1
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Hopper GW, Miller EJ, Haag WR, Vaughn CC, Hornbach DJ, Jones JW, Atkinson CL. A test of the loose-equilibrium concept with long-lived organisms: Evaluating temporal change in freshwater mussel assemblages. J Anim Ecol 2024; 93:281-293. [PMID: 38243658 DOI: 10.1111/1365-2656.14046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 12/12/2023] [Indexed: 01/21/2024]
Abstract
The loose-equilibrium concept (LEC) predicts that ecological assemblages change transiently but return towards an earlier or average structure. The LEC framework can help determine whether assemblages vary within expected ranges or are permanently altered following environmental change. Long-lived, slow-growing animals typically respond slowly to environmental change, and their assemblage dynamics may respond over decades, which transcends most ecological studies. Unionid mussels are valuable for studying dynamics of long-lived animals because they can live >50 years and occur in dense, species-rich assemblages (mussel beds). Mussel beds can persist for decades, but disturbance can affect species differently, resulting in variable trajectories according to differences in species composition within and among rivers. We used long-term data sets (10-40 years) from seven rivers in the eastern United States to evaluate the magnitude, pace and directionality of mussel assemblage change within the context of the LEC. Site trajectories varied within and among streams and showed patterns consistent with either the LEC or directional change. In streams that conformed to the LEC, rank abundance of dominant species remained stable over time, but directional change in other streams was driven by changes in the rank abundance and composition of dominant species. Characteristics of mussel assemblage change varied widely, ranging from those conforming to the LEC to those showing strong directional change. Conservation approaches that attempt to maintain or create a desired assemblage condition should acknowledge this wide range of possible assemblage trajectories and that the environmental factors that influence those changes remain poorly understood.
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Affiliation(s)
- Garrett W Hopper
- School of Renewable Natural Resources, Louisiana State University and Agricultural Center, Baton Rouge, Louisiana, USA
| | - Edwin J Miller
- Kansas Department of Wildlife and Parks, Independence, Kansas, USA
| | - Wendell R Haag
- US Forest Service, Southern Research Station, Center for Bottomland Hardwoods Research, Frankfort, Kentucky, USA
| | - Caryn C Vaughn
- Oklahoma Biological Survey and Department of Biology, University of Oklahoma, Norman, Oklahoma, USA
| | - Daniel J Hornbach
- Department of Environmental Studies, Macalester College, St. Paul, Minnesota, USA
| | - Jess W Jones
- U.S. Fish and Wildlife Service, Department of Fish and Wildlife Conservation and Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Carla L Atkinson
- Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama, USA
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2
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Revell LJ. phytools 2.0: an updated R ecosystem for phylogenetic comparative methods (and other things). PeerJ 2024; 12:e16505. [PMID: 38192598 PMCID: PMC10773453 DOI: 10.7717/peerj.16505] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 10/31/2023] [Indexed: 01/10/2024] Open
Abstract
Phylogenetic comparative methods comprise the general endeavor of using an estimated phylogenetic tree (or set of trees) to make secondary inferences: about trait evolution, diversification dynamics, biogeography, community ecology, and a wide range of other phenomena or processes. Over the past ten years or so, the phytools R package has grown to become an important research tool for phylogenetic comparative analysis. phytools is a diverse contributed R library now consisting of hundreds of different functions covering a variety of methods and purposes in phylogenetic biology. As of the time of writing, phytools included functionality for fitting models of trait evolution, for reconstructing ancestral states, for studying diversification on trees, and for visualizing phylogenies, comparative data, and fitted models, as well numerous other tasks related to phylogenetic biology. Here, I describe some significant features of and recent updates to phytools, while also illustrating several popular workflows of the phytools computational software.
