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Pasciu V, Nieddu M, Sotgiu FD, Baralla E, Berlinguer F. Fecal thyroid hormone metabolites in wild ungulates: a mini-review. Front Vet Sci 2024; 11:1407479. [PMID: 38840625 PMCID: PMC11150844 DOI: 10.3389/fvets.2024.1407479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Accepted: 05/09/2024] [Indexed: 06/07/2024] Open
Abstract
This review aims to analyse the fluctuations of fecal thyroid hormone metabolites (FTMs) related to environmental and individual variables in different species of wild ungulates and provide a collection of assay methods. The great advantage of fecal sampling is being completely non-invasive. A systemic search was conducted from 2019 to 2024, using data sources PubMed, Scopus, Web of Science, and the World Wide Web, and ten studies were found on this topic. Three studies used the radioimmunoassay method for FTMs analysis, while the others used a less expensive enzyme-linked immunosorbent assay. Most of these papers validated the method for the species-specific matrix. Related to the studied variables, some authors analysed FTM fluctuations only concerning individual variables, and others in response to both. Temperature and fecal cortisol metabolites (FCMs) were the most studied environmental and individual variables, respectively. Since FTMs are an integrative measure of plasma thyroid hormones, the information obtained from a non-invasive-assay method regarding wild ungulate physiology is becoming of great interest to the scientific community.
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Affiliation(s)
- Valeria Pasciu
- Department of Veterinary Medicine, University of Sassari, Sassari, Italy
| | - Maria Nieddu
- Department of Medicine, Surgery and Pharmacy, University of Sassari, Sassari, Italy
| | | | - Elena Baralla
- Department of Veterinary Medicine, University of Sassari, Sassari, Italy
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2
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Kamaru DN, Palmer TM, Riginos C, Ford AT, Belnap J, Chira RM, Githaiga JM, Gituku BC, Hays BR, Kavwele CM, Kibungei AK, Lamb CT, Maiyo NJ, Milligan PD, Mutisya S, Ng'weno CC, Ogutu M, Pietrek AG, Wildt BT, Goheen JR. Disruption of an ant-plant mutualism shapes interactions between lions and their primary prey. Science 2024; 383:433-438. [PMID: 38271503 DOI: 10.1126/science.adg1464] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 12/01/2023] [Indexed: 01/27/2024]
Abstract
Mutualisms often define ecosystems, but they are susceptible to human activities. Combining experiments, animal tracking, and mortality investigations, we show that the invasive big-headed ant (Pheidole megacephala) makes lions (Panthera leo) less effective at killing their primary prey, plains zebra (Equus quagga). Big-headed ants disrupted the mutualism between native ants (Crematogaster spp.) and the dominant whistling-thorn tree (Vachellia drepanolobium), rendering trees vulnerable to elephant (Loxodonta africana) browsing and resulting in landscapes with higher visibility. Although zebra kills were significantly less likely to occur in higher-visibility, invaded areas, lion numbers did not decline since the onset of the invasion, likely because of prey-switching to African buffalo (Syncerus caffer). We show that by controlling biophysical structure across landscapes, a tiny invader reconfigured predator-prey dynamics among iconic species.
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Affiliation(s)
- Douglas N Kamaru
- Department of Zoology & Physiology and Program in Ecology & Evolution, University of Wyoming, Laramie, WY, USA
- Ol Pejeta Conservancy, Private Bag 10400, Nanyuki, Kenya
| | - Todd M Palmer
- Department of Biology, University of Florida, Gainesville, FL, USA
| | - Corinna Riginos
- Department of Zoology & Physiology and Program in Ecology & Evolution, University of Wyoming, Laramie, WY, USA
- The Nature Conservancy, Lander, WY, USA
| | - Adam T Ford
- Department of Biology, University of British Columbia, Kelowna, BC, Canada
| | - Jayne Belnap
- Southwest Biological Science Center, US Geological Survey, Moab, UT, USA
| | - Robert M Chira
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - John M Githaiga
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | | | - Brandon R Hays
- Nicholas School of the Environment, Duke University, Durham, NC, USA
| | - Cyrus M Kavwele
- School of Mathematics & Statistics and School of Biodiversity, University of Glasgow, Glasgow, Scotland
- School of Natural Resources, Karatina University, Nyeri, Kenya
| | | | - Clayton T Lamb
- Department of Biology, University of British Columbia, Kelowna, BC, Canada
| | - Nelly J Maiyo
- Ol Pejeta Conservancy, Private Bag 10400, Nanyuki, Kenya
| | - Patrick D Milligan
- Ol Pejeta Conservancy, Private Bag 10400, Nanyuki, Kenya
- Department of Biology, University of Nevada, Reno, NV, USA
| | - Samuel Mutisya
- Ol Pejeta Conservancy, Private Bag 10400, Nanyuki, Kenya
| | | | - Michael Ogutu
- Ol Pejeta Conservancy, Private Bag 10400, Nanyuki, Kenya
| | - Alejandro G Pietrek
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Salta, Argentina
| | - Brendon T Wildt
- Department of Zoology & Physiology and Program in Ecology & Evolution, University of Wyoming, Laramie, WY, USA
| | - Jacob R Goheen
- Department of Zoology & Physiology and Program in Ecology & Evolution, University of Wyoming, Laramie, WY, USA
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3
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Hays BR, Riginos C, Palmer TM, Doak DF, Gituku BC, Maiyo NJ, Mutisya S, Musila S, Goheen JR. Demographic consequences of mutualism disruption: Browsing and big-headed ant invasion drive acacia population declines. Ecology 2022; 103:e3655. [PMID: 35132627 DOI: 10.1002/ecy.3655] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 10/14/2021] [Accepted: 10/26/2021] [Indexed: 11/09/2022]
Abstract
Across the globe, biological invasions have disrupted mutualisms, producing reverberating consequences for ecosystems. Although invasive species frequently trigger mutualism disruptions, few studies have quantified the demographic mechanisms by which mutualism breakdown may generate population effects. In a Kenyan savanna, the invasive big-headed ant (Pheidole megacephala) has disrupted a foundational mutualism between the monodominant whistling-thorn tree (Acacia drepanolobium) and native ants (Crematogaster spp.) that deter browsing by large mammalian herbivores. We conducted experiments to quantify the demographic consequences of this mutualism disruption in the presence and absence of large mammalian herbivores. Invasion by P. megacephala exacerbated population declines of A. drepanolobium, primarily through decreased survival and reproduction of adult trees. However, these fitness reductions were small compared to those resulting from the presence of large mammalian herbivores, which negatively impacted growth and survival. Contrary to expectation, the expulsion of metabolically costly Crematogaster mutualists by P. megacephala did not result in higher population growth rates for trees protected from large mammalian herbivores. Our results suggest that invasive P. megacephala may impose a direct metabolic cost to trees exceeding that of native mutualists while providing no protection from browsing by large mammalian herbivores. Across landscapes, we expect that invasion by P. megacephala will reduce A. drepanolobium populations, but that the magnitude and demographic pathways of this effect will hinge on the presence and abundance of browsers.
