Research Article |
Corresponding author: Taichi Iida ( taiyakiiida@gmail.com ) Academic editor: Pavel Stoev
© 2016 Taichi Iida, Masashi Soga, Shinsuke Koike.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Iida T, Soga M, Koike S (2016) Effects of an increase in population of sika deer on beetle communities in deciduous forests. ZooKeys 625: 67-85. https://doi.org/10.3897/zookeys.625.9116
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The overabundance of large herbivores is now recognized as a serious ecological problem. However, the resulting ecological consequences remain poorly understood. The ecological effects of an increase in sika deer, Cervus nippon Temminck (Cervidae), on three insect groups of beetles was investigated: ground beetles (Carabidae), carrion beetles (Silphidae), and dung beetles (Scarabaeidae and Geotrupidae) on Nakanoshima Island, Hokkaido, northern Japan. We collected beetles on Nakanoshima Island (experimental site) and lakeshore areas (control site) and compared the species richness, abundance, diversity index, and community composition of beetles between the sites. Results showed that although both species diversity and abundance of carabid beetles were significantly higher at the lakeshore site, those of dung and carrion beetles were higher at the island site. It was additionally observed that abundance of larger carabid beetles was higher at the lakeshore site, whereas that of small-sized carabid beetles did not differ between the lakeshore and island sites. For dung beetles, abundance of smaller species was higher at the island site, whereas that of large species did not differ between the lakeshore and island sites. Abundance of two body sizes (small and large) of carrion beetles were both higher at the island site. Overall, the findings of this study demonstrated that an increase in deer population altered the insect assemblages at an island scale, suggesting further changes in ecosystem functions and services in this region.
Ecosystem functions, ecosystem management, forest ecosystems, herbivores overgrazing, species traits
The overabundance of large herbivores is now recognized as one of the serious ecological issues worldwide, especially in the northern hemisphere (
To evaluate the ecological impacts of large herbivore overabundance on ecosystems, previous studies have commonly used manipulations with inclusion/exclusion treatments of large herbivores (
Lake Toya located in western Hokkaido, northern Japan, provides an ideal study site to investigate the long-term impacts of deer overabundance on ecosystems (Fig.
Here, we evaluated the effects of an increase in sika deer population on four taxonomic groups of beetles: carabid (Carabidae), carrion (Silphidae) and dung beetles (Scarabaeidae and Geotrupidae). These beetle groups were selected for several reasons. First, as these beetles inhabit the forest floor and are known to be sensitive to microclimatic changes (
Our study area is located in Western Hokkaido, northern Japan. The deer density at the island site (42°36'N, 140°51'E (DDM)) is dramatically higher than that at the lakeshore site because of artificial introduction. The mean annual temperature of this area is 7.3 °C and the mean monthly temperature ranges from −5.1 °C to 20.2 °C. The mean annual precipitation is 984.8 mm and the mean annual snow depth is 30 cm. The study area is situated in a deciduous forest dominated by Quercus crispula Blume (Fagaceae); Kalopanax septemlobus (Thunb.) Koidz. (Araliaceae); Magnolia obovata Thunb. (Magnoliaceae); Acer pictum Thunb. (Sapindaceae); Maackia amurensis Rupr. et Maxim. (Fabaceae); Tilia japonica (Miq.) Simonk. (Tiliaceae) and Ostrya japonica Sarg. (Betulaceae) (
At both sites, we sampled carabid, carrion and dung beetles using pitfall traps baited with cattle dung and fermented milk. Fermented milk is one of the major bates in collecting ground-dwelling beetles in Japan (
For each beetles group, the insect species collected in the field were divided into different size groups according to body length (see
All analyses were performed using R ver. 3.2.1 (
To investigate the difference in species composition between the island and lakeshore sites, we performed a non-metric multidimensional scaling ordination (NMDS) using the metaMDS function with the Bray–Curtis measure within the package ‘labdsv’ (
3,876 individuals in total were collected, comprising 824 carabid beetles (18 species), 148 carrion beetles (four species) and 2,902 dung beetles (five species) (see Suppl. material
Comparisons between species richness, abundance, and diversity index of insect species between the island and lakeshore sites were summarized in Figs
Abundance of each insect taxonomic and functional group per plot at the island and lakeshore sites estimated by using GLMs. A Carabid B Carrion C Dung beetles. Carabid and carrion beetles were classified into small, medium and large species and dung beetles were classified into small and large species (see the main text). Asterisks indicate a significant difference (p < 0.05).
Species richness of each insect taxonomic and functional group per plot at the island and lakeshore sites estimated by using GLMs. A Carabid B Carrion and C Dung beetles. Carabid and carrion beetles were classified into small, medium and large species and dung beetles were classified into small and large species (see the main text). Asterisks indicate a significant difference (p < 0.05).
Estimates of parameter differences between sites (reference = lakeshore site, i.e., coefficients of lakeshore site are zero), standard errors (SEs), z values, and p values in generalized linear models of each of taxonomic group and body size group abundance. Bold letters represent p < 0.05.
