DOCSLIB.ORG

Resource Competition Shapes Biological Rhythms and Promotes Temporal Niche

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Resource Competition Shapes Biological Rhythms and Promotes Temporal Niche bioRxiv preprint doi: https://doi.org/10.1101/2020.04.22.055160; this version posted April 22, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 1 2 3 Resource competition shapes biological rhythms and promotes temporal niche 4 differentiation in a community simulation 5 6 Resource competition, biological rhythms, and temporal niches 7 8 Vance Difan Gao1,2*, Sara Morley-Fletcher1,4, Stefania Maccari1,3,4, Martha Hotz Vitaterna2, Fred W. Turek2 9 10 1UMR 8576 Unité de Glycobiologie Structurale et Fonctionnelle, Campus Cité Scientifique, CNRS, University of 11 Lille, Lille, France 12 2 Center for Sleep and Circadian Biology, Northwestern University, Evanston, IL, United States of America 13 3Department of Medico-Surgical Sciences and Biotechnologies, University Sapienza of Rome, Rome, Italy 14 4International Associated Laboratory (LIA) “Perinatal Stress and Neurodegenerative Diseases”: University of Lille, 15 Lille, France; CNRS-UMR 8576, Lille, France; Sapienza University of Rome, Rome, Italy; IRCCS Neuromed, Pozzilli, 16 Italy 17 18 19 * Corresponding author 20 E-mail: [email protected] 21 1 bioRxiv preprint doi: https://doi.org/10.1101/2020.04.22.055160; this version posted April 22, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 22 Abstract 23 Competition for resources often contributes strongly to defining an organism’s ecological niche. Biological 24 rhythms are important adaptations to the temporal dimension of niches, but the role of other organisms in 25 determining such temporal niches have not been much studied, and the role specifically of competition even 26 less so. We investigate how interspecific and intraspecific competition for resources shapes an organism’s 27 activity rhythms. For this, communities of one or two species in an environment with limited resource input 28 were simulated. We demonstrate that when organisms are arrhythmic, one species will always be competitively 29 excluded from the environment, but the existence of activity rhythms allows niche differentiation and indefinite 30 coexistence of the two species. Two species which are initially active at the same phase will differentiate their 31 phase angle of entrainment over time to avoid each other. When only one species is present in an environment, 32 competition within individuals of the species strongly selects for niche expansion through arrhythmicity, but the 33 addition of an interspecific competitor facilitates evolution of increased rhythmic amplitude when combined 34 with additional adaptations for temporal specialization. Finally, if individuals preferentially mate with others 35 who are active at similar times of day, then disruptive selection by intraspecific competition can split one 36 population into two reproductively isolated groups. In summary, these simulations suggest that biological 37 rhythms are an effective method to temporally differentiate ecological niches, and that competition is an 38 important ecological pressure promoting the evolution of rhythms and sleep. 39 40 Author summary 41 Why do we sleep? We are interested in the ecological factors which promote the evolution of biological 42 rhythms like the sleep-wake cycle, focusing especially on competition. When animals compete with each other 43 for resources, they often evolve to avoid each other by specializing to use different resources or separating their 2 bioRxiv preprint doi: https://doi.org/10.1101/2020.04.22.055160; this version posted April 22, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 44 activity in other ways. To test hypotheses about how competition shapes rest-activity rhythms, we performed 45 computer simulations of a community of animals who move, reproduce, and compete for resources. We show 46 that biological rhythms let two species divide time so that one species is active while its competitor is resting, 47 thus avoiding depleting shared resources. When a species has no competitors in the simulation, competition 48 between members of the same species cause population and individual rhythms to decrease, since resource 49 availability is low when everybody is active at the same time. However, having competitors allows strong 50 rhythms to evolve from originally arrhythmic organisms. Competition can even cause a single population to split 51 into two species which are separated in time. In summary, these results suggest that competition is a strong 52 factor promoting rest-activity rhythms. 