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Affiliation(s)
- Brandon R Hays
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
| | - Corinna Riginos
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA.,The Nature Conservancy, 258 Main Street, Lander, Wyoming, USA
| | - Todd M Palmer
- Department of Biology, University of Florida, Florida, USA
| | - Daniel F Doak
- Environmental Studies Program, University of Colorado, Boulder, Colorado, USA
| | - Benard C Gituku
- Department of Land Resource Management & Agricultural Technology, University of Nairobi, Nairobi, Kenya.,Conservation Department, Ol Pejeta Conservancy, Nanyuki, Kenya
| | - Nelly J Maiyo
- Conservation Department, Ol Pejeta Conservancy, Nanyuki, Kenya
| | - Samuel Mutisya
- Conservation Department, Ol Pejeta Conservancy, Nanyuki, Kenya
| | - Simon Musila
- Mammalogy Section, National Museums of Kenya, Nairobi, Kenya
| | - Jacob R Goheen
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA
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4
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Zhong Z, Li X, Smit C, Li T, Wang L, Aschero V, Vázquez D, Ritchie M, Cushman JH, Wang D. Large herbivores facilitate a dominant grassland forb via multiple indirect effects. Ecology 2022; 103:e3635. [DOI: 10.1002/ecy.3635] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 10/21/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Zhiwei Zhong
- Institute of Grassland Science, Key Laboratory of Vegetation Ecology, Ministry of Education/Jilin Songnen Grassland Ecosystem National Observation and Research Station Northeast Normal University Changchun China
| | - Xiaofei Li
- College of Resources and Environmental Sciences/Key Laboratory of Sustainable Utilization of Soil Resources in the Commodity Grain Bases in Jilin Province, Jilin Agricultural University Changchun Jilin China
| | - Christian Smit
- Groningen Institute for Evolutionary Life Sciences, Conservation Ecology Group University of Groningen CC Groningen the Netherlands
| | - Tianyun Li
- Institute of Grassland Science, Key Laboratory of Vegetation Ecology, Ministry of Education/Jilin Songnen Grassland Ecosystem National Observation and Research Station Northeast Normal University Changchun China
| | - Ling Wang
- Institute of Grassland Science, Key Laboratory of Vegetation Ecology, Ministry of Education/Jilin Songnen Grassland Ecosystem National Observation and Research Station Northeast Normal University Changchun China
| | - Valeria Aschero
- Argentine Institute for Nivology, Glaciology and Environmental Sciences, CONICET & National University of Cuyo, Av. Ruiz Leal s/n Mendoza Argentina
- Faculty of Exact and Natural Sciences National University of Cuyo, Padre Jorge Contreras 1300 Mendoza Argentina
| | - Diego Vázquez
- Faculty of Exact and Natural Sciences National University of Cuyo, Padre Jorge Contreras 1300 Mendoza Argentina
- Argentine Institute for Dryland Research, CONICET & National University of Cuyo, Av. Ruiz Leal s/n Mendoza Argentina
| | - Mark Ritchie
- Department of Biology Syracuse University Syracuse New York USA
| | - J. Hall Cushman
- Department of Natural Resources & Environmental Science University of Nevada Nevada USA
| | - Deli Wang
- Institute of Grassland Science, Key Laboratory of Vegetation Ecology, Ministry of Education/Jilin Songnen Grassland Ecosystem National Observation and Research Station Northeast Normal University Changchun China
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5
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LaMalfa EM, Riginos C, Veblen KE. Browsing wildlife and heavy grazing indirectly facilitate sapling recruitment in an East African savanna. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2021; 31:e02399. [PMID: 34212437 DOI: 10.1002/eap.2399] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 10/07/2020] [Accepted: 03/03/2021] [Indexed: 06/13/2023]
Abstract
Management of tree cover, either to curb bush encroachment or to mitigate losses of woody cover to over-browsing, is a major concern in savanna ecosystems. Once established, trees are often "trapped" as saplings, since interactions among disturbance, plant competition, and precipitation delay sapling recruitment into adult size classes. Saplings can be directly suppressed by wildlife browsing and competition from adjacent plants, and indirectly facilitated by grazers, such as cattle, which feed on neighboring grasses. Yet few experimental studies have simultaneously quantified the effects of cattle and wildlife on sapling growth, particularly over long time scales. We used a series of replicated 4-ha herbivore-manipulation plots to investigate the net effects of wildlife and moderate cattle grazing on Acacia drepanolobium sapling growth over 10 years that encompassed extended wet and dry periods. We also simulated more intense cattle grazing using grass removal treatments (0.5-m radius around saplings), and we quantified the role of intraspecific tree competition using neighborhood tree surveys (trees within a 3-m radius). Wildlife, which included elephants, had a positive effect on sapling growth. Wildlife also reduced neighbor tree density during the 10-yr study, which likely caused the positive effect of wildlife on saplings. Although moderate cattle grazing did not affect sapling growth, grass removal treatments simulating heavy grazing increased sapling growth. Both grass removal and neighbor tree effects on saplings were strongest during above-average rainfall years following drought. This highlights that livestock-driven reductions in grass cover and catastrophic wildlife damage to trees during droughts present a need, or an opportunity, for targeted management of sapling growth and woody plant cover during ensuing wet periods.
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Affiliation(s)
- Eric M LaMalfa
- Department of Wildland Resources & Ecology Center, Utah State University, Logan, Utah, 84321, USA
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
| | - Corinna Riginos
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- The Nature Conservancy, 258 Main Street, Suite 200, Lander, Wyoming, 82520, USA
| | - Kari E Veblen
- Department of Wildland Resources & Ecology Center, Utah State University, Logan, Utah, 84321, USA
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
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6
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Young TP, Kimuyu DM, Odadi WO, Wells HBM, Wolf AA. Naïve plant communities and individuals may initially suffer in the face of reintroduced megafauna: An experimental exploration of rewilding from an African savanna rangeland. PLoS One 2021; 16:e0248855. [PMID: 33822786 PMCID: PMC8023473 DOI: 10.1371/journal.pone.0248855] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/06/2021] [Indexed: 12/04/2022] Open
Abstract
Excluding large native mammals is an inverse test of rewilding. A 25-year exclosure experiment in an African savanna rangeland offers insight into the potentials and pitfalls of the rewilding endeavor as they relate to the native plant community. A broad theme that has emerged from this research is that entire plant communities, as well as individual plants, adjust to the absence of herbivores in ways that can ill-prepare them for the return of these herbivores. Three lines of evidence suggest that these "naïve" individuals, populations, and communities are likely to initially suffer from herbivore rewilding. First, plots protected from wild herbivores for the past 25 years have developed rich diversity of woody plants that are absent from unfenced plots, and presumably would disappear upon rewilding. Second, individuals of the dominant tree in this system, Acacia drepanolobium, greatly reduce their defences in the absence of browsers, and the sudden arrival of these herbivores (in this case, through a temporary fence break), resulted in far greater elephant damage than for their conspecifics in adjacent plots that had been continually exposed to herbivory. Third, the removal of herbivores favoured the most palatable grass species, and a large number of rarer species, which presumably would be at risk from herbivore re-introduction. In summary, the native communities that we observe in defaunated landscapes may be very different from their pre-defaunation states, and we are likely to see some large changes to these plant communities upon rewilding with large herbivores, including potential reductions in plant diversity. Lastly, our experimental manipulation of cattle represents an additional test of the role of livestock in rewilding. Cattle are in many ways ecologically dissimilar to wildlife (in particular their greater densities), but in other ways they may serve as ecological surrogates for wildlife, which could buffer ecosystems from some of the ecological costs of rewilding. More fundamentally, African savannah ecosystems represent a challenge to traditional Western definitions of "wilderness" as ecosystems free of human impacts. We support the suggestion that as we "rewild" our biodiversity landscapes, we redefine "wildness" in the 21st Century to be inclusive of (low impact, and sometimes traditional) human practices that are compatible with the sustainability of native (and re-introduced) biodiversity.
