Impact of spatial variation of a crucial prey, the molecricket, on hoopoe territory occupancy and reproduction

SummaryFor iteroparous organisms life‐history theory predicts a trade‐off between current and future reproduction, and therefore the evolution of host responses to current parasite infestation that will maximize lifetime reproductive success. The parasite‐induced variation in reproductive success is thus not the net result of parasite infestation alone, but the parasite‐mediated outcome of optimal resource allocation among current and future reproductive events. Understanding the importance of parasites for the evolution of host life history therefore requires an experimental investigation of the effects of parasites over the host's life span. Such studies are currently scant.We manipulated the load of an ectoparasite, the hen flea (Ceratophyllus gallinae), in the nests of its most common host, the great tit (Parus major), over a period of 4 years and recorded, the components of current and future reproductive success including survival, divorce, breeding dispersal and various reproductive parameters. Finally we assessed, for females only as paternity of males was unknown, the lifetime reproductive success as a close correlate of Darwinian fitness.For current reproduction, our experiment demonstrates that parasites reduce current reproductive success via an increase in the probability of nest failure during incubation and the nestling period. In the presence of fleas, clutch size and the number of fledglings were reduced while the incubation and the nestling period were prolonged. Thus parasitism led to an increase in parental effort but nevertheless reduced current reproductive success.For future reproduction, the experiment shows that females breeding in infested nests dispersed over longer distances between breeding attempts. The divorce rate following infestation, the probability of breeding locally in the future and residual reproductive success were not affected significantly by ectoparasites. The study thus suggests that hen fleas play a minor role in shaping the trade‐off between current and future reproduction.Lifetime reproductive success of females, measured as the total number of locally recruiting offspring over the 4 experimental years, was reduced significantly by ectoparasites. The negative effect of parasites arose by a reduction of the number of fledglings per breeding attempt rather than by a reduction of the number of breeding attempts.

<p>Identifying sources of variation in individual reproductive success is crucial to our understanding of population dynamics and evolutionary ecology. In many systems, the determinants of success are not well known. Where species have parental care, for example, determinants of success can be particularly challenging to partition between parents and offspring. In this thesis I investigate drivers and consequences of variable life histories, for a small reef fish that exhibits male parental care (the common triplefin Forsterygion lapillum). I examined the influence of individual life history, phenotype and behaviour on (1) the performance of recently settled juveniles, and (2) the reproductive success adult males. I made field-based observations of adult males during the breeding season, measured their phenotypic traits (body size and condition) and used their otoliths to reconstruct life history characteristics (hatch dates and mean growth rates). My life history trait reconstructions suggested two alternate pathways to ’success’ for adult males. Successful males hatched earlier and therefore had a developmental ’head start’ over less successful males (i.e., males with eggs > male territory holders without eggs > floaters). Alternatively, males can apparently achieve success by growing faster: for males born in the same month, those with eggs grew faster than those with territories and no eggs, and both groups grew faster than floaters. These results suggest that accelerated growth rate may mediate the effects of a later hatch date, and that both hatch dates and growth rates influence the success of adult males, likely through proximate effects on individual phenotypes. Identifying sources of variation in individual reproductive success is crucial to our understanding of population dynamics and evolutionary ecology. In many systems, the determinants of success are not well known. Where species have parental care, for example, determinants of success can be particularly challenging to partition between parents and offspring. Male parental care is common among fishes, where resources such as high quality territories and mates often may be limiting. In such systems, individual success of offspring may result from distinct life history pathways that are influenced by both parental effects (e.g., timing of reproduction) and by the offspring themselves (e.g., ’personalities’). These pathways, in turn, can induce phenotypic variation and affect success later in life. The drivers and consequences of variable life histories are not well understood in the context of reproductive success. In this thesis I investigate drivers and consequences of variable life histories, for a small reef fish that exhibits male parental care (the common triplefin Forsterygion lapillum). I examined the influence of individual life history, phenotype and behaviour on (1) the performance of recently settled juveniles, and (2) the reproductive success adult males. I made field-based observations of adult males during the breeding season, measured their phenotypic traits (body size and condition) and used their otoliths to reconstruct life history characteristics (hatch dates and mean growth rates). Some males showed no evidence of territorial defence and were defined as ’floaters’; others defended territories, and a subset of these also had nests with eggs present. Adult male body size was significantly higher for males that defended breeding territories, and body condition was significantly higher for the males that had eggs (i.e., had successfully courted females). My otolith-based reconstructions of life history traits suggested two alternate pathways to ’success’ for adult males. Successful males hatched earlier and therefore had a developmental ’head start’ over less successful males (i.e., males with eggs > male territory holders without eggs > floaters). Alternatively, males can apparently achieve success by growing faster: for males born in the same month, those with eggs grew faster than those with territories and no eggs, and both groups grew faster than floaters. These results suggest that accelerated growth rate may mediate the effects of a later hatch date, and that both hatch dates and growth rates influence the success of adult males, likely through proximate effects on individual phenotypes. I evaluated the effects of variable life history in a complimentary lab-based study. Specifically, I manipulated the developmental environments (feeding regime and temperature) for young fish and evaluated the direct effects on life history traits and phenotypes. Then, I conducted an assay to quantify the indirect effects of developmental environment, life history traits, and phenotypes on aggression and performance of young fish. These developmental environments did not have a clear, overall effect on juvenile phenotype or performance (i.e. behavioural aggression and the ability to dominate a resource). Instead, individuals (irrespective of developmental environment) that grew faster and/or longer pelagic larval durations had increased odds of dominating a limited resource. I attributed the non-significant direct effect of developmental environment to within-treatment mortality and variation among individuals in terms of their realised access to food (i.e., dominance hierarchies were apparent in rearing chambers, suggesting a non-uniform access to food). Fish that were more likely to dominate a resource were also more aggressive (i.e., more likely to engage in chasing behaviours). Fish that were larger and more aggressive established territories that were deemed to be of higher ’quality’ (inferred from percent cover of cobble resources). Overall, this study suggests a complex interplay between social systems, phenotype and life history. Developmental environments may influence phenotypes, although behavioural differences among individuals may moderate that effect, contributing to additional variation in phenotypes and life history traits which, in turn, shape the success of individuals. Collectively, my thesis emphasises the consequences of life history variability on success at multiple life stages. These results may be relevant to other species that exhibit male parental care or undergo intense competition for space during early life stages. In addition, my results highlight interactions between life history, phenotype and behaviour that can have important implications for population dynamics and evolutionary ecology.</p>

