Spacing of leks in relation to female home ranges,habitat requirements and male attractiveness in the great snipe (Gallinago media)

Summary In an attempt to examine three main hypotheses on the evolution of leks, data on female home ranges, distance between leks and male site fidelity in the great snipe (Gallinago media) were obtained. In a 30 × 40 km area in central Sweden, the locations of 12 leks were identified. Six were within the study area (7 × 11 km) in which probably all leks were known. In the study area, nearest neighbor distances between leks were longer than the predicted drawing area (diameter of female home ranges plus the detection range of leks). Furthermore, in only 1 of 13 radio-tracked females did the estimated home range enclose many leks. These data do not fit the prediction from the hotspot hypothesis on the dispersion of leks, namely, that the distance between leks should be less than the drawing area and hence an average female home range should enclose more than one lek. The observed distance between leks was about the same as predicted by the female preference hypothesis. This hypothesis also predicts females visit mainly one lek; however, we found they sometimes visit two and nest close to a third. We propose that males may first settle according to hotspot rules, but females will resettle according to preferences for certain males and/or larger leks. In this way some hotspot leks are abandoned, and the distance between leks is increased as males become more tightly clumped. However, when all males and females have settled, the leks still existing would be on hotspots. In the female preference hypothesis, males are assumed to aggregate on leks because females prefer clustered males as they can be more easily compared than if they are dispersed. Alternatively, in the attractiveness hypothesis, it is suggested that females prefer certain males, and hence unattractive males surround the attractive are forced to join leks in order to come close to females. Our data on male site fidelity support the attractiveness hypothesis because successful and dominant males return to the same lek and territory, both within and between years, whereas unsuccessful males move to other leks. Attractiveness of certain males may explain why according to hotspot rules in this species males are more clumped than expected. Offprint requests to: J. Höglund     

Benthic Foraminifera: morphology and growth in clone cultures of Heterostegina depressa

A three months old clone of 76 asexually produced F₂ Heterostegina depressa D'Obbigny, 1826 (Foraminifera) was subdivided into two groups which were cultivated for 5 months, one at 300 lux, the other at 600 lux. Nourishment was provided by symbiotic photosynthesizing algae. The 300-lux group added 1 whorl, the 600-lux group added 1/2 a whorl during the experiment, suggesting that the first group was nearer the optimum for growth than the second. Growth rates reacted but slowly to changes in environmental conditions. Also, specimens within the same culture dish showed great differences in response. In the 600-lux group, many specimens ceased to grow entirely, while others continued. Cessation of growth tends to produce a rounded test shape, by filling-in of the apertural angle, while rapid growth tends to be correlated with flaring tests (i.e., tests with an open spiral). In addition, there is a trend toward increased flaring during normal ontogenetic development. Shell damage is greater in rapidly growing individuals; walls are apparently thicker in slowly growing and in resting individuals. Ecological interpretation of morphological characteristics is hampered by: (1) a lag effect between growth response and environmental change; (2) slowing or termination of growth under stressful conditions with corresponding minor changes in morphology; (3) great variation in response between sibling individuals within the same culture dish; (4) aging effects.     

Thermodynamische Modelle für die Bioverfügbarkeit organischer Chemikalien

In aquatic systems, the bioavailability of chemical contaminants is determined via the physicochemical properties of the compounds and the organic matrices as well as through the milieu parameters of the water. The amount of substance freely dissolved in water yields an approximate characterization of the bioavailable fraction, which can be reduced substantially through the sorption of particulate or dissolved organic matter. For ionogenic compounds, a distinction must be made between the initial substance and dissociated or protonated species which, according to recent results, may also contribute to the bioconcentration found in organisms. The lipophilicity model to estimate bioconcentration factors initially refers only to an estimation of the freely dissolved compound concentration. Analysis of the bioaccumulation of sediment-borne contaminants shows that the uptake mainly occurs via the interstitial water and can be adequately described with the lipophilicity model.     

Effects of size and nuptial gifts on butterfly reproduction: can females compensate for a smaller size through male-derived nutrients?

In butterflies and other insects, fecundity generally increases with female adult weight. Hence, most butterflies are essentially "capital breeders", because nutrients acquired during the larval stage are stored and subsequently used for egg production during the adult stage. However, in some species, males transfer a large nutritious ejaculate to the female at mating. These females can partly be characterized as "income breeders", and female mass can potentially be decoupled from fecundity to some extent. In the gift-giving green-veined white butterfly Pieris napi, it has been shown that female fecundity and longevity increase with number of matings and also that females mature at smaller size under poor food conditions compared to males. So it has been suggested that females can compensate for their smaller size through nuptial feeding. Here we test this hypothesis in P. napi by assessing female fecundity and longevity in relation to female mass and polyandry. The results showed no support for the hypothesis. Smaller females were not capable of increasing their mating rate to compensate for a low weight at eclosion. Instead, larger females remated sooner. Also, smaller females suffered from both a reduced daily and total fecundity compared to larger females and this decrease in fecundity was independent of female mating status, i.e. females allowed to mate only once and multiply mated females suffered to the same extent from their smaller size.