Speciation As a Process

Great Ideas in scienceSpring 2008F. Levy

Speciation as a Process

Topic Outline

I. Species Concepts

Morphological - delineation

Phylogenetic - analysis using molecular tools

Biological Species Concept -gene pool assessment

II. Models of Allopatric Reproductive Isolation

Pleiotropy model--Selection driven

Epistatic model (Muller; Dobzhansky)--Neutral model

Chromosomal model--Drift driven (fitness trough)

III. Approaches to Study the Genetics of Reproductive Isolation

Genes, genomes, inheritance patterns

Crossing designs to estimate number of genes and intensity of effects and genome location

Reciprocal crosses and potential results

Backcrosses with marked chromosomes

IV. “Rules” of Speciation

Haldane’s rule

Pathway to RI - Orr’s rate paradigm

Useful Reference Books (Sherrod Library call number in parentheses)

Barigozzi, C. (ed.). 1981. Mechanisms of Speciation : Proceedings from the International Meeting on Mechanisms of Speciation. Accademia nazionale dei Lincei, Rome, Italy. A.R. Liss, New York.

Coyne, JA and HA Orr. 2004. Speciation. Sinauer Assoc., Sunderland, MA. (QH380.C68.2004)

Dieckmann, J. (ed.). 2004. Adaptive Speciation. CambridgeUniv. Pr., Cambridge, UK (QH546.A34.2004)

Endler, J. A. and D. Otte (eds.). 1989. Speciation and its Consequences. Sinauer Associates, Sunderland, MA.

(SHERROD: QH83 .S685 1989)

Giddings, L. V., K. Y. Kaneshiro and W. Anderson (eds.). 1989. Genetics, Speciation, and the Founder Principle. OxfordUniversity Press, New York. (SHERROD: QH455 .G467 1989)

Grant, V. 1981. Plant Speciation, 2nd edition. ColumbiaUniversity Press, New York.

SHERROD (has the first edition): 581.38 G767

Howard, D. J. and S. H. Berlocher (eds.). 1998. Endless Forms : Species and Speciation. OxfordUniversity Press, New York. (Sherrod QH380 .E54 1998)

Levin, D. A. 2000. The Origin, Expansion, and Demise of Plant Species. OxfordUniversity Press, New York. ( Sherrod QK 980 .L48 2000)

Powell, J. R. 1997. Progress and Prospects in Evolutionary Biology: The Drosophila Model. OxfordUniversity Press, New York.

Stebbins, G. L. 1950. Variation and Evolution in Plants. ColumbiaUniversity Press, New York.

(SHERROD: 581.15 St31)

Outline for Discussion of Speciation Genetics

Be ready to discuss:

--The general or “big” question(s) the paper strives to address.

--The specific issues associated with the big questions.

--The approach used in the study.

This does not mean a detailed iteration of all methods. It does mean a concise explanation of how they went about addressing the questions they raise. Are crosses used? If so, what types and why? Molecular methods should be distilled to explain their purpose.

--Results

Without a table by table reading, summarize the results that have bearing on the question. You may copy some tables to highlight points.

--What has the study accomplished. How has it contributed to an understanding of the big questions?

--What aspects of the question(s) remains open.

Some Questions to Address

**What approaches are used to understand the genetic basis of reproductive isolation (RI)?

**How many gene loci contribute to RI? Do they have major or minor effects on fertility?

**What has fine scale genetic mapping of RI factors shown that was not known previously?

**Where are the loci causing RI located (nucleus; cytoplasm; X chromosome; autosomes)?

**What are the genetic explanations for Haldane’s Rule and why is it important to distinguish among them?

**Are generalizations applicable and robust for speciation? If so, which?

**Is there a relationship between genetic distance, morphological divergence and reproductive isolation?

**How can theory and experimentation complement each other?