Competition intra and inter-specific

presentation contain different type of interactions, competition-intra and inter-specific, mechanism of competition-Exploitation and Interference, Mathematical models of Competition i.e. Hutchinson Ratio, Exponential Growth, Logistic Model, Lotka-Volterra Competition Model, Tilman's Resource Model, Results of Competition i.e. Range restriction, Competitive Displacement, Competitive Exclusion , Competitive Displacement Hypothesis, Ecological Niche, Evolution of new species, Factors Affecting Competition, Case studies

1. Competition : Intra & inter-specific Master’s Seminar ENT-591 Speaker :- Ajay Sharma H-2017-01-M

2. Index Introduction Competition Type of competition - Intraspecific and interspecific competition -Interference vs exploitation Mathematical models of competition Results of Competition - Range restriction -Competitive displacement -Competitive exclusion Concept of Ecological Niche Case studies References

3. INTRODUCTION In natural world, no organism exists in absolute isolation, and thus every organism must interact with the environment and other organisms. When populations of different species interact, the effects on one on the other may be positive (+), negative (-) or neutral (0 ). Three of these combinations (+, +) (-, -) (+, -) are subdivided resulting in several type of important interactions & relationships.

4. Important interactions between two species Effect on X Effect on Y Type of Interaction + + Mutualism - - Competition + - Predation + - Parasitism + Commensalism - Amensalism

5. COMPETITION “Competition is a negative type of interaction between individuals, brought about by a shared requirement for a resource, and leading to a reduction in the survivorship, growth and/or reproduction of at least some of the competing individuals concerned.” “OR” “Competition in this strict sense occurs when a number of animals (of the same or of different species) utilize common resources, whose supply is short.” (Birch 1957)

6. Mutual use of a limited resource by populations of two or more species . Each individual adversely affect another in the quest for food (nutrients), living space, or other common needs. They harm one another is attempting to gain a resource. At high densities, competition for food, mates, and oviposition sites reduces fecundity and fertility ( Southwood 1975, 1977 ) . Ecological significance - separation of two closely related or similar organisms by the process of dispersal or adaptations

7. Outline… ! Outcomes of Competition

8. -:Types of competition :- 1. On the basis of taxonomic relationship Intraspecific competition ( within-species )- It is an interaction in  population ecology , whereby members of the same species compete for limited resources. This leads to a reduction in  fitness  for both individuals. Example : Bracon hebetor (minute wasp)- internal parasitoid to larval stage of Indian mealmoth .

9. Individuals of the same species compete for the exact same thing in the environment; Therefore this is the strongest type of competition.

10. Characteristics of Intraspecific Competition :- The ultimate effect : decreased contribution of individuals to the next generations The resource must be in limited supply. Competing individuals are all essentially equivalent. The effect on any individual increases with increasing number of competitors

11. ( B) Interspecific competition ( b/w species ) :- Competition between different species compete for the same resources in an ecosystem. It can be violent, if the competing species are similar; but it is never as strong as intraspecific completion. Example: between entomo -pathogenic nematodes for lepidopterans larva.

12. Interactions in Interspecific C ompetition ( Thomas Schoener ) CONSUMPTION COMPETITION- Occurs when individuals of one species inhibit another species by consuming a shared resource . PREEMPTIVE COMPETITION- Occurs primary among sessile organisms where the competition by one individual precludes establishment (occupation) by others. OVERGROWTH COMPETITION- occurs when one organism literally grows over another (with or without physical contact), inhibiting access to some essential resource.

13. CHEMICAL COMPETITION- chemical growth inhibitors or toxins released by an individual inhibit or kill other species Ex . Sunflower ( A llelopathic ). TERRITORIAL COMPETITION- Results from the behavioral exclusion of others from a specific space that is defended as a territory. ENCOUNTER COMPETITION- when non-territorial meetings between individuals negatively affect one or both of the participant species male female

14. 2 . On the basis of mechanism Exploitation: In many cases, competing individuals do not interact with one another directly . Instead, individuals respond to the level of a resource, which has been depressed by the presence and activity of other individuals. It also referred to as Resource competition. Thus, it is an Indirect competition .

