The delimitation of population units is of primary importance in population management and conservation biology. Moreover, when coupled with landscape data, the description of population genetic ...structure can provide valuable knowledge about the permeability of landscape features, which is often difficult to assess by direct methods (e.g. telemetry). In this study, we investigated the genetic structuring of a roe deer population which recently recolonized a fragmented landscape. We sampled 1148 individuals from a 40 × 55‐km area containing several putative barriers to deer movements, and hence to gene flow, namely a highway, rivers and several canals. In order to assess the effect of these landscape features on genetic structure, we implemented a spatial statistical model known as geneland which analyses genetic structure, explicitly taking into account the spatial nature of the problem. Two genetic units were inferred, exhibiting a very low level of differentiation (FST = 0.008). The location of their boundaries suggested that there are no absolute barriers in this study area, but that the combination of several landscape features with low permeability can lead to population differentiation. Our analysis hence suggests that the landscape has a significant influence on the structuring of the population under study. It also illustrates the use of geneland as a powerful method to infer population structure, even in situations of young populations exhibiting low genetic differentiation.
Changes in agricultural practices and forest fragmentation can have a dramatic effect on landscape connectivity and the dispersal of animals, potentially reducing gene flow within populations. In ...this study, we assessed the influence of woodland connectivity on gene flow in a traditionally forest‐dwelling species — the European roe deer — in a fragmented landscape. From a sample of 648 roe deer spatially referenced within a study area of 55 × 40 km, interindividual genetic distances were calculated from genotypes at 12 polymorphic microsatellite loci. We calculated two geographical distances between each pair of individuals: the Euclidean distance (straight line) and the ‘least cost distance’ (the trajectory that maximizes the use of wooded corridors). We tested the correlation between genetic pairwise distances and the two types of geographical pairwise distance using Mantel tests. The correlation was better using the least cost distance, which takes into account the distribution of wooded patches, especially for females (the correlation was stronger but not significant for males). These results suggest that in a fragmented woodland area roe deer dispersal is strongly linked to wooded structures and hence that gene flow within the roe deer population is influenced by the connectivity of the landscape.
The effect of experimental manipulation of population density on home-range size was investigated in two free-ranging roe deer (Capreolus capreolus) populations under contrasting environmental ...conditions. In these two long-term monitoring studies, one in Bogesund, Sweden (12 years) and one in Dourdan, France (10 years), deer density varied fourfold through varying culling pressure. Home-range data were collected by radio-tracking across the periods of contrasting density of the studies. We predicted that home-range size for females should vary in relation to the level of feeding competition, while for males, competition for mating opportunities should also influence range size, at least in summer when roe bucks are territorial. We found a highly consistent pattern over the two populations, with strong effects of deer density on home-range size, as well as significant differences between winter and summer ranges and between the sexes. Home ranges were consistently smaller at high density compared to low density. Males had larger ranges than females and this was particularly so during summer. Lastly, winter ranges were generally larger than summer ranges, particularly among females, although males at Dourdan had larger summer ranges compared to winter ranges. We suggest that the reduction of range size at high deer density during winter, as well as summer, is linked to the solitary behaviour and territorial social system of roe deer, with possible effects of dominance rank, even outside the mating season.
When individuals disperse, they modify the physical and social composition of their reproductive environment, potentially impacting their fitness. The choice an individual makes between dispersal and ...philopatry is thus critical, hence a better understanding of the mechanisms involved in the decision to leave the natal area is crucial. We explored how combinations of behavioural (exploration, mobility, activity and stress response) and morphological (body mass) traits measured prior to dispersal were linked to the subsequent dispersal decision in 77 roe deer Capreolus capreolus fawns. Using an unusually detailed multi-trait approach, we identified two independent behavioural continuums related to dispersal. First, a continuum of energetic expenditure contrasted individuals of low mobility, low variability in head activity and low body temperature with those that displayed opposite traits. Second, a continuum of neophobia contrasted individuals that explored more prior to dispersal and were more tolerant of capture with those that displayed opposite traits. While accounting for possible confounding effects of condition-dependence (body mass), we showed that future dispersers were less neophobic and had higher energetic budgets than future philopatric individuals, providing strong support for a dispersal syndrome in this species.