53 54 Introduction 55 An ecological niche is the particular “space” a species occupies in an ecosystem, comprising a diversity of 56 concepts including the physical environment where it lives, the resources it uses, its interactions with other 57 species, and the adaptations it has evolved to exploit the niche. Both theory and evidence indicate that 58 competition is a major factor which determines species’ niches [1,2]. Competitors for a resource generally will 59 adjust to avoid each other, differentiating their niches by adapting to utilize different types of resources, thus 60 avoiding the depletion of shared resources (exploitative competition) [3] as well as costly acts of aggression and 61 territorial exclusion (interference competition) [4]. 62 Time is one dimension which defines a niche. Most species live in environments dominated by a day-night 63 cycle and a seasonal cycle, though other cycles such as tides can also strongly define an ecosystem [5]. A 64 temporal niche is defined by both abiotic elements such as light intensity and temperature [6,7], as well the as 65 by predictable temporal patterns of other organisms [8]. Adaptions for a specific temporal niche include for 66 example specializations in vision, coat color, temperature regulation, and importantly, biological rhythms, i.e. 3 bioRxiv preprint doi: https://doi.org/10.1101/2020.04.22.055160; this version posted April 22, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 67 physiological and behavioral traits which cycle regularly according to an internal biological clock . In this article, 68 we consider activity rhythms through the lens of ecological niche theory, viewing them as a way partition niches 69 among competitors and examining how competition shapes the expression of these biological clocks. Time can 70 be thus viewed as a sort of resource or space which is partitioned by organisms in response to competition [9], 71 both interspecific (between different species) and intraspecific (between members of the same species) [10]. 72 While some work has examined predation’s effect on animals’ activity rhythms [11–13], the role of competition 73 has been less examined. 74 A variety of field studies have observed evidence of temporal partitioning between putative competitors. 75 For example, a community of three sympatric species of insectivorous bats were observed to have activity 76 profiles which are displaced from each other, suggesting that they avoid each other [14]. While Argentinian 77 pampas foxes are normally nocturnal, they show a modified half-nocturnal half-diurnal profile in a region where 78 they overlap with crab-eating foxes [15]. Other examples of apparent temporal partitioning have been seen at 79 watering holes [16,17], in desert gerbils [18], carabid beetles [19], and large African carnivores [20]. Stronger 80 evidence comes from semi-natural manipulation experiments. Common spiny mice are nocturnal and golden 81 spiny mice are diurnal in areas where the two species coexist, but when the common spiny mice are 82 experimentally removed, the originally diurnal golden spiny mice shift into nocturnality, suggesting that this 83 species was pushed into diurnality by the competing species [9]. It should be recognized that these examples all 84 occur at the behavioral and ecological time scale, i.e. they are “temporary” displacements from the species’ 85 genetically determined preferred activity time. Although certain pairs of taxa are suggestive of evolutionary- 86 level temporal partitioning—nocturnal owls and diurnal hawks, for instance, or the hypothesized nocturnal 87 origin of mammals [21]—the role of competition in causing these evolutionary divergences is near impossible to 88 establish conclusively. Nonetheless, it is probable that temporal shifts at the behavioral/ecological level cause 89 selection for alleles suited for the new time period, eventually translating into long-term changes at the 90 genetic/evolutionary level. 4 bioRxiv preprint doi: https://doi.org/10.1101/2020.04.22.055160; this version posted April 22, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 91 In this work, we explore ways which competition in ecological niche theory can be applied to biological 92 rhythms, using simulation of a community of two species who compete for limited resources in an environment. 93 We first demonstrate that circadian rhythms are a form of niche differentiation which allows two species to 94 stably coexist without competitive exclusion, and that two rhythmic species will quickly differentiate their 95 circadian phases to avoid competition. We show that arrhythmicity is preferred when there is no interspecific 96 competitor present, but the presence of interspecific competition greatly facilitates the development of strong 97 activity rhythms.
