Relative importance of within‐habitat environment, land use and spatial autocorrelations for determining odonate assemblages in rural reservoir ponds in Japan

Abstract

To clarify the major factors affecting odonate assemblages in rural reservoir ponds among withinhabitat 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.

Home Range, Movement, and Distribution Patterns of the Threatened Dragonfly Sympetrum depressiusculum (Odonata: Libellulidae): A Thousand Times Greater Territory to Protect?

“…This could be explained by the type and especially the structure (height and density) of vegetation; vegetation structure may to be more important than plant species composition, as has been observed for butterflies [42], [43]. A number of studies have highlighted the significant effects of macrophytes as keystone structures influencing dragonfly diversity [9], [18], [42].…”

Environmental Characteristics accounting for Odonate Assemblages in Rural Reservoir Ponds in Japan

“…In addition, the pond classification by cluster analysis in our current study tended to be concordant with the results of RDA. We thus concluded that there was only a slight conglomerate effect of spatial structured environmental factors considering there were only slight overlapping effects between the spatial autocorrelation and the other environment factors 13 . However, in our previous analyses, revetment length and vegetation covers were not predicted to have large effects.…”

“…Ignoring spatial autocorrelation JARQ 45 (2) 2011 K. Hamasaki et al may cause misleading associations between species composition and environmental factors 17,18 . We have already discussed using redundancy analysis (RDA) and variation partitioning to address this problem in Hamasaki et al 13 . On the other hand, environmental factors affecting the species composition may be obscured in such analyses if the environmental factors themselves are spatially structured 19 .…”

“…In addition, RDA combined with a stepwise parameter selection may mask the importance of the factors if there are strong multi-colinearities among the environmental factors 38 . In this paper, we re-analyzed our previous field research data using a different rationale from our previous study 13 . The odonate species composition was summarized objectively by applying three indirect gradient analyses, i.e., cluster analysis, indicator species analysis (IN-SPAN), and non-metric multidimensional scaling (NMDS).…”

The importance of allochthonous litter input on the biomass of an alien crayfish in farm ponds

“…First, this system provides numerous experimental units at the ecosystem level, which differ in surrounding forest cover, allowing us to test effects of allochthonous resources on crayfish population density. Second, although farm ponds are artificial systems, they have histories spanning centuries and are richly biodiverse, comparable to natural Japanese systems (Kadono 1998); many rare species of odonates, aquatic insects, and aquatic plants rely heavily on farm ponds (Kadono and Yuma 1995;Kadono 1998;Hamasaki et al 2009). Thus, the exploration of bottom-up factors influencing alien crayfish abundance is important for biodiversity conservation.…”