. The Canadian field-naturalist. (a) Villosa fabalis. (b) Ptychobranchus fasciolaris Figure 3. Distributions of: (a) Villosa fabalis and (b) Ptychobranchus fasciolaris in the lower Great Lakes drainage basin, based on historical data. mens live or dead at time of collection not noted. With the exception of the OSUMZ, the museums did not have information on whether the specimens in their collections had been collected live or dead. Some other data sources, especially the academic surveys of recent years, did make this distinction. For the purpose of this study, all records, whether of live or d
. The Canadian field-naturalist. (a) Villosa fabalis. (b) Ptychobranchus fasciolaris Figure 3. Distributions of: (a) Villosa fabalis and (b) Ptychobranchus fasciolaris in the lower Great Lakes drainage basin, based on historical data. mens live or dead at time of collection not noted. With the exception of the OSUMZ, the museums did not have information on whether the specimens in their collections had been collected live or dead. Some other data sources, especially the academic surveys of recent years, did make this distinction. For the purpose of this study, all records, whether of live or dead specimens, were treated equally. Because mussel shells may persist in relatively good condition in the environment for years after their inhabitants have died, this approach could underesti- mate the number of species that declined in occur- rence over time in the study area. (4) Sampling effort variable. Sampling effort varied greatly from ama- teurs picking up a few shells for their collections to students conducting intensive sampling for their thesis research, and this has serious implica- tions for conducting time-trend analysis with the data. A measure of sampling effort was usually available for the academic surveys, most of which. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Naturalists' Club
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