Species Diversity of Ground Beetle Assemblages in the Distinctive Landscapes of the Yodo River Flowing Through Northern Osaka Prefecture, Central Japan
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Jpn. J. Environ. Entomol. Zool. 23(2):89− 100(2012) 環動昆 第 23 巻 第2号:89 − 100(2012) 原 著 Species diversity of ground beetle assemblages in the distinctive landscapes of the Yodo River flowing through northern Osaka Prefecture, central Japan Takahiro Fujisawa, Cheol-Min Lee 1)and Minoru Ishii Entomological Laboratory, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531 Japan 1)Present:Division of Forest Ecology, Korea Forest Research Institute, 57 Hoegi-ro, Dongdaemun-gu, Seoul 130-712, Korea (Received:April 17, 2012;Accepted:May 29, 2012) Abstract A field survey of ground beetles belonging to Carabidae was carried out using unbaited pitfall trapping to clarify the faunal characteristics and species diversity of assemblages in the riverbeds of the Yodo River, which runs through northern Osaka Prefecture and is characterized by landscapes such as the reed community at Udono and the“ Wando” ponds at Shirokita. Ground beetles were captured at four sites, Sites 1-4, consisting of a total of 12 sub- sites for two weeks a month, from April-December, 2008. A total of 5,622 individual ground beetles belonging to 51 species were captured. Dominant species in the whole sites were Pheropsophus jessoensis, Pterostichus prolongatus, Pterostichus eschscholtzii, Dolichus halensis and Chlaenius pallipes in decreasing order, and these five species totaled 3,192 individuals, which accounted for 56.8 % of the total individuals captured in this study. Dominant species at most sub- sites, were also common to those in the whole sites. Three out of the five dominant species, P. jessoensis, P. prolongatus and P. eschscholtzii were known as hygrophilous species, which shows that most parts of riverbeds of the Yodo River could be characterized by these hygrophilous species. However, at all three sub-sites of Site 1 at Udono, dominant species were different from those of other sub-sites, and the three sub-sites formed a cluster in a dendrogram drawn by the cluster analysis using a similarity index α . The results suggest that abundance of hygrophilous species has decreased because of aridification of the riverbed at Site 1. Key words:Carabid beetle assemblage, Species diversity, Riverbed, Reed community, The Yodo River. such as the bitterling, Acheilognathus longipinnis, and Introduction the dragon fly, Stylurus annulatus(Osaka Prefecture, 2000b;Ishii et al., 2002). The Yodo River is the largest river in Osaka Since 1971, these landscapes have been heavily Prefecture, central Japan, and is characterized by modified by river regulation works; ground water level landscapes of reed communities and“ Wando” ponds, has decreased and major beds have been dried because which are the calm flowing or dead waters created of extensive excavation, construction of the Amagase by accumulation of sediments on the groynes built to Dam in the upper stream and the Yodo River Weir in moderate water flow along the mainstream(Nishino, the lower stream has been carried out to stabilize the 2009). At Udono, a large reed community, which has water level(Koyama, 1999;Aya, 2004;Nishino, 2009), been maintained by periodical burning since the 1950s, and as a consequence, a number of play grounds have provides habitat for a variety of plants and animals been built on major beds(Aya, 2004). (Koyama, 1988). Similarly, a group of Wando ponds are Resulting from this modification, a number of nature rich in aquatic wildlife, including endangered species restoration projects have been recently carried out to Corresponding author:[email protected] ― 89 ― Fujisawa et al. conserve biodiversity in the landscapes of the Yodo 1996;Gerisch et al., 2006;Follner et al., 2010). In this River. For example, rehabilitation of dried Wando study, we investigated ground beetle assemblages at ponds at Kuzuha and Shirokita led to 20 species of characteristic landscapes in the Yodo River to clarify fish returning and being recorded again in the areas faunal characteristics and species diversity, and to (Nishino, 2009). Recently, an Udono water channel, in determine the relationship between ground beetle which water was being pumped from the Yodo River, assemblages and recent river regulation works. was cut and part of major bed dug down to prevent it from drying(Koyama, 1999;Aya, 2004;Nishino, Study site and Method 2009). These projects have considerably influenced the terrestrial invertebrate fauna in riverbeds of the A field survey using unbaited pitfall trapping was Yodo River. Although some studies have surveyed the carried out at four sites, Sites 1-4, in the riverbed of the change of terrestrial invertebrate assemblages in the Yodo River in Osaka Prefecture