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Affiliation(s)
- Truman P. Young
- Department of Plant Sciences and Ecology Graduate Group, University of California, Davis, Davis, CA, United States of America
- Mpala Research Centre, Nanyuki, Kenya
| | - Duncan M. Kimuyu
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Karatina University, Karatina, Kenya
| | - Wilfred O. Odadi
- Mpala Research Centre, Nanyuki, Kenya
- Department of Natural Resources, Egerton University, Egerton, Kenya
| | - Harry B. M. Wells
- Sustainability Research Institute, School of Earth and Environment, University of Leeds, Leeds, United Kingdom
- Lolldaiga Hills Research Programme, Nanyuki, Kenya
| | - Amelia A. Wolf
- Department of Integrative Biology, University of Texas, Austin, TX, United States of America
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7
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Werner CM, Kimuyu D, Veblen KE, Sensenig RL, LaMalfa E, Young TP. Synergistic effects of long-term herbivory and previous fire on fine-scale heterogeneity of prescribed grassland burns. Ecology 2021; 102:e03270. [PMID: 33340104 DOI: 10.1002/ecy.3270] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/17/2020] [Accepted: 10/26/2020] [Indexed: 11/11/2022]
Abstract
Grassland and savanna ecosystems, important for both livelihoods and biodiversity conservation, are strongly affected by ecosystem drivers such as herbivory, fire, and drought. Interactions among fire, herbivores and vegetation produce complex feedbacks in these ecosystems, but these have rarely been studied in the context of fuel continuity and resultant fire heterogeneity. We carried out 36 controlled burns within replicated experimental plots that had allowed differential access by wild and domestic large herbivores since 1995 in a savanna ecosystem in Kenya. Half of these were reburns of plots burned 5 yr previously. We show here that the fine-scale spatial heterogeneity of fire was greater in plots (1) previously burned, (2) accessible to large herbivores, and especially (3) these two in combination. An additional embedded experiment demonstrated that even small experimental burn-free patches can have strong positive effects on tree saplings, which experienced less damage during controlled burns and quicker postfire recovery. This work highlights the importance of simultaneously examining the interactions between fire and herbivory on fuel heterogeneity, which can have important impacts on the growth of woody saplings in savanna grasslands.
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Affiliation(s)
- Chhaya M Werner
- Department of Plant Sciences and Graduate Group in Population Biology, University of California, Davis, California, 95616, USA.,Department of Physiological Diversity, Helmholtz Center for Environmental Research (UFZ), Leipzig, D-04318, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, D-04103, Germany.,Department of Ecology, University of Oulu, Oulu, FI-90014, Finland
| | - Duncan Kimuyu
- Mpala Research Centre, Nanyuki, Kenya.,Department of Natural Resources, Karatina University, Karatina, 10101, Kenya
| | - Kari E Veblen
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Ryan L Sensenig
- Mpala Research Centre, Nanyuki, Kenya.,Department of Biological Sciences, Goshen College, Goshen, Indiana, 46526, USA
| | - Eric LaMalfa
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA
| | - Truman P Young
- Department of Plant Sciences and Graduate Group in Population Biology, University of California, Davis, California, 95616, USA.,Mpala Research Centre, Nanyuki, Kenya
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8
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Kimuyu DM, Kenfack D, Musili PM, Ang’ila RO. Fine‐scale habitat heterogeneity influences browsing damage by elephant and giraffe. Biotropica 2020. [DOI: 10.1111/btp.12848] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Duncan M. Kimuyu
- Department of Natural Resources Karatina University Karatina Kenya
- Mpala Research Center and Wildlife Foundation Nanyuki Kenya
| | - David Kenfack
- ForestGEO Smithsonian Tropical Research Institute Washington DC USA
| | - Paul M. Musili
- East African Herbarium Botany Department National Museums of Kenya Nairobi Kenya
| | - Robert O. Ang’ila
- Mpala Research Center and Wildlife Foundation Nanyuki Kenya
- Department of Environmental Studies Karatina University Kenya
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9
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Cushman JH, Saunders LE, Refsland TK. Long-term and interactive effects of different mammalian consumers on growth, survival, and recruitment of dominant tree species. Ecol Evol 2020; 10:8801-8814. [PMID: 32884658 PMCID: PMC7452786 DOI: 10.1002/ece3.6578] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 06/15/2020] [Accepted: 06/18/2020] [Indexed: 11/19/2022] Open
Abstract
Throughout the world, numerous tree species are reported to be in decline, either due to increased mortality of established trees or reduced recruitment. The situation appears especially acute for oaks, which are dominant features of many landscapes in the northern hemisphere. Although numerous factors have been hypothesized to explain reductions in tree performance, vertebrate herbivores and granivores may serve as important drivers of these changes. Here, using data from 8- and 14-year-old exclosure experiments, we evaluated the individual and interactive effects of large and small mammalian herbivores on the performance of three widespread oak species in California-coast live oak (Quercus agrifolia), California black oak (Q. kelloggii), and Oregon white oak (Q. garryana). Although impacts varied somewhat by species and experiment, herbivory by black-tailed deer (Odocoileus hemionus columbianus) reduced the height and survival of juvenile coast live oaks and altered their architecture, as well as reduced the abundance of black oak seedlings, the richness of woody species and the cover of nonoak woody species. Small mammals (Microtus californicus and Peromyscus maniculatus) had even more widespread effects, reducing the abundance of black oak seedlings and the height and cover of all three oak species. We also detected numerous interactions between small mammals and deer, with one herbivore having positive or negative effects on oak abundance and cover when the other herbivore was either present or absent. For example, deer often had negative effects on seedling abundance only when, or even more so when, small mammals were present. In summary, mammalian consumers play crucial roles in limiting oak recruitment by reducing seedling abundance, maintaining trees in stunted states, and preventing them from reaching sapling stages and becoming reproductive. Interactions between large and small mammals can also alter the intensity and direction of their effects on trees.
