Three ways of assessing metapopulation structure in the butterfly Plebejus argus

1. Three independent methods were used to investigate population structure in the butterfly Plebejus argus . First, migration and dispersal ability were measured by mark–release–recapture in seven adjacent habitat patches, and by release of butterflies in unoccupied habitat. Secondly, colonization of newly created habitat was observed over 7 years. Finally, genetic differentiation of local populations within a metapopulation was investigated. Sampled local populations included parts of the mark–release–recapture study area.
2. Plebejus argus is relatively sedentary: the maximum movement detected was 395 m, and only 2% of individuals moved further than 100 m between recaptures on different days. None the less, adjacent local populations in the mark–release–recapture study area were linked by occasional migration, with ≈ 1.4% of individuals moving between patches separated by 13–200 m.
3. Despite low mobility, observed colonizations occurred rapidly over distances of 1 km. Because P. argus occurs at high population densities, 1.4% migration can generate enough migrants to colonize newly suitable habitat quickly at this spatial scale.
4. Mark–release–recapture data were used to predict that there would be limited genetic differentiation through drift between local populations at this spatial scale. The prediction was supported by allele frequency data for the same local populations.
5. Genetic differentiation often indicates higher levels of migration than are revealed by the movements of marked individuals. This study shows that when experimental releases and extensive marking are undertaken in areas that are large relative to most movements, indirect measures of gene flow and direct measures of dispersal can concur.
6. Evidence from the three different approaches was complementary, indicating that P. argus occurs as metapopulations within the study area.     

The youngest African clymeniids (Ammonoidea, Late Devonian) – failed survivors of the Hangenberg Event

A co-occurrence of the clymeniid Postclymenia evoluta Schmidt, 1924 and the goniatite Acutimitoceras hilarum Korn, 2002 is reported from the Anti-Atlas of Morocco. Both species occur in the same limestone horizon within the Acutimitoceras prorsum Zone, that has yielded an exclusive conodont fauna of the Upper praesulcata Zone (latest Devonian, above the Hangenberg Black Shale). This record is firm evidence that some clymeniids survived the global Hangenberg Event, but soon later became extinct without descendants.     

Phoretic and parasitic mites infesting the New World screwworm fly, Cochliomyia hominivorax, following sterile insect releases in Libya

During the screwworm eradication programme in Libya in 1991, trapped specimens of Cochliomyia hominivorax (Coquerel) were found infested with phoretic mites, Macrocheles muscaedomesticae (Scopoli), or parasitic mites, Trichotromidium muscarum (Riley). The possible sources of infestation and potential effects of mites on screwworm flies are discussed.     

Shredder–collector interactions in temporary streams of western Oregon

1. Field data and results from laboratory rearing are combined to describe shredder–collector interactions in western Oregon temporary streams.
2. The composition of functional feeding groups in the temporary streams conforms to that predicted for permanent headwaters by the River Continuum Concept (RCC).
3. A distinct functional feeding group phenology was found, with shredders emerging first and collectors emerging last in the season. Scrapers were intermediate.
4. Presence of shredders enhanced collector growth in laboratory experiments ( P < 0.01; n = 12). The species reared in the study trials accounted for 67% of the shredder biomass and 76% of the collector biomass in the natural systems.
5. Field data and laboratory rearing trials both support the hypothesis of a close shredder–collector interaction in the processing of allochthonous material in the summer-dry headwaters studied.     

Effects of warming and nutrients on sediment community respiration in shallow lakes: an outdoor mesocosm experiment

1. Climate warming is expected to change respiration in shallow lakes but to an extent that depends on nutrient state. 2. We measured sediment respiration (SR) over the season in the dark on intact sediment cores taken from a series of flow‐through, heated and unheated, nutrient‐enriched and unenriched mesocosms. The natural seasonal temperature cycle ranged from 2 to 20 °C in the unheated mesocosms. In the heated mesocosms, the temperature was raised 4–6 °C above ambient temperatures, depending on season, following the A2 climate change scenario downscaled to the local position of the mesocosms, but enlarged by 50%. We further measured ecosystem respiration (ER) in the mesocosms based on semi‐continuous oxygen measurements. 3. SR changed over the season and was approximately ten times higher in summer than in winter. SR showed no clear response to warming in the nutrient‐enriched treatment, while it increased with warming in the unenriched mesocosms which also had lower fish densities. 4. ER was not affected by artificial warming or nutrient enrichment, but it was ten times higher in summer than in winter. 5. SR contributed 24–32% to ER. The SR:ER ratio was generally stimulated by warming and was higher in winter than in summer, especially in the nutrient‐enriched mesocosms. 6. Our results indicate that climate warming may lead to higher SR, especially in clear, macrophyte‐dominated systems. Moreover, the contribution of SR to ER will increase with higher temperatures, but decrease as the winters get shorter.     

Estimation of survival rate and oviposition interval of Anopheles balabacensis mosquitoes from mark-recapture experiments in Sabah, Malaysia

An exophilic population of the vector mosquito Anopheles balabacensis Baisas was investigated in two mark-recapture studies (16.ix-13.x.1986 and 6-26.i.1987) at an inland, foothill village in Sabah, Malaysia. Wild female mosquitoes were intercepted as they came to feed on man or buffalo, given a bloodmeal, marked with fluorescent dust and released. The recapture rate was about 12%. A new method of analysis is proposed which uses cross-correlation and a time series model. The estimated survival per oviposition cycle was 0.48-0.54 and the oviposition cycle interval 2-3 days.     

Analysis of Two Rubisco-Deficient Tobacco Mutants, H7 and Sp25; Evidence for the Production of Rubisco Large Subunits in the Sp25 Mutant that Form Clusters and are Inactive

The basis for the lesions in the Sp25 and H7 ribulose-l,5-bisphosphatecarboxylase/oxygenase (Rubisco) mutants of tobacco was studiedin detail because these plants may be suitable hosts for transformationwith the genes for Rubisco enzymes of various origins that havedifferent substrate specificities. We show that the Sp25 mutantlacks active holoenzyme, but contains the large and small subunitpolypeptides, Rubisco activase and the chloroplast chaperonin,Cpn 60. The large subunit polypeptides were not distributeduniformly in the stroma in the Sp25 mutant as they were in thewild-type plants, but had an anomalous distribution being presentonly in aggregated clusters notably in chloroplasts with largestarch grains. Furthermore, these clusters were not uniformlydistributed throughout the photosynthetic cells but were localizedlargely in the mesophyll cells surrounding the vascular tissue.In contrast to the Sp25 mutant, the H7 mutant contained theRubisco holoenzyme, but in this case the enzyme was inactive.It is clear that in both these mutants the Rubisco holoenzymefails to assemble correctly. In the Sp25 mutant assembly islost completely while in the H7 mutant the holoenzyme is formed,but the assembly process fails to produce an active enzyme.We suggest that the flaw in assembly in the Sp25 mutant resultsfrom a defect in chloroplast encoded proteins. Key words: Rubisco, assembly, tobacco, mutants