Madhav Gadgil

Bio: Madhav Gadgil is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Population & Biodiversity. The author has an hindex of 45, co-authored 150 publications receiving 10267 citations. Previous affiliations of Madhav Gadgil include Jawaharlal Nehru Centre for Advanced Scientific Research & Harvard University.

Life Historical Consequences of Natural Selection

Abstract: The tremendous variation in the life-history patterns of organisms is best explained as adaptive.any organism has a limited amount of resources at its disposal, and these have to be partitioned between reproductive and nonreproductive activities. A larger share of resources to reproductive activities, that is, a higher reproductive effort at any age, leads to a better reproductive performance at that age; this may be considered a as profit function. This reproductive effort also leads to a reduction in survival and growth and consequent diminution of the reproductive contribution of the succeeding stages in the life history; this may be considered as a cost function. Natural selection would tend to an adjustment of the reproductive effort at every age such that the overall fitness of the life history would be maximized. A model of life history processes has been developed on the basis of these considerations. It leads to the following predictions: 1. If the form of the profit function is convex, or that o...

Indigenous Knowledge for Biodiversity Conservation

Abstract: Indigenous peoples with a historical continuity of resource-use practices often possess a broad knowledge base of the behavior of complex ecological systems in their own localities. This knowledge has accumulated through a long series of observations transmitted from generation to generation. Such ''diachronic'' observations can be of great value and complement the ''synchronic''observations on which western science is based. Where indigenous peoples have depended, for long periods of time, on local environments for the provision of a variety of resources, they have developed a stake in conserving, and in some cases, enhancing, biodiversity. They are aware that biological diversity is a crucial factor in generating the ecological services and natural resources on which they depend. Some indigenous groups manipulate the local landscape to augment its heterogeneity, and some have been found to be motivated to restore biodiversity in degraded landscapes. Their practices for the conservation of biodiversity were grounded in a series of rules of thumb which are apparently arrived at through a trial and error process over a long historical time period. This implies that their knowledge base is indefinite and their implementation involves an intimate relationship with the belief system. Such knowledge is difficult for western science to understand. It is vital, however, that the value of the knowledge-practice-belief complex of indigenous peoples relating to conservation of biodiversity is fully recognized if ecosystems and biodiversity are to be managed sustainably. Conserving this knowledge would be most appropriately accomplished through promoting the community-based resource-management systems of indigenous peoples.

The Concept of r- and K-Selection: Evidence from Wild Flowers and Some Theoretical Considerations

Abstract: The relationship of the demographic parameters of a population to its ecological niche constitutes one of the central problems of population biology. A most interesting theoretical notion pertinent to this problem is r- and K-selection (MacArthur 1962; Cody 1966; MacArthur and Wilson 1967; Hairston, Tinkle, and Wilbur 1970; Roughgarden 1971). The central idea of r- and K-selection is that populations living in environments imposing high density-independent (D.I.) mortality (r-strategists) will be selectively favored to allocate a greater proportion of resources to reproductive activities at the cost of their capabilities to propagate under crowded conditions, and conversely, populations living in environments imposing high density-dependent (D.D.) regulation (K-strategists) will be selectively favored to allocate a greater proportion of resources to nonreproductive activities, at the cost of their capabilities to propagate under conditions of high D.I. mortality. From the argument just stated, it may be deduced that the birth rate of an r-strategist will be greater than that of a related K-strategist. However, increased birth rate under conditions of high D.I. mortality is not sufficient evidence for an r-strategy, because, as demonstrated later in this paper, any increase in D.I. mortality must by itself produce a new equilibrium of birth and death rates at higher values of both. The crucial evidence needed for r- and K-selection is whether an organism is allocating a greater proportion of its resources to reproductive activities (r-strategists) than another related one (K-strategist) under any and all D.D. and D.I. mortality conditions.

Dispersal: Population Consequences and Evolution

Abstract: Most animal and plant populations are divided into a number of local populations with some dispersal of individuals from one site to another. A theoretical investigation of the phenomenon of dispersal suggests the following consequences: Isolated and poorly accessible sites will tend to become less crowded than an average site as a result of dispersal. An episode of dispersal will result in uneven crowding at the various sites. Variation in the degree of crowding resulting from dispersal will depress the total population size of a species over its entire range. Variation in the carrying capacity with time will lead to an analogous depression of the mean population size. Spatial variation in the carrying capacities of the sites will favor a sensitive response leading to a rapid increase in the emigration rate with crowding, while variation with time will disfavor a response very sensitive to crowding. Variation in space will favor the emigration of a small fraction of the population, while variation in time will favor the emigration of a larger fraction.

This fissured land : an ecological history of India

Abstract: Ecologist Madhav Gadgil and historian Ramachandra Guha offer fresh perspectives both on the ecological history of India and on theoretical issues of interest to environmental historians regardless of geographical specialization. Juxtaposing data from India with the ecological literature on lifestyles as diverse as those of modern Americans and Amazonian Indians, the authors analyze the social conflicts that have emerged over environmental exploitation and explore the impact of changing patterns of resource use on human societies. They present a socio-ecological analysis of the modes of resource use introduced to India by the British, and explore popular resistance to state environmental policies in both the colonial and post-colonial periods.

Biodiversity hotspots for conservation priorities

Abstract: Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Sources, Sinks, and Population Regulation

Abstract: Animal and plant populations often occupy a variety of local areas and may experience different local birth and death rates in different areas. When this occurs, reproductive surpluses from productive source habitats may maintain populations in sink habitats, where local reproductive success fails to keep pace with local mortality. For animals with active habitat selection, an equilibrium with both source and sink habitats occupied can be both ecologically and evolutionarily stable. If the surplus population of the source is large and the per capita deficit in the sink is small, only a small fraction of the total population will occur in areas where local reproduction is sufficient to compensate for local mortality. In this sense, the realized niche may be larger than the fundamental niche. Consequently, the particular species assemblage occupying any local study site may consist of a mixture of source and sink populations and may be as much or more influenced by the type and proximity of other habitats a...

Evidence for the existence of three primary strategies in plants and its relevance to ecological and evolutionary theory

Abstract: It is suggested that evolution in plants may be associated with the emergence of three primary strategies, each of which may be identified by reference to a number of characteristics including morphological features, resource allocation, phenology, and response to stress. The competitive strategy prevails in productive, relatively undisturbed vegetation, the stress-tolerant strategy is associated with continuously unproductive conditions, and the ruderal strategy is characteristic of severely disturbed but potentially productive habitats. A triangular model based upon the three strategies may be reconciled with the theory of r- and K-selection, provides an insight into the processes of vegetation succession and dominance, and appears to be capable of extension to fungi and to animals.