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Affiliation(s)
- J. Hall Cushman
- Department of Natural Resources & Environmental ScienceUniversity of NevadaRenoNVUSA
| | | | - Tyler K. Refsland
- Department of Natural Resources & Environmental ScienceUniversity of NevadaRenoNVUSA
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10
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Forbes ES, Cushman JH, Burkepile DE, Young TP, Klope M, Young HS. Synthesizing the effects of large, wild herbivore exclusion on ecosystem function. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13376] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elizabeth S. Forbes
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - J. Hall Cushman
- Department of Natural Resources and Environmental Science University of Nevada – Reno Reno Nevada
| | - Deron E. Burkepile
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - Truman P. Young
- Department of Plant Sciences University of California, Davis Davis California
| | - Maggie Klope
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
| | - Hillary S. Young
- Department of Ecology, Evolution, and Marine Biology University of California, Santa Barbara Santa Barbara California
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11
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Lloyd KJ, Vetter S. Generalist trophic ecology in a changing habitat: The case of the four‐striped mouse in a woody‐encroached savannah. Afr J Ecol 2019. [DOI: 10.1111/aje.12613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Kyle J. Lloyd
- Department of Botany Rhodes University Grahamstown South Africa
| | - Susanne Vetter
- Department of Botany Rhodes University Grahamstown South Africa
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12
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Ellis TD, Cushman JH. Indirect effects of a large mammalian herbivore on small mammal populations: Context-dependent variation across habitat types, mammal species, and seasons. Ecol Evol 2018; 8:12115-12125. [PMID: 30598804 PMCID: PMC6303759 DOI: 10.1002/ece3.4670] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 09/12/2018] [Accepted: 09/13/2018] [Indexed: 11/28/2022] Open
Abstract
Multiple consumer species frequently co-occur in the same landscape and, through effects on surrounding environments, can interact in direct and indirect ways. These interactions can vary in occurrence and importance, and focusing on this variation is critical for understanding the dynamics of interactions among consumers. Large mammalian herbivores are important engineers of ecosystems worldwide, have substantial impacts on vegetation, and can indirectly affect small-mammal populations. However, the degree to which such indirect effects vary within the same system has received minimal attention. We used a 16-year-old exclosure experiment, stratified across a heterogeneous landscape, to evaluate the importance of context-dependent interactions between tule elk (Cervus canadensis nannodes) and small mammals (deer mice [Peromyscus maniculatus], meadow voles [Microtus californicus], and harvest mice [Reithrodontymys megalotis]) in a coastal grassland in California. Effects of elk on voles varied among habitats and seasons: In open grasslands, elk reduced vole numbers during fall 2013 but not summer 2014; in Lupinus-dominated grasslands, elk reduced vole numbers during summer 2014 but not fall 2013; and in Baccharis-dominated grasslands, elk had no effect on vole numbers in either season. Effects of elk on the two mice species also varied among habitats and seasons, but often in different ways from voles and each other. In fall 2013, elk decreased mice abundances in Lupinus-dominated grasslands, but not in Baccharis-dominated or open grasslands. In summer 2014, elk decreased the abundance of harvest mice consistently across habitat types. In contrast, elk increased deer-mice numbers in open grasslands but not other habitats. Within the same heterogenous study system, the influence of elk on small mammals was strongly context-dependent, varying among habitats, mammal species, and seasons. We hypothesize that such variability is common in nature and that failure to consider it may yield inaccurate findings and limit our understanding of interactions among co-occurring consumers.
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Affiliation(s)
- Taylor D. Ellis
- Department of BiologySonoma State UniversityRohnert ParkCalifornia
- Present address:
Point Reyes National SeashoreCalifornia
| | - J. Hall Cushman
- Department of Natural Resources and Environmental ScienceUniversity of NevadaRenoNevada
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13
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Goheen JR, Augustine DJ, Veblen KE, Kimuyu DM, Palmer TM, Porensky LM, Pringle RM, Ratnam J, Riginos C, Sankaran M, Ford AT, Hassan AA, Jakopak R, Kartzinel TR, Kurukura S, Louthan AM, Odadi WO, Otieno TO, Wambua AM, Young HS, Young TP. Conservation lessons from large-mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments. Ann N Y Acad Sci 2018; 1429:31-49. [DOI: 10.1111/nyas.13848] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 04/03/2018] [Accepted: 04/06/2018] [Indexed: 11/26/2022]
Affiliation(s)
- Jacob R. Goheen
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
- Mpala Research Centre; Nanyuki Kenya
| | | | - Kari E. Veblen
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
| | - Duncan M. Kimuyu
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Todd M. Palmer
- Department of Biology; University of Florida; Gainesville Florida
- Mpala Research Centre; Nanyuki Kenya
| | | | - Robert M. Pringle
- Department of Ecology and Evolutionary Biology; Princeton University; Princeton New Jersey
- Mpala Research Centre; Nanyuki Kenya
| | | | | | - Mahesh Sankaran
- National Centre for Biological Sciences, TIFR; Bangalore India
- School of Biology, University of Leeds; Leeds United Kingdom
| | - Adam T. Ford
- Department of Biology; University of British Columbia; Kelowna British Columbia Canada
| | | | - Rhiannon Jakopak
- Department of Zoology and Physiology; University of Wyoming; Laramie Wyoming
| | - Tyler R. Kartzinel
- Department of Ecology and Evolutionary Biology; Brown University; Providence Rhode Island
| | | | | | - Wilfred O. Odadi
- Department of Natural Resources; Egerton University; Egerton Kenya
- Mpala Research Centre; Nanyuki Kenya
| | | | - Alois M. Wambua
- Department of Wildland Resources and Ecology Center; Utah State University; Logan Utah
- Mpala Research Centre; Nanyuki Kenya
| | - Hillary S. Young
- Department of Ecology, Evolution and Marine Biology; University of California; Santa Barbara California
| | - Truman P. Young
- Department of Plant Sciences; University of California; Davis California
- Mpala Research Centre; Nanyuki Kenya
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14
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Young HS, McCauley DJ, Dirzo R, Nunn CL, Campana MG, Agwanda B, Otarola-Castillo ER, Castillo ER, Pringle RM, Veblen KE, Salkeld DJ, Stewardson K, Fleischer R, Lambin EF, Palmer TM, Helgen KM. Interacting effects of land use and climate on rodent-borne pathogens in central Kenya. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0116. [PMID: 28438909 PMCID: PMC5413868 DOI: 10.1098/rstb.2016.0116] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2016] [Indexed: 12/13/2022] Open
Abstract
Understanding the effects of anthropogenic disturbance on zoonotic disease risk is both a critical conservation objective and a public health priority. Here, we evaluate the effects of multiple forms of anthropogenic disturbance across a precipitation gradient on the abundance of pathogen-infected small mammal hosts in a multi-host, multi-pathogen system in central Kenya. Our results suggest that conversion to cropland and wildlife loss alone drive systematic increases in rodent-borne pathogen prevalence, but that pastoral conversion has no such systematic effects. The effects are most likely explained both by changes in total small mammal abundance, and by changes in relative abundance of a few high-competence species, although changes in vector assemblages may also be involved. Several pathogens responded to interactions between disturbance type and climatic conditions, suggesting the potential for synergistic effects of anthropogenic disturbance and climate change on the distribution of disease risk. Overall, these results indicate that conservation can be an effective tool for reducing abundance of rodent-borne pathogens in some contexts (e.g. wildlife loss alone); however, given the strong variation in effects across disturbance types, pathogen taxa and environmental conditions, the use of conservation as public health interventions will need to be carefully tailored to specific pathogens and human contexts. This article is part of the themed issue ‘Conservation, biodiversity and infectious disease: scientific evidence and policy implications’.
