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Guild Structure - Introduction to Community Ecology - Lecture Slides, Slides of Ecology and Environment

Bundelkhand UniversityEcology and Environment

These are the lecture slides of Ecology. Key important points are: Guild Structure, Division of Available Resources, Insectivorous Birds, Shrubland Systems, Constancy of Niche Structure, Niche Requirements, Clusters of Species, Guild Membership

Typology: Slides

2012/2013

Uploaded on 01/25/2013

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Guild Structure
•Cody (1975) demonstrated that the division of
available resources amongst sets of
insectivorous birds in shrub grasslands results
in the projection upon each resource
dimension of almost identical niches within
Californian chaparral, Chilean matorall and
South African machia
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Guild Structure

  • Cody (1975) demonstrated that the division of available resources amongst sets of insectivorous birds in shrub grasslands results in the projection upon each resource dimension of almost identical niches within Californian chaparral, Chilean matorall and South African machia

Guild Structure

  • While a set of resources may be divided by consumers in an infinite number of ways, in reality the realized niches of each species showed a remarkable similarity in these three shrubland systems – despite the fact each is colonized by a taxonomically distinct set of species

Guild Structure

  • Similar constancy of niche structure in parallel communities is recorded among assemblages of montane lizards in Chile and California (Fuentes 1976), coral reef fish assemblages of the Atlantic and Pacific (Gladfelter et al. 1980) and ‘finch’ communities (Schluter 1986)

Guild Structure

  • What is a guild?

“Any group of species that exploit the same class of environmental resources in a similar way”

Guild Structure

  • Furthermore, you do not have to group species together in terms taxonomic positions, but rather on their niche requirements

Guild Structure: evidence

  • The basic idea is that within a community there are clusters of species interacting among themselves more strongly than with other species in the community

Guild Structure: evidence

  • Inger and Colwell (1977) made the first attempt at objective identification of guild structure within community matrices by seeking sharp discontinuities in the arrangement of resource use curves along resource axes (e.g. sudden increases in the variance of mean overlap)

Guild Structure

objective grouping

  • Joern and Lawlor (1981; Oikos) determined group membership of guilds through use of a clustering technique, progressively linking together (in unidimensional space) pairs and then clusters of species with highest overlap

Guild Structure

  • Joern and Lawlor’s analysis clusters together groups of species whose competitive interactions with others are strongest with that same guild (greater overlap)
  • This approach can be extended to multidimensional space using a range of clustering techniques (e.g. PCA or FA)

Guild Structure

  • While this approach effectively defines groups and identifies species, it does provide statistical significance to the clusters identified (but see Jaksic and Medel 1990)

Guild Structure: null model

  • Two deviations from the null model are possible: the difference in guild frequencies between the source pool and the assemblage might be unusually small or large

Guild Structure: null model

  • When the deviations are large, certain guilds are over- or under-represented in local assemblages
  • For example, in many land-bridge islands, there is a consistent absence of some bird families (MacArthur et al. 1972; Ecology)
  • Why?

Guild Structure: null model

  • How to achieve a correct null model?
  • Solution: drawing species randomly from an appropriate source pool to evaluating the ‘expected’ amount of variation in such island (or small) assemblages

Guild Structure: null model

  • Gotelli and Abele (1982; J of Biogeography) used the hypergeometric distribution to test for deviations in species richness of West Indian landbird families