Load more

Recommended publications
  • Photopigments and Color Vision in the Nocturnal Monkey, Aotus GERALD H
    Vision Res. Vol. 33, No. 13, pp. 1773-1783, 1993 0042-6989/93 $6.00 + 0.00 Printed in Great Britain. All rights reserved Copyright 0 1993 Pergamon Press Ltd Photopigments and Color Vision in the Nocturnal Monkey, Aotus GERALD H. JACOBS,*? JESS F. DEEGAN II,* JAY NEITZ,$ MICHAEL A. CROGNALE,§ MAUREEN NEITZT Received 6 November 1992; in revised form 3 February 1993 The owl monkey (Aotus tridrgutus) is the only nocturnal monkey. The photopigments of Aotus and the relationship between these photopigments and visual discrimination were examined through (1) an analysis of the tlicker photometric electroretinogram (ERG), (2) psychophysical tests of visual sensitivity and color vision, and (3) a search for the presence of the photopigment gene necessary for the production of a short-wavelength sensitive (SWS) photopigment. Roth electrophysiological and behavioral measurements indicate that in addition to a rod photopigment the retina of this primate contains only one other photopigment type-a cone pigment having a spectral peak cu 543 nm. Earlier results that suggested these monkeys can make crude color discriminations are interpreted as probably resulting from the joint exploitation of signals from rods and cones. Although Aotus has no functional SWS photopigment, hybridization analysis shows that A&us has a pigment gene that is highly homologous to the human SWS photopigment gene. Aotus trivirgatus Cone photopigments Monkey color vision Monochromacy Photopigment genes Evolution of color vision INTRODUCTION interest to anyone interested in visual adaptations for two somewhat contradictory reasons. On the one hand, The owl monkey (A&us) is unique among present study of A&us might provide the possibility of docu- day monkeys in several regards.
    [Show full text]
  • Regional Neutrality Evolves Through Local Adaptive Niche Evolution
    Regional neutrality evolves through local adaptive niche evolution Mathew A. Leibolda,1, Mark C. Urbanb, Luc De Meesterc, Christopher A. Klausmeierd,e,f, and Joost Vanoverbekec aDepartment of Biology, University of Florida, Gainesville, FL 32611; bDepartment of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269; cDepartment of Biology, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium; dKellogg Biological Station, Michigan State University, Hickory Corners, MI 49060; eDepartment of Plant Biology, Michigan State University, Hickory Corners, MI 49060; and fProgram in Ecology, Evolutionary Biology & Behavior, Michigan State University, Hickory Corners, MI 49060 Edited by Nils C. Stenseth, University of Oslo, Oslo, Norway, and approved December 11, 2018 (received for review May 22, 2018) Biodiversity in natural systems can be maintained either because Past theoretical work in this area suggests that, depending on niche differentiation among competitors facilitates stable coexis- assumptions, the effects of local adaptation can either cause com- tence or because equal fitness among neutral species allows for peting species to diverge (17) or converge (18–22) in niche traits, their long-term cooccurrence despite a slow drift toward extinc- facilitating niche partitioning or neutral cooccurrence of species, tion. Whereas the relative importance of these two ecological respectively. This research, however, neglects the regional scale mechanisms has been well-studied in the absence of evolution, the and the process by which communities assemble through re- role of local adaptive evolution in maintaining biological diversity peated colonization, extinction, and competition.Taking this through these processes is less clear. Here we study the contribu- more regional perspective, local adaptive evolution can generate tion of local adaptive evolution to coexistence in a landscape of evolution-mediated priority effects wherein early colonizers adapt to interconnected patches subject to disturbance.
