Showing papers by "Jean Clobert published in 1995"
TL;DR: Unified Life Models (ULM) as mentioned in this paper is a powerful tool to study the life cycle of species and meta-populations in the general framework of discrete dynamical systems and symbolic computation.
Abstract: Matrix models for population dynamics have recently been studied intensively and have many applications to theoretical and applied problems (conservation, management). The computer program ULM (Unified Life Models) collects a good part of the actual knowledge on the subject. It is a powerful tool to study the life cycle of species and meta-populations. In the general framework of discrete dynamical systems and symbolic computation, simple commands and convenient graphics are provided to assist the biologist. The main features of the program are shown through detailed examples: a simple model of a starling population life cycle is first presented leading to basic concepts (growth rates, stable age distribution, sensitivities); the same model is used to study competing strategies in a varying environment (extinction probabilities, stochastic sensitivities); a meta-population model with migrations is then presented; some results on migration strategies and evolutionary stable strategies are eventually proposed.
162 citations
TL;DR: In this article, the authors used numerical estimation to illustrate the increasing bias in return rate as an estimator of annual survival probability as recapture/resighting probability decreases, and showed that return rates generally are poor estimators.
Abstract: Studies of life history evolution in passerine birds often depend on examination of annual survival probability of adult birds. Most studies rely on return rates (proportion of marked individuals released in one year that are recaptured in the next year) to estimate annual survival probability. Yet, return rate includes both the probability of survival and the probability of recapturing or resighting the bird in the next time interval. We use numerical estimation to illustrate the increasing bias in return rate as an estimator of annual survival probability as recapture/resighting probability decreases. Recapture/resighting probability is normally assumed to be high and relatively invariant for recapture/resighting studies of color-banded territorial birds. We tested this assumption through examination of 11 color-banding studies of passerines. These studies showed that recapture/resighting probabilities vary strongly and cannot be generalized as high. In short, return rates generally are poor estimators ...
132 citations
TL;DR: The results are consistent with those reported in two previous studies of squamate reptiles, suggesting that these aspects of locomotor abilities are relatively free to evolve independently, such that natural selection could increase both speed and endurance.
Abstract: We used quantitative genetic analyses to test the hypothesis of a trade-of between locomotor speed and endurance in a population of the European lizard Lacerta vivipara, which is the subject of long-term demographic studies. We estimated the heritability of maximal sprint speed, treadmill endurance, and tail length, a morphometric trait that may afect locomotor performance, as well asphenotypic, genetic, and environmental correlations between these traits. Gravid females were captured in the field and held in the laboratory under standardized conditions until giving birth; traits were then measured on their ofspring. Prior to genetic analyses, we used multiple regressions to remove the efects of such covariates as body size (mass and snout-vent length), dam age, and length of time dams were held in captivity prior toparturition. When we examined the residual characters, heritability was low and statistically nonsignficant for speed but relatively high for both endurance (0.46) and tail length (0.51). None...
102 citations
TL;DR: If high parasite loads arise from long exposure time to a constant population of parasites, and if the negative effects of parasites are additive over time, hosts could reduce the impact of parasites simply by investing more during the earlier stages of life.
Abstract: We studied the effect of maternal ectoparasite load (measured at parturition) on the life-history traits of the offspring of the host Lacerta vivipara, the European common lizard. The ectoparasite, a mite belonging to the family Laelapidae, had a detrimental effect on its host: parasite load was associated with increased host mortality, and was negatively correlated with host body mass. Parasite load was persistent over time, suggesting that parasite load can be predictable. Offspring of highly parasitised mothers had higher values of several fitness components early in life than offspring of parasite-free mothers or lightly infested mothers. This was expressed in terms of increased F1 yearling growth rate, and reproductive investment at first reproduction (measured as F2 hatchling mass). These results are interpreted as a host adaptation to attenuate the impact of parasites. Indeed, if high parasite loads arise from long exposure time to a constant population of parasites, and if the negative effects of parasites are additive over time, hosts could reduce the impact of parasites simply by investing more during the earlier stages of life. Naturally, having better performance early in life should lead to higher mortality rates and/or lower fecundity later in life.
94 citations
TL;DR: This work experimentally tested the existence of such a maternal effect (food availability during gestation) on dispersal of offspring in the common lizard (Lacerta vivipara), and found the first evidence of a prenatal effect on disperseal.
Abstract: Prenatal effects caused by the maternal environment during gestation are known to contribute to the phenotype of the offspring. Whether they have some adaptive value is currently under debate. We experimentally tested the existence of such a maternal effect (food availability during gestation) on dispersal of offspring in the common lizard (Lacerta vivipara). Pregnant females were captured and kept in the laboratory until parturition. During this period, females were offered two rates of food delivery. After parturition, we released mothers and offspring at the mother's capture point. Dispersal of young was significantly affected by the mother's nutrition. To our knowledge, this is the first evidence of a prenatal effect on dispersal. Offspring of well fed mothers dispersed at a higher rate than those of less well fed mothers. As current hypotheses clearly predict the opposite result, our evidence calls for their reassessment. Dispersers are not always the least fit individuals or those coming from the poorest environments.
92 citations