Adoptions in a coδoperative population of Carrion Crow Corvus corone corone

Capsule Adoptions occurred at low rate (2.6% of successful nests and 1.1% of fledglings), probably as a result of a mistake in early offspring recognition.     

Costs and benefits of joint colony founding in Australian Acacia thrips

Facultative joint colony founding by social insects (pleometrosis) provides an outstanding opportunity to analyze the costs and benefits of sociality. Pleometrosis has been documented for a range of social insects, but most studies on the adaptive benefits of this behavior are restricted to the Hymenoptera. In this study, we provide the first analysis of costs and benefits associated with pleometrosis for Australian Dunatothrips, which form domiciles by glueing together phyllodes (leaves) of their Acacia host plant. In Dunatothrips aneurae, the distribution of foundress numbers per nest indicated that females formed associations non-randomly. Furthermore, average group size was independent of both the number of foundresses on the host plant and the number of mature colonies, suggesting that this behavior was not simply a response to limited availability of nesting sites. Although per capita reproduction declined with increasing group size, we also identified two benefits of pleometrosis: (1) individual foundresses in groups had higher survival than solitary foundresses during the brood development period, and (2) larger colony sizes resulting from pleometrosis provided a benefit later in colony development, because a higher proportion of D. aneurae adults survived invasions by the kleptoparasite Xaniothrips mulga when colony size was larger. These results demonstrate that the reproductive costs of pleometrosis are at least partially counterbalanced by survival benefits. Received 4 April 2006; revised 9 September 2006; accepted 20 September 2006.     

The Spanish co-operation programme in Equatorial Guinea: a ten-year review of research and nature conservation in Bioko

The Research and Nature Conservation Programme in Equatorial Guinea was launched in 1985, financed by the Spanish Technical Co-operation Agency. The Programme's main objectives were to: (i) increase scientific research; (ii) set up a Museum of Natural History for the country; (iii) update environmental legislation; (iv) create a network of protected natural areas; (v) promote Equatorial Guinea's participation in international forums on the environment; (vi) train local personnel and (vii) implement environmental education programmes. Actions undertaken and results obtained over a ten-year period are reviewed herein. The Programme has been important in raising the level of scientific awareness of the country's resources but more importantly, it has catalysed the inception of the country's existing legal framework for environmental protection (Ley 8/1988). Within this law, regulations with respect to wildlife, protected areas and hunting were promulgated. These include the legal basis to create other reserve areas and non-profit organizations related to wildlife protection. The Programme has been able to employ the law to stop exploitation and road-building along the south of Bioko.     

Failure of caffeine to influence induced mutation frequencies and the independence of cell killing and mutation induction in V79 Chinese hamster cells

Using V79 Chinese hamster cells and replating assay, no effect of caffeine post-treatment on spontaneous or UV- or EMS-induced mutation frequencies to 8-azaguanine resistance was demonstrable. However, considerable potentiation of cell killing was observed. Previous reports that caffeine enhances induced mutation frequencies are explained by an artefact in the in situ method used; a similar artefact may also explain the cumulative in situ mutation dose-responde curves. Furthermore, the relationship between mutation induction and dose has been shown to be qualitatively distinct from that between cell killing an dose. These differences suggest that cell killing and mutation induction are mediated via independent mechanisms and that pre-mutational lesions may be qualitatively distinct from pre-lethal lesions.     

Trade-off between reciprocal mutualists: local resource availability-oriented interaction in fig/fig wasp mutualism

