Invasive species control with apex predators: increasing presence of wolves is associated with reduced occurrence of the alien raccoon dog

The role of an alien predator in the community depends on its interaction with native predators. The absence of apex predators may facilitate outbreaks of invasive mesopredators, but the effect of apex predators may vary between species and environments. We analysed the occurrence of a common invasive mesopredator in Europe, the raccoon dog (Nyctereutes procyonoides), and native mesopredators, the red fox and the Eurasian badger, in camera-trap data from Finland. The observations in cameras were analysed in relation to the presence of apex predators in the landscape (grey wolf and Eurasian lynx), human density, and habitat. We observed negative effect of increasing presence of wolves and lynxes on the occurrence of raccoon dogs. This effect appeared clear compared to the effects of habitat and human density. The effect of lynxes on raccoon dogs was clearer in areas with short growth season. For the occurrence of badgers, the presence of wolves had a weak negative effect and the presence of lynxes had a positive effect. For the occurrence of red foxes, wolves had a positive effect when agricultural fields were sparse in the landscape and lynxes had no effect. We also observed that the invasive raccoon dog currently appears to be the most common mesopredator within the study area. We conclude that the effect of apex predators on mesopredators depends on the environment and, in our case, was more suppressive on the alien mesopredator than on the native mesopredators. Thus, apex predators can play an important role in controlling invasive mesopredators.

Sympatric divergence and clinal variation in multiple coloration traits of Ficedula flycatchers

Geographic variation in phenotypes plays a key role in fundamental evolutionary processes such as local adaptation, population differentiation and speciation, but the selective forces behind it are rarely known. We found support for the hypothesis that geographic variation in plumage traits of the pied flycatcher Ficedula hypoleuca is explained by character displacement with the collared flycatcher Ficedula albicollis in the contact zone. The plumage traits of the pied flycatcher differed strongly from the more conspicuous collared flycatcher in a sympatric area but increased in conspicuousness with increasing distance to there. Phenotypic differentiation (PST ) was higher than that in neutral genetic markers (FST ), and the effect of geographic distance remained when statistically controlling for neutral genetic differentiation. This suggests that a cline created by character displacement and gene flow explains phenotypic variation across the distribution of this species. The different plumage traits of the pied flycatcher are strongly to moderately correlated, indicating that they evolve non-independently from each other. The flycatchers provide an example of plumage patterns diverging in two species that differ in several aspects of appearance. The divergence in sympatry and convergence in allopatry in these birds provide a possibility to study the evolutionary mechanisms behind the highly divergent avian plumage patterns.

Quantitative genetics of behavioural reaction norms: genetic correlations between personality and behavioural plasticity vary across stickleback populations

Behavioural ecologists have proposed various evolutionary mechanisms as to why different personality types coexist. Our ability to understand the evolutionary trajectories of personality traits requires insights from the quantitative genetics of behavioural reaction norms. We assayed > 1000 pedigreed stickleback for initial exploration behaviour of a novel environment, and subsequent changes in exploration over a few hours, representing their capacity to adjust their behaviour to changes in perceived novelty and risk. We found heritable variation in both the average level of exploration and behavioural plasticity, and population differences in the sign of the genetic correlation between these two reaction norm components. The phenotypic correlation was not a good indicator of the genetic correlation, implying that quantitative genetics are necessary to appropriately evaluate evolutionary hypotheses in cases such as these. Our findings therefore have important implications for future studies concerning the evolution of personality and plasticity.

Blood parasites mediate morph-specific maintenance costs in a colour polymorphic wild bird

Parasites can mediate profound negative effects on host fitness. Colour polymorphism has been suggested to covary genetically with intrinsic physiological properties. Tawny owl colour polymorphism is highly heritable with two main morphs, grey and brown. We show that experimental medication acts to reduce blood parasites and that medicated grey females maintain body mass during breeding, whereas medicated brown females decline in body mass similar to control females of both morphs. We find no effect of medication on general immunoglobulin levels, antigen-specific humoral response or H/L ratio. In the descriptive data, both morphs have similar blood parasite infection rates, but blood parasite infection is associated with decreased body mass in brown but not in grey females. We conclude that blood parasite infection primarily has somatic costs, which differ between the two highly heritable tawny owl colour morphs with more pronounced costs in the grey (little pigmented) morph than in the brown (heavily pigmented) morph. Because our descriptive results imply the opposite pattern, our findings highlight the need of experimental manipulation when studying heritable variation in hosts' response to parasitism.

