Concha Mateos

Disposable-soma senescence mediated by sexual selection in an ungulate.

Senescence may result from an optimal balance between current reproductive investment and bodily repair processes required for future reproduction, a theoretical prediction difficult to prove especially in large, long-lived animals. Here we propose that teeth that have fixed dimensions early in life, but that wear during chewing, can be taken as a measure of total lifetime ‘repair’, and their wear rate as a measure of current expenditure in performance. Our approach also considers the sexual selection process to investigate the advance of senescence in males compared with females, when selection favouring competition over mates reduces the reproductive lifespan of males. We studied carcasses of 2,141 male and 739 female red deer (Cervus elaphus) of different ages, finding that male molariform teeth emerged at a far smaller size than expected from body size dimorphism. This led to higher workload, steeper wear rate and earlier depletion of male teeth than in females, in concordance with sex-specific patterns of lifetime performance and reproduction. These findings provide the empirical support for the disposable-soma hypothesis of senescence, which predicts that investment in bodily repair will decrease when the return from this investment may not be realized as a result of other causes that limit survival or reproduction.

Effects of male dominance and courtship display on female choice in the ring-necked pheasant

Abstract Male traits and behaviours acting in mate choice and intrasexual competition are expected to be congruent. When studying their evolution, this often makes it difficult to differentiate between these two components of sexual selection. Studies are therefore needed on mate choice in conjunction with the role of displays and dominance. We present the results from two experiments conducted to investigate the effects of male dominance and courtship displays on female choice in the ring-necked pheasant, Phasianus colchicus, controlling for differences in morphological male traits. We found: (1) different courtship behaviours had different effects on female choice: females were mainly attracted by the feeding courtship behaviour, while another courtship display (the lateral display) was effective in producing the copulation-acceptance response by the females; (2) subordinate males performed the courtship behaviour before females less frequently than dominant males, and females reinforced intrasexual selection by choosing dominant males, and (3) subordinate males in visual contact with a dominant became less attractive to females. The results support the idea (armament-ornament model) that female pheasants may benefit from using traits selected in male-male competition as clues for mate choice.

Sexual selection in the ring-necked pheasant: a review

The common pheasant, Phasianus colchicus, is now considered a classic example of the difficulty of establishing a clear distinction between inter- and intrasexual selection since a role for male spurs as cues used by females in mate choice has been reported. Field and experimental studies on sexual selection in the ring-necked pheasant show that the dimorphic morphological (and behavioural) male traits have a dual function according to the armament-ornament model. They are weapons or reliable signals of male quality directed both to females and rivals, and the relative importance between them depends on a suite of factors affecting the decision-making processes of females, including the outcome of male-male encounters. Different mechanisms and models of sexual selection have been suggested in order to classify the overall competitive strategies found in nature; but the amount of empirical data on the evolution of epigamic traits suggests that what determines the reproductive success of males is a complex ...

Signals in intra-sexual competition between ring-necked pheasant males ☆ ☆☆

Abstract Many sexual ornaments are signals commonly used in both sexual selection contexts: mate choice and intra-sexual competition. Previous studies show that female choice in ring-necked pheasants, Phasianus colchicus , is influenced by features of some male ornaments. Experiments and correlational data were used in this study to investigate the role of male ornaments in male–male agonistic encounters. Some traits used by females in mate choice, namely tail length and black points in the wattle, had no effect in male–male competition, but the length of ear tufts had a role in both contexts. The most important traits appeared to be the head ornaments, which include ear tufts, but also wattle size. Head ornaments function as coverable signals that are displayed to rival males informing about readiness to fight, fighting ability and resource-holding power; and the total time spent displaying correlated with testosterone level, physical condition and rank. Thus, the costs of displaying head ornaments appear to be both inherent and target-receiver dependent.

The subordination stress paradigm and the relation between testosterone and corticosterone in male ring-necked pheasants

The relations linking glucocorticoids, testosterone, social and sexual behaviour in vertebrates are complex and poorly understood. The conventional view is that: (1) subordinate individuals should have higher glucocorticoid concentrations (the subordination stress paradigm); (2) dominant and more active males during the breeding season should have higher testosterone concentrations; and (3) the relation between glucocorticoid and testosterone concentrations should be negative. I investigated the relation between hormones and behaviour in male ring-necked pheasants, Phasianus colchicus. Dominant and high-displaying males over the whole mating period had a higher level of both testosterone and corticosterone. As a consequence, testosterone and glucocorticoid levels were positively correlated. These results do not support the subordination stress paradigm, but they may support the stress-mediated version of the immunocompetence handicap hypothesis.