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Affiliation(s)
- Liam J. Revell
- Department of Biology, University of Massachusetts Boston, Boston, MA, USA
- Facultad de Ciencias, Universidad Católica de la Santísima Concepción, Concepción, Chile
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3
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Downs KN, Kelly PT, Ascanio A, Vanni MJ. Ontogenetic variation in the ecological stoichiometry of 10 fish species during early development. Ecology 2023; 104:e4176. [PMID: 37782823 DOI: 10.1002/ecy.4176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 07/14/2023] [Accepted: 07/28/2023] [Indexed: 10/04/2023]
Abstract
The chemical composition and stoichiometry of vertebrate bodies changes greatly during ontogeny as phosphorus-rich bones form, but we know little about the variation among species during early development. Such variation is important because element ratios in animal bodies influence which element limits growth and how animals contribute to nutrient cycling. We quantified ontogenetic variation from embryos through 2-3 months of age in 10 species of fish in six different families, ranging in adult size from 73 to 720 mm in length. We measured whole-body concentrations (percentage of dry mass) and ratios of carbon (C), nitrogen (N), and phosphorus (P) as fish developed. We also quantified whole-body concentrations of calcium (Ca), because Ca should reflect bone development, and RNA, which can be a major pool of body P. To account for interspecific differences in adult size, we also examined how trends changed with relative size, defined as body length divided by adult length. Ontogenetic changes in body composition and ratios were relatively similar among species and were more similar when expressed as a function of relative size compared to age. Body P increased rapidly in all species (likely because of bone development) from embryos until individuals were ~5%-8% of adult size. Body N also increased, while body C, C:N, C:P, and N:P all decreased over this period. Body Ca increased with development but was more variable among species. Body RNA was low in embryos, increased rapidly in young larvae, then decreased as fish reached 5%-8% of adult size. After fish were about 5%-8% of adult size, changes in body composition were relatively slight for all elements and ratios. These results reveal a consistency in the dynamics of body stoichiometry during early ontogeny, presumably because of similar constraints on the allocation of elements to bones and other body pools. Because most changes occur when individuals are <1 month old (<10% of adult size for that species), early ontogenetic variation in body stoichiometry may be especially important for growth limitation of individuals and ecosystem-level nutrient cycling.
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Affiliation(s)
- Kelsea N Downs
- Department of Biology, Miami University, Oxford, Ohio, USA
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4
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El-Sabaawi RW, Lemmen KD, Jeyasingh PD, Declerck SAJ. SEED: A framework for integrating ecological stoichiometry and eco-evolutionary dynamics. Ecol Lett 2023; 26 Suppl 1:S109-S126. [PMID: 37840025 DOI: 10.1111/ele.14285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 06/01/2023] [Accepted: 06/04/2023] [Indexed: 10/17/2023]
Abstract
Characterising the extent and sources of intraspecific variation and their ecological consequences is a central challenge in the study of eco-evolutionary dynamics. Ecological stoichiometry, which uses elemental variation of organisms and their environment to understand ecosystem patterns and processes, can be a powerful framework for characterising eco-evolutionary dynamics. However, the current emphasis on the relative content of elements in the body (i.e. organismal stoichiometry) has constrained its application. Intraspecific variation in the rates at which elements are acquired, assimilated, allocated or lost is often greater than the variation in organismal stoichiometry. There is much to gain from studying these traits together as components of an 'elemental phenotype'. Furthermore, each of these traits can have distinct ecological effects that are underappreciated in the current literature. We propose a conceptual framework that explores how microevolutionary change in the elemental phenotype occurs, how its components interact with each other and with other traits, and how its changes can affect a wide range of ecological processes. We demonstrate how the framework can be used to generate novel hypotheses and outline pathways for future research that enhance our ability to explain, analyse and predict eco-evolutionary dynamics.
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Affiliation(s)
- Rana W El-Sabaawi
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Kimberley D Lemmen
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands
| | - Punidan D Jeyasingh
- Department of Integrative Biology, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Steven A J Declerck
- Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands
- Department of Biology, Laboratory of Aquatic Ecology, Evolution and Conservation, KULeuven, Leuven, Belgium
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5
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Holdridge EM, Vasseur DA. Intraspecific variation promotes coexistence under competition for essential resources. THEOR ECOL-NETH 2022. [DOI: 10.1007/s12080-022-00539-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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6
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Zhang B, Chen H, Deng M, Li J, González AL, Wang S. High dimensionality of stoichiometric niches in soil fauna. Ecology 2022; 103:e3741. [PMID: 35524916 DOI: 10.1002/ecy.3741] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 02/25/2022] [Accepted: 03/18/2022] [Indexed: 11/09/2022]
Abstract
The ecological niche is a fundamental concept to understand species coexistence in natural communities. The recently developed framework of the multidimensional stoichiometric niche (MSN) characterizes species niches using chemical elements in living organisms. Despite the fact that living organisms are composed by multiple elements, stoichiometric studies have so far mostly focused on carbon (C), nitrogen (N), and phosphorus (P), and therefore a quantitative analysis of the dimensionality of the MSN in living organisms is still lacking, particularly for animals. Here we quantified ten elements composing the biomass of nine soil animal taxa (958 individuals) from three trophic groups. We found that all ten elements exhibited large variation among taxa, which was partially explained by their phylogeny. Overlaps of MSNs among the nine soil animal taxa were relatively smaller based on ten elements, compared with those based on only C, N, and P. Discriminant analysis using all ten elements successfully differentiated among the nine taxa (accuracy: 90%), whereas that using only C, N, and P resulted in a lower accuracy (60%). Our findings provide new evidence for MSN differentiation in soil fauna and demonstrate the high dimensionality of organismal stoichiometric niches beyond C, N, and P.