Whither Pst? The approximation of Qst by Pst in evolutionary and conservation biology

Local adaptation through natural selection can be inferred in case the additive genetic divergence in a quantitative trait across populations (Q(st)) exceeds the neutral expectation based on differentiation of neutral alleles across these populations (e.g. F(st)). As such, measuring Q(st) in relation to neutral differentiation presents a first-line investigation applicable in evolutionary biology (selection on functional genes) and conservation biology (identification of locally adapted coding genes). However, many species, especially those in need of conservation actions, are not amenable for the kind of breeding design required to estimate either narrow- or broad-sense Q(st). In such cases, Q(st) has been approximated by the phenotypic divergence in a trait across populations (P(st)). I here argue that the critical aspect for how well P(st) approximates Q(st) depends on the extent that additive genetic effects determine variation between populations relative to within populations. I review how the sensitivity of conclusions regarding local adaptation based on P(st) have been evaluated in the literature and find that many studies make a anticonservative null assumption in estimating P(st) and/or use a nonconservative approach to explore sensitivity of their conclusions. Data from two studies that have provided a second, independent assessment of selection in their system suggest that P(st)-F(st) comparisons should be interpreted very conservatively. I conclude with recommendations for improving the robustness of the inferences drawn from comparing P(st) with neutral differentiation.

Low genetic differentiation in a sedentary bird: house sparrow population genetics in a contiguous landscape

The house sparrow Passer domesticus has been declining in abundance in many localities, including Finland. We studied the genetic diversity and differentiation of the house sparrow populations across Finland in the 1980s, at the onset of the species' decline in abundance. We genotyped 472 adult males (the less dispersive sex) from 13 locations in Finland (covering a range of 400 × 800 km) and one in Sweden (Stockholm) for 13 polymorphic microsatellite markers. Our analysis of Finnish ringing records showed that natal dispersal distances are limited (90% <16 km), which confirmed earlier finding from other countries. The Finnish populations were panmictic, and genetically very homogeneous and the limited dispersal was sufficiently large to maintain their connectivity. However, all Finnish populations differed significantly from the Stockholm population, even though direct geographical distance to it was often smaller than among Finnish populations. Hence, the open sea between Finland and Sweden appears to form a dispersal barrier for this species, whereas dispersal is much less constrained across the Finnish mainland (which lacks geographical barriers). Our findings provide a benchmark for conservation biologists and emphasize the influence of landscape structure on gene flow.

The rate of ageing in a long-lived bird is not heritable

A senescent decline in performance occurs in late age in many organisms, and is thought to be partly due to additive genetic effects. Here annual fitness, estimated as the age-specific sum of survival and reproduction, was used to test for genetic variance in ageing in a population of common gulls, Larus canus. Data on 3986 individuals collected over a 34-year period indicate a dramatic senescent decline in late life. We also find that annual fitness is heritable and that individuals vary in their rates of ageing. However, counter to theoretical expectations, we find no support for a heritable component to the variance in rates of senescence. Increases in the among-individual (permanent environment) and residual variance components initiate an increase in the total phenotypic variance for annual fitness with age. This finding suggests that older birds are more sensitive to environmental effects, and that old age causes an overall pattern of declining h(2) of annual fitness. Our findings suggest that individual-specific factors do have a role in determining the rate of senescence in this population, but that additive genetic variance for the rate of senescence is either absent or small.

A possible link between parasite defence and residual reproduction

Life-history theory centres around trade-offs between current and future reproduction, but we have little understanding of how such trade-offs are mediated. We supplementary fed Ural owls (Strix uralensis) during the nestling period and quantified parents' current and future life-history components as well as their physiological health by monitoring haematocrit, leucocyte profile, intra- and extracellular blood parasites. Feeding led to reduced parental effort but did not improve offspring viability, male parasite defence, or parental survival. Intracellular leucocytozoan infection was reduced in fed females which lasted to the following year's reproductive season (carry-over effect), when fed females also laid larger and earlier clutches. Leucocytozoon infection therefore may mediate the life-history trade-off between current and residual reproduction in this species.

The evolutionary ecology of individual phenotypic plasticity in wild populations

The ability of individual organisms to alter morphological and life-history traits in response to the conditions they experience is an example of phenotypic plasticity which is fundamental to any population's ability to deal with short-term environmental change. We currently know little about the prevalence, and evolutionary and ecological causes and consequences of variation in life history plasticity in the wild. Here we outline an analytical framework, utilizing the reaction norm concept and random regression statistical models, to assess the between-individual variation in life history plasticity that may underlie population level responses to the environment at both phenotypic and genetic levels. We discuss applications of this framework to date in wild vertebrate populations, and illustrate how natural selection and ecological constraint may alter a population's response to the environment through their effects at the individual level. Finally, we present future directions and challenges for research into individual plasticity.

The evolution of fitness in life-history theory

Theory concerning the evolution of life history (the schedule of reproduction and survival) focuses on describing the life history which maximises fitness. Although there is an intuitive link between life history and fitness, there are in fact several measures of the 'black box' concept of fitness. There has been a debate in the bio-mathematical literature on the predictive difference between the two most commonly used measures; intrinsic rate of increase r and net reproductive ratio R0. Although both measures aim to describe fitness, models using one of the measures may predict the opposite of similar models using the other measure, which is clearly undesirable. Here, I review the evolution of these fitness measures over the last four decades, the predictive differences between these measures and the resulting shift of the fitness concept. I focus in particular on some recent developments, which have solved the dilemma of predictive differences between these fitness measures by explicitly acknowledging the game-theoretical nature of life-history evolution.