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Evolutionary ecology studies have increasingly focused on the impact of intraspecific variability on population processes. However, the role such variation plays in the dynamics of spatially structured populations and how it interacts with environmental changes remains unclear. Here we experimentally quantify the relative importance of intraspecific variability in dispersal-related traits and spatiotemporal variability of environmental conditions for the dynamics of two-patch metapopulations using clonal genotypes of a ciliate in connected microcosms. We demonstrate that in our simple two-patch microcosms, differences among genotypes are at least as important as spatiotemporal variability of resources for metapopulation dynamics. Furthermore, we show that an important proportion of this effect results from variability of dispersal syndromes. These syndromes can therefore be as important for metapopulation dynamics as spatiotemporal variability of environmental conditions. This study demonstrates that intraspecific variability in dispersal syndromes can be key in the functioning of metapopulations facing environmental changes. [ABSTRACT FROM AUTHOR]

Enhanced thermal conditions have been credited as a driving force for the evolution of viviparity, particularly in squamate reptiles, among which it has independently evolved more than 100 times. However, maternal thermoregulation is also a critical component of reproduction in oviparous squamates, for which considerable embryonic development occurs prior to oviposition. When carrying eggs, oviparous mothers modify thermoregulation in amanner similar to that of pregnant females. To further understand the role of temperature in influencing reproductive strategies, it is critical that we elucidate the degree to which thermal sensitivity varies across developmental stages. We studied stage-dependent embryonic sensitivity in a viviparous snake, the aspic viper (Vipera aspis). We manipulated female body temperature at different stages of pregnancy–early development, early embryonic growth, and late embryonic growth–by imposing two contrasting daily thermal cycles that mimicked reproductive (warm) and nonreproductive (cool) female temperature profiles. Thermal sensitivity of offspring phenotype was stage dependent, with offspring quality more negatively affected when exposure to cool temperatures occurred early in development. In contrast, developmental rate was slowed by the cooler cycle, independent of the timing of the exposure. Given the more persistent effect on phenology, phenological effects likely provide a greater driving force for complete embryonic retention (i.e., viviparity). [ABSTRACT FROM AUTHOR]

It is well known that for an isolated population, the probability of extinction is positively related to population size variation: more variation is associated with more extinction. What, then, is the relation of extinction to population size variation for a population embedded in a metapopulation and subjected to repeated extinction and recolonization? In this case, the extinction risk can be measured by the extinction rate, the frequency at which local extinction occurs. Using several population dynamics models with immigration, we find, in general, a negative correlation between extinction and variation. More precisely, with increasing length of the time series, an initially negative regression coefficient first becomes more negative, then becomes less negative, and eventually attains positive values before decreasing again to 0. This pattern holds under substantial variation in values of parameters representing species and environmental properties. It is also rather robust to census interval length and the fraction of missed individuals but fails to hold for high thresholds (population size values below which extinction is deemed to occur) when quasi extinction rather than true extinction is represented. The few departures from the initial negative correlation correspond to populations at risk: low growth rate or frequent catastrophes. [ABSTRACT FROM AUTHOR]

We describe new ESS models of density regulation driven by genic selection to explain the cyclical dynamics of a social system that exhibits a rock-paper-scissors (RPS) set of three alternative strategies. We tracked changes in morph frequency and fitness of Lacerta vivipara and found conspicuous RPS cycles. Morphs of Uta and Lacerta exhibited parallel survival-performance trade-offs. Frequency cycles in both species of lizards are driven by genic selection. In Lacerta, frequency of each allele in adult cohorts had significant impacts on juvenile recruitment, similar to mutualistic, altruistic, and antagonistic relations of RPS alleles in Uta. We constructed evolutionarily stable strategy (ESS) models in which adults impact juvenile recruitment as a function of self versus nonself color recognition. ESS models suggest that the rapid 4-year RPS cycles exhibited by Lacerta are not possible unless three factors are present: behaviors evolve that discriminate self versus nonself morphs at higher rates than random, self- versus non-self-recognition contributes to density regulation, and context-dependent mate choice evolves in females, which choose sire genotypes to enhance progeny survival. We suggest genic selection coupled to density regulation is widespread and thus fundamental to theories of social system evolution as well as theories of population regulation in diverse animal taxa. [ABSTRACT FROM AUTHOR]

