in local functional diversity but neither is related to the functional homogenization observed. Fire exclusion and climate change also interacted negatively to affect local functional diversity, suggesting that future climate change and succession may soon reduce alpha functional diversity. Main conclusions: Our study provides a rare record of long-term functional dynamics and demonstrates that fire exclusion and climate change can interact to affect the functional composition of plant communities. Thus, we should consider changes in local ecological conditions as we seek to predict how climate change will affect the functional composition of plant communities
Where have all the flowers gone? A call for federal leadership in deer management in the United States
Forests in the United States continue to lose biodiversity and many fail to regenerate due to high deer (family Cervidae) abundance. Declines in biodiversity and overall ecosystem health due to high deer populations increases prevalence of wildlife and human diseases associated with increasing tick abundances and decreases forest resilience and the ability to deliver benefits provided by healthy ecosystems. In the eastern and midwestern United States, white-tailed deer (Odocoileus virginianus) are the main stressor, while in the western U.S. elk (Cervus elaphus) and black-tailed and mule deer (Odocoileus hemionus) can become equally problematic. Federal and State Wildlife Agencies are responsible for environmental stewardship and management of deer, migratory and endangered species, yet they lack authority to address human health concerns or commercial interests (we acknowledge tribal authority to manage wildlife as an important contributor to conservation). Furthermore, State Wildlife Agencies have retained their traditional focus to manage wildlife for recreational hunters while neglecting their obligations to manage wildlife in the interest of all citizens rather than special interest groups. Fragmented institutional arrangements and widely scattered responsibilities for human health, environmental conservation and management, agriculture, and commerce among tribal, federal, and state agencies have allowed deer impacts to grow into nationwide conservation and human health crises. Given that local, regional, and state-level initiatives have failed to provide appropriate remedies, federal leadership is now essential to integrate concerns among disciplines, policy domains, regions, habitats, and biota. We recommend developing a National Strategy to build strong collaborative efforts and diverse and inclusive relationships across environmental, human health and economic interests. These should reach beyond state boundaries to comprehensively address interrelated deer, human health, forest, and conservation crises. A well-coordinated and collaborative approach has the potential to overcome traditional turf battles between tribal, state, and federal interests by recognizing joint responsibilities and obligations to manage wildlife as a public trust resource. This collective approach can protect species before they become endangered, avoiding further declines in environmental and human health
Complex trait‒environment relationships underlie the structure of forest plant communities
Traits differentially adapt plant species to particular conditions generating compositional shifts along environmental gradients. As a result, community-scale trait values show concomitant shifts, termed trait‒environment relationships. Trait‒environment relationships are often assessed by evaluating community-weighted mean (CWM) traits observed along environmental gradients. Regression-based approaches (CWMr) assume that local communities exhibit traits centred at a single optimum value and that traits do not covary meaningfully. Evidence suggests that the shape of trait‒abundance relationships can vary widely along environmental gradients—reflecting complex interactions—and traits are usually interrelated. We used a model that accounts for these factors to explore trait‒environment relationships in herbaceous forest plant communities in Wisconsin (USA). We built a generalized linear mixed model (GLMM) to analyse how abundances of 185 species distributed among 189 forested sites vary in response to four functional traits (vegetative height—VH, leaf size—LS, leaf mass per area—LMA and leaf carbon content), six environmental variables describing overstorey, soil and climate conditions, and their interactions. The GLMM allowed us to assess the nature and relative strength of the resulting 24 trait‒environment relationships. We also compared results between GLMM and CWMr to explore how conclusions differ between approaches. The GLMM identified five significant trait‒environment relationships that together explain ~40% of variation in species abundances across sites. Temperature appeared as a key environmental driver, with warmer and more seasonal sites favouring taller plants. Soil texture and temperature seasonality affected LS and LMA; seasonality effects on LS and LMA were nonlinear, declining at more seasonal sites. Although often assumed for CWMr, only some traits under certain conditions had centred optimum trait‒abundance relationships. CWMr more liberally identified (13) trait‒environment relationships as significant but failed to detect the temperature seasonality‒LMA relationship identified by the GLMM. Synthesis. Although GLMM represents a more methodologically complex approach than CWMr, it identified a reduced set of trait‒environment relationships still capable of accounting for the responses of forest understorey herbs to environmental gradients. It also identified separate effects of mean and seasonal temperature on LMA that appear important in these forests, generating useful insights and supporting broader application of GLMM approach to understand trait‒environment relationships.Fil: Rolhauser, AndrĂ©s Guillermo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Parque Centenario. Instituto de Investigaciones FisiolĂłgicas y EcolĂłgicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de AgronomĂa. Instituto de Investigaciones FisiolĂłgicas y EcolĂłgicas Vinculadas a la Agricultura; ArgentinaFil: Waller, Donald M.. University of Wisconsin; Estados UnidosFil: Tucker, Caroline M.. University of North Carolina; Estados Unido
Can functional traits account for phylogenetic signal in community composition?