    [Show full text]
  • Interspecific Competition: • Lecture Summary: • Definition
    BIOS 6150: Ecology Dr. Stephen Malcolm, Department of Biological Sciences • Week 5: Interspecific Competition: • Lecture summary: • Definition. Semibalanus balanoides • Examples. James P. Rowan, http://www.emature.com • Outcomes. • Lotka-Volterra model. Chthamalus stellatus Alan J. Southward, http://www.marlin.ac.uk/ BIOS 6150: Ecology - Dr. S. Malcolm. Week 5: Interspecific Competition Slide - 1 2. Interspecific Competition: • Like intraspecific competition, competition between species can be defined as: • “Competition is an interaction between individuals, brought about by a shared requirement for a resource in limited supply, and leading to a reduction in the survivorship, growth and/or reproduction of at least some of the competing individuals concerned” BIOS 6150: Ecology - Dr. S. Malcolm. Week 5: Interspecific Competition Slide - 2 3. Interspecific competition between 2 barnacle species (Fig. 8.2 after Connell, 1961): “Click for pictures” BIOS 6150: Ecology - Dr. S. Malcolm. Week 5: Interspecific Competition Slide - 3 4. Gause's Paramecium species compete interspecifically (Fig. 8.3): BIOS 6150: Ecology - Dr. S. Malcolm. Week 5: Interspecific Competition Slide - 4 5. Tilman's diatoms exploitation/scramble (Fig. 8.5): BIOS 6150: Ecology - Dr. S. Malcolm. Week 5: Interspecific Competition Slide - 5 6. A caveat: “The ghost of competition past:” • Lack observed 5 tit species in a single British wood: • 4 weighed 9.3-11.4g and 1 weighed 20.0g. • All have short beaks and hunt for insect food on leaves & twigs + seeds in winter. • Concluded that they coexisted because they exploited slightly different resources in slightly different ways. • But is this a justifiable explanation? Did species change or were species eliminated? • Connell (1980) emphasized that current patterns may be the product of past evolutionary responses to competition - “the ghost of competition past” ! BIOS 6150: Ecology - Dr.
    [Show full text]
  • Is Ecological Succession Predictable?
    Is ecological succession predictable? Commissioned by Prof. dr. P. Opdam; Kennisbasis Thema 1. Project Ecosystem Predictability, Projectnr. 232317. 2 Alterra-Report 1277 Is ecological succession predictable? Theory and applications Koen Kramer Bert Brinkman Loek Kuiters Piet Verdonschot Alterra-Report 1277 Alterra, Wageningen, 2005 ABSTRACT Koen Kramer, Bert Brinkman, Loek Kuiters, Piet Verdonschot, 2005. Is ecological succession predictable? Theory and applications. Wageningen, Alterra, Alterra-Report 1277. 80 blz.; 6 figs.; 0 tables.; 197 refs. A literature study is presented on the predictability of ecological succession. Both equilibrium and nonequilibrium theories are discussed in relation to competition between, and co-existence of species. The consequences for conservation management are outlined and a research agenda is proposed focusing on a nonequilibrium view of ecosystem functioning. Applications are presented for freshwater-; marine-; dune- and forest ecosystems. Keywords: conservation management; competition; species co-existence; disturbance; ecological succession; equilibrium; nonequilibrium ISSN 1566-7197 This report can be ordered by paying € 15,- to bank account number 36 70 54 612 by name of Alterra Wageningen, IBAN number NL 83 RABO 036 70 54 612, Swift number RABO2u nl. Please refer to Alterra-Report 1277. This amount is including tax (where applicable) and handling costs. © 2005 Alterra P.O. Box 47; 6700 AA Wageningen; The Netherlands Phone: + 31 317 474700; fax: +31 317 419000; e-mail: [email protected] No part of this publication may be reproduced or published in any form or by any means, or stored in a database or retrieval system without the written permission of Alterra. Alterra assumes no liability for any losses resulting from the use of the research results or recommendations in this report.
    [Show full text]
  • Misaligned Feeding Impairs Memories Dawn H Loh1,5*, Shekib a Jami2,5
    1 Misaligned feeding impairs memories 2 Dawn H Loh1,5*, Shekib A Jami2,5, Richard E Flores1, Danny Truong1, Cristina A Ghiani1,3, 3 Thomas J O’Dell4,5, Christopher S Colwell1,5*. 4 5 1Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine, 6 University of California Los Angeles, Los Angeles, CA 90095, USA. 7 2Molecular, Cellular, and Integrative Physiology Ph.D. Program, University of California Los 8 Angeles, Los Angeles, CA 90095, USA. 9 3Department of Pathology & Laboratory Medicine, David Geffen School of Medicine, 10 University of California Los Angeles, Los Angeles, CA 90095, USA. 11 4Department of Physiology, David Geffen School of Medicine, University of California Los 12 Angeles, Los Angeles, CA 90095, USA. 13 5UCLA Integrative Center for Learning and Memory, University of California Los Angeles, Los 14 Angeles, CA 90095, USA. 15 16 *Correspondence to: [email protected], [email protected]. 1 17 Abstract 18 Robust sleep/wake rhythms are important for health and cognitive function. Unfortunately, many 19 people are living in an environment where their circadian system is challenged by inappropriate 20 meal- or work-times. Here we scheduled food access to the sleep time and examined the impact 21 on learning and memory in mice. Under these conditions, we demonstrate that the molecular 22 clock in the master pacemaker, the suprachiasmatic nucleus (SCN), is unaltered while the 23 molecular clock in the hippocampus is synchronized by the timing of food availability. This 24 chronic circadian misalignment causes reduced hippocampal long term potentiation and total 25 CREB expression. Importantly this mis-timed feeding resulted in dramatic deficits in 26 hippocampal-dependent learning and memory.