Amongst raptor species, individuals with specialized diets are commonly observed to have higher reproductive output than those with general diets. A suggested cause is that foraging efficiency benefits accrue to diet specialists. This diet specificity hypothesis thus predicts that diet breadth and reproductive success should be inversely related within species. We highlight, however, that a prey availability hypothesis also makes the same prediction in some circumstances. Hence, when high diet specificity results from high encounter rates with an abundant, preferred prey, then prey availability may affect reproductive success, with diet specialization as an incidental correlate. Using three insular study areas in western Scotland, we examine diet specificity and reproductive success in Golden EaglesAquila chrysaetos. Diet breadth and breeding productivity were not negatively related in any of our study areas, even though birds with specific diets did tend to have a higher incidence of preferred prey (grouse and lagomorphs) in the diet. Indeed, in two study areas there was evidence that diet generalists had higher breeding productivity. Our results therefore failed to support the diet specificity hypothesis but were consistent with the prey availability hypothesis. We highlight that although many other studies are superficially consistent with the diet specificity hypothesis, our study is not alone in failing to provide support and that the hypothesis does not provide a generic explanation for all relevant results. Diet specificity in predators can be at least partially a response to prey diversity, availability and distribution, and benefits associated with different prey types, so that being a generalist is not necessarily intrinsically disadvantageous. We suggest that the available evidence is more consistent with variation in prey abundance and availability as a more influential factor explaining spatial and temporal variation in breeding productivity of ‘generalist’ species such as the Golden Eagle. Under this argument, prey abundance and availability are the main drivers of variation in reproductive output. Diet specificity is a consequence of variation in prey availability, rather than a substantial cause of variation in reproductive success.

