Quantifying the influence of measured and unmeasured individual differences on demography.

1. Demographic rates can vary not only with measured individual characters like age, sex and mass but also with unmeasured individual variables like behaviour, genes and health. 2. Predictions from population models that include measured individual characteristics often differ from models that exclude them. Similarly, unmeasured individual differences have the potential to impact predictions from population models. However, unmeasured individual differences are rarely included in population models. 3. We construct stage- and age-structured models (where stage is mass) of a roe deer population, which are parameterized from statistical functions that either include, or ignore, unmeasured individual differences. 4. We found that mass and age structures substantially impacted model parameters describing population dynamics, as did temporal environmental variation, while unmeasured individual differences impacted parameters describing population dynamics to a much smaller extent once individual heterogeneity related to mass and age has been included in the model. We discuss how our assumptions (unmeasured individual differences only in mean trait values) could have influenced our findings and under what circumstances unmeasured individual differences could have had a larger impact on population dynamics. 5. There are two reasons explaining the relative small influence of unmeasured individual differences on population dynamics in roe deer. First, individual body mass and age both capture a large amount of individual differences in roe deer. Second, in large populations of long-lived animals, the average quality of individuals (independent of age and mass) within the population is unlikely to show substantial variation over time, unless rapid evolution is occurring. So even though a population consisting of high-quality individuals would have much higher population growth rate than a population consisting of low-quality individuals, the probability of observing a population consisting only of high-quality individuals is small.

Cytochrome b phylogeography of chamois (Rupicapra spp.). Population contractions, expansions and hybridizations governed the diversification of the genus.

The chamois provides an excellent model for exploring the effect of historical and evolutionary events on diversification. We investigate cytochrome b (cytb) sequences in the 10 recognized subspecies of Rupicapra classified within 2 species: Rupicapra pyrenaica, with the subspecies parva, pyrenaica, and ornata, and Rupicapra rupicapra, with cartusiana, rupicapra, tatrica, carpatica, balcanica, asiatica, and caucasica. A fragment of 349 bp of the cytb was sequenced in 189 individuals. We identified 3 cytb lineages: Clade West in Iberia and Western Alps; Clade Central in the Apennines and the Massif of Chartreuse; and Clade East present in populations to the east of the Alps. The 2 proposed species were polyphyletic; the clades West and Central are represented in both, whereas the Clade East is restricted to R. rupicapra. In contrast to the current systematic, cytb phylogenies suggest the classification of the 10 subspecies of chamois into a single species, R. rupicapra. Phylogeny and geographical distribution of the 3 lineages show the effects of limited latitudinal range expansions, contractions, and hybridizations among highly divergent lineages, along with a major role of the glacial ice sheets of the Alps and the Pyrenees as barriers to gene flow, on the diversification of extant taxa.

Sex- and age-specific survival of the highly dimorphic Alpine ibex: evidence for a conservative life-history tactic.

1. Age-specific survival of 215 males and 117 females of the highly sexually dimorphic Alpine ibex Capra ibex (L.) was assessed from a 21-year capture-mark-recapture (CMR) programme (1983-2004). The study covered two contrasted periods of population performance (high performance from 1983 to 1997 vs. low performance from 1998 onwards). 2. Based on current life-history theories for sexually dimorphic species, we expected that survival should decrease with age in both sexes, female survival should be buffered against environmental variations, male survival should decrease during the low performance period, and adult survival should be lower in males than females during the low performance period. 3. Survival of both sexes was strongly affected by age, with the four age classes (yearling, prime-aged adults of 2-8 years of age, old adults of 8-13 years of age, and senescent adults from 13 years of age onwards) generally reported for large herbivores. 4. Survival of females at all ages, and of yearling and prime-aged males, was buffered against environmental variations and was the same during periods of high and low population performance. The survival of old males decreased in years of low population performance. 5. All marked yearlings (32 females, 56 males) survived to age 2. Survival of prime-aged females (0.996 +/- 0.011) was higher than for other large herbivores, but similarly to other large herbivore species, it declined slowly and regularly with increasing age afterwards. Male survival was 5-15% higher each year than that of males of other large herbivores. Males enjoyed very high survival when prime-aged (0.981 +/- 0.009) and as old adults (high-performance period: 0.965 +/- 0.028, low-performance period: 0.847 +/- 0.032). 6. The very high survival of males, coupled with their prolonged mass gain, suggests a highly conservative reproductive tactic. Male ibex differ from similar-sized herbivores by showing a nearly indeterminate growth in horn size and body mass. By surviving to an advanced age, males may enjoy high reproductive success because of their large size.