Land management impacts on the feeding preferences of the woodlouse Porcellio dilatatus (Isopoda: Oniscidea) via changes in plant litter quality

Abstract

The detritivore woodlouse Porcellio dilatatus was selected to test the effects of home-field advantage and land management on the isopod feeding preferences and ingestion rates. Woodlice specimens and plant litter from two neighbouring farms were used in “cafeteria” experiments. The farms are cork-oak agro-forests with a similar litter matrix but different land-use history and current management (organic vs. conventional farms). The plant litter species selected were Quercus suber L. and Agrostis pouretti L. Leaf litter lignin, N and C concentrations, total phenolics, and fungal biomass were measured on both litter species for the assessment of litter quality. A higher preference for cork-oak litter from the conventional site was observed, both in isopods collected from the organic farm and from the conventional farm. This can be explained by the significant differences in litter quality that were found between Quercus litter types collected in the two farms. The differences in the nutritional content (lower C:N ratio for Quercus of the conventional farm) of litter from the same plant species support the assumption of a management effect on decomposition by changing plant litter quality. Yet, this pattern was not found for the other plant litter tested in this study – the grass species Agrostis pouretti. Also, despite the remarkable differences in litter traits between Quercus and Agrostis, no significant differences were found between the ingestion rates of the litter from the two plant species. Although, depending on the plant species, litter quality resulting from different management influenced P. dilatatus feeding preferences and ingestion rates.