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Affiliation(s)
- Hillary S Young
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA .,Mpala Research Centre, Box 555, Nanyuki, Kenya
| | - Douglas J McCauley
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA.,Mpala Research Centre, Box 555, Nanyuki, Kenya
| | - Rodolfo Dirzo
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Charles L Nunn
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.,Duke Global Health Institute, Duke University, Durham, NC 27710, USA
| | - Michael G Campana
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | | | | | - Eric R Castillo
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Robert M Pringle
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA
| | - Kari E Veblen
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Wildland Resources and Ecology Center, Utah State University, Logan, UT 84322, USA
| | - Daniel J Salkeld
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | - Kristin Stewardson
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | - Robert Fleischer
- Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC 20008, USA
| | - Eric F Lambin
- Department of Earth System Science and Woods Institute for the Environment, Stanford University, Stanford, CA 94305, USA
| | - Todd M Palmer
- Mpala Research Centre, Box 555, Nanyuki, Kenya.,Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Kristofer M Helgen
- Division of Mammals, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,School of Biological Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
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15
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Acanakwo EF, Sheil D, Moe SR. Termites and large herbivores influence seed removal rates in an African savanna. Ecology 2017; 98:3165-3174. [PMID: 28977679 DOI: 10.1002/ecy.2038] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 07/20/2017] [Accepted: 09/11/2017] [Indexed: 11/12/2022]
Abstract
Seed removal can influence plant community dynamics, composition, and resulting vegetation characteristics. In the African savanna, termites and large herbivores influence vegetation in various ways, likely including indirect effects on seed predators and secondary dispersers. However, the intensity and variation of seed removal rates in African savannas has seldom been studied. We experimentally investigated whether termites and large herbivores were important factors in the mechanisms contributing to observed patterns in tree species composition on and off mounds, in Lake Mburo National Park, Uganda. Within fenced (excluding large herbivores) and unfenced termite mound and adjacent savanna plots, we placed seeds of nine native tree species within small open "cages," accessed by all animals, roofed cages that only allowed access to small vertebrates and invertebrates, and closed cages that permitted access by smaller invertebrates only (5 mm wire mesh). We found that mean seed removal rate was high (up to 87.3% per 3 d). Mound habitats experienced significantly higher removal rates than off-mound habitats. The mean removal rate of native seeds from closed cages was 11.1% per 3 d compared with 19.4% and 23.3% removed per 3 d in the roofed and open cages, respectively. Smaller seeds experienced higher removal rates than larger seeds. Large herbivore exclusion on mounds reduced native seed removal rates by a mean of 8.8% in the open cages, but increased removal rates by 1.7% in the open cages when off-mound habitats were fenced. While removal rates from open cages were higher on active mounds (30.9%) than on inactive mounds (26.7%), the removal rates from closed cages were lower on active vs. inactive mounds (6.1% vs. 11.6%, respectively). Thus, we conclude that large herbivores and Macrotermes mounds influence seed removal rates, though these effects appear indirect.
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Affiliation(s)
- Erik Francis Acanakwo
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway
| | - Douglas Sheil
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway
| | - Stein R Moe
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway
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16
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Granados A, Brodie JF, Bernard H, O'Brien MJ. Defaunation and habitat disturbance interact synergistically to alter seedling recruitment. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2017; 27:2092-2101. [PMID: 28660670 DOI: 10.1002/eap.1592] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 05/31/2017] [Indexed: 06/07/2023]
Abstract
Vertebrate granivores destroy plant seeds, but whether animal-induced seed mortality alters plant recruitment varies with habitat context, seed traits, and among granivore species. An incomplete understanding of seed predation makes it difficult to predict how widespread extirpations of vertebrate granivores in tropical forests might affect tree communities, especially in the face of habitat disturbance. Many tropical forests are simultaneously affected by animal loss as well as habitat disturbance, but the consequences of each for forest regeneration are often studied separately or additively, and usually on a single plant demographic stage. The combined impacts of these threats could affect plant recruitment in ways that are not apparent when studied in isolation. We used wire cages to exclude large (elephants), medium, (sambar deer, bearded pigs, muntjac deer), and small (porcupines, chevrotains) ground-dwelling mammalian granivores and herbivores in logged and unlogged forests in Malaysian Borneo. We assessed the interaction between habitat disturbance (selective logging) and experimental defaunation on seed survival, germination, and seedling establishment in five dominant dipterocarp tree species spanning a 21-fold gradient in seed size. Granivore-induced seed mortality was consistently higher in logged forest. Germination of unpredated seeds was reduced in logged forest and in the absence of small to large-bodied mammals. Experimental defaunation increased germination and reduced seed removal but had little effect on seed survival. Seedling recruitment however, was more likely where logging and animal loss occurred together. The interacting effects of logging and hunting could therefore, actually increase seedling establishment, suggesting that the loss of mammals in disturbed forest could have important consequences for forest regeneration and composition.
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Affiliation(s)
- Alys Granados
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Jedediah F Brodie
- Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
- Division of Biological Sciences and Wildlife Biology Program, University of Montana, Missoula, Montana, 59812, USA
| | - Henry Bernard
- Institute for Tropical Biology and Conservation, University Malaysia Sabah, Kota Kinabalu, Sabah, Malaysia
| | - Michael J O'Brien
- Consejo Superior de Investigaciones Científicas, Estación Experimental de Zonas Áridas, Carretera de Sacramento s/n, E-04120, La Cañada, Almería, Spain
- The South East Asia Rainforest Research Partnership, Danum Valley Field Centre, P.O. Box 60282, 91112, Lahad Datu, Sabah, Malaysia
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17
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Ng’weno CC, Maiyo NJ, Ali AH, Kibungei AK, Goheen JR. Lions influence the decline and habitat shift of hartebeest in a semiarid savanna. J Mammal 2017. [DOI: 10.1093/jmammal/gyx040] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Ford AT, COOKE SJ, Goheen JR, Young TP. Conserving Megafauna or Sacrificing Biodiversity? Bioscience 2017. [DOI: 10.1093/biosci/biw163] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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Petipas RH, González JB, Palmer TM, Brody AK. Habitat-specific AMF symbioses enhance drought tolerance of a native Kenyan grass. ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 2017. [DOI: 10.1016/j.actao.2016.12.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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20
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Veblen KE, Porensky LM, Riginos C, Young TP. Are cattle surrogate wildlife? Savanna plant community composition explained by total herbivory more than herbivore type. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2016; 26:1610-1623. [PMID: 27755702 DOI: 10.1890/15-1367.1] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 12/12/2015] [Accepted: 01/28/2016] [Indexed: 06/06/2023]
Abstract
The widespread replacement of wild ungulate herbivores by domestic livestock in African savannas is composed of two interrelated phenomena: (1) loss or reduction in numbers of individual wildlife species or guilds and (2) addition of livestock to the system. Each can have important implications for plant community dynamics. Yet very few studies have experimentally addressed the individual, combined, and potentially interactive effects of wild vs. domestic herbivore species on herbaceous plant communities within a single system. Additionally, there is little information about whether, and in which contexts, livestock might functionally replace native herbivore wildlife or, alternatively, have fundamentally different effects on plant species composition. The Kenya Long-term Exclosure Experiment, which has been running since 1995, is composed of six treatment combinations of mega-herbivores, meso-herbivore ungulate wildlife, and cattle. We sampled herbaceous vegetation 25 times between 1999 and 2013. We used partial redundancy analysis and linear mixed models to assess effects of herbivore treatments on overall plant community composition and key plant species. Plant communities in the six different herbivore treatments shifted directionally over time and diverged from each other substantially by 2013. Plant community composition was strongly related (R2 = 0.92) to residual plant biomass, a measure of herbivore utilization. Addition of any single herbivore type (cattle, wildlife, or mega-herbivores) caused a shift in plant community composition that was proportional to its removal of plant biomass. These results suggest that overall herbivory pressure, rather than herbivore type or complex interactions among different herbivore types, was the main driver of changes in plant community composition. Individual plant species, however, did respond most strongly to either wild ungulates or cattle. Although these results suggest considerable functional similarity between a suite of native wild herbivores (which included grazers, browsers, and mixed feeders) and cattle (mostly grazers) with respect to understory plant community composition, responses of individual plant species demonstrate that at the plant-population-level impacts of a single livestock species are not functionally identical to those of a diverse group of native herbivores.
