The cuckoo bee genus Kelita : its systematics, biology, and larvae. American Museum novitates ; no. 2631

24 p. : ill., map ; 26 cm.Includes bibliographical references (p. 23-24)."Three new species (toroi, penai, and tuberculata) are added to the Chilean cuckoo bee genus Kelita heretofore thought to be monotypic (type species: chilensis Friese). Presented are descriptions of adults of all taxa, comparative illustrations of the male genitalia and other taxonomic features, a key to species, and a distribution map of the species. The anatomical parts of the complicated male genitalia are homologized. An attempt to analyze the phylogenetic relationships of Kelita to other Nomadini indicates that it is most closely related to Paranomada, Triopasites, Melanomada, Brachynomada, and Hesperonomada. Kelita tuberculata and chilensis are reported to be parasitic on small panurgines. Details of adult and larval activity and larval development indicate that the biology of Kelita is not substantially different from that of other Nomadini. Taxonomic descriptions of the first and last larval instars of tuberculata reveal that these stages are similar in most respects to those of other Nomadinae although the mature larva, unlike the larvae of most members of the subfamily, bears paired dorsal body tubercles"--P. [1]

Effects of exotic plant invasions on soil nutrient cycling processes.

ABSTRACT Although it is generally acknowledged that invasions by exotic plant species represent a major threat to biodiversity and ecosystem stability, little attention has been paid to the potential impacts of these invasions on nutrient cycling processes in the soil. The literature on plant-soil interactions strongly suggests that the introduction of a new plant species, such as an invasive exotic, has the potential to change many components of the carbon (C), nitrogen (N), water, and other cycles of an ecosystem. I have reviewed studies that compare pool sizes and flux rates of the major nutrient cycles in invaded and noninvaded systems for invasions of 56 species. The available data suggest that invasive plant species frequently increase biomass and net primary production, increase N availability, alter N fixation rates, and produce litter with higher decomposition rates than co-occurring natives. However, the opposite patterns also occur, and patterns of difference between exotics and native species show no trends in some other components of nutrient cycles (for example, the size of soil pools of C and N). In some cases, a given species has different effects at different sites, suggesting that the composition of the invaded community and/or environmental factors such as soil type may determine the direction and magnitude of ecosystem-level impacts. Exotic plants alter soil nutrient dynamics by differing from native species in biomass and productivity, tissue chemistry, plant morphology, and phenology. Future research is needed to (a) experimentally test the patterns suggested by this data set; (b) examine fluxes and pools for which few data are available, including whole-site budgets; and (c) determine the magnitude of the difference in plant characteristics and in plant dominance within a community that is needed to alter ecosystem processes. Such research should be an integral component of the evaluation of the impacts of invasive species

Effects of Vegetation Removal and Urea Application on Iron and Nitrogen Redox Chemistry in Riparian Forested Soils

International audienceRiparian wetlands are subject to nitrogen enrichment from upgradient agricultural and urban land uses and also from flooding by nitrogen-enriched surface waters. The effects of this N enrichment on wetland soil biogeochemistry may be mediated by both the presence of plants and the presence of redox-active compounds, specifically iron oxides in the soil. Despite the extensive research on wetland N cycling, the relative importance of these two factors on nitrogen is poorly known, especially for forested wetlands. This study evaluates the responses of the N and the Fe cycles to N enrichment in a riparian forested wetland, contrasting vegetated field plots with plots where the vegetation was removed to test the role of plants. Furthermore, in vitro anaerobic incubations of the experimental soils were performed to track Fe chemical changes over time under anoxic or flooded conditions. Wetland soils treated with N in form of urea, as expected, had significantly higher amounts inorganic nitrogen. In the soils where vegetation was also removed, in addition to inorganic nitrogen pool, increase in organic nitrogen pool was also observed. The results demonstrate the role of vegetation in limiting the effects excess urea has on different soil nitrogen pools. Results from anaerobic incubation of the experimental soils demonstrated the effects of N enrichment on the wetland Fe cycle. The effects of excess nitrogen and the role of vegetation on the Fe cycle in riparian wetland soil became more evident during anaerobic incubation experiments. At the end of the field experiment, Fe concentrations in the soils under the treatments were not significantly different from the control soils at the 5% confidence level. However, during the anaerobic incubation experiment of soils collected at the end of the experiment from these plots, the N-enriched soils and the unvegetated soils maintained significantly elevated concentrations of reducible Fe(III) for the initial 2-week period of incubation, and the soils collected from the plots with both the treatments had the highest Fe(III) concentrations. After 20 days of incubation, however, the Fe (III) concentrations decreased to the similar concentrations in all the incubated soils. The study clarifies the roles vegetation play in mediating the effects of N enrichment and also demonstrates that N enrichment does affect wetland redox cycle, which has strong implications on ecosystem services such as water quality improvement

Codice diplomatico padovano dell'Ab. Giovanni Brunacci

Tomo second