Parameters | Estimates | SEs | z values | p values | |
---|---|---|---|---|---|
Carabid beetles | |||||
Whole species | (Intercept) | 2.892 | 0.043 | 67.271 | < 0.001 |
Island | -0.596 | 0.072 | -8.266 | < 0.001 | |
Small species | (Intercept) | 0.170 | 0.484 | 0.351 | 0.73 |
Island | 0.799 | 0.682 | 1.172 | 0.24 | |
Medium species | (Intercept) | 2.526 | 0.052 | 48.911 | < 0.001 |
Island | -0.707 | 0.090 | -7.864 | < 0.001 | |
Carrion beetles | |||||
Whole species | (Intercept) | -0.511 | 0.236 | -2.168 | 0.03 |
Island | 1.985 | 0.251 | 7.897 | < 0.001 | |
Medium species | (Intercept) | -0.051 | 0.316 | -0.160 | 0.88 |
Island | 1.280 | 0.340 | 3.767 | < 0.001 | |
Large species | (Intercept) | -2.226 | 0.736 | -3.023 | 0.003 |
Island | 3.536 | 0.745 | 4.758 | < 0.001 | |
Dung beetles | |||||
Whole species | (Intercept) | 2.686 | 0.048 | 56.330 | < 0.001 |
Island | 1.776 | 0.052 | 34.450 | < 0.001 | |
Small species | (Intercept) | 2.230 | 0.060 | 37.250 | < 0.001 |
Island | 2.165 | 0.063 | 34.260 | < 0.001 | |
Large species | (Intercept) | 1.680 | 0.079 | 21.319 | < 0.001 |
Island | 0.031 | 0.111 | 0.276 | 0.78 |
Estimates of parameter differences between sites (reference = lakeshore site, i.e., coefficients of lakeshore site are zero), standard errors (SEs), z values, and p values in generalized linear models of each of taxonomic group and body size group species richness. Bold letters represent p < 0.05.
Parameters | Estimates | SEs | z values | p values | |
---|---|---|---|---|---|
Carabid beetles | |||||
Whole species | (Intercept) | 0.588 | 0.136 | 4.319 | < 0.001 |
Island | -0.139 | 0.200 | -0.696 | 0.49 | |
Small species | (Intercept) | -2.015 | 0.500 | -4.028 | < 0.001 |
Island | -0.693 | 0.866 | -0.800 | 0.42 | |
Medium species | (Intercept) | 0.210 | 0.164 | 1.276 | 0.20 |
Island | 0.196 | 0.222 | 0.882 | 0.38 | |
Carrion beetles | |||||
Whole species | (Intercept) | -0.836 | 0.277 | -3.015 | 0.003 |
Island | 1.149 | 0.318 | 3.609 | < 0.001 | |
Medium species | (Intercept) | -1.003 | 0.302 | -3.327 | < 0.001 |
Island | 0.738 | 0.367 | 2.012 | 0.04 | |
Large species | (Intercept) | -2.708 | 0.707 | -3.830 | < 0.001 |
Island | 2.197 | 0.745 | 2.948 | 0.003 | |
Dung beetles | |||||
Whole species | (Intercept) | 0.758 | 0.125 | 6.061 | < 0.001 |
Island | 0.426 | 0.161 | 2.651 | 0.008 | |
Small species | (Intercept) | 0.154 | 0.169 | 0.912 | 0.36 |
Island | 0.693 | 0.207 | 3.348 | < 0.001 | |
Large species | (Intercept) | -0.034 | 0.186 | -0.183 | 0.86 |
Island | -0.035 | 0.265 | -0.132 | 0.90 |
Estimates of parameter differences between sites (reference = lakeshore site, i.e., coefficients of lakeshore site are zero), standard errors (SEs), t values, and p values in generalized linear models of each of taxonomic group and body size group Shannon-Wiener diversity index. Bold letters represent p < 0.05.
Parameters | Estimates | SEs | t values | p values | |
---|---|---|---|---|---|
Carabid beetles | (Intercept) | 0.841 | 0.105 | 7.995 | < 0.001 |
Island | -0.302 | 0.149 | -2.030 | 0.05 | |
Carrion beetles | (Intercept) | 0.067 | 0.069 | 0.971 | 0.34 |
Island | 0.285 | 0.097 | 2.935 | 0.005 | |
Dung beetles | (Intercept) | 0.828 | 0.051 | 16.300 | < 0.001 |
Island | 0.347 | 0.072 | 4.828 | < 0.001 |
The indicator species values of each species. Bold letters represent p < 0.05.
