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Red List index and Red List assessments as indicators of genetic erosion

Red List index and Red List assessments as indicators of genetic erosion. Caroline Pollock IUCN Red List Programme. Outline of talk. IUCN Red List : Red List categories and criteria Red List criteria and genetic erosion Red List Indices : Calculation

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Red List index and Red List assessments as indicators of genetic erosion

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  1. Red List index and Red List assessments as indicators of genetic erosion Caroline Pollock IUCN Red List Programme

  2. Outline of talk • IUCN Red List: • Red List categories and criteria • Red List criteria and genetic erosion • Red List Indices: • Calculation • Results for birds and amphibians • Interpreting RLI in terms of the 2010 target • Strengths and weaknesses, development of a sampled RLI

  3. Extinction risk IUCN Red List Categories • Extinct • Extinct in the wild • Critically Endangered • Endangered • Vulnerable • Near Threatened • Least Concern • Data Deficient • Not Evaluated

  4. THREATENED CATEGORIES A Population reduction Critically Endangered (CR) Restricted geographic range B Endangered (EN) Quantitative thresholds Small population size & decline C Vulnerable (VU) Very small or restricted population D E Quantitative analysis IUCN Red List Categories CRITERIA

  5. Population Size Time CriterionA Past, present or future population reduction Decline rates over 10 years or three generations: CR>80%(>90% for A1) EN>50%(>70% for A1) VU>30%(>50% for A1)

  6. Criterion B Restricted geographic range and fragmentation, continuing decline or extreme fluctuations Extent of occurrence or area of occupancy thresholds: EOO (km²) AOO (km²) CR<100 <10 EN <5,000 <500 VU <20,000 <2,000

  7. Criterion C Small population size and continuing decline Population size thresholds: CR<250 EN<2,500 VU<10,000 ... and number of mature individuals continuing to decline

  8. Criterion D Very small or restricted population Population size thresholds: CR<50 EN<250 VU<1,000 (or AOO <20 km²/5 locations (VU D2))

  9. = oh ohh! Criterion E Quantitative analysis Probability of extinction in the wild at least: CR50% in 10 years or three generations EN20% in 20 years or five generations VU10% within 100 years

  10. Red List Criteria and Genetic Erosion • Hybridisation • Inbreeding depression • Loss of reproductive individuals • etc… Loss of individuals = genetic erosion

  11. Red List Criteria and Genetic Erosion • Criterion A(rate of loss of mature individuals in the population) • Criterion B1b(v)+2b(v)(restricted range and continuing decline number of mature individuals) • Criterion C(small population size and continuing loss of mature individuals in the population) • Criterion E(quantitative analysis showing probability of extinction in the wild) Direct indication of genetic erosion

  12. Red List Criteria and Genetic Erosion • Criterion B (restricted range, fragmentation, continuing decline, extreme fluctuations) • Criterion D(small population size) Susceptible to rapid genetic erosion; inbreeding risks

  13. Red List Criteria and Genetic Erosion • Red List criteria attached to threatened categories can indicate loss of mature individuals in the population. • Near Threatened category can be used if criteria that are nearly met are recorded. • Population declines in lower categories not detected by Red List assessments: population-level studies more appropriate. • Course resolution.

  14. IUCN Red List Indices Measuring global trends in the status of biodiversity: Red List Indices for birds (Stuart Butchart et al., in prep.) Public Library of Science (PLoS) journal: PLoS Biology (http://www.plosbiology.org)

  15. How can we measure the rate of loss of biodiversity? For trends in components of biodiversity, CBD recommended indicators for trends in: 1. Extent of biomes/habitats 2. Abundance/distribution of species 3. Threat status of species 4. Genetic diversity of domesticated animals & cultivated plants 5. Coverage of protected areas 1. Extent of biomes/habitats 2. Abundance/distribution of species 3. Threat status of species 4. Genetic diversity of domesticated animals & cultivated plants 5. Coverage of protected areas

  16. IUCN Red List strengths: • Credible classification system, even if data incomplete/ imprecise; applicable at multiple scales • Comprehensive assessments for some groups & regions • Effective & extensive network gathering data • Well-organised programme to store & analyse data • Clear relevance for biodiversity loss (species extinctions) • High profile & widely used by decision-makers IUCN Red List weaknesses: • Categories provide course resolution of status • No discrimination of species with low levels of threat • Groups other than large vertebrates still poorly represented

  17. The IUCN Red List as an Indicator Smith et al. 1993: rate of increase of no. of species & net movement between categories • But approach criticised because: • Categories subjective • Listings biased • Most changes due to knowledge or taxonomy

  18. Red List Indices • Based on: • Assessments using quantitative criteria (IUCN 1994; IUCN 2001) • Completely assessed taxonomic groups (or a representative sample) • Category changes owing to genuine status changes only

  19. Red List Indices • Illustrate net changes over time in overall threat status (relative projected extinction risk) of species • Calculated for any representative set of species that have been fully assessed at least twice • So far applied to birds and amphibians

  20. 1988 2000 2004 1994 Birds: the best documented class of organisms

  21. Amphibians: first assessment 2004 & retrospective assessment 1980

  22. Calculating Red List Indices For species assessed in two consecutive assessments, no. of species in each category is multiplied by category weight Near Threatened 1 Vulnerable 2 Endangered 3 Critically Endangered 4 Extinct/Extinct in the Wild 5 Sum products to give score for the assessment

