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Neighborhood scale assessment of soil invertebrates
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Amynthas, 2006, Photo: Kathy Szlavecz
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Earthworm invasion has recently become a widely discussed topic in North America. In the Mid-Atlantic Region, the Asian pheretimoids are of special importance, because in the growing season they can dominate urban and suburban habitats. Very little is known about the life history of megascolecids in their new environment. We monitored a suburban population of Amynthas hilgendorfi, a common Asian invader, from early April, when the first juveniles emerge. The objective of the study was to obtain information on the population structure over time as well as to compare growth rates in the laboratory and in the field. Field samples (about 100 animals) were taken biweekly, weighed, and returned to the field. For the laboratory experiments we collected 50 Amynthas from the same backyard and placed them individually into containers. We also collected 10 large Amynthas from another urban area and placed them individually into containers as well. These animals were weighed weekly. Contrary to our expectations, the laboratory population did not grow better than the field population. Mortality rates were also high in the laboratory. It is not clear why Amynthas is difficult to keep in the lab. While average live weight increased over time in the field population, so did variance indicating that small juveniles were continuously emerging. These can be either offspring of the large individuals or hatched late from last fall’s cocoons.
Currently we are comparing reproductive characteristics of terrestrial isopods in several habitats and geographical regions. Our hypothesis is that habitat quality has a stronger effect on reproductive output than geographical distance or latitude.
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Collaborators
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Csaba Csuzdi (Hungarian Natural History Museum)
Elisabeth Hornung (Szent Istvan University, Budapest)
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Paper
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Hornung, E., F. Vilicsics, K. Szlavecz. Conservation issues of terrestrial isopods (Isopoda, Oniscidea): a case study for two cities, Budapest and Baltimore. Cons. Biol Lett. Hung. In press
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