3.6 Ground Beetles (Coleoptera: Carabidae) in the Forest Canopy: Species Composition, Seasonality, and Year-To-Year fluctuation
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Ground beetles in the canopy 3.6 Ground beetles (Coleoptera: Carabidae) in the forest canopy: species composition, seasonality, and year-to-year fluctuation Erik Arndt1 & Stephan Hielscher We present a two-year examination of ground beetles (Carabidae) in the canopy of a Central European flood plain forest using window traps and branch-eclectors. The carabid fauna was analysed in 25 trees of Quercus robur, Tilia cordata, Fraxinus excelsior, and some neophytic trees. All traps were fixed at two levels: window traps at heights of 26.6 m and 21.8 m average, branch-eclectors at 26.6 m and 19.8 m average respectively. A total number of 27 species with 242 specimens were recorded in window traps and four species with 19 specimens in branch-eclectors. The most common species in both trap types was Dromius quadrimaculatus, a carabid with arboricolous life history. The maximum activity of Dromius quadrimaculatus was recorded at the end of July/beginning of August which probably corresponds with appearance of adults of the new generation. The species set of the canopy can be linked to five ecological groups: (1) arboricolous species; (2) species with ground-canopy-interaction; (3) migrating forest species; (4) migrating urban species; (5) aerial plankton. Migrating urban species were recorded five times more often than migrating forest species in the canopy. INTRODUCTION MATERIALS AND METHODS The data presented here are derived from a two year Ground beetles (Carabidae) are one of the most im- examination (2002–2003). The carabid fauna of the portant invertebrate indicator groups. They live in tree crowns was examined using window traps and all terrestrial habitat types in large numbers. Sev- branch eclectors. For details see Arndt & Unter- eral species are known to occur in Central European seher, this volume. flood plain forests (Zulka 1994a, b; Spang 1996; The sample design made possible a statistical anal- Wohlgemuth-von Reiche & Grube 1999; Rink ysis of the main trees but also showed trends of species & Hettrich 2001). Ground beetles indicate eco- composition in neophytic trees which are a result of logical changes in these forests, e.g. in water regime, forest use. Relations between carabid species and much earlier than plant species do (Arndt, unpubl., trees or structural parameters were calculated us- but see Arndt & Pellmann 1996: p. 51). Hy- ing Pearson- or a Kendall’s-Tau-b-correlation respec- grophilous forest species disappear and ruderal species tively. occur when ecological conditions in flood plain forests change. However, as in many other taxa the carabid fauna of temperate flood plain forests has only been ex- amined at the ground. It is unknown how many arboricolous species live there, if species from the soil surface are also climbing in the trees, if there are any interactions between carabids and other carnivorous invertebrates, or if migrating carabids occur in the canopy. The possibilities of the crane could bring a lot of new details and solve many open questions of this species rich indicator group. Figure 1 – Dromius quadrimaculatus (Linn´e), the most com- mon species in the forest canopy (redrawn from Lindroth 1986). 1corresponding author 106 E. Arndt & S. Hielscher Table 1 – Ground beetles (Carabidae) recorded in window traps (WT) and branch-eclectors (BE) in the study period 2002/03 of the LAK project. The species are listed according to their frequency. Species WT 2002 WT 2003 BE 2002 BE 2003 Dromius quadrimaculatus (Linn´e) 85 85 6 6 Trechus quadristriatus (Schrank) 18 6 1 0 Limodromus assimilis (Paykull) 6 1 5 0 Dromius agilis (Fabricius) 1 3 0 1 Amara aenea (De Geer) 5 0 0 0 Paratachys bistriatus (Duftschmid) 2 0 0 0 Anchomenus dorsalis (Pontoppidan) 2 0 0 0 Ophonus rufibarbis (Fabricius) 2 3 0 0 Loricera pilicornis (Fabricius) 2 0 0 0 Calodromius spilotus (Illiger) 2 0 0 0 Amara similata (Gyllenhal) 2 0 0 0 Harpalus tardus (Panzer) 1 1 0 0 Syntomus foveatus (Geoffroy) 1 0 0 0 Acupalpus parvulus (Sturm) 1 0 0 0 Acupalpus flavicollis (Sturm) 1 0 0 0 Amara aulica (Panzer) 1 0 0 0 Amara consularis Stephens 1 0 0 0 Badister bullatus (Schrank) 1 0 0 0 Bembidion properans (Stephens) 1 0 0 0 Bradycellus verbascii (Duftschmid) 1 0 0 0 Calathus mollis (Marsham) 1 0 0 0 Demetrias monostigma (Samouelle) 1 0 0 0 Microlestes minutulus (Goeze) 1 0 0 0 Amara communis (Panzer) 0 1 0 0 Anisodactylus binotatus (Fabricius) 0 1 0 0 Nothiophilus biguttatus (Fabricius) 0 1 0 0 Pterostichus oblongopunctatus (Fabricius) 0 1 0 0 total 139 103 12 7 RESULTS pletely known life history. Larvae and adults are only found in the canopy, and derived from morphological Species composition characters and life history of closely related taxa, it is a carnivorous species. A total number of 27 species with 242 specimens were recorded in window traps and four species with The used sample design allowed us to test correla- 19 