2000 BES Abstracts

Exotic invertebrates in urban forest soils

Katalin Szlavecz, Elisabeth Hornung, Csaba Csuzdi, Zoltan Korsos

Among the central questions of BES is the significance of non-native species in urban ecosystems. To assess the diversity and dominance of introduced soil invertebrates we qualitatively and quantitatively surveyed nine forests in the Baltimore area. We focused on three saprophagous taxa: Oligochaeta (earthworms), Isopoda (terrestrial isopods) and Diplopoda (millipedes).

No endemic isopods have been found: all of the ten species are non-native, most likely introduced from Europe. Ours is the first record for Chaetophiloscia sicula Verhoeff, 1908 (Isopoda: Philosciidae), a species of Mediterranean origin. In Europe it is widely distributed from Spain to Greece. The entire genus Chaetophiloscia is new to the fauna of North America.

Out of the eight earthworm species found so far, two are endemic, one came from Asia, and the rest are European lumbricids. The Diplopoda group has also three non-native species: two from Europe, one from SE Asia. Cylindroiulus punctatus, an Atlantic species is recorded here for the second time. Previously it was reported only in Newfoundland 50 years ago. The endemic millipedes belong to the Iulidae and Polydesmidae families.

Oligochaeta species richness is highest in the rural forest (8), whereas abundance was higher in the urban forest. Density varied between 0 and 136 ind/m2. Isopods in the rural forest are extremely rare. Most isopods were collected in city parks (e.g. May 2000, >1400 ind/10 traps). Two isopod species (Cylisticus convexus and Trachelipus rathkei) dominated these samples. Abundance of millipedes was an order of magnitude lower (e.g. May 2000, 166 ind/10 traps). Our results show that non-native species within these taxa are well established in urban forests. In some cases they clearly dominate both diversity and abundance of the soil fauna. They are macro-decomposers therefore their high proportion in the soil biota greatly influences the rate and pathways of decomposition, and the structure of mesofauna and microbial community.