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Affiliation(s)
- Kari E Veblen
- Department of Wildland Resources and Ecology Center, Utah State University, Logan, Utah, 84322, USA.
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya.
| | - Lauren M Porensky
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- USDA-ARS Rangeland Resources Research Unit, Fort Collins, Colorado, 80526, USA
| | - Corinna Riginos
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, 82071, USA
| | - Truman P Young
- Mpala Research Centre, P.O. Box 555, Nanyuki, Kenya
- Department of Plant Sciences, University of California, Davis, California, 95616, USA
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21
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Vieira-Neto EHM, Vasconcelos HL, Bruna EM. Roads increase population growth rates of a native leaf-cutter ant in Neotropical savannahs. J Appl Ecol 2016. [DOI: 10.1111/1365-2664.12651] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ernane H. M. Vieira-Neto
- Department of Wildlife Ecology and Conservation; University of Florida; Gainesville FL 32611-0430 USA
| | - Heraldo L. Vasconcelos
- Instituto de Biologia; Universidade Federal de Uberlândia; Av. Pará 1720 Uberlândia MG 38405-320 Brazil
| | - Emilio M. Bruna
- Department of Wildlife Ecology and Conservation; University of Florida; Gainesville FL 32611-0430 USA
- Center for Latin American Studies; University of Florida; Gainesville FL 32611-5530 USA
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22
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Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation. Proc Natl Acad Sci U S A 2015; 113:847-55. [PMID: 26504223 DOI: 10.1073/pnas.1502545112] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Until recently in Earth history, very large herbivores (mammoths, ground sloths, diprotodons, and many others) occurred in most of the World's terrestrial ecosystems, but the majority have gone extinct as part of the late-Quaternary extinctions. How has this large-scale removal of large herbivores affected landscape structure and ecosystem functioning? In this review, we combine paleo-data with information from modern exclosure experiments to assess the impact of large herbivores (and their disappearance) on woody species, landscape structure, and ecosystem functions. In modern landscapes characterized by intense herbivory, woody plants can persist by defending themselves or by association with defended species, can persist by growing in places that are physically inaccessible to herbivores, or can persist where high predator activity limits foraging by herbivores. At the landscape scale, different herbivore densities and assemblages may result in dynamic gradients in woody cover. The late-Quaternary extinctions were natural experiments in large-herbivore removal; the paleoecological record shows evidence of widespread changes in community composition and ecosystem structure and function, consistent with modern exclosure experiments. We propose a conceptual framework that describes the impact of large herbivores on woody plant abundance mediated by herbivore diversity and density, predicting that herbivore suppression of woody plants is strongest where herbivore diversity is high. We conclude that the decline of large herbivores induces major alterations in landscape structure and ecosystem functions.
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23
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Su H, Liu W, Xu H, Wang Z, Zhang H, Hu H, Li Y. Long-term livestock exclusion facilitates native woody plant encroachment in a sandy semiarid rangeland. Ecol Evol 2015; 5:2445-56. [PMID: 26120433 PMCID: PMC4475376 DOI: 10.1002/ece3.1531] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 04/08/2015] [Accepted: 04/12/2015] [Indexed: 11/08/2022] Open
Abstract
The role of livestock grazing in regulating woody cover and biomass in grass-dominant systems is well recognized. However, the way in which woody plant populations in respond when livestock are removed from grazing in the absence of other disturbances, such as fire, remains unclear. We conducted a 10-year, replicated fencing experiment in a sandy semiarid rangeland in northern China (which has a mean annual rainfall of 365 mm), where fires have been actively suppressed for decades. Fencing dramatically influenced the growth and age structure of the native tree species, Ulmus pumila, which is the sole dominant tree in the area. After a decade, the density of the U. pumila tree population in the fencing plots increased doubly and canopy cover increased triply. The proportion of both saplings (U2) and young trees (U3) increased in fencing plots but decreased in grazing plots after the 10-year treatment period. The effects of fencing on U. pumila trees varied by age class, with potential implications for the future structure of the U. pumila tree community. Decadal fencing led to approximately 80-fold increase in recruitment and a nearly 2.5-fold decrease in the mortality of both U2 and U3. Further, livestock grazing generated a “browsing trap” to the recruitment of both U2 and U3, and had a small impact on the mortality of old trees. A long-term, fencing-driven shift in woody species composition was mediated via its effects on both recruitment and mortality rates. Synthesis and applications. Our results demonstrate that in the long-term absence of both fire and livestock, native woody plant encroachment tends to occur in sandy rangelands, transforming the woody plant demography in the process. The feasibility of full livestock exclusion in sandy rangelands requires further discussion. A balanced amount of livestock grazing may provide critical ecosystem services by regulating woody cover and mediating woody plant encroachment.
