Extinctions Who goes extinct? When do they go extinct? Why do they go extinct?

47%G 16%F 82%G 51%F 57%G 22%F 60%G 26%F 53%G 22%F 50%G

ammonites *

brachiopods

Importance of Contingency Some Clades Within a Lineage Do Better Than Others ammonites: P/TR 2 lineages survive and re-radiate K/T all extinct Ecological Roles Filled by Different Lineages; e.g., “Reefs” ~550 Cambrian calcified microbes; archeocyanthans (sponge-like) ~450 Ordovician bryozoans; stromatoporoids; sponges ~250 Permian scleractinian corals ???

and maybe the end-Permian mass extinction: Basu et al. 2003 Science 302:1388

What Enhances Survival During a Mass Extinction Event? Jablonski 1986; Jablonski and Raup 1995 end-Cretaceous most recent, best fossil record bivalves, gastropods is survival random ? do traits which enhance survival during non-mass extinctions also affect survival during mass extinction events?

larval feeding ecology affects background extinction rates of species

long-lived clades have broad geographic ranges

body size does not affect the probability of survival

geographically widespread taxa are less likely to become extinct

Contingency plus Opportunity Mammals replaced dinosaurs

Lineage replacement may be either passive or competitive one lineage causes the extinction of another one lineage becomes extinct, another radiates

dinosaurs, mammals angiosperms, conifers; horses in NA only bivalves, brachiopods are an example of competitive replacement enhanced by a mass extinction event

Extinctions Africa/Eurasia Few extinctions. In Africa ancient In Eurasia mammoths, mastodons, wooly rhinos Australia (~40,000BP) Essentially all large mammals. 4 large species remained. Giant koalas, giant (hippo-sized) Diprotodon, giant kangaroos, giant wombats. 45 large species. 90%+ extinct. Also giant lizards, tortoises, snakes and large, flightless birds

North/South America (~12,000BP). Most extinguished North/South America (~12,000BP) Most extinguished. Exceptions are also ice age migrants (deer, puma, bison, caribou, moose, musk oxen). Mammoths, mastodons, ground sloths, giant camels, bison, bears, wolves, N. Am 33 genera S. Am. 46 genera (20 genera in previous 3 million years) New Zealand (~1000 yrs) Essentially all large species Moas, giant kiwis, Madagascar (~1000 yrs) Essentially all large mammals and birds. Giant lemurs, Elephant birds

%loss of large mammals Africa 14% N. America 73% S. America 79% Australia 86% Extinction happened at different times It is always soon after the arrival of humans Nobody else had invaded

Humans and extinction Human invasion associated with widespread extinction post-Pleistocene faunas of North America, northern Eurasia megafauna of Australia Avifauna of Pacific islands Steadman 1995 Science 267:1123 examined bone deposits on 40 Pacific islands bone deposits predate human colonization by tens of thousands of years two waves of human colonization Polynesians 1000-3500 yrs bp Europeans 100-300 yrs bp

Lanai hookbill Hawaiian rail Bishop’s o’o Black mamo Moa nalo Laysan rail

Extinction of the Polynesian avifauna Hawaii (colonized ~500-600 A.D.) endemic finches (honeycreeepers); flightless ducks, geese, ibis 60 endemic species extinct before European arrival 20-25 more extinctions in the last 200 years New Zealand (colonized ~800-1100 A.D.) endemic moas, kiwis, waterfowl 44 endemic species extinct within the last 1000 years 7 more extinctions in the last 200 years Easter Island (colonized ~500-1000 A.D.) complete deforestation 550 years b.p. fossil evidence of 2 rails, 1 heron, 2 parrots, 1 owl (all extinct) originally 25-30 nesting seabirds 8-10 species nest only offshore 13-16 species no longer nest anywhere nearby 1 species remains nesting on the main island

Galapagos Islands not inhabited until European discovery in 1535; minor human impact until ~1800 A.D. 0-3 vertebrate species extinct in 4,000-8,000 years << humans 21-24 extinctions since European discovery and human settlement

Reasons for Polynesian avifaunal extinction habitat loss human predation introduced predators (pigs, dogs, rats, snakes) introduced competitors (goats, mynahs*) introduced pathogens (esp., avian malaria) Steadman estimates that 10 species/populations lost from each of the islands (n=800) ---> 8000 species, ~2000 species of rails

Mass extinctions represent rare events on a continuum of extinction intensities Lineages may be lost, may become rare, or may diversify as a consequence of a mass extinction event Recovery is characterized by: 1) initial interval of low diversity dominated by geographically widespread, ecologically generalist species 2) expansion of opportunistic species 3) relatively rapid ecological diversification Because they so greatly change species composition, subsequent lineage diversification is not predictable but is contingent on which clades survive Heterogeneity in the recovery of molluscan faunas after the Cretaceous mass extinction may reflect sampling error or ecological contingency Humans are producing another mass extinction event, largely through habitat destruction