    [Show full text]
  • S00265-020-02831-2
    Fear of the dark? A mesopredator mitigates large carnivore risk through ANGOR UNIVERSITY nocturnality, but humans moderate the interaction. Haswell, Peter; Kusak, Josip; Jones, Katherine; Hayward, Matt Behavioral Ecology and Sociobiology PRIFYSGOL BANGOR / B Published: 04/05/2020 Publisher's PDF, also known as Version of record Cyswllt i'r cyhoeddiad / Link to publication Dyfyniad o'r fersiwn a gyhoeddwyd / Citation for published version (APA): Haswell, P., Kusak, J., Jones, K., & Hayward, M. (2020). Fear of the dark? A mesopredator mitigates large carnivore risk through nocturnality, but humans moderate the interaction. Behavioral Ecology and Sociobiology, 74(62). http://10.1007/s00265-020-02831-2 Hawliau Cyffredinol / General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. 27. Sep. 2021 Behavioral Ecology and Sociobiology (2020) 74: 62 https://doi.org/10.1007/s00265-020-02831-2 FEATURED STUDENT RESEARCH PAPER Fear of the dark? A mesopredator mitigates large carnivore risk through nocturnality, but humans moderate the interaction Peter M.
    [Show full text]
  • Competition, Predation and Nest Niche Shifts Among Tropical Cavity Nesters: Ecological Evidence
    JOURNAL OF AVIAN BIOLOGY 36: 74Á/83, 2005 Competition, predation and nest niche shifts among tropical cavity nesters: ecological evidence Donald J. Brightsmith Brightsmith, D. J. 2005. Competition, predation and nest niche shifts among tropical cavity nesters: ecological evidence. Á/ J. Avian Biol. 36: 74Á/83. I studied cavity-nesting birds in an undisturbed site in lowland Peru to determine the relative roles of competition and predation in favoring termitarium nesting over tree cavity nesting. Occupancy rates of both nest boxes and natural tree cavities near 2% suggest that competition for tree cavities is not favoring the use of termitaria. Artificial nests and bird nests in termitaria suffer significantly lower predation rates than similar nests in old tree cavities showing that predation is favoring the use of termitaria over old tree cavities. Bird nests in newly excavated tree cavities also show lower predation rates than older cavities suggesting that cavity age is more important than substrate (tree or termitaria) per se. This study suggests that nest predation has a greater influence than nest competition on life history evolution for many cavity-nesting birds. D. J. Brightsmith, Department of Biology, Duke University, Durham NC 27708-0338, E-mail: [email protected] Nest site selection greatly influences avian natural transitions from nesting in tree cavities to nesting in history. Traits like clutch size, nestling period, renesting arboreal termite mounds. These transitions correlated probability, nest initiation date and nest predation rates with an increase in nestling period suggesting that all correlate with nesting niche (Lack 1968, Martin 1995, predation rates in termite mounds are significantly lower Robinson et al.
