populations

1. How do _____ evolve? microevolution populations allele frequencies - genetic drift - natural selection - migration

2. How do _____ evolve? microevolution populations species over time, populations can diverge & produce two or more daughter species from one ancestral species each species must be reproductively isolated each species becomes adapted to its niche by natural selection allele frequencies reproductive isolation - genetic drift - natural selection - migration adaptation

3. How do _____ evolve? microevolutionmacroevolution populations species lineages (clades of species) allele frequencies reproductive isolation diversification - genetic drift - natural selection - migration why do some groups have more species than related groups? adaptation

4. one common ancestor clade of 3 surviving (modern) species 1 surviving species 2 daughter lineages, of equal age Evolutionary success = number of living species  Why does one lineage diversify into many more species than its less-successful sister lineage?

5. 2 living species of Bosellia - flat sea slugs - eat one algal genus - tropical only 134 species in sister clade Plakobranchidae - sides rolled up - eat >20 algal genera - tropics to poles

6. Some lineages undergoadaptive radiations, filling all available ecological niches and diversifying into many species 1) opportunity: ancestor colonized an empty habitat with many unoccupied niches... - went from marine into freshwater or terrestrial habitat - got into a new lake, or onto a new island - survived mass extinction of dominant competitors 2) specialization: when related species exploit different ecological niches (i.e., food or host), many related species can co-exist in one place without competing 3) key innovation: evolution of a trait that allows exploitation of new niches, or greater competitive ability

7. Adaptive radiation When an ancestor colonizes a new habitat, its offspring may undergo an adaptive radiation - descendents diversify (get different) and occupy all the available ecological niches - each lineage adapts, becomes phenotypically differentiated by natural selection (= ecological speciation in action) May follow colonization of islands, newly-formed lakes - could provide opportunities for sympatric speciation Often follows mass extinction events that remove previously dominant competitors

8. Adaptive radiation via natural selection Example: cichlid fishes in volcanic crater lakes in Africa - monophyletic assemblage of fishes arose in sympatry by descent from common ancestor that colonized new lake - each species maintains its differences by assortative mating: depends on ecological differences and mating preferences

9. Evidence for sympatric speciation in cichlids All fishes from Lake Mbo are each other’s closest relatives All fishes from Lake Bermin also group together Suggests they arose in sympatry, following an initial colonization event

10. Adaptive radiation 1: Disruptive selection Lake Victoria was completely dry 12,000 years ago - now contains 500 species of cichlid fish An adaptive radiation happened after an ancestral fish got washed into the empty lake when a river flooded Most species pairs have different feeding behaviors, due to the adaptive evolution of their jaws - by occupying different ecological niches, species avoid competing with each other (necessary for co-existence) Disruptive selection on feeding specializations can drive adaptive radiation, by promoting species divergence

11. Disruptive selection on feeding: Cichlid jaws (1) Diversification: each species feeds something different, due to adaptive evolution of their jaws front jaws - catching food back jaws - processing food

12. Adaptive radiation 2: Sexual selection Within a “feeding type,” there are often several sister species (each other’s closest relatives) that differ only in color All weird predators group together (sponge-eaters) All plankton-feeding species group together All normal predatory species group together

13. Adaptive radiation 2: Sexual selection Females with eye pigment alleles that see blue better prefer bluer males; females that see red better like redder males Sexual selection: female preference for color keeps different species from hybridizing reproductive isolation End up with a blue, a yellow, and a red sponge eater; .. a blue, a yellow, and red clam eater... etc males can be red, yellow, or blue with different markings

14. Adaptive radiation 2: Sexual selection sexual selection thus splits one group in two Mate choice is determined by coloration - strong assortative mating quickly leads to isolation of different color morphs - different species can interbreed without loss of fertility, but normally they are pre-zygotically isolated by mate choice Disruptive selection on feeding fueled diversification of sister species; sexual selection provided reproductive isolation one-two punch that drove the most explosive speciation in the history of vertebrates

15. Adaptive radiation 3: end of cichlid diversity? Recently, pollution has clouded Lake Victoria so badly, fish are unable to see color differences - species barriers are collapsing, as different species start hybridizing with each other Human activities that cloud the water are thus destroying cichlid biodiversity - unravels the mechanism of reproductive isolation by relaxing sexual selection - loss of evolutionary novelty, due to human disruption of the environment

16. 2) Specialization: why are there so many beetles? ~25% of described living species are beetles (flying insects) - more than 135,000 species of beetles feed only on angiosperms (flowering plants) other beetles are: - fungus-eaters - predators - aquatic evolution.berkeley.edu

17. 2) Specialization: why are there so many beetles? 2 factors may favor diversification in herbivorous beetles 2-A) Co-speciation - when one plant speciates (evolves into 2 new species), its pollinators and the herbivores that eat it may also speciate 2-B) Ecological specialization + host-shifting - specialization = eat one species of host plant (or animal, if you are a parasite) - many related species can co-occur without competing, which allows greater diversity of species in an area - speciation can occur by host-shifting (as in Rhagoletis flies)

18. 2-A) Plant-insect coevolution When a plant speciates, so may its pollinators and specialized herbivores herbivore (beetle) pollinator (butterfly)