Understanding the genetic and environmental mechanisms governing variation in morphology or phenology in wild populations is currently an important challenge. While there is a general consensus that ...selection is stronger under stressful conditions, it remains unclear whether the evolutionary potential of traits should increase or decrease with increasingly stressful conditions. Here, we investigate how contrasting environmental conditions during growth may affect the maternal and genetic components of body mass in roe deer, the most abundant and widespread wild ungulate in Western Europe. Body mass is a key life history trait that strongly influences both survival and reproductive performance in large herbivores. We used pedigrees and animal models to determine the variance components of juvenile and adult winter body mass in two populations experiencing contrasting early-life conditions.
Our analyses showed that roe deer at Chizé, where habitat was poor and unpredictable, exhibited very low genetic variance in juvenile body mass. Instead, variance in mass was mainly driven by among-cohort differences in early-life conditions and maternal environment. In contrast, roe deer at Bogesund, where resource availability during the critical period of fawn rearing was higher, displayed a substantial level of genetic variance in body mass. We discuss the potential role of past demography and viability selection on fawn body mass on the erosion of genetic variance in the poor habitat.
Our study highlights the importance of accounting for both spatial (i.e. between-population variation) and temporal (i.e. cohort variation) heterogeneity in environmental conditions, especially in early life, to understand the potential for adaptive responses of wild populations to selection.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
According to the principle of allocation, trade-offs are inevitable when resources allocated to one biological function are no longer available for other functions. Growth, and to a lesser extent, ...immunity are energetically costly functions that may compete with allocation to reproductive success and survival. However, whether high allocation to growth impairs immune system development during the growing period or immune system performance during adulthood is currently unknown in wild mammals. Using three roe deer (Capreolus capreolus) populations experiencing contrasting environmental conditions, we tested for potential costs of growth on immune phenotype over both the short-term (during growth), and the long-term (during adulthood) over the course of an individuals’ life. We investigated potential costs on a set of 12 immune traits that reflect both innate and adaptive responses, and compared them between sexes and populations. Although fast growth tended to be associated with low levels of some humoral traits (globulins) during the growing period and some cellular immune traits (i.e. eosinophil and neutrophil counts) during adulthood, evidence for a trade-off between growth and other immune components was limited. Unexpectedly, no detectable growth costs on immunity were found in females from the population experiencing the least favourable environment. We discuss our findings in the light of the complex interplay between resource allocation strategies among reproduction, maintenance and immunity, in relation to local environmental conditions experienced by roe deer.
Lay Summary Do all individuals of a population adopt a similar pattern of habitat use or are there different tactics linked to an individual's personality? We show that a priori more reactive ...individuals minimize risk by using safer habitats, thus gaining only limited access to forage-rich habitats, whereas less reactive individuals prioritize access to high-quality resources by using riskier open habitat, but may thus be subject to higher risk of predation. This suggests the existence of a risk management syndrome in wild populations.The way an individual reacts to the risk of predation or disturbance may have important consequences for its immediate and future survival. Risk is likely perceived differently by individuals in relation to among-individual differences in correlated behavioral traits, that is, syndromes or personalities. Given that animals can avoid the risk of predation/disturbance through modification of their habitat use, we might expect individuals of differing behavioral types to adopt contrasting tactics of habitat use when faced with risky or stressful situations. We studied the relationship between habitat use and among-individual variation in behavioral profile in a population of roe deer. We hypothesized that an individual's habitat use tactics should be related to their capacity to cope with risky situations. In particular, we predicted that more reactive (risk-averse) roe deer, with relatively high behavioral response and high body temperature at capture, long flight distances and which were more vigilant during feeding, should use riskier open habitat less, particularly when risk is high. We found that although the use of open habitat during the day was negatively correlated with the indices of reactivity at capture, it was also positively correlated with indices of reactivity while foraging in open habitat. Furthermore, most of the behavioral parameters we measured were intercorrelated and moderately repeatable, potentially indexing personality traits. We conclude that there is substantial interindividual variability in how individuals manage risky situations which imposes constraints on how they are able to exploit high-risk habitats, suggesting the existence of a risk management syndrome in this large herbivore.