1. The mechanisms that prevent competition (conflict) between the recipient and co-operative actor in co-operative systems remain one of the greatest problems for evolutionary biology. Previous hypotheses suggest that self-restraint, dispersal or spatial constraints can prevent direct competition for local resources or any other common resources, thereby maintaining stable co-operation interactions. In this study, we use the obligate fig-fig-wasp mutualism to examine whether the above mechanisms can maintain stable co-operation sufficiently between figs and fig wasps. 2. Our data on obligate co-operation between figs (Ficus racemosa Linn.) and fig wasps (Ceratoslen fusciceps Mayr) show that the number of viable seeds of figs is positively correlated with the number of pollinator offspring when the number of vacant female flowers is high while the foundress number is low (two foundresses). Meanwhile, they are negatively correlated when the number of vacant female flowers is low and the number of foundresses is increased manually (eight foundresses). The correlation coefficient between viable seeds and wasp offspring (galls) depends on vacant female flower availability. 3. Our data suggest that the interaction between figs and fig wasps is conditional, and that they co-operate when local resource availability is plentiful but are in conflict when local resource availability is limited. The self-restraint, dispersal and spatial heterogeneity previously hypothesized in maintaining stable co-operation cannot sufficiently prevent the symbionts from utilizing more local resources at the expense of the recipients. The conflict, which can disrupt the co-operation interaction, exists after the local resource is saturated with symbionts. The repression of symbiont increase, therefore repressing the utilization of local resources in the conflict period, is crucial in the maintenance and evolution of co-operation.     

Kin in space: social viscosity in a spatially and genetically substructured network

Population substructuring is a fundamental aspect of animal societies. A growing number of theoretical studies recognize that who-meets-whom is not random, but rather determined by spatial relationships or illustrated by social networks. Structural properties of large highly dynamic social systems are notoriously difficult to unravel. Network approaches provide powerful ways to analyse the intricate relationships between social behaviour, dispersal strategies and genetic structure. Applying network analytical tools to a colony of the highly gregarious Galápagos sea lion (Zalophus wollebaeki), we find several genetic clusters that correspond to spatially determined 'network communities'. Overall relatedness was low, and genetic structure in the network can be interpreted as an emergent property of philopatry and seems not to be primarily driven by targeted interactions among highly related individuals in family groups. Nevertheless, social relationships between directly adjacent individuals in the network were stronger among genetically more similar individuals. Taken together, these results suggest that even small differences in the degree of relatedness can influence behavioural decisions. This raises the fascinating prospect that kin selection may also apply to low levels of relatedness within densely packed animal groups where less obvious co-operative interactions such as increased tolerance and stress reduction are important.     

Co-operative Group Predation in a Sit-and-wait Cheyletid Mite

The Cheyletidae is a family of trombidiform mites with more than 100 predatory and parasitic species. The cheyletid Hemicheyletia morii Ehara is a predatory species occurring on leaves of tropical trees. Observations on the life history and behaviour of this species revealed a new type of sit-and-wait predacious tactic and a sociality previously unknown in Acari. In addition, nest cleaning by a member of the colony was observed. Our results show that this species possesses subsociality. These results are remarkable as group living, co-operative hunting and feeding are rare phenomena in this subclass. Furthermore, the occurrence of thelytoky observed suggests the importance of kin selection.     

Lifetime reproductive output in a hermaphrodite cestode when reproducing alone or in pairs: a time cost of pairing

The cestode Schistocephalus solidus is a facultatively self-fertilising simultaneous hermaphrodite. Here we test for differences in the starting point, the rate, and the magnitude of egg production between individuals allowed to reproduce alone (only self-fertilisation possible) or in pairs (both self- and cross-fertilisation possible). Specifically, we want to distinguish between alternative processes responsible for the lower egg production in paired individuals observed in an earlier study (Wedekind et al., 1998). We designed an improved in vitro system, replacing the bird final host that allows us to measure, with high temporal resolution, the timing and magnitude of lifetime egg production of worms in these two social situations. We found that the experimental groups did not differ significantly in the starting point of egg production. However, the temporal pattern in egg production differed between them, in that paired individuals had a lower rate of egg production. This, however, did not lead to a significant reduction in lifetime egg production, as pairs compensated for the lower rate by producing eggs longer than single individuals. We argue that the lower rate of egg production may nevertheless lead to a time cost of pairing in the study species, and that this cost is likely to represent a cost of outcrossing due to sexual selection. This revised version was published online in July 2006 with corrections to the Cover Date.