19. 2-A) Plant-insect coevolution When a plant speciates, so may its pollinators and specialized herbivores Rain forest species Desert species Pollinators and herbivores may also form new species when their host plant speciates coevolution promotes speciation

20. 2-B) Specialization and “inordinate fondness” Each time a lineage of beetles started to feed on angiosperms (flowering plants), it quickly evolved into many more species than did its sister lineage that did not eat flowers - its rate of speciation increased, suggesting the association with flowering plants in turn promoted beetle biodiversity Farrell (1998) proposed that beetle diversity resulted from their associations with flowering plants: as plants diversified, so did their beetle pests Farrell 1998

21. Hunt et al. (2007) argued the radiation of beetles was due to: A) specialization on different plant parts in some groups (roots, flowers, fruit, leaves) 14,000 35,000  herbivory  predation  aquatic  eat fungus

22. Hunt et al. (2007) argued the radiation of beetles was due to: A) specialization on different plant parts B) frequent ecological shifts amongmajor feeding strategies 23,000 14,000 48,000 35,000 35,000  herbivory  predation  aquatic  eat fungus

23. Hunt et al. (2007) argued the radiation of beetles was due to: A) specialization on different plant parts B) frequent ecological shifts amongmajor feeding strategies C) partly just because beetle lineages rarely go extinct 23,000 14,000 48,000 35,000 35,000  herbivory  predation  aquatic  eat fungus

24. Some lineages undergoadaptive radiations, filling all available ecological niches and diversifying into many species 1) opportunity: ancestor colonized an empty habitat with many unoccupied niches... - went from marine into freshwater or terrestrial habitat - got into a new lake, or onto a new island - survived mass extinction of dominant competitors 2) specialization: when related species exploit different ecological niches (i.e., food or host), many related species can co-exist in one place without competing 3) key innovation: evolution of a trait that allows exploitation of new niches, or greater competitive ability

25. 3) key innovation: evolution of a trait that allows exploitation of new niches, or greater competitive ability For instance, one group of fish diversified in the Antarctic after evolving anti-freeze glycoproteins, allowing them to survive water temperatures below freezing 9 species, non-Antarctic (no anti-freeze) 123 species, Antarctic - anti-freeze glycoproteins - within Antarctic, species also diversified into benthic and pelagic forms, like lake fish

26. ‘Big 5’ mass extinction events During 5 mass extinctions, 50-90% of species disappeared over a period of one million years - the ‘big 5’ eliminated 20-60% of families of plants + animals (whole families, or kinds of organisms) end Permian extinction: 90% of marine species gone end Cretaceous K-T extinction, 65 Mya ago: bye-bye dinosaurs Triassic-Jurassic boundary, 215 Mya

27. Mass extinctions vs. background extinctions Despite their immediate impact, the Big 5 mass extinctions only account for 4% of total extinctions over the last 500 million yrs - 96% of species suffer background extinctions - they just die out, or differentiate into new species Episodic mass extinctions are important because they clear the way for new adaptive radiations (1) what causes them? (2) why do some species survive them?

28. Causes of mass extinction: Deep Impact Many forms of evidence support asteroid impact theory of K-T mass extinction, possibly others as well (1) iridium layer in rocks at the K-T boundary - rare on earth, common in meteors (2) microtektites also found in rocks at K-T boundary - little glass particles formed when minerals melt at impact - cool while flying through the air (3) huge crater found off Mexican coast, 180 Km diameter, dating to K-T boundary (4) extraterrestrial origin suggested for noble gases trapped in “buckey balls”, carbon spheres found at extinction boundaries

29. Causes of mass extinction: Deep Impact K-T Impact likely had numerous environmental consequences (1) injected SO2 and water into atmosphere, producing acid rain (2) global cooling as dust blocked sunlight (3) huge wildfires (4) massive earthquake and tidal wave, supported by geological evidence (5) massive die-off in ocean phytoplankton (photosynthetic plankton) disrupted marine food chains

30. Survivor’s guide to mass extinction Studies on marine snails (good fossil record) indicate that the lineages which survived mass extinctions had member species scattered in many different biomes, or environmentally different regions of the world - surviving lineages had some species in the deep sea, some in the tropics, some in cold water, etc In other words, more biogeographically diverse lineages were less likely to be wiped out by asteroid impact - hedges against the total wipeout of any one niche or region following a deep impact

31. Plant Evolution following Mass Extinctions Gymnosperms dominate Seedless plants # of families Angiosperms dominate First gymnosperms First angiosperms Lineages are often around, but not very successful, until a mass extinction event wipes out the dominant competitors  clears the way for adaptive radiation Mackenzie 2003

32. What makes a lineage an evolutionary “winner”...? 1) specialization to exploit different niches (co-existence without competition) 2) something that promotes rapid speciation: - sexual signaling - strong host association - tendency to get allopatrically isolated (dispersal) - fast-evolving gamete recognition proteins 3) key innovation (trait) allowing exploitation of new niches or greater competitive ability 4) in the long run, being biogeographicallywidespread – more likely to survive mass extinctions

33. Why only 2 Bosellia but 134 plakos? - flat sea slugs - eat one algal genus - tropical only 134 species in clade Plakobranchidae... - have sides of body rolled up, which protects stored chloroplasts from sun (key innovation?) - each species feeds on just one of >20 kinds of algae (specialized) - species live and mate on their host - colonized cold water habitats