    [Show full text]
  • Unit Title: Population Ecology
    Colorado Teacher-Authored Instructional Unit Sample Science High School - Biology Unit Title: Population Ecology INSTRUCTIONAL UNIT AUTHORS Monte Vista School District Kana Condon Schuyler Fishman Loree Harvey Eric Hotz BASED ON A CURRICULUM OVERVIEW SAMPLE AUTHORED BY Boulder Valley School District Tammy Hearty Jefferson County School District Chalee McDougal Poudre School District Laura Grissom Colorado’s District Sample Curriculum Project This unit was authored by a team of Colorado educators. The template provided one example of unit design that enabled teacher- authors to organize possible learning experiences, resources, differentiation, and assessments. The unit is intended to support teachers, schools, and districts as they make their own local decisions around the best instructional plans and practices for all students. DATE POSTED: MARCH 31, 2014 Colorado Teacher-Authored Sample Instructional Unit Content Area Science Grade Level High School Course Name/Course Code Biology Standard Grade Level Expectations (GLE) GLE Code 1. Physical Science 1. Newton’s laws of motion and gravitation describe the relationships among forces acting on and between SC09-GR.HS-S.1-GLE.1 objects, their masses, and changes in their motion – but have limitations 2. Matter has definite structure that determines characteristic physical and chemical properties SC09-GR.HS-S.1-GLE.2 3. Matter can change form through chemical or nuclear reactions abiding by the laws of conservation of mass and SC09-GR.HS-S.1-GLE.3 energy 4. Atoms bond in different ways to form molecules and compounds that have definite properties SC09-GR.HS-S.1-GLE.4 5. Energy exists in many forms such as mechanical, chemical, electrical, radiant, thermal, and nuclear, that can be SC09-GR.HS-S.1-GLE.5 quantified and experimentally determined 6.
    [Show full text]
  • Biodiversity and Habitat Complexity: Niche Differentiation in an African
    Brittany Huntington San Francisco State University, California Biodiversity and Habitat Complexity: Niche Differentiation in an African Lake Overview Importance Findings Lake Tanganyika is an ideal system to test Increasing impacts from overfishing and My results suggest that habitat complexity plays the theory that complex habitats support deforestation make it crucial that we an important role in structuring species diversity. greater biodiversity. This lake has: understand the factors supporting the These trends warrant further research into niche • A highly diverse ecosystem extraordinary biodiversity of this lake so that differentiation in this system. • Numerous endemic species, including littoral snails we can better protect this ecosystem. Productivity • Distribution and diversity patterns that are poorly Species Richness vs. Algal Biomass Gastropod diversity vs. Algal Biomass Species Richness vs. GPP 1.8 12 10 e 2 2 R = 0.4042 R2 = 0.6524 understood R = 0.3315 9 10 1.4 Scientific Approach P = 0.0491 8 8 1 7 6 6 0.6 Species Richness Species 5 Species Richness 4 Ind H Diversity Shannon 0.2 4 Hypothesis 0.00 5.00 10.00 15.00 20.00 0.00 5.00 10.00 15.00 20.00 0.00 50.00 100.00 150.00 Sites with high benthic primary productivity (snail food supply) Benthic Algal Biomass (ug/cm2) Benthic Algal Biomass (ug/cm2) GPP (mg C / m2-h) and high habitat complexity (high niche complementarity) Fig 1Fig 2Fig 3 support greater diversity of snails. Fig 1 & 2 Increased primary productivity is correlated to decreased Observed snail distributions on rocky substrate species richness and diversity.
    [Show full text]
  • Hominid Paleoecology and Competitive Exclusion
    YEARBOOK OF PHYSICAL ANTHROPOLOGY 24:101-121(1981) Hominid Paleoecology and Competitive Exclusion: Limits to Similarity, Niche Differentiation, and the Effects of Cultural Behavior BRUCE WINTERHALDER Department of Anthropology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514 KEY WORDS Paleoanthropology, Hominid paleoecology, Competitive exclusion principle, Single species hypothesis, Compression hypothesis ABSTRACT Fossil evidence from the Plio-Pleistocene of Africa apparently has confirmed a multi-lineage interpretation of early hominid evolution. Empir- ical refutation of the single species hypothesis must now be matched to the ev- olutionary ecology theory, which can underwrite taxonomic assessment and help to explain sympatric hominid coexistence. This paper contributes to that goal by reassessing the ecological rationale provided for the single-species hypothesis. Limiting similarity concepts indicate that the allowable ecological overlap be- tween sympatric competitors is greater than the degrees of metric overlap often advanced as standards for identifying fossil species. Optimal foraging theory and the compression hypothesis show that the initial ecological reaction of a hominid to a sympatric competitor would likely be micro-habitat divergence and possibly also temporal differentiation of resource use. The long-term, evolutionary re- sponse is niche divergence, probably involving diet as well. General niche par- titioning studies suggest that diet and habitat are the most common dimensions of niche separation, although temporal separation is unusually frequent in car- nivores. The equation of niche with culture, basic to the single-species hypothesis, has no analytic meaning. Finally, four minor points are discussed, suggesting that (a) extinction is not unlikely, even for a long-lived and competitively com- petent hominid lineage, (b) parsimony is fickle, (c) interspecific mutualism may jeopardize survival, and (d) generalists are subordinate competitors, but for hom- inids, seemingly, successful ones.
