Water-filled tree holes are abundant microhabitats in forests worldwide and are inhabited by specialized communities of invertebrates. Despite their importance, the temporal dynamics of communities within and between years are largely unknown. Here, I present a case study on the phenology of insect larvae in two holes in a beech tree (lower and upper canopy) located in southern Germany over a period of three years. I asked whether water temperature and the characteristics of insect larvae at the community and population levels are similar in periodicity every year and whether they differ in the lower and upper canopy. The water temperature in tree holes differed greatly from air temperature, and this effect was more pronounced in the lower than in the upper canopy, which resulted in a lower probability of drying out occurring in the lower canopy. This was associated with a higher species richness in the lower canopy and greater abundance of drought tolerant species in the upper canopy. There was a significant periodicity in larval abundance, biomass, species richness and body size distribution of abundant species in both tree holes, but it was not seasonal. This result indicates that unpredictable drying out of tree holes are more important drivers of tree hole community dynamics than changes in water temperature. The community of larvae in the tree hole in the upper canopy lagged behind that in the lower canopy, which indicates that most species mainly colonize the more stable microhabitats in the lower canopy. Hopefully this case study will encourage future larger-scale phenological studies to test (1) whether the patterns observed in this study can be generalized over larger spatial scales and (2) the relative importance of abiotic and biotic drivers of the dynamics of communities in tree holes., Martin M. Gossner., and Obsahuje bibliografii
The first detailed description of larvae of Ptecticus Loew is presented for P. brunettii and P. flavifemoratus from West Malaysia. There are pronounced morphological and behavioural differences between the last larval instar, inside whose cast cuticle the pupa remains, and earlier instars. The larval mouthparts are similar to those of other known Stratiomyidae larvae but may display a set of autapomorphic characters. The structure of the mandibular-maxillary complex suggests that larvae of Ptecticus are micropantophagous scavengers that feed chiefly upon microorganisms. The larvae of both species are associated with decaying bamboo shoots; P. brunettii inhabits the space between the culm sheaths and P. flavifemoratus lives in water-filled shoot stumps. This is the first record of aquatic Sarginae larvae and egg plastron in the Stratiomyidae. The life cycle and behaviour of P. brunettii and P. flavifemoratus is described and the resource partitioning of stratiomyids and xylomyids associated with bamboo is discussed.