ecosystems%20student%20s08

ecosystems%20student%20s08 - Native mussel distribution...

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1 1986 1990 1992 1994 Native mussel Zebra mussel distribution distribution These figures show the spread of zebra mussels (green highlighted area, which represents >100 mussels per m2) and the simultaneous decline of native mussels (blue highlighted area, which represents >1 mussel per m2) for 1986 (top panel) through 1994 (bottom panel). Lake St. Clair (fed by Lake Huron). ht p:/ www.glerl.noaa.gov/pubs/brochures/mus elpop/mus elpop.pdf Individual native mussels (46 species) from 30 lake-wide sampling sites 1986 1990 1992 1994 100 200 300 Zebra Mussels, continued…. Lythrum salicaria L. Purple Loosestrife • Non-US, introduced late 1800s – 1 stalk Æ 300,000 tiny seeds/yr – densities up to 80,000 stalks/acre = potential 24 billion seeds/acre Problems: disrupts water flow in rivers/canals, detrimental to wetland diversity/habitats Can completely out-compete cattails Emerald Ash Borer Agrilus planipennis Asia native, found near Detroit, 2002 Adult beetles nibble on ash foliage Æ little damage Larvae feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients Æ kill tree Adult insect Larvae Healthy Ash Tree Diseased Ash Path of Larva - On this continent, EAB attacks only ash species - EAB is a good flyer but tends to fly only relatively short distances (about 1/2 mile) - EAB has no known predators in North America, although wood- peckers will eat them. - EAB infestation is always fatal to ash trees; within 1-3 yrs.
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2 Species with a large impact on community structure • Dominant species • Keystone species • Ecosystem “engineers” (Foundation species) Dominant species In Eastern Wisconsin, Beech trees are often the dominant forest species Why does a species become dominant in a community?
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ecosystems%20student%20s08 - Native mussel distribution...

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