Conservation Biology Midterm-Biodiversity 2

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Devonian

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-75 % of animal spp, 35% of animal families-most plants are algaes, another Pangea - evidence of meteor strike- may have been double whammy

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Permian

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290-250mya
-boundary of paleozoic and mesozoic
-95% of all marine and terrestrial spp -most massive extinction
-trilobites, tree groups, amphibian groups, pangea formed, may have been high vulcanism resulting in a lot of competition and lost of habitats-coastal shelves and inland deserts-90% of spp, 50% of families-

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Triassic

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-180 mya, 65% of species, 35% of families-reptiles, marine mollusks

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Cretaceous

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65 mya
-lost 75% of spp on planet (modest # of families)
-dinosaurs, ptaurosaurs (flying dinos), mollusks, foraminiforins,

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Why are we worried about losing species

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-some species have large effect on other species-much of current extinction rate seems to be anthropogenic induced-rate of extinction seems to be higher now than over much of geologic time (historical rate over geological time is ~2spp per year)~ 10-50 million years to recover diversity lost in extinction events

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Are we at the beginning of the 6th major extinction-evidence for accelerated extinction

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Islands, many have lost bird species
-HI (50 lost during Polynesian invasion, 18 since Europeans)
-Guam (brown tree snakes have extirpated all 16 endemic birds since WWII)
-Polynesia (lost 2000 spp of birds in last 3000 years)
Continents
-New World (72-88% of large (>100lb) mammals have been lost since human colonization) human colonization in other places had a larger impact than in Africa because animals in Africa co-evolve with early humans but without them on other continents so when humans arrived animals weren’t wary
-Lake Victoria ciclids -were 300 spp very diverse but small, nile perch was introduced for food in 1920-have lost 200 spp by 1990-not all are extinct but in very small hiding spots
-Sentinal ridge in Andes had abundance of unknown plants -botanist in 1978 id’d 97 spp, by 1986 people and ag had moved in and 90 spp were gone
~some estimates of current extinction rate
~17,000-18,000 per year
~5-50% gone by 2020
some may be suspect but no denying large rate of extinction-not as big as other 5 yet-how it goes depends on us

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alpha-richness

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number of species found in a small, homogenous area
~areas with high alpha-richness often have many rare species

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beta-richness

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rate of change in species composition across habitats or among communities
~high beta-richness means that the cumulative number of species recorded rapidly increases as additional areas are censused along some environmental gradient-species may also drop out rapidly along such gradients, resulting in high rate of species turnover

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gamma-richness

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changes across larger landscape gradients

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species richness

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number of species of organisms present in an area, habitat or evolutionary lineage

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measures of evenness or species diversity indices

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weigh species by some index of their importance, such as their abundance, productivity, or size

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indices of similarity

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measures degree of difference among species (or populations, or biotas
~also to assess the degree of genetic simiarity among evolutionary lineages, or the diversity of habitat types across landscapes or ecosystems