Phylogeny and Speciation. Early Human Evolution and Migration. Mitochondrial Eve 2/15/17

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1 Phylogeny and Speciation Early Human Evolution and Migration Using phylogenies to understand evolution Human history Speciation Species concepts Allopatric and sympatric Reproductive isolating mechanisms February 15, 2017 Mitochondrial Eve Similar results from another study (Ingman 2000) All non- Africans are in this major clade Ancestor of all modern humans That does not mean only one individual was alive at that time! In a finite population, any set of homologous sequences can eventually be traced to a single individual. Similar results from another study (Ingman 2000) Ancestor of all modern humans All non- Africans are in this major clade 1

2 Synapomorphies have been highlighted (Ingman 2000) What about other genes? Mitochondrion is easy because there is no recombination (crossing over). All genes on the mitochondrion are inherited together so they have the same history. For nuclear genes, each gene will have it s own history! The phylogenetic relationships of the Y chromosome haplotypes of African and other world populations. The Y chromosome shows the same general pattern Y Ke et al. Science 2001;292: NY Times 20 What is a species? What is a species? Western Meadowlark Eastern Meadowlark Biological species concept Can they interbreed? Phylogenetic species concept Do they share a recent common ancestor? Morphological species concept Can you tell them apart? 2

3 Meadowlark phylogeny Eastern Western How do new species arise? Allopatric Speciation Allopatric Speciation on Islands Hawaiian Honeycreepers and Island age Frog speciation in response to habitat isolation Kok et al 2017 J. Biogeography 3

4 Figure 24.8 A. formosus A. nuttingi Reproductive Isolating Mechanisms Prezygotic barriers Habitat Temporal Behavioral Mechanical Gametic Atlantic Ocean Individuals of different species MATING ATTEMPT FERTILIZATION (a) (c) (e) (f) (g) Isthmus of Panama Pacific Ocean (d) (b) A. panamensis A. millsae Reduced Hybrid Viability Postzygotic barriers Reduced Hybrid Fertility Hybrid Breakdown Temporal : timing of reproduction differs FERTILIZATION VIABLE, FERTILE OFFSPRING (h) (i) (l) (j) (k) Behavioral : courtship behavior in Drosophila Mechanical isolation pygidium paramere 4

5 Damselfly genitalia Toad Hybrid Zone Figure Behavioral in Mating Calls According to the biological species concept, two animals are considered members of different species if they a) are members of different populations b) cannot mate and produce viable, fertile offspring c) are geographically isolated d) live in different habitats e) look different Extras Cynotilapia afra, introduced at West Thumbi Island in Lake Malawi in the 1960s, has split into two genetically distinct populations, located at the north and south ends of the island. How can scientists determine whether these populations are now different species, according to the biological species concept? a) See whether the two populations are morphologically different from each other: coloring, bone structure, and so on. b) Determine whether captured individuals from the two different populations will mate and produce offspring in a laboratory fish tank. c) Determine whether individuals from one population will interbreed with individuals from the other population when introduced into each other s native habitats. 5

6 Figure EXPERIMENT Some flies raised on starch medium RESULTS Starch Female Initial population of fruit flies (Drosophila pseudoobscura) Mating experiments after 40 generations Maltose Some flies raised on maltose medium Female Starch population 1 Starch population 2 Male Maltose Starch Male Starch Starch population 2 population Number of matings in experimental group Number of matings in control group 6