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Affiliation(s)
- Hua Su
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences Beijing, 100093, China
| | - Wei Liu
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences Beijing, 100093, China
| | - Hong Xu
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences Beijing, 100093, China
| | - Zongshuai Wang
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences Beijing, 100093, China ; National Engineering and Technology Center for Information Agriculture Key Laboratory of Crop Physiology and Ecology in Southern China, Ministry of Agriculture, Nanjing Agricultural University Nanjing, Jiangsu Province, 210095, China
| | - Huifang Zhang
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences Beijing, 100093, China ; National Engineering and Technology Center for Information Agriculture Key Laboratory of Crop Physiology and Ecology in Southern China, Ministry of Agriculture, Nanjing Agricultural University Nanjing, Jiangsu Province, 210095, China
| | - Haixiao Hu
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences Beijing, 100093, China ; University of Chinese Academy of Sciences Beijing, 100049, China
| | - Yonggeng Li
- State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences Beijing, 100093, China
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24
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Forsyth DM, Wilson DJ, Easdale TA, Kunstler G, Canham CD, Ruscoe WA, Wright EF, Murphy L, Gormley AM, Gaxiola A, Coomes DA. Century-scale effects of invasive deer and rodents on the dynamics of forests growing on soils of contrasting fertility. ECOL MONOGR 2015. [DOI: 10.1890/14-0389.1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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25
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Qi G, Hu Y, Owens JR, Dai Q, Hou R, Yang Z, Qi D. Habitat suitability for chiru ( Pantholops hodgsonii
): Implications for conservation management across the Tibetan region of Chang Tang. J Wildl Manage 2015. [DOI: 10.1002/jwmg.846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Guilan Qi
- The Key Laboratory for Conservation Biology of Endangered Wildlife, Sichuan Province; Chengdu Research Base of Giant Panda Breeding; Chengdu Sichuan 610081 China
- Chengdu Academy of Agriculture and Forestry Sciences; Chengdu Sichuan 611130 China
| | - Yibo Hu
- Key Laboratory for Animal Ecology and Conservation Biology; Institute of Zoology; Chinese Academy of Sciences; 1-5 Beichenxi Road Beijing 100101 China
| | - Jacob R. Owens
- The Key Laboratory for Conservation Biology of Endangered Wildlife, Sichuan Province; Chengdu Research Base of Giant Panda Breeding; Chengdu Sichuan 610081 China
| | - Qiang Dai
- Chengdu Institute of Biology; Chinese Academy of Sciences; Chengdu Sichuan 610081 China
| | - Rong Hou
- The Key Laboratory for Conservation Biology of Endangered Wildlife, Sichuan Province; Chengdu Research Base of Giant Panda Breeding; Chengdu Sichuan 610081 China
| | - Zhisong Yang
- Institute of Rare Animals and Plants; China West Normal University; Nanchong 637009 China
| | - Dunwu Qi
- The Key Laboratory for Conservation Biology of Endangered Wildlife, Sichuan Province; Chengdu Research Base of Giant Panda Breeding; Chengdu Sichuan 610081 China
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26
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Young HS, McCauley DJ, Dirzo R, Goheen JR, Agwanda B, Brook C, Otarola-Castillo E, Ferguson AW, Kinyua SN, McDonough MM, Palmer TM, Pringle RM, Young TP, Helgen KM. Context-dependent effects of large-wildlife declines on small-mammal communities in central Kenya. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2015; 25:348-60. [PMID: 26263659 DOI: 10.1890/14-0995.1] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Many species of large wildlife have declined drastically worldwide. These reductions often lead to profound shifts in the ecology of entire communities and ecosystems. However, the effects of these large-wildlife declines on other taxa likely hinge upon both underlying abiotic properties of these systems and on the types of secondary anthropogenic changes associated with wildlife loss, making impacts difficult to predict. To better understand how these important contextual factors determine the consequences of large-wildlife declines on other animals in a community, we examined the effects of three common forms of large-wildlife loss (removal without replacement [using fences], removal followed by replacement with domestic stock, and removal accompanied by crop agricultural use) on small-mammal abundance, diversity, and community composition, in landscapes that varied in several abiotic attributes (rainfall, soil fertility, land-use intensity) in central Kenya. We found that small-mammal communities were indeed heavily impacted by all forms of large-wildlife decline, showing, on average: (1) higher densities, (2) lower species richness per site, and (3) different species assemblages in sites from which large wildlife were removed. However, the nature and magnitude of these effects were strongly context dependent. Rainfall, type of land-use change, and the interaction of these two factors were key predictors of both the magnitude and type of responses of small mammals. The strongest effects, particularly abundance responses, tended to be observed in low-rainfall areas. Whereas isolated wildlife removal primarily led to increased small-mammal abundance, wildlife removal associated with secondary uses (agriculture, domestic stock) had much more variable effects on abundance and stronger impacts on diversity and composition. Collectively, these results (1) highlight the importance of context in determining the impacts of large-wildlife decline on small-mammal communities, (2) emphasize the challenges in extrapolating results from controlled experimental studies to predict the effects of wildlife declines that are accompanied by secondary land-uses, and (3) suggest that, because of the context-dependent nature of the responses to large-wildlife decline, large-wildlife status alone cannot be reliably used to predict small-mammal community changes.
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27
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Tjelele J, Ward D, Dziba L. The effects of seed ingestion by livestock, dung fertilization, trampling, grass competition and fire on seedling establishment of two woody plant species. PLoS One 2015; 10:e0117788. [PMID: 25695765 PMCID: PMC4335069 DOI: 10.1371/journal.pone.0117788] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 12/31/2014] [Indexed: 11/19/2022] Open
Abstract
The increasing rate of woody plant encroachment in grasslands or savannas remains a challenge to livestock farmers. The causes and control measures of woody plant encroachment are of common interest, especially where it negatively affects the objectives of an agricultural enterprise. The objectives of this study were to determine the effects of gut passage (goats, cattle), dung (nutrients), fire, grass competition and trampling on establishment of A. nilotica and D. cinerea seedlings. Germination trials were subjected to the following treatments: 1) seed passage through the gut of cattle and goats and unpassed/ untreated seeds (i.e. not ingested), 2) dung and control (no dung), 3) grass and control (mowed grass), 4) fire and control (no fire), 5) trampling and control (no trampling). The interaction of animal species, grass and fire had an effect on seedling recruitment (P < 0.0052). Seeds retrieved from goats and planted with no grass and with fire (6.81% ± 0.33) had a significant effect on seedling recruitment than seeds retrieved from goats and planted with grass and no fire (2.98% ± 0.33). Significantly more D. cinerea and A. nilotica seeds germinated following seed ingestion by goats (3.59% ± 0.16) than cattle (1.93% ± 0.09) and control or untreated seeds (1.69% ± 0.11). Less dense grass cover, which resulted in reduced grass competition with tree seedlings for light, space and water, and improved seed scarification due to gut passage were vital for emergence and recruitment of Acacia seedlings. These results will contribute considerably to the understanding of the recruitment phase of woody plant encroachment.