specimens in branch-eclectors (Table 1). By far tions between D. quadrimaculatus and the examined the most common species in both trap types was tree species as well as structural parameters (height Dromius quadrimaculatus (Linn´e) (Fig. 1) represent- of trap, dead wood portion, leaf coverage). The ac- ing 69.7% of the total catch. This species was not tivity of this beetle in various tree species differed recorded at the ground indicating an arboricolous way significantly (ANOVA of window traps, both years of live. Two further arboricolous species (Dromius SS = 32.68, MS = 10.89, F = 32.878, p = 0.0466*, agilis (Fabricius) and Calodromius spilotus (Illiger)) regarding only 2003 the differences are highly signifi- occurred only in scattered specimens in the traps and cant). Fraxinus excelsior was slightly preferred by D. seem to be much rarer than D. quadrimaculatus. The quadrimaculatus. No one of the structural parameters great majority of the species were recorded in 1 or 2 correlated with the activity of D. quadrimaculatus sig- specimens only. Therefore, only data of D. quadri- nificantly. maculatus are available for statistical analyses. The seasonal activity of this ground beetle was very similar in 2002 and 2003 (Fig. 2). In both years, the Life history of Dromius quadrimaculatus activity of D. quadrimaculatus was highest at the end of July/beginning of August. About 40% of specimens The only abundant carabid species in the canopy is were caught at this time (Fig. 2). Only one larva was Dromius quadrimaculatus (182 recorded specimens). recorded (first instar, first trap period April-middle It is one of the arboricolous species with an incom- of May). The early period of this larval record indi- 107 Ground beetles in the canopy cates however a completion of larval development in exceptionally do species have two larval instars com- summer and the maximum activity of adults there- bined with a very large first instar larva. fore most probably corresponds with the appearance of the new adult generation. The comparable large It should be noted that these data are in contrast size of this first instar larva furthermore indicates a to data and presumptions published earlier on D. shortened larval development of D. quadrimaculatus. quadrimaculatus (Burmeister 1939, Turin 2000). Nearly all carabids have three larval instars. Only Figure 2 – Seasonal activity of Dromius quadrimaculatus in the forest canopy. 5 Canopy Ground 4 3 Dominance 2 1 0 5 spp 15 spp 9 spp Abax 2 spp Amara aenea Nebria brevicollis Platynus assimilisLoricera pilicornis Carabus granulatus Carabus coriaceusPterostichusCarabus 3 spp nemoralis Trechus quadristriatus Notiophilus biguttatus Dromius quadrimaculatus Figure 3 – Dominance and distribution of ground beetles in window traps + branch-eclectors (Canopy) and pitfall traps (Ground) (after Arndt 2005). The figure shows only data of 2002. Species are listed in dominance classes according to Engelmann (1978). 1: < 1.0%. 2: 1.0–3.19%. 3: 3.2–9.99%. 4: 10.0–31.99%. 5: 32.0%. The dominance classes are calculated separately for ≥ ground and canopy. 108 E. Arndt & S. Hielscher DISCUSSION in our study were correspondingly low. Limodromus assimilis (Paykull) is the only species in our sam- Ecological classification of the ground beetles ples which should be related to this group. It was recorded in the canopy recorded in pitfall traps, stem- and branch-eclectors as well as in window traps. L. assimilis hibernates The total number of 27 carabid species in the canopy under bark of dead wood, but our results show that was much higher than that on the ground (Fig. 3), the species is also active in the canopy to feed or mate. even if we take into consideration the shorter sam- ple period of the pitfall traps at the ground (Arndt Migrating forest species 2005). On the other side the low number of species Several carabid species living at the forest ground are and specimens in branch-eclectors shows that many macropterous and able to fly to other forest sites but species may fly through the forest but only few species were not observed climbing as L. assimilis. Pteros- are active in the canopy. A detailed analysis of the tichus oblongopunctatus (Fabricius) is one example. species list brings to light many ruderal ground bee- The eurytopic Loricera pilicornis (Fabricius) in the tles untypical of a flood plain forest and shows the widest sense also belongs to this group. It should be close connection to urban habitats which are within noted that only 1.1% of the total catch falls in this 500 m from the plot. group. The conclusion is that most forest species are Based on faunistic (Arndt & Pellmann 1997, unable to fly or do not regularly fly. Arndt & Richter 1996, Winkler, unpubl. mas- ter thesis) and ecological data (Turin 2000) we Migrating urban species classify five different ecological groups of the cara- The study site is near to the forest edge and the ur- bid species recorded in window traps and branch- ban areas border the site on the south and north-east eclectors: within 500 metres.