Natal dispersal (i.e. movements between the natal range of an individual and its first breeding site) is a complex process which can have profound impacts on population dynamics. In most species, ...only a proportion of juveniles actually disperse, but few empirical data are available on the factors that drive the decision to disperse. To understand the behavioural ontogeny of the decision to disperse, we investigated the ranging behaviour of 66 juvenile roe deer, Capreolus capreolus, monitored with GPS collars prior to and during the dispersal phase. We compared the number and features (distance and duration) of exploratory movements during the period prior to dispersal between philopatric individuals and dispersers. Overall, 76% of the juveniles that dispersed during their first spring performed exploratory movements prior to the dispersal period. Indeed, exploration prior to the dispersal phase was much more common among future dispersers than among future philopatric individuals, suggesting that dispersal of juveniles is facilitated to some degree by predispersal exploration forays. Furthermore, the direction of the dispersal event was correlated with the direction of previous exploration, although there was no relationship between exploration distance and subsequent dispersal distance. Thus, it appears that individuals that subsequently disperse first explore their environment, prior to definitively leaving their natal range, probably to obtain information on potential suitable adult ranges. Exploratory movements prior to dispersal can thus provide information that influences an individual's decision on whether or not to disperse and, if so, in which direction.
•We investigated the ranging behaviour of juvenile roe deer prior to dispersal.•Exploration is more common among future dispersers than future philopatric animals.•Dispersal direction is correlated with the direction of previous exploration.•Exploration prior to dispersal is a critical component of the natal dispersal process.•Exploration can provide information that influences an individual's dispersal decision.
We examined the long-term effects (28 years) of habitat loss and phenotypebased selective harvest on body mass, horn size, and horn shape of mouflon (Ovis gmelini musimon) in southern France. This ...population has experienced habitat deterioration (loss of 50.8% of open area) since its introduction in 1956 and unrestricted selective hunting of the largest horned males since 1973. Both processes are predicted to lead to a decrease in phenotype quality by decreasing habitat quality and by reducing the reproductive contribution of individuals carrying traits that are targeted by hunters. Body mass and body size of both sexes and horn measurements of males markedly decreased (by 3.4-38.3%) in all age classes from the 1970s. Lamb body mass varied in relation to the spatiotemporal variation of habitat closure within the hunting-free reserve, suggesting that habitat closure explains part of these changes. However, the fact that there was no significant spatial variation in body mass in the early part of the study, when a decline in phenotypic quality already had occurred, provided support for the influence of selective harvesting. We also found that the allometric relationship between horn breadth and horn length changed over the study period. For a given horn length, horn breadth was lower during the second part of the study. This result, as well as changes in horn curve diameter, supports the interpretation that selective harvesting of males based on their horn configuration had evolutionary consequences for horn shape, since this phenotypic trait is less likely to be affected by changes in habitat characteristics. Moreover, males required more time (approximately four years) to develop a desirable trophy, suggesting that trophy hunting favors the reproductive contribution of animals with slow-growing horns. Managers should exploit hunters' desire for trophy males to finance management strategies which ensure a balance between the population and its environment. However, for long-term sustainable exploitation, harvest strategy should also ensure that selectively targeted males are allowed to contribute genetically to the next generations.
Most forests in Europe are patchily distributed within the agricultural landscape. Therefore, forest biogeochemistry in Europe cannot be understood without considering the connectivity of nutrient ...cycles between forest patches and fertilized cropland. In this paper, we quantified the role of roe deer, the most widespread wild ungulate in Europe, as a vector of nitrogen and phosphorus from fertilized fields to forest patches, in a typical agricultural landscape of southwestern Europe. We derived a model of nutrient transfer from a data set on deer density, landscape-use by individual deer, and nutrient content in feces. The model shows that the magnitude of nutrient transfer is highly sensitive to the proportion of forest patches within the landscape, and to the way deer use the landscape to feed and defecate. Hence, the magnitude of nutrient transfer varies substantially across the landscape. Locally, deer may significantly fertilize the forest, transferring the equivalent of almost 20% of the atmospheric deposition of nitrogen, and the equivalent of 0.13% of the total stock of phosphorus from cropland to forest patches each year. These inputs may markedly influence the biogeochemistry of forests in the long run, and the nitrogen to phosphorus ratio available to trees and forest plants. These results highlight the significant, but, heterogeneous, role of wild ungulates in forest biogeochemistry across Europe.
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