R AND K SELECTED SPECIES powerpoint presentation

life history strategies of r and k selected species and their role on population ecology

1. R- AND K -SELECTED SPECIES- power point presentation.

2. LIFE HISTORY STATEGIES Life history strategy is correlated with many aspects of an organisms reproductive strategy and life history , as well as with demographic variables such as -generation time -life span -population parameters such as population density and population dynamics. Invoked to predict the relative influences of density dependant versus density independent ecological influences on life stages and age classes. The most notable example of life history theory is that of r and k selection ( Mac Arthur and Wilson ,1967) based on their work on island biogeography.

3. POPULATION GROWTH The variable r and k in r/k selection comes from the logistic equation for population growth.i.e dN / dt = rN ( 1 – N/K ) r represents the intrinsic rate of natural increase of a species. Mathematically, r = (birth rate + immigration rate ) – (death rate + emigration rate) K refers to the carrying capacity of the environment ,that is the maximum density at which a population is able to exist in a given environment.

4. R selected species

5. K selected species

6. R vs K selected species

7. Equilibrium strategists

8. Opportunistic strategists

9. Periodic strategists

10. Kirk Winemuller’s (2005) triangular model of life history

11. Conclusion The distinguishing feature of the r- and k- selection paradigm was the focus on density-dependent selection as the important agent of selection on organisms’ life histories. The paradigm was challenged as it became clear that other factors, such as age-specific mortality, could provide a more mechanistic causative link between an environment and an optimal life history.(Streams 1976, 1977). The r- and k- selection paradigm was replaced by a new paradigm that focussed on age –specific mortality (Streams, 1976; Charlesworth , 1980). This new life-history paradigm has matured into one that uses age-structured models as a framework to incorporate many of the themes important to the r-k paradigm.

12. References Winemuller , KO. 2005. LIFE HISTORY STRATEGIES, POPULATION REGULATION, AND IMPLICATIONS FOR FISHERIES MANAGEMENT. Can.J.Fish.Aquat.Sci.62:872-885. Roff , D.A.1992. THE EVOLUTION OF LIFE HISTORIES: THEORY AND ANALYSIS. Chapman and Hall, New York. Stearns, S.C.1992. THE EVOLUTION OF LIFE HISTORIES. Oxford University Press, Oxford. King, Charles E. and watt W. Anderson, 1971. AGE-SPECIFIC SELECTION.2. The interaction between r- and k- during population growth. Am. Naturalist 105:137-156. MacArthur, Robert H. and Edward O.Wilson , 1967. THE THEORY OF ISLAND BIOGEOGRAPHY. Princeton University Press, Princeton, New Jearsey . Margalef , Ramon, 1958. Mode of evolution of species in relation to their places in ecological succession. 15 th Int. cong. Zool. Proc. 10:787-789. Charlesworth and Michael R.Rose , 1980 ; EVOLUTIONARY BIOLOGY OF AGING King. J.R. and G.A. McFarlane, 2003. Marine fish life history strategies: applications to fishery management. Fish. Manage. Ecol. 10:249-264.

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