Taxa | Community | IndVals | p values | |
---|---|---|---|---|
Caccobius jessoensis Harold | Scarabaeidae | island | 0.988 | 0.001 |
Onthophagus ater Waterhouse | Scarabaeidae | island | 0.822 | 0.001 |
Eusilpha japonica (Motschulsky) | Silphidae | island | 0.604 | 0.001 |
Silpha perforata Gebler | Silphidae | island | 0.405 | 0.01 |
Pterostichus leptis Bates | Carabidae | island | 0.375 | 0.001 |
Liatongus phanaeoides (Westwood) | island | 0.345 | 0.001 | |
Nicrophorus quadripunctatus Kraatz | Silphidae | island | 0.177 | 0.23 |
Copris ochus Motschulsky | Scarabaeidae | island | 0.172 | 0.02 |
Chlaenius pallipes Gebler | island | 0.115 | 0.39 | |
Pterostichus planicollis (Motschulsky) | Carabidae | island | 0.103 | 0.11 |
Pterostichus yoritomus Bates | Carabidae | island | 0.069 | 0.21 |
Pterostichus haptoderoides (Tschitscherin) | Carabidae | island | 0.034 | 0.49 |
Chlaenius variicornis Morawitz | island | 0.034 | 0.49 | |
Lithochlaenius noguchii (Bates) | island | 0.034 | 0.49 | |
Pterostichus samurai (Lutshnik) | Carabidae | island | 0.034 | 0.48 |
Hemicarabus tuberculosus (Dejean et Boisduval) | island | 0.034 | 0.48 | |
Oiceoptoma thoracicum (Linnaeus) | island | 0.034 | 0.47 | |
Pterostichus prolongatus Morawitz | Carabidae | island | 0.031 | 0.74 |
Synuchus spp. Gyllenhal | Carabidae | lakeshore | 0.827 | 0.001 |
Pterostichus thunbergi Morawitz | Carabidae | lakeshore | 0.806 | 0.001 |
Geotrupes laevistriatus Motschulsky | Geotrupidae | lakeshore | 0.477 | 0.56 |
Leptocarabus arboreus (Lewis) | Carabidae | lakeshore | 0.355 | 0.001 |
Trichotichnus longitarsis Morawitz | Carabidae | lakeshore | 0.075 | 0.58 |
Pterostichus orientalis (Motschulsky) | Carabidae | lakeshore | 0.065 | 0.50 |
Damaster blaptoides Kollar | Carabidae | lakeshore | 0.065 | 0.50 |
Cychrus morawitzi Gehin | lakeshore | 0.065 | 0.49 | |
Leptocarabus opaculus (Putzeys) | Carabidae | lakeshore | 0.032 | 1.00 |
The abundance and species richness of carrion beetles at the island site were higher than those at the lakeshore site (p < 0.001; Figs
For dung beetles, the abundance (p < 0.001) and species richness (p = 0.008) at the island site were higher than those at the lakeshore site (Figs
NMDS and cluster analysis identified a significant difference in species composition between the island and lakeshore sites (Fig.
The current study demonstrated that an increase in sika deer at Lake Toya significantly changed both the abundance and species richness of beetle species belonging to three different taxonomic groups. The abundance and diversity index of carabid beetles at the island site were significantly lower than that at the lakeshore site (Figs
Conversely, carrion and dung beetles responded positively to deer overabundance, with abundance, species richness and the diversity index higher at the island site (Figs
Although small carabid species were not affected by deer overabundance, medium and large carabid species were negatively affected by deer overabundance (note: large carabid species were not sampled at the island site). This result suggests that larger carabid species are more sensitive to changing habitat condition than smaller species (
Although the abundance of small dung beetle species was significantly higher at the island site than at the lakeshore site, that of large species did not differ between the two sites. This result suggests that small species are likely to favor a deer abundant environment. In contrast to our results, in Japan,
In our study, NMDS showed a difference in species composition between the island and lakeshore sites (Fig.
Although our study brings a valuable contribution, the survey data is limited in its ability for generalizing the current results. Indeed, since the data used in this study was obtained from short term surveys with a limited number of samples (see also the species accumulation curves in Suppl. material
In the present study, evidence is provided that an increase in deer population altered species richness, abundance and diversity of beetles within three different taxonomical groups. Whether such changes affect the ecosystem functions provided by these beetles is unknown. Nevertheless, the observed change in compositions of the three taxonomic beetles groups raises the potential that ecosystem functions may be altered through cascading effects (
We thank K. Kaji, T. Yoshida, T. Ikeda, T. Hino and Toyako Town for providing valuable information of the study areas. We thank T Ikeda for providing the picture of study sites (Fig.
Table 1
Data type: Data table
Explanation note: A list of beetle species observed in our study.
Table 2
Data type: Data table
Explanation note: Estimated and observed values of beetle abundance at the island and lakeshore sites.
Table 3
Data type: Data table
Explanation note: Estimated and observed values of beetle species richness at the island and lakeshore sites.
Table 4
Data type: Data table
Explanation note: Estimated and observed values of beetle diversity (Shannon-Wiener diversity index) at the island and lakeshore sites.
Figure 1
Data type: Figure
Explanation note: Species accumulation curves for carabid, carrion and dung beetles at the island (blue lines) and lakeshore sites (red lines).