Definitions of diversity. Measuring species diversity. Choosing an index and interpreting diversity measures. Sampling problems. Structural diversity. Applications of diversity measures. Summary.

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Ecological Diversity and its Measurement

This book is the second of two volumes in a series on terrestrial and marine comparisons, focusing on the temporal complement of the earlier spatial analysis of patchiness and pattern (Levin et al. 1993). The issue of the relationships among pattern, scale, and patchiness has been framed forcefully in John Steele’s writings of two decades (e.g., Steele 1978). There is no pattern without an observational frame. In the words of Nietzsche, “There are no facts… only interpretations.”

https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1941447

The Problem of Pattern and Scale in Ecology: The Robert H. MacArthur Award Lecture

Three commonly used measures of diversity, Simpson's index, Shannon's entropy, and the total number of species, are related to Renyi's definition of a generalized entropy. A unified concept of diversity is presented, according to which there is a continuum of possible diversity measures. In a sense which becomes apparent, these measures provide estimates of the effective number of species present, and differ only in their tendency to include or to ignore the relatively rarer species. The notion of the diversity of a community as opposed to that of a sample is examined, and is related to the asymptotic form of the species—abundance curve. A new and plausible definition of evenness is derived.

Diversity and Evenness: A Unifying Notation and Its Consequences

Evolution and measurement of species diversity

To understand resource partitioning, essentially a community phenomenon, we require a holistic theory that draws upon models at the individual and population level. Yet some investigators are still content mainly to document differences between species, a procedure of only limited interest. Therefore, it may be useful to conclude with a list of questions appropriate for studies of resource partitioning, questions this article has related to the theory in a preliminary way. 1) What is the mechanism of competition? What is the relative importance of predation? Are differences likely to be caused by pressures toward reproductive isolation? 2) Are niches (utilizations) regularly spaced along a single dimension? 3) How many dimensions are important, and is there a tendency for more dimensions to be added as species number increases? 4) Is dimensional separation complementary? 5) Which dimensions are utilized, how do they rank in importance, and why? How do particular dimensions change in rank as species nuimber increases? 6) What is the relation of dimensional separation to difference in phenotypic indicators? To what extent does the functional relation of phenotype to resource characteristics constrain partitioning? 7) What is the distance between mean position of niches, what is the niche standard deviation, and what is the ratio of the two? What is the niche shape?

https://science.sciencemag.org/content/sci/185/4145/27.full.pdf

Resource Partitioning in Ecological Communities

Breeding bird censuses were made in Puerto Rico, Panama, and temperate United States, and a profile of foliage density was made for each. Using information theory formulae both diversity indices and measurements of difference between censuses and difference between habitats can be made. Based on these, the following can be verified directly from the data: 1. Puerto Rico has nearly as many bird species per layer as Panama and the temperate regions, but the Puerto Rican species appear to recognize fewer layers and certainly subdivide habitats much less. Thus different habitats are likely to have quite similar species in Puerto Rico, unlike Panama and temperate United States.

On the Relation between Habitat Selection and Species Diversity

The results of this study make possible the following generalizations. The members of avian communities resident in simple grassland habitats coexist by virtue of differences in habitat preferences and feeding behavior and in very tall vegetation by differences in feeding height. The sum of these ecological differences is constant for all communities. Using only two habitat indexes, vegetation height and its standard deviation, it is possible to predict (1) the number of species, (2) the differences in their feeding ecology, and (3) their relative habitat separation in the community which occupies this habitat. As these predictions are made for South American communities on the basis of the communities studied in North America, and as the predictions hold regardless of grazing or irrigation programs, it is suggested that these communities have a full quota of species which are optimally adapted to their current environment.

https://www.jstor.org/stable/info/2459081

On the Methods of Resource Division in Grassland Bird Communities

Evolutionary biologists (Hutchinson, 1957; MacArthur, 1965, and earlier; Patrick, 1963) have often discussed the possibility that a particular habitat contains the maximum number of species it is able to support. The question asked is, if additional (appropriate) species were available, could the habitat absorb them, with or without the elimination of species already present? If the answer to this question is negative and the habitats are saturated, we can expect to find similar numbers of species (of similar types morphologically) in habitats which are widely separated geographically but of like physical features. Little evidence can be found in the literature to verify this hypothesis, but Elton (1950, Ch. II) mentions the similarity between the numbers of species found in surveys of Greenland and southern England heaths (data from Longstaff and Roberts, respectively), and concludes that cc. . . the number of different kinds of animals that can live together in an area of uniform type rapidly reaches a saturation point.\" More extensive is the evidence presented by Patrick (1961, 1963, 1964), whose limnological studies reveal striking similarity in the numbers of species from all groups found in numerous rivers in North America and in some Amazon tributaries, in spite of a large species turnover.

Martin L. Cody

Papers

On the Relation between Habitat Selection and Species Diversity

On the Methods of Resource Division in Grassland Bird Communities

The Consistency of Intra- And Inter-Continental Grassland Bird Species Counts