    [Show full text]
  • Scanned by Scan2net
    BERICHTE aus dem INSTITUT FÜR MEERESKUNDE an der CHRISTIAN-ALBRECHTS-UNIVERSITÄT ·KIEL NR. 293 Factcrs causing the zonation of three Fucus species (Phaeophyta) in the intertidal zone of Helgeland (German Bight, North Sea) Testing the validity of Keddy's 'competitive hierarchy model' "'.".~~~ / ........r,:"' ~ < ; -. ~-""} '"-''' '""""- "-"''' by Ralf Karez Kiel 1997 Kopien dieser Arbeit können bezogen werden durch: Institut für Meereskunde an der Universität Kiel -Bibliothek- Düsternbrooker Weg 20 D-241 05 Kiel Germany ISSN 0341-8561 Diese Arbeit wurde von der Mathematisch­ Naturwissenschaftlichen Fakultät der Universität Kiel 1996 als Dissertation angenommen. CONTENTS Glossary ................................................................................................................................ 1 Summary .............................................................................................................................. 3 Zusammenfassung .............................................................................................................. 5 1 General Introduction .................................................................................................... 7 1.1 Description of the study site ................................................................................ 2 2 2 Competition................................................................................................................... 27 2.1 Introduction ..........................................................................................................
    [Show full text]
  • Competition and Niche Differentiation in Barley (Hordeum Vulgare) and Wheat (Triticum Aestivum) Mixtures Under Rainfed Conditions in the Central Highlands Oferitrea
    Netherlands Journal ofAgricultural Science 49 (2001) 95-112 Competition and niche differentiation in barley (Hordeum vulgare) and wheat (Triticum aestivum) mixtures under rainfed conditions in the Central Highlands ofEritrea A. WOLDEAMLAKI,2, L. BASTIAANS2 AND P.C. STRUIK2 * I University ofAsmara, College ofAgriculture and Aquatic Sciences, Department ofPlant Science, P. O. Box 1220, Asmara, Eritrea 2 Wageningen University, Department ofPlant Sciences, Crop and Weed Ecology Group, Haarweg 333, NL-6709 RZ Wageningen, The Netherlands • Corresponding author (fax: +31-317-485572; e-mail: [email protected]) Received 23 February 2001; accepted 30 June 2001 Abstract Barley and wheat mixtures were grown in the field using additive and replacement ratios at two locations (Halhale and Mendefera) in Eritrea during the 1997 and 1998 seasons. The aim was to assess yield advantage and to analyse competition and niche differentiation using a hyperbolic regression model. It proved advantageous to grow barley and wheat in mixtures because more land area was required to obtain the same yield in sole crops. The hyperbolic regression approach confirmed that barley and wheat grown in mixtures resulted in yield ad• vantages as a result of complementary use of resources. Barley showed greater competitive ability than wheat; for wheat, interspecific competition was larger than the intraspecific competition while for barley the intraspecific competition was greater than the interspecific competition. Niche differentiation indices were always above 1.0 indicating that the compo• nent crops did not inhibit each other from sharing resources in a complementary way. Key words: Competition, niche differentiation, yield advantage, mixed cropping, barley, wheat Introduction The cropping system hanfetz is practised in the highlands of Eritrea.
    [Show full text]