from April-December, Yodo River(Yasui et al., 2011), quantitative surveys 2008(Fig. 1). Plastic cups(7 cm in diameter and 10 of terrestrial invertebrate are needed to clarify their cm in depth)with five holes(about 2 or 3 mm in actual condition. diameter)on the bottom for drainage were used for Ground beetles have been studied widely as trapping. Traps were placed in a row at intervals of bioindicators of ecosystems affected by farmland, about 3 m for two weeks a month and emptied one and human disturbance and fragmentation(Luff, 1987; two weeks after the traps placement. Each of the four Lövei, 1996;Ishitani, 1996;Rainio and Niemelä, 2003), sites included two to four sub-sites, and 10 traps were because they are distributed in various terrestrial set up at each sub-site. The location and environment ecosystems, and each species has a different habitat of each site were as follows: preference(Ishitani, 1996, 2003;Hiramatsu, 2007). In Site 1:The right bank of the Yodo River at Takatsuki riverbeds, ground beetles are considered bioindicators City located about 31 km upstream from the estuary. of human disturbance and flood events(eg. Ishii et al., The width of the river was about 150 m. This site is Fig. 1 Location of four study sites in the riverbed of the Yodo River, central Japan. The contour interval is 200 m. ― 90 ― Species diversity of ground beetle assemblages in the distinctive landscapes called“Udono”, which has the largest reed community from the Sugawara-shirokita-ohashi Bridge. Sub-site 4B in the Yodo River. The vegetation was predominately was an area of bare ground, dominated by S. glauca and Pharagmites australis, Miscanthus sacchariflorus, and T. repens in autumn, located about 50 m upstream from Humulus japonicus. Three sub-sites, Sub-sites 1Ra, the Akagawa Bridge. 1Rb and 1Rc(R stands for reed community), were According to data obtained from field sampling of established in this site:Sub-sites 1Ra and 1Rb were ground beetles, Simpson’s index 1−λ was calculated burnt in March, 2008, but no burning was made at as a species diversity index by the following equation: Sub-site 1Rc in 2008. However, at Sub-site 1Rc part of 1−λ = 1−Σn(i ni−1)/ N(N−1) the reed community was mown twice in August and where ni and N are numbers of individuals of ith November, 2008. species and total numbers of individuals(Simpson, Site 2:The right bank of the Yodo River at 1949), respectively. Takatsuki City located about 2 km downstream The degree of overlap of species captured between from the Hirakataohashi Bridge. This site is the two sub-sites was calculated by the quotient of lower riverbank immediately downstream from the similarity(Qs): confluence of the Akuta River with the Yodo River. Qs = 2c /(a + b) The width of the river was about 300 m. Two sub-sites, Where a and b are the numbers of species captured at Sub-sites 2W and 2G(W and G stand for woodland sub-sites a and b, respectively, and c is the number of and the grass, respectively), were established in this species common to both sub-sites(Sφrensen, 1948). site:Sub-site 2W was woodland dominated by Salix Moreover, we made an UPGMA(the unweighted spp. and Celtis sinensis, while Sub-site 2G was grassland pair group method with arithmetic mean)cluster dominated by Artemisia indica, Solidago canadensis, and analysis using the Pianka’s α index(Pianka, 1973)to Setaria glauca. examine differences in the structure of ground beetle Site 3:The right bank of the Yodo River at assemblages among the 12 sub-sites. The index was Settsu City located about 1 km downstream from the calculated by the following equation: Torigainiwajiohashi Bridge. The river was about 300 2 2 m wide with Wando ponds in the riverbed. This site αab = Σpaj・pbj/ Σ( paj) ・ Σ(pbj) consisted of three sub-sites, Sub-sites 3R, 3W and 3G: paj= naj / Na pbj= nbj / Nb Sub-site 3R was a reed community dominated by M. sacchariflorus and P. karka at the major bed, and part where naj and nbj, and Na and Nb are numbers of of the reed community was mown in December, 2008. individuals of jth species and total numbers of Sub-site 3W was woodland dominated by Salix spp. and individuals collected at sub-sites a and b, respectively. C. sinensis at the minor bed. Sub-site 3G was grassland In this survey, we could not classify three individuals dominated by A. indica, S. canadensis and Trifolium repens into particular species, although they were regarded adjoining a Wando pond at the minor bed. Part of the as species belonging to the genus Harpalus on the Sub-site 3G grass was mown in October, 2008. basis of morphology. Therefore, we dealt with them Site 4:The left bank of the Yodo River at Osaka as Harpalus spp. in the species list, but excluded them City, with abundant Wando ponds, located about 12 from comparisons of species richness, species diversity, km upstream from the estuary.