Relative importance of within-habitat environment,land use and spatial autocorrelations for determining odonate assemblages in rural reservoir ponds in Japan |
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Authors: | Kenji Hamasaki Takehiko Yamanaka Koichi Tanaka Yukinobu Nakatani Nobusuke Iwasaki David S Sprague |
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Institution: | (1) Biodiversity Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba Ibaraki, 305-8604, Japan;(2) Natural Resources Inventory Center, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba Ibaraki, 305-8604, Japan;(3) Ecosystem Informatics Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba Ibaraki, 305-8604, Japan |
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Abstract: | To clarify the major factors affecting odonate assemblages in rural reservoir ponds among within-habitat environments, land
use around ponds and spatial autocorrelation, we surveyed odonate adults (Zygoptera and Anisoptera) in 70 study ponds in Ibaraki
Prefecture, Japan, during three sampling periods in 2005. Redundancy analyses (RDA) for these three factor groups were executed
to determine their strength in explaining the odonate species composition. Their relative contributions were also evaluated
by the method of variation partitioning. A total of 41 odonate species were recorded in the study ponds, and 24 of them, excluding
rare species, were used for our analysis. Summed effects including all three factor groups explained approximately 39% of
the variation in odonate species composition. We found that spatial autocorrelation was the most important, though the within-habitat
environment and land use had comparable effects. We conclude that spatial autocorrelation should be considered in this type
of analysis, though we could not clearly explain what caused such a spatial structure. Pond area and debris that had accumulated
at the bottom of ponds were selected as the within-habitat environment, and the forests and paddy fields around ponds were
selected for land use after the procedure of forward stepwise selection. These results suggest that the recent decrease of
forests around the ponds has had a negative effect on the odonate assemblages. |
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Keywords: | Freshwater ecosystem Spatial autocorrelation Principal coordinates of neighbor matrices (PCNM) Redundancy analysis (RDA) Variation partitioning |
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