Sampling adequacy of freshwater mussel surveys and variation of mussel species richness in Illinois wadeable streams

sampling adequacy;freshwater mussels;species richness;Random Forests;Adaptive Sampling;timed sampling;Illinois streams

Huang, Jian ; Cao ; Yong

关键词: sampling adequacy;    freshwater mussels;    species richness;    Random Forests;    Adaptive Sampling;    timed sampling;    Illinois streams;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/24475/Huang_Jian.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Freshwater mussels are one of the most imperiled groups of animals in North America. Effective conservation strategies and resource management of freshwater mussels require adequately characterizing local mussel assemblages. However, sampling protocols for mussel surveys, including sampling efforts, have not been well established and tested. Furthermore, the percentage of all species captured with a standard sampling effort (e.g., search of man-hours) may vary greatly among sites, introducing biases into our understanding of species-diversity patterns and temporal trends. In addressing both questions, I focused on time-based search, one commonly used sampling technique in stream mussel surveys in the present study. I sampled 18 wadeable-stream sites mainly in east-central Illinois, selected based on watershed size, dominant-substrate type, and historic species diversity. With 16 man-hour search per site, my sampling crew collected 27-942 individuals and 5-18 species per site. I estimated the total species richness at a site with Chao-1 method that accounted for imperfect species detectability. I measured sampling adequacy at a given effort as the % of all estimated species recorded. A frequently used effort, 4 man-hour search, captured 15-100% of all species with an average of 61%. Observed species richness was not significantly correlated with the estimated total richness until sampling effort reached 8 man-hours (Pearson’s r = 0.59, p < 0.05), which captured over 70% of all species at 2/3 of sites. A 10 man-hour search yielded much stronger correlation (Pearson’s r = 0.78, p < 0.01) and over 70% of all species at 72 % of sites. A Random-Forests (RF) regression model based on watershed and habitat characteristics accounted for 45% of total variance in sampling adequacy among sites at 4 man-hours. Sampling adequacy decreased with increasing stream size and substrate size, but increased with % of forests in the riparian zone and logs in streams. A second RF model was developed based on the same environmental variables to predict man-hours required for capturing 70% of all species (pesduo-R2 of 41%) at specific sites. I also showed that species richness at a site tended to increase with watershed size, stream size, % of open water in the riparian zone, but decrease with % of agricultural land-use. These findings should serve as a guide for setting standard sampling efforts (e.g., 10 man-hour search) for mussel surveys in Illinois and likely other Midwest states, and provide critical information for setting site-specific efforts in the future studies.