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Species Diversity and Preservation I. Potential Test Questions. Distinguish threatened, endangered, and extinct species. Explain four characteristics common to many endangered species. Discuss the main human causes for endangered species.
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Potential Test Questions • Distinguish threatened, endangered, and extinct species. Explain four characteristics common to many endangered species. • Discuss the main human causes for endangered species. • Discuss ways to slow or stop the decline in species diversity.
Factors Affecting Biological Resources Natural Processes (e.g., fires) Land Use (e.g., urban development) Water Use (e.g., hydroelectric) Climate Change (e.g., global warming) (http://observer.guardian.co.uk/international/story/0,6903,1153513,00.html) Nonindigenous Species Environmental Contaminants (e.g., oil spills) Harvest (e.g., overfishing)
Definitions • Extinction:the irreversible loss or ‘death’ of a species. • Endangered species (ESA):a species in imminent danger of extinction throughout all or a significant portion of its range. (What is a species?) • Threatened species:a species that is likely to become endangered in all or a significant portion of its range.
Characteristics of Endangered Species • Extremely small range - lily on single hilltop near SF. • Large territories - California condor. (+ issue of Minimum Viable Populations) • Living on islands - endemics (living nowhere else); evolved in isolation from predators, disease, and competition. • Low biotic potential - blue whales. • Specialized breeding areas - green sea turtles. • Specialized feeding habitats - pandas and bamboo.
Extinction If extinction is a natural process, why should we be concerned about extinction?
Human-based Extinction: • Human disturbance dominates many landscapes, making • the processes of many ecosystems human-dominated.
Human-based Extinction: • :We affect species through: • 1. Habitat Destruction • 2. Hunting and Fishing • 3. Predator Control • 4. Pollution • 5. Genetic Assimilation • Diseases • Exotic Species Introductions
Habitat Destruction: conversion of wilderness into human-based habitat; mainly for farming, range use, and forestry, but also for urban centers. Iowa has lost much greater than 90% of its wetlands. Fragmentation can cause forests (or prairies) to slowly become small islands of wooded area that can be too small to maintain breeding populations. Fragmentation eliminates the core environment, expanding the amount of edge available for weedy species to invade, and eliminates the environment some species need to survive.
Critical Size of an Ecosystem Amazonia example: Thomas Lovejoy created patches of various sizes (from 1 to 1000 ha and a 10,000 ha 'mainland'). A hectare (ha) = 10,000 sq kilometers or ~ 2.5 acres
Results from Lovejoy’s Amazonia Studies A guild of insectivorous birds (that feed on insects fleeing swarming army ants) disappeared in 1, 10 hectare, and some 100 ha fragments plots. Pollinators, euglossine bees, would not cross 100 m cleared strips, so population biology of at least 30 plant families dramatically affected.
Results from Lovejoy’s Amazonia Studies Rain forest fragments in central Amazonia were experienced a dramatic loss of above-ground tree biomass that was not offset by recruitment of new trees. These losses were largest within 100 meters of fragment edges, where tree mortality was sharply increased by microclimatic changes and elevated wind turbulence. Permanent study plots within 100 meters of edges lost up to 36% of their biomass in the first 10 to 17 years after fragmentation.
Results from Lovejoy’s Amazonia Studies Dung and carrion feeding beetles responded similarly to other insects, so the decomposition process slowed. Much of the primate diversity went almost immediately extinct in the isolated fragments. Only 7 of 20 mammal species present in reserve areas persisted in the first isolated fragments, and many of those that persisted were those capable of surviving in disturbed areas or secondary vegetation.
Minimum Viable Populations • Populations that are large enough that inbreeding does not cause the species to go extinct. • If Minimum Viable Populationsare not maintained, the species cannot survive. (Plus, chance events have a greater likelihood of eliminating a species that is already reduced in numbers.) • Greater Prairie Chicken
Planned reserves on an ecosystem basis. For example, in Yellowstone National Park (for watershed and wildlife resources), more land would have to be added.
Preservation and Park Usage in the U.S.A. Habitat destruction does not end just because land is placed into a reserve/preserve/park. Threats to Parks: Islands of nature surrounded by destructive land use. 2. Roads, trails (especially ATVs and off-road vehicles). 3. Visitor impact:Yosemite National Park - 25,000 visitors for a 3-day weekend (cars, laundries, concessions, guest rooms, etc).
Strips of habitat running between patches of habitat. Corridors • Used to allow movement of species from one area to another to help maintain genetic exchange and prevent extinction. • However, corridors can also be a risk because they may act as a corridor fordisease, invasive species, or as traps for the species you are trying to protect.
Consider the large Pleistocene mammals - extinctions probably caused by human hunting - mammoths, mastadons wooly rhinos, and ground sloths. Hunting and Fishing
Hunting and Fishing • In the recent past, whales have been hunted to the brink of extinction. Bison were once in the 10’s of millions, but were reduced to less than 1000 individuals. Passenger pigeons - now extinct; once over 3 billion.
Predator/Pest Control • Involves top predators (keystone species). Wolves, mountain lions, gators. • American alligator: • top predator - keeps gar populations in check. • creates habitat diversity - islands created by nest mounds • gator trails - prevent marsh establishment • gator holes - provide habitat for other species in drought
Pollution Amphibians as early warning indicators. In North America, and world-wide, amphibian populations have drastically declined and deformities have increased.
Pollution Environmental estrogens: (DDT, PCBs, Dioxins) disrupt hormones; impact fish, reptilian, and amphibian reproduction. Acid precipitation: alters pH of water, thereby affecting species. Ozone depletion (due to CFCs): cause increased UV light penetration and so cause higher mutation rates, thereby affecting populations. Global warming: temperature alterations can cause population declines.
Genetic Assimilation Classic definition is that genes of species at low population numbers are at risk of being swamped if they hybridize with close relatives. With the use of genetically modified (GM) species in farming, for example, could include the assimilation of native species into closely related GM species.
Genetic Assimilation Red wolf: predator control and destruction of mature woodland caused a reduction in range and population size. By 1970s, the species had dwindled to a single population in eastern Texas, and this population is threatened by interbreeding with the close relative, the coyote (Canis latrans).
Disease Dutch elm disease owes its name to the fact that it was first identified in the Netherlands in 1921. Dutch elm disease was first found in the United States in Ohio in 1930. It has now spread throughout North America and has destroyed over half the elm trees in the northern United States.Dutch elm disease is caused by the fungus Ophiostoma ulmi which is transmitted by two species of bark beetles or by root grafting.
Powdery Mildew on Dogwoods (Dogwood Anthracnose) Powdery mildew, which is caused by the fungus Microsphaeria penicillata. Probably introduced into the United States near Connecticut and Washington State simultaneously in the mid-1970s. Although it entered the U.S.A. at two separate points, genetic analysis has shown that the causal organism is the same. However, the origin of this pathogen remains unknown, as it has yet to be identified on any species of dogwood occurring outside the U.S.
Disease American chestnut trees were once 1/4th of all trees in the Appalachian Mountains. Infection by a fungal blight destroyed all chestnuts of reproductive size.
Introduced Species The fungus that destroys the American chestnut was introduced with a shipment of nursery stock from China in 1904, so it was in actuality an introduced exotic species.
