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Context for extinction How many species are there? How do we find out?

Context for extinction 1.Extrapolate numbers based on observation that for every temperate species, there are two tropical counterparts = 3-5 million. 2.Use information on rate of discovery of new species to project forward, group by group = 6-7 million. 3.Species size:species richness relationship – in terrestrial animals (~ 1 cm to a few meters), approximate empirical rule for each 10-fold reduction in length there are 100 x the number of species = 10 million. 4.Do intensive counts in small areas of each taxa, extrapolate to rest of available habitat

Estimates of beetle species richness (more than 1000 species recorded in one tree) in the canopies of tropical trees (about 50,000 species), and assumptions about the proportion of non-beetle arthropods that will also be present in the canopy, plus others that do not occupy the canopy – 30 million arthropods.

Total # Described PhylumOrderE & Tspecies ChordatesMammals 361 5,702 Birds 316 9,956 Reptiles 124 9,347 Amphibians 35 15,000 Fishes ,000 ArthropodsInsects 71 1,065,000 Crustaceans 22 40,000 PlantsFlowering plants ,655 Conifers and cycads Ferns and allies 30 13,025 Molluscs126 70,000 Cnidaria Corals2 2,175

Total # Described PhylumOrderE & Tspecies ChordatesMammals 361 5,702 Birds 316 9,956 Reptiles 124 9,347 Amphibians 35 15,000 Fishes ,000 ArthropodsInsects 71 1,065,000 Crustaceans 22 40,000 PlantsFlowering plants ,655 Conifers and cycads Ferns and allies 30 13,025 Molluscs126 70,000 Cnidaria Corals2 2,175 Viruses0 5,000 Bacteria0 4,750 Protists0 80,000 Fungi0 80,000 Platyhelminthes0 25,000 Rotifera0 1,800 Bryozoa0 5,000 Nematoda0 25,000

Total # Described% PhylumOrderE & TspeciesDescribed ChordatesMammals 361 5, Birds 316 9, Reptiles 124 9, Amphibians 35 15, Fishes ,000 75? ArthropodsInsects 71 1,065, Crustaceans 22 40,000 ? PlantsFlowering plants , Conifers and cycads Ferns and allies 30 13, Molluscs126 70, Cnidaria Corals2 2,175 ? Viruses0 5,000 1 Bacteria0 4, Protists0 80,000 5 Fungi0 80,000 5 Platyhelminthes0 25,000 ? Rotifera0 1,800 ? Bryozoa0 5,000 ? Nematoda0 25,000 ?

How many species are there?? So far, the Census of Marine Life comprised 15,304 species of fish and 194,696 to 214,696 species of animals and plants, estimated to be roughly 10 percent of the world's total. The census is adding about 150 to 200 species of fish and 1,700 species of animals and plants each year.

Total Endangered & Threatened Species US Foreign Total Mammals Birds Reptiles Amphibians Fishes Molluscs Insects Arachnids Crustaceans Corals Animal totals ,234 Flowering plants Conifers and cycads Ferns and allies Lichens Plant totals Grand totals 1, ,054

Context for extinction How many species are there? How do we find out? How many have recently gone extinct? Are current rates of extinction higher than historic (pre-human) rates?

Trends in recorded animal species extinctions since 1600, for which a date is known

All extant species will become extinct eventually – more than 99% of species that ever existed are now extinct. All extant species will become extinct eventually – more than 99% of species that ever existed are now extinct. Individual species last on average million years. If we assume 10 million species, we would then predict 100 to 1000 extinctions each century. Individual species last on average million years. If we assume 10 million species, we would then predict 100 to 1000 extinctions each century. Current rate: birds and mammals = 1% per century ( x background rate). Current rate: birds and mammals = 1% per century ( x background rate). Nene - Branta sandvicensis

Extinction: happens to all species eventually

Extinction stochastic results from normal, random changes; more important for smaller populations conservation solution: maintain large population sizes deterministic consequence of some progressive change in environment - addition of predator, loss of food source, degradation/loss of habitat conservation solution: identify and manage causes

Extinction Probability of extinction increases as population size decreases Probability increases with length of time

Extinction higher probability per unit time for species with: smaller range fewer subpopulations low migration among subpopulations highly stochastic environment low genetic diversity?

Extinction primary species of concern tend to be large animals no clonal propagation long generation time small number of progeny low dispersal rates – inability to recolonize or escape catastrophic events species in stable environments

Causes of extinction Population extinctions occur due to: intrinsic factors –demographic stochasticity – changes in sex ratio, reproduction, survival

Causes of extinction Population extinctions occur due to: intrinsic factors –demographic stochasticity – changes in sex ratio, reproduction, survival Allee effect - threshold density or N below which population goes to extinction due to social interactions, physical alterations of environment, probability of finding a mate, etc. stanfordalumni.org

Causes of extinction Population extinctions occur due to: intrinsic factors –demographic stochasticity –genetic stochasticity - founder effect, genetic drift, inbreeding – genetic load

Causes of extinction Population extinctions occur due to: intrinsic factors –demographic stochasticity –genetic stochasticity extrinsic factors –environmental stochasticity variation in predators, pathogens, food supply (biotic) –catastrophe fires, floods, droughts (abiotic)

N ~ , N =13, mostly males 1932 and severe winter extrinsic factorsintrinsic factors

Most extinctions are due to multiple factors interacting simultaneously For example: causes of fish extinctions in N. America: physical habitat alteration (73%) introduced species (68%) chemical pollution (38%) hybridization (38%) overharvest (15%)

Extinction vortices

F vortex A vortex

Extinction vortices R vortex (demographic, based on intrinsic rate of increase, r) chance decrease in N increases variance of the population growth rate Var(r) population becomes more vulnerable to environmental stochasticity Time N normal demographic fluctuations decline in N – small catastrophe increased pop’n variance

Extinctions are forever - ? ivory-billed woodpecker smoky madtom blue pike spoonhead sculpin deepwater sculpin

Extinctions are forever - ? ivory-billed woodpecker smoky madtom blue pike spoonhead sculpin deepwater sculpin 1942 – last seen in US waters of L. Ontario 1972 – last seen in Canadian waters 1999 – 3 caught in targeted trawls 2004 – – 17 in standard assessment trawls 2009 > 75 (depth > 90 m) Lazarus effect…

When is population size too small (hopeless)? Przewalski’s horse13 Guam rail10 black-footed ferret 6 European bison 6 Speke’s gazelle 4 dusky seaside sparrow 2…1..…0 note: these are all captive (regulated) populations….