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Affiliation(s)
- Bing Zhang
- Key Laboratory for Earth Surface Processes of the Ministry of Education, Institute of Ecology, College of Urban and Environmental Science, Peking University, Beijing, China
| | - Haozhen Chen
- Key Laboratory for Earth Surface Processes of the Ministry of Education, Institute of Ecology, College of Urban and Environmental Science, Peking University, Beijing, China
| | - Mingqin Deng
- Key Laboratory for Earth Surface Processes of the Ministry of Education, Institute of Ecology, College of Urban and Environmental Science, Peking University, Beijing, China
| | - Jingyi Li
- Key Laboratory for Earth Surface Processes of the Ministry of Education, Institute of Ecology, College of Urban and Environmental Science, Peking University, Beijing, China
| | - Angélica L González
- Department of Biology & Center for Computational and Integrative Biology, Rutgers University, Camden, NJ, USA
| | - Shaopeng Wang
- Key Laboratory for Earth Surface Processes of the Ministry of Education, Institute of Ecology, College of Urban and Environmental Science, Peking University, Beijing, China
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7
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Hopper GW, Buchanan JK, Sánchez González I, Kubala ME, Bucholz JR, Lodato MB, Lozier JD, Atkinson CL. Little clams with big potential: nutrient release by invasive Corbicula fluminea can exceed co-occurring freshwater mussel (Unionidae) assemblages. Biol Invasions 2022. [DOI: 10.1007/s10530-022-02792-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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8
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Atkinson CL, Forshay KJ. Community patch dynamics governs direct and indirect nutrient recycling by aggregated animals across spatial scales. Funct Ecol 2022. [DOI: 10.1111/1365-2435.13982] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Carla L. Atkinson
- Department of Biological Sciences University of Alabama Tuscaloosa AL USA
| | - Kenneth J. Forshay
- Robert S. Kerr Environmental Research Center Office of Research and Development United States Environmental Protection Agency Ada OK USA
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9
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Hewitt TL, Haponski AE, Foighil DÓ. Evolution of diverse host infection mechanisms delineates an adaptive radiation of lampsiline freshwater mussels centered on their larval ecology. PeerJ 2021; 9:e12287. [PMID: 34820162 PMCID: PMC8603817 DOI: 10.7717/peerj.12287] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 09/21/2021] [Indexed: 11/25/2022] Open
Abstract
North American watersheds contain a high diversity of freshwater mussels (Unionoida). During the long-lived, benthic phase of their life cycle, up to 40 species can co-occur in a single riffle and there is typically little evidence for major differences in their feeding ecology or microhabitat partitioning. In contrast, their brief parasitic larval phase involves the infection of a wide diversity of fish hosts and female mussels have evolved a spectrum of adaptations for infecting host fish with their offspring. Many species use a passive broadcast strategy: placing high numbers of larvae in the water column and relying on chance encounters with potential hosts. Many other species, including most members of the Lampsilini, have a proactive strategy that entails the use of prey-mimetic lures to change the behavior of the hosts, i.e., eliciting a feeding response through which they become infected. Two main lure types are collectively produced: mantle tissue lures (on the female’s body) and brood lures, containing infective larvae, that are released into the external environment. In this study, we used a phylogenomic approach (ddRAD-seq) to place the diversity of infection strategies used by 54 North American lampsiline mussels into an evolutionary context. Ancestral state reconstruction recovered evidence for the early evolution of mantle lures in this clade, with brood lures and broadcast infection strategies both being independently derived twice. The most common infection strategy, occurring in our largest ingroup clade, is a mixed one in which mimetic mantle lures are apparently the predominant infection mechanism, but gravid females also release simple, non-mimetic brood lures at the end of the season. This mixed infection strategy clade shows some evidence of an increase in diversification rate and most members use centrarchids (Micropterus & Lepomis spp.) as their predominant fish hosts. Broad linkage between infection strategies and predominant fish host genera is also seen in other lampsiline clades: worm-like mantle lures of Toxolasma spp. with sunfish (Lepomis spp.); insect larvae-like brood lures (Ptychobranchus spp.), or mantle lures (Medionidus spp., Obovaria spp.), or mantle lures combined with host capture (Epioblasma spp.) with a spectrum of darter (Etheostoma & Percina spp.) and sculpin (Cottus spp.) hosts, and tethered brood lures (Hamiota spp.) with bass (Micropterus spp.). Our phylogenetic results confirm that discrete lampsiline mussel clades exhibit considerable specialization in the primary fish host clades their larvae parasitize, and in the host infection strategies they employ to do so. They are also consistent with the hypothesis that larval resource partitioning of fish hosts is an important factor in maintaining species diversity in mussel assemblages. We conclude that, taking their larval ecology and host-infection mechanisms into account, lampsiline mussels may be legitimately viewed as an adaptive radiation.
