Differential responses to humidity and soil type among clones of triploid parthenogenetic Trichoniscus pusizzus (Isopoda, Crustacea)

In an attempt to clarify the background of differential distributions of Trichoniscus pusillus clones in the field, two series of laboratory preference experiments were undertaken. One tested clonal reactions towards respectively increasing and decreasing moisture content of substrate, the other, distributions of clones over pairs of selected types of soilllitter. The results of the moisture preference experiments showed highly significant differences in behaviour towards extreme water conditions. These results indicate that moisture is an important ecological factor underlying clonal distributions. The observed patterns in behaviour are in accordance with observed temporal fluctuations in clonal frequencies in nature, but cannot explain that in respectively dry and wet habitats clones with different types of behaviour tend to coexist. The soil type preference experiments showed significantly different responses among clones. In general, however, some clones responded while others did not, and “true” differential responses were not found. Even then, these results indicate that differential microhabitat preference is of potential importance for the coexistence of clones.