Evolution of mixed maturation strategies in semelparous life histories: the crucial role of dimensionality of feedback environment

We study the evolution of age at maturity in a semelparous life history with two age classes. An individual may either breed in the first year of its life and die, or delay breeding to the second year. In this setting a mixed strategy means that a fraction of the individual''s offspring breed in the first possible breeding event, while the remaining fraction delay breeding. Current theory seems to imply that mixed strategies are not evolutionarily stable strategies (ESSs) under a steady-state population dynamical regime. We show that a two-dimensional feedback environment may allow the evolution of mixed age at maturity. Furthermore, different phenotypes need to perceive the environment differently. The biological reasoning behind these conditions is different resource usage or predation pressure between two age classes. Thus, the conventional explanations for the occurrence of mixed strategies in natural populations, environmental stochasticity or complex dynamics, are not needed. <br>     

Evolution of resource allocation between growth and reproduction in animals with indeterminate growth

We review the recent theoretical developments explaining the evolution of age-schedules of reproduction in animals with indeterminate growth. Indeterminate growth, i.e. growth that continues past maturation and may continue until the end of life, is characteristic for a large number of invertebrate taxa (e.g. clams, cladocerans and crayfish) and ‘lower’ vertebrate taxa (e.g. fish, amphibians, lizards and snakes). Many plants also exhibit indeterminate growth, and we liberally include studies focused on plants when they can be interpreted in terms of animal life histories. We focus on different measures used to determine the fittest life histories, on indeterminate growth as a problem of resource allocation and on the effects of environment to the evolution of the resource allocation schemes.     

Participatory Development and Community-Based Conservation: Opportunities Missed for Lessons Learned?

This paper traces the evolution as well as key elements, and provides examples of implementation of participatory development and community-based conservation, two concepts that resemble distant cousins in the intersecting worlds of development assistance and environmental conservation. The paper examines the connections between the concepts, the implications of participatory development for community-based conservation, and the reasons for the differences in their conceptualization and implementation. The paper is based on a review of the literature in both fields and on the authors' research and experience with participatory development and community-based conservation. Several keys to understanding the disconnection between the concepts emerge; intellectual and pragmatic origins of and impetus for the concepts, the expertise and interests of their promoters, and the differing emphasis on participation as means versus end. Results may inform our understandings of why many participatory approaches to conservation have failed to achieve meaningful participation in practice.     

Genetic structuring in fluctuating populations

The effect of genetic drift in spatially distributed dispersal-linked and density-regulated populations is studied in a classical one-locus two-allele system. We analyse emergence of genetic differentiation assuming random drift only, where the noise-like variability is due to demographic stochasticity. We find emergence of clusters of sub-units with local allele fixation and persistence of both alleles in lengthy simulations. We demonstrate that local allele fixation (extending over a number of adjoining spatial sub-units) – without global loss of alleles – may occur when the carrying capacities of local patches are small, under a full range population dynamic regimes, when dispersal rate is small, and when redistribution (through dispersal) does not act as global mixer. These results are novel. The key to the observations is that drift is simultaneously influenced by distance-dependent dispersal, demographic stochasticity and autocorrelated population fluctuations due to delayed-density dependence. These are standard elements of contemporary population models in spatially structured context. With stable large populations, no stochasticity and dispersal limited to neighbours only, our model collapses to the stepping-stone model, while with dispersal being random and global, the model collapses to Wright's island model.     

Do Egg Carrying and Protracted Copulation Affect Mobility in the Golden Egg Bug?

Golden egg bug Phyllomorpha laciniata (Heteroptera, Coreidae) females oviposit on male and female conspecifics that carry ova until they hatch. Embryos benefit from being carried because of diminished risks of predation. Female carriers are never the parents of carried eggs, and males are only rarely the fathers of any carried eggs. Eggs develop and hatch without being carried in the laboratory. Egg carriers may be viewed as victims, exploited by females that encumber them with eggs. The intensity of selection favouring resistance to egg carrying should be proportional to the costs of this behaviour. One possible cost could be a reduction in mobility caused by carried eggs. We compare movement rates among encumbered and unencumbered golden egg bugs of both sexes. Protracted copulations (often exceeding 20 h) typical of this species and mating may also cause reduction in bugs mobility. Therefore, we also evaluate rates of movement of coupled pairs of bugs. Our results indicate that egg loads do not affect the mobility and speed of either males or females. However, copulating pairs are significantly slowed as compared to single bugs. Thus protracted copulations have a clear cost in rates of movement and possibly risks of predation, but there are no apparent mobility costs for egg carrying.