Knowledge about the diet of fish-eating predators is critical when evaluating conflicts with the fishing industry. Numerous primary studies have examined the diet of grey sealsHalichoerus grypusand common sealsPhoca vitulinain a bid to understand the ecology of these predators. However, studies of large-scale spatial and temporal variation in seal diet are limited. Therefore this review combines the results of seal diet studies published between 1980 and 2000 to examine how seal diet varies at a range of spatial and temporal scales. Our results revealed extensive spatial variation in gadiform, perciform and flatfish consumption, likely reflecting variation in prey availability. Flatfish and gadiform consumption varied between years, reflecting changes in fish assemblages as a consequence of factors such as varying fishing pressures, climate change and natural fluctuations in populations. Perciform and gadiform consumption varied seasonally: in addition there was a significant interaction between season and seal species, indicating that grey and common seals exhibited different patterns of seasonal variation in their consumption of Perciformes and Gadiformes. Multivariate analysis of grey seal diet revealed spatial variation at a much smaller scale, with different species dominating the diet in different areas. The existence of spatial and temporal variation in seal diet emphasizes that future assessments of the impact of seal populations should not be based on past or localized estimates of diet and highlights the need for up-to-date, site specific estimates of diet composition in the context of understanding and resolving seal/fisheries conflict.

Recent theory predicted that male advertisement will reliably signal investment in paternal care in species where offspring survival requires paternal care and males allocate resources between advertisement and care. However, the predicted relationship between care and advertisement depended on the marginal gains from investment in current reproductive traits. Life history theory suggests that these fitness gains are also subject to a trade-off between current and future reproduction. Here, we investigate whether male signalling remains a reliable indicator of parental care when males allocate resources between current advertisement, paternal care and survival to future reproduction. We find that advertisement is predicted to remain a reliable signal of male care but that advertisement may cease to reliably indicate male quality because low-quality males are predicted to invest in current reproduction, whereas higher-quality males are able to invest in both current reproduction and survival to future reproduction.