Management practices and their association with Mycobacterium tuberculosis complex prevalence in red deer populations in Southwestern Spain

Intensification of game management may increase the prevalence of tuberculosis (TB) in wildlife despite eradication programs implemented in cattle herds in the same areas. In this cross-sectional study, we investigated the association between wild game management practices and the presence of tuberculosis in red deer populations in Southwestern Spain. Five hundred and fifty-one animals were examined by necropsy to detect tuberculosis-like lesions in the main lymph nodes. Prevalence, as determined by TB-like lesions, was estimated to be 5.1% of animals, with 77% of TB-like lesions confirmed by PCR. Our results suggest that population density, in addition to factors which promote the local aggregation of animals, is factors associated with increased prevalence of TB in red deer populations. We suggest that management practices including supplementary feeding, fencing, water ponds and interaction with domestic livestock should be revised in order to prevent TB in wild deer both.

Fluctuating asymmetry of red deer antlers negatively relates to individual condition and proximity to prime age

After about 50 years of research on fluctuating asymmetry (FA) as a reliable indicator of both individual quality and environmental stress, the enthusiasm is beginning to decline. The findings of many studies are inconsistent and the relationship between FA and stress appears both weaker and more complex than first thought. To provide clarification of the debate, new studies should use more efficient and unified statistical protocols, large sample sizes and joint analysis of several related traits. In addition, fitnesseFA associations should be tested at the individual level, in different populations and under different environmental conditions. To achieve these criteria, we describe a 9-year study in which we measured six antler traits of 3 000 Iberian red deer, Cervus elaphus hispanicus, from three study areas in southwest Spain. Males were harvested during hunting activities and measured, weighed and aged post mortem. We found evidence of correlations between traits in FA, an association between asymmetry and stress conditions and a weak but significant negative relationship between FA and fitness surrogates (body mass and antler size), thus supporting some assumptions of the FA hypothesis. As also predicted by theory, antler traits of less functional importance were more asymmetric and more sensitive to stress than those directly used in fighting behaviour. The relationship between age and antler asymmetry was U-shaped, suggesting an effect of sexual selection on antler development in favour of larger and more symmetrical antlers during prime age.

Polygyny can increase rather than decrease genetic diversity contributed by males relative to females: evidence from red deer

Polygyny is expected to erode genetic variability by reducing the diversity of genetic contribution of males to the next generation, although empirical evidence shows that genetic variability in polygynous populations is not lost as rapidly as expected. We used microsatellite markers to study the genetic variability transmitted by mothers and fathers to offspring during a reproductive season in wild populations of a polygynous mammal, the red deer. Contrary to expectations, we found that males contributed more genetic diversity than females. Also, we compared study populations with different degrees of polygyny to find that polygyny was not related to a decrease in genetic diversity contributed by males. On the contrary, when population genetic diversity was relatively low, polygyny associated with higher genetic diversity of paternal lineage. Our results show that sexual selection, by favouring heterozygote individuals, may compensate the potential reduction of effective population size caused by polygyny, thus contributing to explain why genetic diversity is not depleted in polygynous systems.

Parents' genetic dissimilarity and offspring sex in a polygynous mammal.

Offspring quality may benefit from genetic dissimilarity between parents. However, genetic dissimilarity may trade‐off with additive genetic benefits. We hypothesized that when sexual selection produces sex‐specific selective scenarios, the relative benefits of additive genetic vs. dissimilarity may differ for sons and daughters. Here we study a sample of 666 red deer (Cervus elaphus) microsatellite genotypes, including males, females and their foetuses, from 20 wild populations in Spain (the main analyses are based on 241 different foetuses and 190 mother‐foetus pairs). We found that parental lineages were more dissimilar in daughters than in sons. On average, every mother was less related to her mate than to the sample of fathers in the population when producing daughters not sons. Male foetuses conceived early in the rutting season were much more inbred than any other foetuses. These differences maintained through gestation length, ruling out intrauterine mortality as a cause for the results, and indicating that the potential mechanism producing the association between parents’ dissimilarity and offspring sex should operate close to mating or conception time. Our findings highlight the relevance of considering the sex of offspring when studying genetic similarity between parents.

The tragedy of the commons: unsustainable population structure of Iberian red deer in hunting estates

Hunting can influence population structure with consequences in ecological and evolutionary processes. Populations of Iberian red deer (Cervus elaphus hispanicus) in Spain occur under two different management regimes: fenced and unfenced (open) estates. We compared census data, hunting bags and data from hunted individuals between both types of estates. Harvest on stags was moderate in fenced estates but strong in open ones, probably due to the competition between neighbouring landowners over the same deer populations. On the contrary, female culling was low in open estates compared to fenced ones. As a result, populations in open estates have mostly young males and strongly female-biased sex ratios. Female-biased population structure in open estates did not result in higher number of males being harvested per year compared with fenced estates, probably due to negative effects on development, survival and reproduction, and harvested males were younger, and hence, with smaller antlers. There is published evidence for undesirable effects of biased population sex ratio and age structure in these red deer populations. Our results indicate that this type of management may be unsustainable and recommend that harvest on males in open estates should be reduced and that on females increased, in order to maintain a more balanced population structure that may allow sustainable population dynamics and the operation of natural evolutionary processes.