the real world
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DESCRIPTIONTHE REAL WORLD. Context for extinction. How many species are there? How do we find out?. Context for extinction. Extrapolate numbers based on observation that for every temperate species, there are two tropical counterparts = 3-5 million. - PowerPoint PPT Presentation
THE REAL WORLD...
Context for extinctionHow many species are there?
How do we find out?
Context for extinctionExtrapolate numbers based on observation that for every temperate species, there are two tropical counterparts = 3-5 million.
Use information on rate of discovery of new species to project forward, group by group = 6-7 million.
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.
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. http://www.youtube.com/watch?v=gZRgibEVXJU
Total # DescribedPhylumOrderE & TspeciesChordatesMammals 361 5,702 Birds 316 9,956 Reptiles 124 9,347 Amphibians 35 15,000 Fishes 165 40,000 ArthropodsInsects 71 1,065,000 Crustaceans 22 40,000 PlantsFlowering plants 783 272,655 Conifers and cycads 5 980 Ferns and allies 30 13,025 Molluscs126 70,000 Cnidaria Corals2 2,175
Total # DescribedPhylumOrderE & TspeciesChordatesMammals 361 5,702 Birds 316 9,956 Reptiles 124 9,347 Amphibians 35 15,000 Fishes 165 40,000 ArthropodsInsects 71 1,065,000 Crustaceans 22 40,000 PlantsFlowering plants 783 272,655 Conifers and cycads 5 980 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 & TspeciesDescribedChordatesMammals 361 5,702 99Birds 316 9,956 99Reptiles 124 9,347 99Amphibians 35 15,000 99Fishes 165 40,000 75?ArthropodsInsects 71 1,065,000 12Crustaceans 22 40,000 ?PlantsFlowering plants 783 272,655 55Conifers and cycads 5 980 1 Ferns and allies 30 13,025 87 Molluscs126 70,000 35Cnidaria Corals2 2,175 ?Viruses0 5,000 1 Bacteria0 4,750 0.5 Protists0 80,000 5 Fungi0 80,000 5 Platyhelminthes0 25,000 ? Rotifera0 1,800 ? Bryozoa0 5,000 ? Nematoda0 25,000 ?
http://ocean.si.edu/oceancensusHow 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 SpeciesUS Foreign TotalMammals 85276361Birds 93223316Reptiles 36 88124Amphibians 26 9 35Fishes 153 12165Molluscs123 3126Insects 67 4 71Arachnids 12 0 12Crustaceans 22 0 22Corals 2 0 2Animal totals619615 1,234
Flowering plants 782 1783Conifers and cycads 3 2 5Ferns and allies 30 0 30Lichens 2 0 2Plant totals817 3820
Grand totals 1,436618 2,054
Context for extinctionHow 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.
Individual species last on average 1- 10 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 (100-1000 x background rate).
Nene - Branta sandvicensis
Extinction: happens to all species eventually
Extinctionstochasticresults from normal, random changes; more important for smaller populationsconservation solution: maintain large population sizes
deterministicconsequence of some progressive change in environment - addition of predator, loss of food source, degradation/loss of habitat conservation solution: identify and manage causes
ExtinctionProbability of extinction increases as population size decreases
Probability increases with length of time
Extinctionhigher probability per unit time for species with:
smaller rangefewer subpopulationslow migration among subpopulations highly stochastic environmentlow genetic diversity?
Extinctionprimary species of concern tend to be large animals
no clonal propagationlong generation timesmall number of progenylow dispersal rates inability to recolonize or escape catastrophic eventsspecies in stable environments
Causes of extinctionPopulation extinctions occur due to:intrinsic factorsdemographic stochasticity changes in sex ratio, reproduction, survival
Causes of extinctionPopulation extinctions occur due to:intrinsic factorsdemographic stochasticity changes in sex ratio, reproduction, survivalAllee effect - threshold density or N below which population goes to extinctiondue to social interactions, physical alterations of environment, probability of finding a mate, etc.stanfordalumni.org
Causes of extinctionPopulation extinctions occur due to:intrinsic factorsdemographic stochasticitygenetic stochasticity - founder effect, genetic drift, inbreeding genetic load
Causes of extinctionPopulation extinctions occur due to:intrinsic factorsdemographic stochasticity genetic stochasticityextrinsic factorsenvironmental stochasticity variation in predators, pathogens, food supply (biotic)catastrophefires, floods, droughts (abiotic)
N ~ 501927, N =13,mostly males1932and severe winterextrinsic 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 vorticesF vortex
Extinction vorticesR 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
TimeNnormal demographic fluctuationsdecline in N small catastropheincreased popnvariance
Extinctions are forever - ?ivory-billed woodpeckersmoky madtomblue pikespoonhead sculpindeepwater sculpin
Extinctions are forever - ?ivory-billed woodpeckersmoky madtomblue pikespoonhead sculpindeepwater sculpin1942 last seen in US waters of L. Ontario1972 last seen in Canadian waters1999 3 caught in targeted trawls2004 12005 17 in standard assessment trawls2009 > 75 (depth > 90 m)Lazarus effect
When is population size too small (hopeless)?Przewalskis horse13Guam rail10black-footed ferret 6European bison 6Spekes gazelle 4dusky seaside sparrow 21..0
note: these are all captive (regulated) populations.
*About 1.8 million species but understood to be a significant under-estimate**Consider biases Conservationist letter example; species we tried globally to eradicate*Does this reflect relative abundance, importance, knowledge of each taxon, human biases?****************ask how many would recognize each species (woodpecker vs. sculpin)What do these species have in common (obscure)Which extinction is more likely to be true?how to tell if something is extinct? (sculpin example small, obscure, deep)