1. Lecture 10 Species Concepts 1)Why are there species? 2)Species concepts: retrospective vs prospective, categories vs processes 3)PSC vs BSC: examples 4)Evolution of reciprocal monophyly: sorting of ancestral variation 5)Barcoding: species discovery and species identification

2. What are species?

3. Why are organisms grouped in clusters separated by phenotypic gaps? Darwin sums it up: "Firstly, why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms? Why is not all nature in confusion instead of species being, as we see them, well defined?” - Charles Darwin, The Origin of Species Why are there species?

4. Discrete units (species) are an inevitable consequence of: Why are there species?

5. Species Concepts A-Z: Agamospecies Concept Biological Species Concept Cladistic Species Concept Cohesion Species Concept Composite Species Concept Ecological Species Concept Evolutionary Significant Unit Evolutionary Species Concept Genealogical Concordance Genetic Species Concept Genotypic Cluster Concept Hennigian Species Concept Internodal Species Concept Morphological Species Concept Non-dimensional Species Concept Phenetic Species Concept Phylogenetic Species Concept I Phylogenetic Species Concept II Phylogenetic Species Concept III Polythetic Species Concept Recognition Species Concept Reproductive Competition Successional Species Concept Taxonomic Species Concept How do we recognize species?

6. “It is clear that arguments [about species concepts] will persist for years to come, but equally clear that, like barnacles on a whale, their main effect is to retard slightly the progress of the field.” Coyne (1992) “Given the recent pace of new proposals, each evolutionary biologist may soon have his or her own definition of species.” Schemske (2000) “It is as if on one hand we know just what ‘species’ means, and on the other hand, we have no idea what it means.” Hey (2001)

7. Why do we spend so much time on this?

8. Why do we recognize species? (Hey 2001 TREE)

9. The Typological Species Concept (TSC, Linnaeus) Group of inds differ from other groups by constant diagnostic characters “Type specimen” How do we recognize species?

10. Problems with the TSC: How do we recognize species?

12. Species Concepts A-Z: Agamospecies Concept Biological Species Concept Cladistic Species Concept Cohesion Species Concept Composite Species Concept Ecological Species Concept Evolutionary Significant Unit Evolutionary Species Concept Genealogical Concordance Genetic Species Concept Genotypic Cluster Concept Hennigian Species Concept Internodal Species Concept Morphological Species Concept Non-dimensional Species Concept Phenetic Species Concept Phylogenetic Species Concept I Phylogenetic Species Concept II Phylogenetic Species Concept III Polythetic Species Concept Recognition Species Concept Reproductive Competition Successional Species Concept Taxonomic Species Concept How do we recognize species?

13. BSC: Prospective PSC: Retrospective Emphasis on:

14. Darwin : -Explanation of how new species arise Modern Synthesis : Dobzhansky (1937)Mayr (1942) Genetics and the Origins of Species Systematics and the Origins of Species Species Concepts

15. Biological Species Concept (BSC) Ernst Mayr Every naturalist and every evolutionist is awed by the diversity of living nature. One cannot help asking oneself why there are so many species. Indeed, why are there species at all? Why is not the organic world a single continuity? Why has nature, and more precisely natural selection, favored the discontinuities among the species? What is the meaning of species? The answer the evolutionist gives to these questions is the Biological Species Concept.

16. Why interbreeding? Biological Species Concept (BSC) Ernst Mayr

17. South America North America BSC Example: Geminate Species Pacific Ocean Atlantic Ocean

18. Gradual formation of the Central American Landbridge

19. Snapping shrimp (Alpheus) Nancy Knowlton Smithsonian Tropical Research Institute

20. Geminate species P = Pacific C = Caribbean Knowlton et al. 1993 Science

22. 1) Pre-mating isolating mechanisms a) Temporal isolation. Individuals of different species do not mate because they are active at different times of day or in different seasons. b) Ecological isolation. Individuals mate in their preferred habitat, and therefore do not meet individuals of other species with different ecological preferences. c) Behavioral isolation. Potential mates meet, but choose members of their own species. d) Mechanical isolation. Copulation is attempted, but transfer of sperm does not take place. 2) Post-mating isolating mechanisms a) Gametic incompatibility. Sperm transfer takes place, but egg is not fertilized. b) Zygotic mortality. Egg is fertilized, but zygote does not develop. c) Hybrid inviability. Hybrid embryo forms, but of reduced viability. d) Hybrid sterility. Hybrid is viable, but resulting adult is sterile. e) Hybrid breakdown. First generation (F1) hybrids are viable and fertile, but further hybrid generations (F2 and backcrosses) may be inviable or sterile. Alternative: contrast pre-zygotic isolation (items 1+ 2a above) with post-zygotic isolation (2b-2e)

23. Hybridization Microbes and fossils Biological Species Concept (BSC)

24. Phylogenetic Species Concept (PSC) Joel Cracraft

26. A “cosmopolitan” copepod, Eurytemora affinis

27. Phylogenetic analyses: at least 8 cryptic species Lee (2000) Evolution

28. Phylogenetic Species Concept (PSC) Gene trees versus species trees (?) Expensive (?)

29. Discovered in 1986 (S. Chisholm) Very small (<1 µm), Ps picoplankton Probably most abundant autotroph on earth 100,000 cells per drop of sw 50% of atmosph O 2 Prochlorococcus

30. Why so successful? Light harvesting capabilities

31. Gulf Stream Sargasso Sea Flow cytometry signatures (chlorophyll fluorescence) Chlorophyll fluorescence Forward angle light scatter Moore et al. 1998 Science

33. 16S rRNA Low-light lineages Not monophyletic Monophyletic

34. Lee (2000) Evolution DNA Barcoding

35. Application of the PSC to DNA Barcoding Use of organelle genomes Animals: -mtDNA: cytochrome c oxidase-1 (CO1) Plants: -plastid: rbcL, matK, trn-psbA

36. Two rules for species discovery DNA Barcoding

37. Hickerson et al. 2006 Systematic Biology 10X