15. For example - Aphid  species competing over the sap in plant  phloem . Each aphid species that feeds on host plant sap uses some of the resource, leaving less for competing species . In case of grasshoppers , a thriving population of grasshoppers (all of one species) feeding on a field of grass (also of one species). The more grasshoppers there are, an increased energy expenditure in search of food and a decreased rate of food intake may all decrease a grasshopper’s chances of survival .

16. (b) Interference : Here individuals interact directly with each other, and one individual will actually prevent another from exploiting the resources within a portion of the habitat. These individuals interfere with foraging, survival, reproduction of others, or by directly preventing their physical establishment in a portion of the habitat. so it is also called Direct competition .

17. For example - Different species of Burying Beetles ( Nicrophorus sp. ) compete to other species of same genera for reproductive success . In another example, the presence of a barnacle on a rock prevents any other barnacle from occupying that same position, even though the supply of food at that position may exceed the requirements of several barnacles. In such cases, space can be seen as a resource in limited supply . ( Joseph Connell)

18. Mathematical Models of Competition

19. Hutchinson ratio By G. E. Hutchinson (1959)   The ratio of the size differences between similar  species when they were living together as compared to when they were isolated . V arious key attributes in species varied according to the ratio of 1.1-1.3 For Co-existence Morphological displacement in harvesting organs( C h. Disp.) of Closely related species

20. Exponential growth By Thomas Robert Malthus Any species can potentially increase in number according to geometric series. When t- is large, then this equation can be approximated by an exponential function N t = N Rt Nt = N e rt R- Offspring N- Population t- 1,2,3,…

21. There are 3 possible model outcomes :- Population exponentially declines (r < 0) Population exponentially increases (r > 0) Population does not change (r = 0) Parameter r is called: Malthusian parameter Intrinsic rate of increase Instantaneous rate of natural increase Population growth rate . Assumptions of Exponential Model: Continuous reproduction (e.g., no seasonality) All organisms are identical (e.g., no age structure) Environment is constant in space and time (e.g., resources are unlimited )

22. Very rare in nature because resources are finite and so not every individual in a population can survive, leading to intraspecific competition for the scarce resources. Applications of the exponential model Microbiology (growth of bacteria), Conservation biology (restoration of disturbed populations), Insect rearing (prediction of yield), Plant or insect quarantine (population growth of introduced species), Fishery (prediction of fish dynamics).

23. Logistic model by Pierre Verhulst ( 1838)- The rate of population increase may be limited, i.e., it may depend on population density : Logistic equation At low densities (N < < K), the population growth rate is maximum = r o . Population growth rate declines with population numbers, N, and reaches 0 when N = K. Parameter K is the upper limit of population growth (carrying capacity).

24. Carrying capacity K - The maximum number of individuals that can live in a population stably; numbers larger than this will suffer a negative population growth until eventually reaching the carrying capacity, whereas populations smaller than the carrying capacity will grow until they reach it. Three possible model outcomes Population increases and reaches a plateau (No < K). This is the logistic curve. Population decreases and reaches a plateau (No > K) Population does not change (No= K or No = 0) Assumptions of the logistic model: Each individual has identical ecological properties Instantaneous response to environmental change Limited space and constant food supply Age distribution is stable

25. Lotka - Volterra Competition Model Alfred James Lotka (1925) Vito Volterra (1926) Independently developed a general model of competition between species

26. Explain the outcome of competition between two species. Used to understand how different factors affect the outcomes of competitive interactions. It combines the effects of each species on the other. These effects are calculated separately for the first and second population respectively : N-  is the population size, t-  is time,  K-  is the carrying capacity,   r-  is the intrinsic rate of increase α - the relative competition coefficients (effect of one sp on other) dN / dt -Population growth rate

27. In the first equation: When α 12 <1 the effect of species 2 on species 1 is less than the effect of species 1 on its own members. Conversely, when α 12 >1 the effect of species 2 on species 1 is greater than the effect of species 1 on its own member. The α 21 N1 term in the second equation is interpreted in the same way.

