Clutch-size variation in the Pied Flycatcher Ficedula hypoleuca

Variation in clutch-size of the Pied Flycatcher Ficedula hypoleuca was studied simultaneously in relation to latitude, longitude, altitude, laying date and habitat, using data from 103 areas from north Africa to north Norway (latitudinal range about 3900 km). Clutch-size variation was significantly related to altitude and habitat, small clutches being laid at high altitude and in coniferous forests. In contrast to some earlier studies, latitudinal or longitudinal clutch-size trends were not found.     

Dispersal Behavior and the Connectivity Between Wolf Populations in Northern Europe

ABSTRACT The isolated gray wolf (Canis lupus) population of the Scandinavian Peninsular is suffering from inbreeding depression. We studied dispersal of 35 wolves fitted with very high frequency (20) or Global Positioning System—global system for mobile (15) radiocollars in the neighboring Finnish wolf population. The growing wolf population in Finland has high numbers of dispersing individuals that could potentially disperse into the Scandinavian population. About half (53%) of the dispersing wolves moved total distances that could have reached the Scandinavian population if they had been straight-line moves, but because of the irregular pattern of movements, we detected no wolves successfully dispersing to the Scandinavian population. Dispersal to the Scandinavian population was also limited by high mortality of wolves in reindeer (Rangifer tarandus) management areas and by dispersal to Bothnian Bay at times of the year when ice was not present. We suggest that when a small wolf population is separated from source populations by distance, barriers, and human exploitation, wildlife managers could promote the population's viability by limiting harvest in the peripheral areas or by introducing wolves from the source population.     

Apomictic Parthenogenesis and the Pattern of the Environment

Advantages of obligatory apomixis are modeled, and curculionidweevils are used as examples. It is suggested that the allegedtwofold number of female offspring in relation to sexual parentalsshould not be exaggerated. Instead, specific circumstances facilitatingthe origin of especially heterotic genotypes capable of apomixisshould be sought; crosses between differentiated (long-isolated)populations (preferably followed by a population flush) seempromising. Optimal strategies in temporally heterogeneous environmentsare studied, and situations favoringsexual reproduction bothin fine-grained and coarse-gained environments seem common (apomictsare capable only for individual adaptability, but sexual populationsmay track even one-generation changes by evolving). In apomicts,diapause determination and other seasonal constraints need specificattention, as they may interfere with geographical dispersal,and only life-cycles of one or more years seem possible. Inrich biotic communities, which evolve continuously, evolutionaryrigidity of apomicts may lead to their extinction. This showsthat the dichotomy between immediate and long-term advantagesof apomixis needs revision; if the number of generations neededfor competitive exclusion between asexual and sexual organismsis relatively high, the greater evolutionary potential of sexualpopulations must be considered (there are directional changesboth in the physical and biotic environments). Apomixis thenseems most advantageous in low-competitive, early successionhabitats which are recurrent and change relatively slowly (increasedcolonization ability of apomicts is here advantageous). Also,apomixis may succeed in spatially coarse-grained environmentin stable patches small enough to exclude high-competitive communityat the site. Then reduced vagility (loss of flight) may facilitatethe origin of apomixi     

A meta-analytic study of the effects of female age on laying-date and clutch-size in the Great Tit Parus major and the Pied Flycatcher Ficedula hypoleuca

The effects of age (1 year-old vs older females) on laying-date and clutch-size of the Great Tit Parus major (in eight independent study areas) and the Pied Flycatcher Ficedula hypoleuca (five areas) were meta-analysed using both published and unpublished records. To standardize comparisons between areas and species, the standardized difference between the means of the two age groups was used as a measure of the magnitude of the age-effect (effect size).
In Great Tits the laying-date of 'young' females was 0.30 standard deviation units later and clutch-size 0.31 units smaller than that of 'old' females. In the Pied Flycatcher the corresponding figures were 0.45 and 0.81, respectively. All the effect size measures were highly significant but for clutch-size the effect size of the Pied Flycatcher was significantly greater than that of the Great Tit. In the Great Tit the effect size of clutch-size was heterogeneous across the different study areas.
It was estimated that the following numbers of unpublished studies showing null results would have to have accumulated in file-drawers before we could say that the results concerning effect sizes are due to sampling bias: for Great Tits 121 studies of laying-date and 196 studies of clutch-size; and for Pied Flycatchers 45 studies of laying-date and 139 studies of clutch-size.