© 2017 The Authors. New Phytologist © 2017 New Phytologist Trust Phylogenetic and functional trait-based analyses inform our understanding of community composition, yet methods for quantifying the overlap in information derived from functional traits and phylogenies remain underdeveloped. Does adding traits to analyses of community composition reduce the phylogenetic signal in the residual variation? If not, then measured functional traits alone may be insufficient to explain community assembly. We propose a general statistical framework to quantify the proportion of phylogenetic pattern in community composition that remains after including measured functional traits. We then illustrate the framework with applications to two empirical data sets. Both data sets showed strong phylogenetic attraction, with related species likely to co-occur in the same communities. In one data set, including traits eliminated all phylogenetic signals in the residual variation of both abundance and presence/absence patterns. In the second data set, including traits reduced phylogenetic signal in residuals by 25% and 98% for abundance and presence/absence data, respectively. Our framework provides an explicit way to estimate how much phylogenetic community pattern remains in the residual variation after including measured functional traits. Knowing that functional traits account for most of the phylogenetic pattern should provide confidence that important traits for phylogenetic community structure have been identified. Conversely, knowing that there is unexplained residual phylogenetic information should spur the search for additional functional traits or other processes underlying community assembly
Shifts in Southern Wisconsin Forest Canopy and Understory Richness, Composition, and Heterogeneity
We resurveyed the under- and overstory species composition of 94 upland forest stands in southern Wisconsin in 2002–2004 to assess shifts in canopy and understory richness, composition, and heterogeneity relative to the original surveys in 1949–1950. The canopy has shifted from mostly oaks (Quercus spp.) toward more mesic and shade-tolerant trees (primarily Acer spp.). Oak-dominated early-successional stands and those on coarse, nutrient-poor soils changed the most in canopy composition. Understories at most sites (80%) lost native species, with mean species density declining 25% at the 1-m2 scale and 23.1% at the 20-m2 scale. Woody species have increased 15% relative to herbaceous species in the understory despite declining in absolute abundance. Initial canopy composition, particularly the abundance of red oaks (Quercus rubra and Q. velutina), predicted understory changes better than the changes observed in the overstory. Overall rates of native species loss were greater in later-successional stands, a pattern driven by differential immigration rather than differential extirpation. However, understory species initially found in early-successional habitats declined the most, particularly remnant savanna taxa with narrow or thick leaves. These losses have yet to be offset by compensating increases in native shade-adapted species. Exotic species have proliferated in prevalence (from 13 to 76 stands) and relative abundance (from 1.2% to 8.4%), but these increases appear unrelated to the declines in native species richness and heterogeneity observed. Although canopy succession has clearly influenced shifts in understory composition and diversity, the magnitude of native species declines and failure to recruit more shade-adapted species suggest that other factors now act to limit the richness, heterogeneity, and composition of these communities
Where have all the flowers gone? A call for federal leadership in deer management in the United States
Forests in the United States continue to lose biodiversity and many fail to regenerate due to high deer (family Cervidae) abundance. Declines in biodiversity and overall ecosystem health due to high deer populations increases prevalence of wildlife and human diseases associated with increasing tick abundances and decreases forest resilience and the ability to deliver benefits provided by healthy ecosystems. In the eastern and midwestern United States, white-tailed deer (Odocoileus virginianus) are the main stressor, while in the western U.S. elk (Cervus elaphus) and black-tailed and mule deer (Odocoileus hemionus) can become equally problematic. Federal and State Wildlife Agencies are responsible for environmental stewardship and management of deer, migratory and endangered species, yet they lack authority to address human health concerns or commercial interests (we acknowledge tribal authority to manage wildlife as an important contributor to conservation). Furthermore, State Wildlife Agencies have retained their traditional focus to manage wildlife for recreational hunters while neglecting their obligations to manage wildlife in the interest of all citizens rather than special interest groups. Fragmented institutional arrangements and widely scattered responsibilities for human health, environmental conservation and management, agriculture, and commerce among tribal, federal, and state agencies have allowed deer impacts to grow into nationwide conservation and human health crises. Given that local, regional, and state-level initiatives have failed to provide appropriate remedies, federal leadership is now essential to integrate concerns among disciplines, policy domains, regions, habitats, and biota. We recommend developing a National Strategy to build strong collaborative efforts and diverse and inclusive relationships across environmental, human health and economic interests. These should reach beyond state boundaries to comprehensively address interrelated deer, human health, forest, and conservation crises. A well-coordinated and collaborative approach has the potential to overcome traditional turf battles between tribal, state, and federal interests by recognizing joint responsibilities and obligations to manage wildlife as a public trust resource. This collective approach can protect species before they become endangered, avoiding further declines in environmental and human health
Origin and distribution of epipolythiodioxopiperazine (ETP) gene clusters in filamentous ascomycetes
<p>Abstract</p> <p>Background</p> <p>Genes responsible for biosynthesis of fungal secondary metabolites are usually tightly clustered in the genome and co-regulated with metabolite production. Epipolythiodioxopiperazines (ETPs) are a class of secondary metabolite toxins produced by disparate ascomycete fungi and implicated in several animal and plant diseases. Gene clusters responsible for their production have previously been defined in only two fungi. Fungal genome sequence data have been surveyed for the presence of putative ETP clusters and cluster data have been generated from several fungal taxa where genome sequences are not available. Phylogenetic analysis of cluster genes has been used to investigate the assembly and heredity of these gene clusters.</p> <p>Results</p> <p>Putative ETP gene clusters are present in 14 ascomycete taxa, but absent in numerous other ascomycetes examined. These clusters are discontinuously distributed in ascomycete lineages. Gene content is not absolutely fixed, however, common genes are identified and phylogenies of six of these are separately inferred. In each phylogeny almost all cluster genes form monophyletic clades with non-cluster fungal paralogues being the nearest outgroups. This relatedness of cluster genes suggests that a progenitor ETP gene cluster assembled within an ancestral taxon. Within each of the cluster clades, the cluster genes group together in consistent subclades, however, these relationships do not always reflect the phylogeny of ascomycetes. Micro-synteny of several of the genes within the clusters provides further support for these subclades.</p> <p>Conclusion</p> <p>ETP gene clusters appear to have a single origin and have been inherited relatively intact rather than assembling independently in the different ascomycete lineages. This progenitor cluster has given rise to a small number of distinct phylogenetic classes of clusters that are represented in a discontinuous pattern throughout ascomycetes. The disjunct heredity of these clusters is discussed with consideration to multiple instances of independent cluster loss and lateral transfer of gene clusters between lineages.</p
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