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Affiliation(s)
- Trevor L Hewitt
- Department of Ecology and Evolutionary Biology and Museum of Zoology, University of Michigan - Ann Arbor, Ann Arbor, MI, United States of America
| | - Amanda E Haponski
- Department of Ecology and Evolutionary Biology and Museum of Zoology, University of Michigan - Ann Arbor, Ann Arbor, MI, United States of America
| | - Diarmaid Ó Foighil
- Department of Ecology and Evolutionary Biology and Museum of Zoology, University of Michigan - Ann Arbor, Ann Arbor, MI, United States of America
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10
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Allgeier JE, Weeks BC, Munsterman KS, Wale N, Wenger SJ, Parravicini V, Schiettekatte NMD, Villéger S, Burkepile DE. Phylogenetic conservatism drives nutrient dynamics of coral reef fishes. Nat Commun 2021; 12:5432. [PMID: 34521825 PMCID: PMC8440548 DOI: 10.1038/s41467-021-25528-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 08/11/2021] [Indexed: 11/09/2022] Open
Abstract
The relative importance of evolutionary history and ecology for traits that drive ecosystem processes is poorly understood. Consumers are essential drivers of nutrient cycling on coral reefs, and thus ecosystem productivity. We use nine consumer "chemical traits" associated with nutrient cycling, collected from 1,572 individual coral reef fishes (178 species spanning 41 families) in two biogeographic regions, the Caribbean and Polynesia, to quantify the relative importance of phylogenetic history and ecological context as drivers of chemical trait variation on coral reefs. We find: (1) phylogenetic relatedness is the best predictor of all chemical traits, substantially outweighing the importance of ecological factors thought to be key drivers of these traits, (2) phylogenetic conservatism in chemical traits is greater in the Caribbean than Polynesia, where our data suggests that ecological forces have a greater influence on chemical trait variation, and (3) differences in chemical traits between regions can be explained by differences in nutrient limitation associated with the geologic context of our study locations. Our study provides multiple lines of evidence that phylogeny is a critical determinant of contemporary nutrient dynamics on coral reefs. More broadly our findings highlight the utility of evolutionary history to improve prediction in ecosystem ecology.
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Affiliation(s)
- Jacob E Allgeier
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA.
| | - Brian C Weeks
- School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA
| | - Katrina S Munsterman
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Nina Wale
- Department of Microbiology and Molecular Genetics and Department of Integrative Biology & Ecology Evolution and Behavior Program, Michigan State University, Lansing, MI, USA
| | - Seth J Wenger
- Odum School of Ecology, University of Georgia, Athens, GA, USA
| | - Valeriano Parravicini
- PSL Université Paris: EPHE-UPVD-CNRS, USR 3278 CRIOBE, Université de Perpignan, Perpignan, France.,Laboratoire d'Excellence "CORAIL", Perpignan, France
| | - Nina M D Schiettekatte
- PSL Université Paris: EPHE-UPVD-CNRS, USR 3278 CRIOBE, Université de Perpignan, Perpignan, France.,Laboratoire d'Excellence "CORAIL", Perpignan, France
| | - Sébastien Villéger
- MARBEC, Université de Montpellier, CNRS, IFREMER, IRD, Montpellier, France
| | - Deron E Burkepile
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA.,Marine Science Institute, University of California, Santa Barbara, CA, USA
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11
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Meng W, Dai Q, Ren Q, Tu N, Leng T. Ecological stoichiometric characteristics of soil-moss C, N, and P in restoration stages of karst rocky desertification. PLoS One 2021; 16:e0252838. [PMID: 34191821 PMCID: PMC8244914 DOI: 10.1371/journal.pone.0252838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/24/2021] [Indexed: 11/18/2022] Open
Abstract
Rocky desertification is the most serious ecological disaster in karst areas. Comprehensive control of rocky desertification plays an important role in promoting the economic development of karst areas. Studying the stoichiometric characteristics of mosses and soil can provide a powerful reference for the ecological restoration and evaluation of ecosystems experiencing rocky desertification. Soil and mosses were collected from sites representing different stages of ecological restoration (bare rock, grassland, shrubland, and secondary forest), and the contents of carbon (C), nitrogen (N), and phosphorus (P) were detected for ecological stoichiometric analysis. The results indicate that in different restoration stages following karst rocky desertification, the contents of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) and the stoichiometric ratios in the shrub habitat are higher than those in the bare rock, grassland, and secondary forest habitats. However, the TP and available P contents were low at all stages (0.06 g/kg and 0.62 mg/kg, respectively). The N and P contents and stoichiometric ratios in the mosses showed no significant differences among the succession stages. The C contents in the mosses had a significant positive correlation with SOC and TN and TP content, and the P content had a significant positive correlation with the soil available P. However, there was a significant negative correlation between the C: N and C:P ratios of the bryophytes and soil C: N. In summary, during the process of natural restoration of karst rocky desertification areas, SOC and soil TN contents accumulate with each succession stage. Soil nutrients are higher in shrub habitats than in other succession stages. Mosses have a strong effect on improving soil nutrients in rocky desertification areas.
