. Critical trends assessment Program 2003-04 report. Critical Trends Assessment Project; Ecosystem management; Environmental monitoring; Natural resources surveys. Critical Trends Assessment Program 2003-2004 Report. Perlesta Neoperia Acroneuria Paragnetina Agnetina Attaneuria Perlinella Fig. 5. Comparison of recorded versus extirpated + extinct perlid species by genus in Illinois. 1950s (Fig. 6b). All genera were a component of the perlid assemblage early m the century, but Acroneuria were by far the most commonly collected. As decades progressed, several genera were no longer routinely colle
. Critical trends assessment Program 2003-04 report. Critical Trends Assessment Project; Ecosystem management; Environmental monitoring; Natural resources surveys. Critical Trends Assessment Program 2003-2004 Report. Perlesta Neoperia Acroneuria Paragnetina Agnetina Attaneuria Perlinella Fig. 5. Comparison of recorded versus extirpated + extinct perlid species by genus in Illinois. 1950s (Fig. 6b). All genera were a component of the perlid assemblage early m the century, but Acroneuria were by far the most commonly collected. As decades progressed, several genera were no longer routinely collected, and one, Perlesta became very abundant, even "weedy". The latter is now the most commonly collected stonefly genus in terms of the number of sites visited and in abundance at those sites during summer. A significant, negative correlation exists between the percentage of records of Perlesta and Acroneuria, indicative of a wholesale change in perlid communities in Illinois streams. •Are changes more pronounced in certain reg/o/J5.^-Historically, the most diverse natural divisions in Illinois were the Grand Prairie, Shawnee Hills, and the Wabash Border, all with 30 or more species (Fig. 7). Other diverse divisions included the Upper Mississippi and Illinois River Bottomland and the Coastal Plain, both large river habitats. Losses varied greatly across natural divisions with three having one or zero losses, eight having lost more than one species, and three having added species. The Shawnee Hills, Wabash Border, and Middle Mississippi Border have maintained a diverse fauna. The Shawnee Hills, due to its topography, has retained nearly its full complement of species. The Wabash Border has maintained its species richness by the recent addition of small, unnoticed species, at the expense of several large perlids. The Middle Mississippi Border contains bluff streams influenced by groundwater. These streams, while not extremely diverse, maintain a nearly natural fauna.
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