  23. Calculating Red List Indices • For each period between assessments, calculate % increase in score owing to genuine status changes • Index value for previous assessment scaled up or down by this % • Plotted on negative scale with index value set to 100 in the baseline year

  24. T = Wc.Nc(t) c  P = [(Wc(t,s)–Wc(t-1,s)).Gs]/Tt-1 s It = I(t-1).(1-Pt)where I(t-1) = 100 for first assessment year Calculating Red List Indices T = total score; Wc = the weight for category c; Nc(t) = number of species in category c at time t; P = proportional genuine change; c(t,s) = the category of species s at time t; It = the value of the index at time t; Gs = 1 if change (from t-1 to t) in category of species s is genuine (otherwise Gs = 0).

  25. Red List Index for Birds

  26. Red List Index for Birds Declines equivalent to 10% of species in NT and above deteriorating by one category

  27. The Red List Index for birds in different biogeographic realms

  28. The Red List Index for birds in different ecosystems

  29. The Red List Index for birds relevant to different treaties

  30. Category weights • 1. Equal steps (NT=1, VU=2, EN=3, etc) • Simple: reflects ordinal ranks of categories in terms of relative extinction risk • But steps between higher categories translate to greater increases in extinction risk 2. Weight categories according to relative extinction risk in order to examine trends in the most threatened species

  31. The Red List Index for birds (weighted by extinction risk) EX = 1, CR = 0.5, EN = 0.05, VU = 0.005, NT = 0.0005

  32. Emphasises loss of biodiversity due to imminent or potential species extinctions Captures large changes in populations of less threatened species Category weights: equal steps versus extinction risk approaches • Extinction Risk • Based on principles of extinction dynamics • Movement between lower categories have less influence over the index • Equal Steps • Simple • Trends driven by larger number of species (more robust) • But, weights reflect linear hierarchy of categories only

  33. Red List Indices for amphibians • First complete assessment for all 5,700 amphibian species completed 2004 • Categories for 1980 back-casted based on information on population trends, disease, habitat loss, spread of alien invasives

  34. A preliminary Red List Index for amphibians

  35. A preliminary Red List Index for amphibians in different biogeographic realms

  36. Yunnan newt Tylototriton shanjing:NT - overharvested in China Northern gastric brooding frog Rheobatrachus vitellinus:EX - ?chytridomycosis in Queensland Harlequin frog Atelopus varius:CR - chytridomycosis in Costa Rica & Panama

  37. Red List Indices for birds and amphibians

  38. Red List Indices weighted by extinction risk for birds and amphibians

  39. Interpreting Red List indices • Red List categories ranked according to relative projected extinction risk • RLI proportional to rate species slip towards extinction • RLI for birds shows rate of loss is still accelerating

  40. Identifying drivers of RLI trends • All Red Listed species have threats identified and classified according to a standard scheme • Genuine status changes for a species occurring in >1 realm assigned to realm(s) where the deterioration or improvement occurred

  41. Saker falcon Falco cherrug occurs in Palearctic, Indomalayan & Afrotropical realms. • Uplisted to EN in 2004 due to unsustainable exploitation in central Asia. • Genuine change assigned to Palearctic only Identifying drivers of RLI trends

  42. Red List Indices: strengths • Red List process: effective way of making meaningful inferences from imprecise/ incomplete data • RLI shows high representation within taxonomic group (based on status of all species worldwide) • Current population-based indices restricted to regions with adequate data, or based on potentially biased sample of common, easily surveyed & often widespread species

  43. Red List Indices: potential weaknesses • Distinguishing genuine status changes • Course resolution: wild populations need to undergo quite significant changes in size, trend or range to move into a different category • Data on trends in Least Concern taxa not captured; time lags between change occurring and this being detected

  44. Birds: 19881994 2000 2004 2009 • Amphibians: (1980) 2004 2009 • Mammals: 1996 2005 2010 • First assessments for: • reptiles (8,000 spp.) • freshwater fish (10,000 spp.) • sharks, rays & chimeras (1,000 spp.) • freshwater molluscs (5,000 spp.) • some plant groups Red List Indices for 2010

  45. Red List Indices after 2010 • Assessments for invertebrate & other marine groups • But regularly repeated complete assessments impractical for large and less well-known groups e.g. fungi (70,000 spp.); plants (280,000 spp.); insects (0.9 million spp.) • Aggregated Red List Index

  46. Sampled Red List Index Objective: Index representative of all taxonomic groups, biogeographic realms, ecosystems & status of species within each of these

  47. Sampled Red List Index

  48. Sampled Red List Index • Mammals • Birds • Reptiles • Amphibians • Fish

  49. Sampled Red List Index Stratified sample of species from major taxonomic groups, biogeographic realms, ecosystems & Red List categories (incl. Least Concern) • Stratify according to natural distribution in taxonomic groups, realms, ecosystems and Red List categories • But: • Not known for many groups • Can’t extrapolate from known groups • Large samples sizes required • Data limitations • Stratify equally between taxonomic groups, realms and Red List categories (smaller sample size required; data available; could weight to reflect natural distribution across groups, realms & categories when information becomes available) • But some bias towards smaller groups, threatened species and species-poor realms

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