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Affiliation(s)
- Wenping Meng
- College of Forestry, Guizhou Universtry, Guiyang, China
- Guizhou Botanical Garden, Guiyang, China
- Puding Karst Ecosystem Research Station, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
| | - Quanhou Dai
- College of Forestry, Guizhou Universtry, Guiyang, China
- Institute for Forest Resources & Environment of Guizhou, Guiyang, China
| | - Qingqing Ren
- Affiliated Hospital of Zunyi Medical University, Zunyi, China
| | - Na Tu
- College of Forestry, Guizhou Universtry, Guiyang, China
- Institute for Forest Resources & Environment of Guizhou, Guiyang, China
| | - Tingjiao Leng
- College of Forestry, Guizhou Universtry, Guiyang, China
- Institute for Forest Resources & Environment of Guizhou, Guiyang, China
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12
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Hopper GW, Chen S, Sánchez González I, Bucholz JR, Lu Y, Atkinson CL. Aggregated filter‐feeders govern the flux and stoichiometry of locally available energy and nutrients in rivers. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13778] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Garrett W. Hopper
- Department of Biological Sciences University of Alabama Tuscaloosa AL USA
| | - Shuo Chen
- Department of Geological Sciences University of Alabama Tuscaloosa AL USA
| | | | - Jamie R. Bucholz
- Department of Biological Sciences University of Alabama Tuscaloosa AL USA
| | - YueHan Lu
- Department of Geological Sciences University of Alabama Tuscaloosa AL USA
| | - Carla L. Atkinson
- Department of Biological Sciences University of Alabama Tuscaloosa AL USA
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13
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Filter-feeders have differential bottom-up impacts on green and brown food webs. Oecologia 2021; 195:187-198. [PMID: 33389154 DOI: 10.1007/s00442-020-04821-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 12/04/2020] [Indexed: 10/22/2022]
Abstract
Nutrient recycling by consumers can strongly impact nutrient availability for autotrophic and heterotrophic microbes, thus impacting functions such as primary production and decomposition. Filter-feeding freshwater mussels form dense, multispecies assemblages in aquatic ecosystems and have been shown to play a critical role in nutrient cycling. Mussel excretion can enhance benthic primary production and influence algal species composition. However, the role of mussels in brown or detritus-based food webs and species-specific differences has received considerably less attention. Here, using mesocosm experiments, we assessed how three species of freshwater mussels that occupy three different phylogenetic tribes influenced benthic algal accrual, ecosystem metabolism, cotton strip decomposition, leaf litter (Acer saccharum) decomposition, and litter-associated fungal biomass measured as ergosterol. Additionally, we measured mussel excretion and biodeposition rates and assessed the stoichiometry (C:N, C:P, and N:P) of the benthic algae, cotton strips, and leaf litter. In comparison to controls without mussels, generally, mussel treatments had higher benthic algal biomass composed of more diatoms, higher gross primary productivity and net ecosystem production rates, and higher cotton strip tensile strength loss, but there was not a difference in ecosystem respiration rates, leaf litter decomposition rates, or fungal biomass. Benthic algae had lower C:N and higher N:P in mussel treatment tanks and cotton strip C:N was lower in mesocosms with mussels. Our results suggest that nutrient regeneration by mussels most strongly regulates green food webs, with some impacts to brown food webs, suggesting that consumers have interactive effects on microbial functioning in freshwaters.
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