What Makes Populations and Species Vulnerable? Brook Milligan - PowerPoint PPT Presentation

What Makes Populations and Species Vulnerable? Brook Milligan Department of Biology New Mexico State University Las Cruces, New Mexico 88003 brook@nmsu.edu Fall 2009 Brook Milligan What Makes Populations and Species Vulnerable?

Rarity What makes populations and species vulnerable? Brook Milligan What Makes Populations and Species Vulnerable?

Rarity What makes populations and species vulnerable? Rarity But . . . Brook Milligan What Makes Populations and Species Vulnerable?

Rarity What makes populations and species vulnerable? Rarity But . . . Many types of rarity exist Examples of rarity Argyroxiphium macrocephalum (Haleakala silversword): limited to Haleakala Volcano, Maui, Hawaii, but very common within crater Setaria geniculata (knotroot bristlegrass): distributed from Massachusetts to California, south to Argentina and Chile; not selective regarding habitat, but everywhere sparse; 2 specimens in NM (Hidalgo and Do˜ na Ana Counties) Brook Milligan What Makes Populations and Species Vulnerable?

Dimensions of Rarity Geographic distribution narrow wide Habitat requirements restricted broad Local population size everywhere small somewhere large Brook Milligan What Makes Populations and Species Vulnerable?

British flora survey 160 species categorized by experts Geographic Distribution Wide Narrow Habitat Specificity Habitat Specificity Local Population Size Broad Restricted Broad Restricted Somewhere large 58 (36%) 71 (44%) 6 (4%) 14 (9%) common Everywhere small 2 (1%) 6 (4%) 0 (0%) 3 (2%) Brook Milligan What Makes Populations and Species Vulnerable?

Factors inreasing vulnernability Rarity narrow geographic range one or a few populations small population size specialized niche requirements restriction to rare habitat low population density Brook Milligan What Makes Populations and Species Vulnerable?

Factors inreasing vulnernability Rarity Correlates of rarity large home range large body size ineffective dispersers Brook Milligan What Makes Populations and Species Vulnerable?

Factors inreasing vulnernability Rarity Correlates of rarity Direct human exploitation subject to human hunting or harvesting Brook Milligan What Makes Populations and Species Vulnerable?

Factors inreasing vulnernability Rarity Correlates of rarity Direct human exploitation Correlated effects of human-induced habitat alteration aggregate permanently or temporarily characteristic of stable, pristine environments no prior contact with humans Brook Milligan What Makes Populations and Species Vulnerable?

Factors inreasing vulnernability Rarity Correlates of rarity Direct human exploitation Correlated effects of human-induced habitat alteration Evolutionary indications low genetic variability related to extinct or threatened species Brook Milligan What Makes Populations and Species Vulnerable?

Factors inreasing vulnernability Rarity Correlates of rarity Direct human exploitation Correlated effects of human-induced habitat alteration Evolutionary indications Complex habitat requirements seasonal migrants Brook Milligan What Makes Populations and Species Vulnerable?

Factors inreasing vulnernability Rarity Correlates of rarity Direct human exploitation Correlated effects of human-induced habitat alteration Evolutionary indications Complex habitat requirements Immediate indicators declining population size Brook Milligan What Makes Populations and Species Vulnerable?

International Union for the Conservation of Nature (IUCN) system Categories of species Categories applicable to worldwide status extinct extinct in the wild critically endangered endangered vulnerable near threatened least concern: include widespread and abundant species data deficient not evaluated Additional categories applicable to regional status regionally extinct not applicable: species not occuring naturally in a region or a rare migrant Brook Milligan What Makes Populations and Species Vulnerable?

Distribution of Species Total IUCN Red List: 41,415 species Extinct: 785 species Extinct in the wild: 65 species Endangered and vulnerable: 16,306 species critically endangered endangered vulnerable Brook Milligan What Makes Populations and Species Vulnerable?

Status of Major Taxonomic Groups Endangered and vulnerable species Mammals: 25% Birds: 12.5% Amphibians: 33% Assessed plants: 70% Brook Milligan What Makes Populations and Species Vulnerable?

IUCN Evaluation criteria Population size: total number of mature individuals Geographic range: total geographic area (B) currently alive (D) Population dynamics observable decline in numbers of individuals (A) predicted decline in numbers of individuals (C) extinction probability: probability of extinction within a specified time or number of generations (E) rarely used, but correlated with other factors how to calculate: PVA methods upcoming Brook Milligan What Makes Populations and Species Vulnerable?

IUCN Red List Criteria v3.1 IUCN Red List Criteria v3.1 A. Population size B. Geographic C. Declining D. Pop. E. Extinction reduction 1 Category range pop. size size probability km 2 % indiv. indiv. % Years Gen. Critically endangered ≥ 80–90 < 10-100 < 250 < 50 ≥ 50 10 3 Endangered ≥ 50–70 < 500–5,000 < 2,500 < 250 ≥ 20 20 5 Vulnerable ≥ 30–50 < 2,000–20,000 < 10,000 < 1000 ≥ 10 100 Source: http://data.iucn.org/themes/ssc/redlists/RLcats2001booklet.html 1. Reduction over 10 years or 3 generations. Brook Milligan What Makes Populations and Species Vulnerable?

Case study: Rocky Mountain locust ( Melanophus spretus ) Brook Milligan What Makes Populations and Species Vulnerable?

Case study: Rocky Mountain locust ( Melanophus spretus ) Major agricultural pest in 1870s $200 million in crop damage between 1873 and 1877 in Colorado, Nebraska and other states Brook Milligan What Makes Populations and Species Vulnerable?

Case study: Rocky Mountain locust ( Melanophus spretus ) Major agricultural pest in 1870s $200 million in crop damage between 1873 and 1877 in Colorado, Nebraska and other states “Greatest concentration of animals” (The Guinness Book of World Records) A swarm of Rocky Mountain locusts that flew over Nebraska on July 20–30, 1874, covered an area estimated at 198,000 square miles (almost twice the size of Colorado). The swarm must have contained at least 12.5 trillion insects with a total weight of 27.5 million tons. Brook Milligan What Makes Populations and Species Vulnerable?

Rocky Mountain Locust Distribution Brook Milligan What Makes Populations and Species Vulnerable?

Case study: Rocky Mountain locust ( Melanophus spretus ) Current status Now (virtually?) extinct Brook Milligan What Makes Populations and Species Vulnerable?

Case study: Rocky Mountain locust ( Melanophus spretus ) Current status Now (virtually?) extinct Historical causes Permanent and migratory phases of life cycle Waves of expansion from Rockies to plains Vulnerable because of habitat limitation in permanent breeding grounds: riparian regions in Rocky Mountains of Colorado Brook Milligan What Makes Populations and Species Vulnerable?

Case study: Rocky Mountain locust ( Melanophus spretus ) Current status Now (virtually?) extinct Historical causes Permanent and migratory phases of life cycle Waves of expansion from Rockies to plains Vulnerable because of habitat limitation in permanent breeding grounds: riparian regions in Rocky Mountains of Colorado Conservation status Rare or not? Conserve or not? Brook Milligan What Makes Populations and Species Vulnerable?