We assessed genetic factors on progeny dispersal due to sire color morph genotypes in a field pedigree and lab crosses, and we measured maternal effects by studying both natural and experimentally induced egg size variation. Progeny were released into nature upon hatching, but we recorded dispersal distance at maturity, which reflects effective dispersal after viability selection has run its course. Progeny dispersal was significantly affected by sire genotype. Progeny from orange sires dispersed the farthest. Progeny from blue sires dispersed intermediate distances. Progeny from yellow sires were the most philopatric. Sire genotype effects interacted with egg size. In particular, enlarged progeny from orange sires dispersed farther, while enlarged progeny from yellow sires were more philopatric. Progeny from blue sires were unaffected by egg size manipulations. Egg manipulations and natural variation generally had concordant effects indicative of causation. However, asymmetry of gigantization and miniaturization on progeny dispersal from some sire genotypes suggest the involvement of maternal factors besides egg size. Results of laboratory crosses with progeny released into nature confirmed key sire genotype effects and identified additional maternal effects that modulated dispersal as a function of progeny gender. We discuss the adaptive implications of progeny dispersal in the context of male (rock-paper-scissors) and female strategies (r- and K-density cycle) that are associated with color morphs. [ABSTRACT FROM AUTHOR]

Analyzes extinction patterns for two species of orb spiders monitored annually on 77 islands over a continuous 20 year period. Description of the population of argioope argentata; Data showing that life cycle characteristics interact with the various sources of stochasticity and hence have to be taken into account to produce a model of the extinction process.

We address the question of whether freeze-tolerance, freeze-avoidance, or mixed strategy represents the best adaptation for overwintering ectotherms to endure severe winter. To this end, we develop an optimization fitness model that takes into account different physiological parameters such as energetic level, the physiological stress associated with each strategy, and climatic variables. The results show that the freeze-tolerance strategy is strongly dependent on a low sensitivity to the number of freezing days and on a capacity to reduce stress associated with freezing. This strategy is also favored when the initial energetic level is low compared to the freeze-avoidance strategy, which is favored by a high initial energetic level, a low stress associated with the supercooling, and a low sensitivity of this strategy to climatic conditions. From a theoretical point of view, the mixed strategy permits survival in harsher environments but requires the optimization of all parameters involved in both cold-hardiness strategies. However, the mixed strategy shows energetic advantages in variable environments allowing animals to resist the harshest periods. From the model results, it appears that the physiological processes developed by ectotherms to reduce these stresses might be a key to understanding the evolution of the cold-hardiness strategies. [ABSTRACT FROM AUTHOR]

abstract: Underlying the many causes of extinction of small pop-ulations is the random fate of each constituent individual or, in other words, demographic stochasticity. Demographic stochasticity is in-herent to any demographic process, regardless of the environment, and its strength increases as population size gets smaller. In particular, random fluctuations in the proportion of males and females and the way they pair for reproduction (i.e., the social mating system) are usually neglected. To assess the potential importance of demographic stochasticity to the extinction process, a two-sex model with an ex-plicit mating system was built. Extinction probabilities computed via Monte Carlo simulation were compared to real data, the case of passerines introduced to New Zealand a century ago. This minimal model of extinction allowed assessment of the importance of the mating system in the colonization process. Monogamous mating led to a higher extinction risk than did polygynous mating. Demographic uncertainty imposes high extinction probabilities on short-lived bird species as compared to long-lived bird species. Theoretical results for two-sex models are provided. [ABSTRACT FROM AUTHOR]

Studies the equal numbers of immigrations and emigrations between neighboring populations of different sizes of breeding collared flycatchers. Methodology and materials used to carry out the study; Results of the study; Discussion on the study.

Compares the nest predation and life-history traits of songbirds from Europe with that from North America. Lower nest predation rates in Europe than in North America; Correlation of higher fecundity in Europe with lower adult survival; Comparison of the nest predation and life-history traits of hole-nesting birds with that of open nesting.