biol862a

Biology 862 - Structure and Evolution of Communities

Time: Thursday 2:10 - 4:00 pm. Place: HHS 156

Instructor: Ed Connor Office: Hensill Hall 545

Phone: 338-6997 E-mail: efc@sfsu.edu

This is a seminar course in which students will be exposed the the primary scientific literature on patterns in the structure of ecological communities and the processes that might lead community structure. We will focus on contrasting the extent to which ecological communities are structured by on-going, current ecological processes, by evolutionary changes in component species, or are apparently not structured at all.

During the first part of the semester the class as a group will read and discuss papers selected by the instructor, and the class members will individually select topics on which they will make a presentation, lead a discussion, and submit an annotated bibliography later in the semester. The topics selected should be relevant to the class focus on the Structure and Evolution of Communities.

The class grade will be based on the quality of the class presentation (50%), annotated bibliography (30%), and participation in discussions (20%).

The Varieties of Community Structure

Community structure usually is viewed as the presence of regularities in some quantitative measure of the species in a community that are likely to have arisen as a result of interactions between species. For example, the observation that at all sites where species A is present, species B is absent, or where species A and B are present together, species B uses different habitats than when species B occurs in the absence of species A. These sorts of observation have been taken as evidence that interactions between species affect the composition of a community and the physical forms and ecological niches of the component species. Secondarily, community structure is sometimes viewed as arising, at least in part, because of the effect of the physical environment on organisms. For example, different communities of rocky inter tidal algae and invertebrates occur in areas exposed to different wave energies.

The presence of "structure" in biological communities has been inferred from a variety data and community patterns. The data viewed as evidence of community structure include data on: morphology, behavior, food and habitat use, species richness, abundance, spatial pattern, geographical distribution, species composition, and trophic composition.

Community structure could arise because species are presently involved in intense ecological interactions that affect each other's behavior, use of resources, survival, and reproduction. Alternatively, community structure could reflect interactions that have occurred in the past which have lead, via natural selection, to community patterns that minimize fitness losses caused by negative species interactions, or maximize fitness gains caused by positive interactions.

To what extent is the structure of communities determined by on-going ecological processes or to an evolutionary response to past interactions? Furthermore, to what extent can we be confident that communities are indeed structured?

Suggested Topics

Morphology

Character Displacement in Anolis lizards

Character Displacement in Mustelids and Canids

Size ratios Limiting similarity

Trophic Structure

Scale dependence

Geographical Distribution

Patterns of overlap in geographical range

Patterns of species co-occurrence

Patterns of species richness

Habitat Use

Habitat partitioning in fish and birds

Species Composition

Species/Genus ratios

Binary species similarity data

Community Convergence

Phylogenetic Constraints

Coevolution