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Affiliation(s)
- Julius Tjelele
- Agricultural Research Council, Animal Production Institute, Irene, 0062, South Africa
- School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Scottsville 3209, South Africa
- * E-mail:
| | - David Ward
- School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Scottsville 3209, South Africa
| | - Luthando Dziba
- CSIR: Natural Resources and the Environment, Pretoria 0001, South Africa
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28
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Kimuyu DM, Sensenig RL, Riginos C, Veblen KE, Young TP. Native and domestic browsers and grazers reduce fuels, fire temperatures, and acacia ant mortality in an African savanna. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2014; 24:741-749. [PMID: 24988772 DOI: 10.1890/13-1135.1] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Despite the importance of fire and herbivory in structuring savanna systems, few replicated experiments have examined the interactive effects of herbivory and fire on plant dynamics. In addition, the effects of fire on associated ant-tree mutualisms have been largely unexplored. We carried out small controlled burns in each of 18 herbivore treatment plots of the Kenya Long-term Exclosure Experiment (KLEE), where experimentally excluding elephants has resulted in 42% greater tree densities. The KLEE design includes six different herbivore treatments that allowed us to examine how different combinations of megaherbivore wildlife, mesoherbivore wildlife, and cattle affect fire temperatures and subsequent loss of ant symbionts from Acacia trees. Before burning, we quantified herbaceous fuel loads and plant community composition. We tagged all trees, measured their height and basal diameter, and identified the resident ant species on each. We recorded weather conditions during the burns and used ceramic tiles painted with fire-sensitive paints to estimate fire temperatures at different heights and in different microsites (under vs. between trees). Across all treatments, fire temperatures were highest at 0-50 cm off the ground and hotter in the grass under trees than in the grassy areas between trees. Plots with more trees burned hotter than plots with fewer trees, perhaps because of greater fine woody debris. Plots grazed by wildlife and by cattle prior to burning had lower herbaceous fuel loads and experienced lower burn temperatures than ungrazed plots. Many trees lost their ant colonies during the burns. Ant survivorship differed by ant species and at the plot level was positively associated with previous herbivory (and lower fire temperatures). Across all treatments, ant colonies on taller trees were more likely to survive, but even some of the tallest trees lost their ant colonies. Our study marks a significant step in understanding the mechanisms that underlie the interactions between fire and herbivory in savanna ecosystems.
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In a long-term experimental demography study, excluding ungulates reversed invader's explosive population growth rate and restored natives. Proc Natl Acad Sci U S A 2014; 111:4501-6. [PMID: 24616522 DOI: 10.1073/pnas.1310121111] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A major goal in ecology is to understand mechanisms that increase invasion success of exotic species. A recent hypothesis implicates altered species interactions resulting from ungulate herbivore overabundance as a key cause of exotic plant domination. To test this hypothesis, we maintained an experimental demography deer exclusion study for 6 y in a forest where the native ungulate Odocoileus virginianus (white-tailed deer) is overabundant and Alliaria petiolata (garlic mustard) is aggressively invading. Because population growth is multiplicative across time, we introduce metrics that correctly integrate experimental effects across treatment years, the cumulative population growth rate, λc, and its geometric mean, λper-year, the time-averaged annual population growth rate. We determined λc and λper-year of the invader and of a common native, Trillium erectum. Our results conclusively demonstrate that deer are required for the success of Alliaria; its projected population trajectory shifted from explosive growth in the presence of deer (λper-year = 1.33) to decline toward extinction where deer are excluded (λper-year = 0.88). In contrast, Trillium's λper-year was suppressed in the presence of deer relative to deer exclusion (λper-year = 1.04 vs. 1.20, respectively). Retrospective sensitivity analyses revealed that the largest negative effect of deer exclusion on Alliaria came from rosette transitions, whereas the largest positive effect on Trillium came from reproductive transitions. Deer exclusion lowered Alliaria density while increasing Trillium density. Our results provide definitive experimental support that interactions with overabundant ungulates enhance demographic success of invaders and depress natives' success, with broad implications for biodiversity and ecosystem function worldwide.
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Rebollo S, Milchunas DG, Stapp P, Augustine DJ, Derner JD. Disproportionate effects of non-colonial small herbivores on structure and diversity of grassland dominated by large herbivores. OIKOS 2013. [DOI: 10.1111/j.1600-0706.2013.00403.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Disentangling herbivore impacts on Populus tremuloides: a comparison of native ungulates and cattle in Canada’s Aspen Parkland. Oecologia 2013; 173:895-904. [PMID: 23649757 DOI: 10.1007/s00442-013-2676-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 04/24/2013] [Indexed: 10/26/2022]
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Bergstrom BJ. Would East African savanna rodents inhibit woody encroachment? Evidence from stable isotopes and microhistological analysis of feces. J Mammal 2013. [DOI: 10.1644/12-mamm-a-146.1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Goheen JR, Palmer TM, Charles GK, Helgen KM, Kinyua SN, Maclean JE, Turner BL, Young HS, Pringle RM. Piecewise disassembly of a large-herbivore community across a rainfall gradient: the UHURU experiment. PLoS One 2013; 8:e55192. [PMID: 23405122 PMCID: PMC3566220 DOI: 10.1371/journal.pone.0055192] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 12/19/2012] [Indexed: 11/19/2022] Open
Abstract
Large mammalian herbivores (LMH) strongly influence plant communities, and these effects can propagate indirectly throughout food webs. Most existing large-scale manipulations of LMH presence/absence consist of a single exclusion treatment, and few are replicated across environmental gradients. Thus, important questions remain about the functional roles of different LMH, and how these roles depend on abiotic context. In September 2008, we constructed a series of 1-ha herbivore-exclusion plots across a 20-km rainfall gradient in central Kenya. Dubbed "UHURU" (Ungulate Herbivory Under Rainfall Uncertainty), this experiment aims to illuminate the ecological effects of three size classes of LMH, and how rainfall regimes shape the direction and magnitude of these effects. UHURU consists of four treatments: total-exclusion (all ungulate herbivores), mesoherbivore-exclusion (LMH >120-cm tall), megaherbivore-exclusion (elephants and giraffes), and unfenced open plots. Each treatment is replicated three times at three locations (“sites”) along the rainfall gradient: low (440 mm/year), intermediate (580 mm/year), and high (640 mm/year). There was limited variation across sites in soil attributes and LMH activity levels. Understory-plant cover was greater in plots without mesoherbivores, but did not respond strongly to the exclusion of megaherbivores, or to the additional exclusion of dik-dik and warthog. Eleven of the thirteen understory plant species that responded significantly to exclusion treatment were more common in exclusion plots than open ones. Significant interactions between site and treatment on plant communities, although uncommon, suggested that differences between treatments may be greater at sites with lower rainfall. Browsers reduced densities of several common overstory species, along with growth rates of the three dominant Acacia species. Small-mammal densities were 2–3 times greater in total-exclusion than in open plots at all sites. Although we expect patterns to become clearer with time, results from 2008–2012 show that the effects of excluding successively smaller-bodied subsets of the LMH community are generally non-additive for a given response variable, and inconsistent across response variables, indicating that the different LMH size classes are not functionally redundant. Several response variables showed significant treatment-by-site interactions, suggesting that the nature of plant-herbivore interactions can vary across restricted spatial scales.
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Affiliation(s)
- Jacob R. Goheen
- Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, United States of America
- Department of Botany, University of Wyoming, Laramie, Wyoming, United States of America
- Mpala Research Centre, Nanyuki, Kenya
| | - Todd M. Palmer
- Mpala Research Centre, Nanyuki, Kenya
- Department of Biology, University of Florida, Gainesville, Florida, United States of America
| | | | - Kristofer M. Helgen
- Division of Mammals, National Museum of Natural History, Washington, District of Columbia, United States of America
| | - Stephen N. Kinyua
- Mpala Research Centre, Nanyuki, Kenya
- Department of Wildlife Management, Moi University, Eldoret, Kenya
| | - Janet E. Maclean
- Mpala Research Centre, Nanyuki, Kenya
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Hillary S. Young
- Mpala Research Centre, Nanyuki, Kenya
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America
| | - Robert M. Pringle
- Mpala Research Centre, Nanyuki, Kenya
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, United States of America
- * E-mail:
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