28. The two graphs below show the zero isoclines for species 1 and species 2 NOTE:- The sp have higher carrying capacity always win ( sp endure more crowding than other sp ) Isocline: Zero population growth for a species. Zero isocline for N 1

29. Four possible outcome of the model Species 1 inhibits growth of species 2 and latter goes extinction Species 2 inhibits growth of species 1 and latter goes extinction

30. Unstable situation, both inhibit in a density dependent manner. Depending on initial density, either can make other extinct Each species inhibits its own population growth more than competitor. Neither can eliminate competitor

31. Assumptions:- Environment is homogenous & stable . Migration is not important . Co- existance requires a stable equilibrium point. Carrying capacities and competition coefficients for both sp is constants

32. Tilman's  Resource Competition Model or R-star concept R* - Tilman (1982, 1987) alternative Need to know the dependence of an organism's growth on the availability of resources

33. chap08 Competition and coexistence 35 Growth or loss rate Growth or loss rate Population size (a) (b) (c) 100 Species A Species B Species A Species B Loss 10 R* A R* B Loss Growth Resource level (R) Time Growth 10 R* B R* Resource level (R) Tilman ’ s R star concept of competition between two species A and B, based on their resource utilization curves. Initially A grows faster than species B Outcompetes species A, as resources become more scarce. R *- concentration of the resource required for growth of the species to equal its loss rate.

34. Results of Competition

35. Results of Intraspecific competition Dispersal Social interactions D ominance T erritoriality

36. Results of interspecific competition Usually leads to one of three possible evolutionary outcomes:- Range restriction-- each species is confined to a subset of the range where it is able to out-compete the other species. Competitive displacement-- the two species evolve in divergent directions , adapting to different resources or specializing in other ways that allow them to co-exist with little or no direct competition . Competitive exclusion-- one species is competitively superior and drives the other species to extinction.

37. Competitive Displacement Hypothesis If two competing species coexist in a stable environment, then they do so as a result of niche differentiation . If, however, there is no such differentiation , then one competing species will eliminate or exclude the other. ( Begon et. al. 1996) Different species having identical ecological niches (that is, ecological homologues) cannot coexist for long in the same habitat. Those one will be a better competitor and thus have higher fitness and eventually exclude the other. This hypothesis has been recognized as ' Gause's law’ or hypothesis', and 'the Competitive exclusion principle ’.

38. Eg . The replacement of the mediterranean fruit fly, Ceratitis caoitata W. around Sydney, Australia by the Queensland fruit fly, Dacus trvoni F.   (Andrewartha and Birch, 1954). In Israel the mealybug parasitoid,  Clausenia   purpurea  Ishii, displaced the established parasitoids  Leptomastix flavus   Mercet and Anagyrus kivuensis Compere ( Rivnay , 1964).

39. Ecological Niche The Ecological niche describes the functional position of an organism in its environment. A Niche comprises: The habitat in which the organism lives. The organism’s activity pattern : the periods of time during which it is aactive . The resources it obtains from the habitat.

40. Hutchinson (1957) defined niche- “a region (n-dimensional hyper volume) in a multi-dimensional space of environmental factors that affect the welfare of a species.” n- number of environmental factors important to survival and reproduction of a species. Each species occupies a unique ecological niche within its community.

41. The niche and interspecific competition Resource Use Use Species A Species B Competition When niches overlap, competition results Intensity of competition ∝ degree of niche overlapping

42. Role of Competition in evolution of new species influence natural selection Darwin’s theory natural selection and origin of new species completely based on competition .

43. Following Phenomenal evidences are used to deduce that competition has occurred in the past and has resulted in the origin of new species:- 1. Niche separation or Resource Partitioning 2. Habitat shift 3. Character displacement 4. Competitive exclusion 5. Competitive release Darwin’s finches are a good example to prove the end results of competition

44. FACTORS AFFECTING COMPETITION A. Physical factors i ) Temperature – ii) Light– iii) Moisture – iv) Climate – B. Nutritional factors i ) Availability of food regulate population abundance. ii) Kind and quality of food influence life cycle. iii) Host selection – monophagous , polyphagous – chemical factors in host selection .

