Exotic earthworm species that have traditionally been used for composting are purportedly intolerant of low temperatures, which may explain why they are rarely found outside of compost bins in temperate zones of North America. In contrast, numerous exotic European earthworm species have invaded previously earthworm-free temperate forests of North America where they impact native forest communities and ecosystem processes. A European species, Dendrobaena veneta, has recently become prevalent in the vermicomposting and bait industries, and its European origins and anecdotal reports of cold tolerance suggest that this species has the potential to become established in northern climates outside of its native range. Here we compare the survivorship of traditionally used composting species (Eisenia fetida and Perionyx excavatus) to D. veneta, and to a well established invasive European earthworm species (Lumbricus rubellus) at a low temperature (1.5 C) and room temperature (18 C), as a means of assessing the invasiveness of these species. Additionally, we compared the effect of this cold temperature treatment on the number of hatchlings that emerged from E. fetida and D. veneta cocoons. Adult earthworms exhibited near-100% survival in the room-temperature treatment, but survivorship varied appreciably among species in the low-temperature treatment. Perionyx excavatus and E. fetida mortality was similar, and each was greater than that of D. veneta, which was similar to L. rubellus. Dendrobaena veneta cocoons produced more hatchlings than E. fetida overall, and the number of hatchlings decreased in the low-temperature treatment relative to the room-temperature treatment for both species. When temperature corrected hatching rates were examined, the number of hatchlings was still less in the low-temperature treatment relative to the room-temperature treatment, suggesting embryonic mortality and not simply slowed development. Collectively, these results suggest that D. veneta shows greater cold tolerance than E. fetida, a trait that may increase its success as an invader.
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