45. C. Host Plant association factors- rapidity of growth, foliage characteristics, taste factors etc . D. Biotic Factors- i ) Type of Competition – within and among different species (Inter and intra specific). ii) Parasites and predators parasites like fungi, bacteria, protozoo , nematodes and various arthropods – predators like birds, mammals, reptiles, amphibions and insects check the population.  iii) Human population trend – Rapidly growing world population – growth rate projected world population – Indian population – resources

46. Case study-1 Crombie (1945, 1946, 1947 ) Red flour beetle, Tribolium confusum and the saw-toothed grain beetle, Qryzaephilus surinamensis as competitors with wheat flour as food. Tribolium was always the superior species, probably because it would eat the eggs and pupae of Qryzaephilus . While the latter would only eat Tribolium eggs. Tribolium eliminated Orvzaephilus from all environments . Different result occurred when cracked wheat instead of flour was used as food. Qryzaephilus could not pupate within the wheat grains, which provided a sufficient refuge for both species to coexist, in which the immature stages of the latter were especially protected .

47. Case study-2 Park and colleagues (Park , 1954, 1957 and Park et al., 1964). Between two Red flour beetle Tribolium confusum and Tribolium castaneum . Found that replacement of one species by the other was the rule, but critically dependent upon a variety of conditions . T . castaneum was always the superior competitor at 34°C and 70% R.H. and always inferior at 24°C and 30% R.H. But at intermediate temperatures and humidities , the outcome would vary from replicate to replicate. Park also found an additional factor affecting the outcome — the presence or absence of a pathogenic microsporidian parasite, Adelina tribolii which affects both species, but particularly T. castaneum .

48. chap08 Competition and coexistence 50 10 20 30 40 50 60 70 80 90 100 Hot Temperate Wet Cold Hot Temperate Dry Cold T. confusum T. castaneum Percent wins T. confusum generally wins in dry conditions T. castaneum did better in moist environments

49. CAse study-3 Bai and Macuar ( 1991) Parasitoids   Aphidius ervi H. ( Aphidiidae ) and  Aphelinus asychis W. ( Aphelinidae ) . attack pea aphid did not oviposit in pea aphids parasitized by the other species. Host discrimination depended on the recognition of internal cues. But Aphelinus asychis either could not recognize or ignored Aphidius ervi sexternal host marking pheromone. Under most conditions, A . ervi survived in super-parasitized hosts, killing competing  A. asychis larvae by physical attack and possibly physiological suppression. A . asychis survived only when it had substantially completed larval development before the host was super-parasitized by  A. ervi . It is suggested that competition for host resources incurs a cost, for the winner in terms of reduced size or increased development time and for the loser in terms of lost progeny and searching time.

50. summary Competition- The interaction between the two organisms of the same or different species striving for the same resource. Type- Intra-specific and Interspecific competition. It can be exploitative or interference type. Competition as a regulatory mechanisms of population dynamics and plays an important role in ecological and evolutionary processes. D ifferent competition models are helpful in understanding the competition among the members of a population Strategies of Competition can be: i ) complete exclusion of one species either 1 or 2 ii ) stable-The stable equilibrium may be achieved by - Niche separation , resource portioning or character displacement iii ) unstable equilibrium between the two species. Darwin’s theory of natural selection and origin of new species completely based on competition. Individual reduces the direct competition by specific physiological, morphological and behavioral adaptations for the existence of a species .

51. references: Bacaer N. 2011.Verhulst and the logistic equation (1838) In : A Short History of Mathematical Population Dynamics. Springer, London. pp 35-39. Birch LC. 1957. The meanings of competition. The American Naturalist 91:5-18. Southwood TRE. 1977. The relevance of population dynamics theory to pest status. In : Origins of Pest, Parasite, Disease and Weed Problems. Symposium of the British Ecological Society 18 (J.M. Cherrett , and G.R. Sagar , Eds.), British Ecological Society, London, UK. pp. 35–54. Southwood TRE. 1975. The dynamics of insect populations. In Insects, Science, and Society (D. Pimentel, Ed.), Academic Press, San Diego, CA. pp. 151–199. Tilman D. 1982.  Resource competition and community structure . Princeton: Princeton University Press. 296 p . Park T, Leslie PH and Mertz DB. 1964. Genetic strains and competition in populations of  Tribolium .  Physiological Zoology 37:97–162. Bai B and Mackauer M. 1991. Recognition of heterospecific parasitism: Competition between Aphidiid ( Aphidius ervi ) and Aphelinid ( Aphelinus asychis ) parasitoids of Aphids (Hymenoptera: Aphidiidae ; Aphelinidae ). Journal of Insect Behavior 4 :333-45 . Crombie AC. 1947. Interspecific competition. Journal of Animal Ecology 16:44-73 .