<p>In order to gain a comprehensive understanding of population dynamics, it is vital to identify the key factors that contribute to variation in both survival and reproductive success throughout the life history of an organism. The population dynamics of reef fishes may be influenced by events occurring across multiple life stages, throughout the entire life cycle. For instance, the input of new individuals into a population (recruitment) is heavily shaped by mortality in the larval and juvenile stages, which is influenced by conspecific interactions and habitat characteristics. For individuals that survive, variation in somatic growth histories during development may influence mating success among fish that successfully recruit into the adult population, and particular developmental histories may receive a disproportionate amount of a population’s reproductive output. However, female preferences for particular phenotypes may also be modified by events occurring in adult life, such as parasite infection. Finally, absolute reproductive success (i.e., the number of offspring that survive to reproductive age) may be dependent upon early larval mortality of offspring, and variation in larval mortality among spawning sites could have consequences for metapopulation dynamics. In this thesis, I investigated how recruitment, growth and reproductive success varied among individuals of a small temperate reef fish, Forsterygion lapillum, the common triplefin, based upon their developmental histories, morphological traits, and habitat characteristics (including conspecific densities, regional locations, etc.). Specifically, I examined: - how the spatial distribution and survival of juveniles is influenced by age-class interactions (Chapter 2) - verified methods to measure somatic growth rates during development using scale structures (Chapter 3) - explored how previous growth rates influence reproductive success (Chapter 4) - evaluated how reproductive success is modified by the presence of ectoparasites (Chapter 5) - and finally, assessed how natal origin modifies larval survival probabilities among offspring (Chapter 6). The larvae of many reef fishes settle into habitats that are already occupied by adults, and interactions between age classes (intercohort interactions) may affect spatial variation in recruitment strength across settlement sites. In Chapter 2, I evaluated spatial covariation in juvenile and adult densities of F. lapillum (within the preferred settlement habitats of juveniles) to investigate correlations between adult and juvenile densities potentially caused by age-class interactions. The relationship between juvenile and adult densities followed a dome-shaped curve, with a negative correlation between juveniles and adults at higher adult densities. The shape of this curve was temporally variable, but was otherwise unaffected by particular features of the site (algal species identity). Using a laboratory-based experiment that used a “multiple predator effects” (MPE) design, I tested the hypothesis that increased settler mortality, caused by either (i) intercohort competition leading to enhanced predation risk or (ii) cannibalism by adults on juveniles, contributed to the observed negative relationship between juvenile and adult densities. Results suggested overall mortality attributable to cannibalism was low; however, smaller settlers appeared to be more vulnerable to cannibalism. There was no evidence that combined or interacting effects between predators (F. lapillum adults and Forsterygion varium [the variable triplefin]) increased predation risk in settlers of F. lapillum. Overall, these results highlight the potentially complex effects adult residents may have on shaping patterns of recruitment and the distributions of new juveniles. Somatic growth rates through ontogeny are one of the most important metrics for understanding fish populations and in Chapter 3, I evaluate the use of spacing between growth increments on fish scales (called circuli) as a measurement technique for assessing historical growth in F. lapillum. First, I established the relationship between scale growth and body size, and determined how variable this relationship was among populations. The body-scale size relationship was strongly positive and was unaffected by gender; however, there did appear to be significant differences between certain populations. Second, I monitored somatic and fish scale growth in the laboratory to measure the relationship between somatic growth and spacing between growth increments (intercirculus spacing). New scale growth and circuli deposition were both positively correlated with somatic growth. Average intercirculus spacing was also positively correlated with somatic growth rate, but this appeared to differ between age/size classes, with the older and larger individuals showing a weaker relationship. Results suggest that intercirculus spacing can be used to determine previous growth histories, but may be limited to particular size/age ranges (e.g., juveniles). In Chapter 4, I employ the techniques developed in Chapter 3 to examine how early growth rates (derived from fish scales) and male morphological traits explain variation in reproductive output between individual males in F. lapillum. I measured the reproductive success of breeding males in relation to their size and growth rates over the breeding season at two different spawning locations. Clutch size (number of eggs per nest) was highly variable among individuals over the study period; however, I detected a significant, albeit subtle, negative correlation between clutch size and growth rates after settlement. Although growth explained relatively small amounts of total variation, it was the only male trait I measured that significantly correlated with clutch size. The negative effects of faster growth on clutch size were greatest during the period of growth after settlement suggesting that growth at this early stage may be important for later reproductive success (early post-settlement). In Chapter 5, I examined how infection with an ectoparasite modified reproductive success among individual males using a field survey. Females often preferentially mate with unparasitised males, and therefore parasitised males experience lowered reproductive success. In this study, individuals of greater total length were more likely to be infected with an ectoparasite, but were also more likely to have an egg nest. Parasite infection had no effect on reproductive success (either the presence of a nest, or the average surface area of eggs if a nest was present). Positive covariation in total length, reproductive success, and parasite infection potentially suggest that the influence of parasitic infection on reproductive success may depend upon the strength of selection for larger male body size. In addition, this study provides the first quantitative measurement of ectoparasite infection for both the focal parasite species (Caligus buechlerae) and the host (F. lapillum). Finally, in Chapter 6, I explore how larval survival is mediated by spawning location. In marine reef fish, spatially isolated adult populations may be connected (i.e., have gene flow) via larval dispersal; however, differential larval survival between source populations may mediate both the degree of population connectivity as well as the reproductive success of individuals within those source populations. To evaluate variation in larval quality among different spawning locations, I conducted a laboratory assay to measure the potential effects of source population on larval time to starvation, as starvation is often proposed as a major source of mortality for larval fish. Average survival time was 3.75 days, but survival analysis indicated that starvation resistance did not differ between the two natal sources. For individual nests, mean larval size was negatively correlated with their mean survival time, although this was only apparent in larvae collected from one population (the south coast). My findings indicate that variation in larval traits between source populations does exist, but that on average, source populations had equal resistance to starvation. Given the differences between source populations in (i) the relationship between larval mortality and larval size (i.e., the absence of size effects in one source population) and (ii) overall variation in larval size (larger larvae on the south coast), the relative contribution of larvae from each source population may vary under certain conditions (e.g., low levels of food availability). In conclusion, the field surveys and laboratory experiments conducted in this thesis demonstrate the potential for a variety of factors across multiple life history stages to influence recruitment, growth and reproduction. These findings suggest that factors across multiple life stages (e.g., conspecific density, previous growth histories, or spawning site) have the ability to influence individual success, and in turn populations. By carefully considering and integrating these factors into our studies of population dynamics, we may be able to gain a more comprehensive understanding of the spatio-temporal fluctuations in populations for marine reef fish.</p>

The combination of spatial structure and non‐linear population dynamics can promote the persistence of coupled populations, even when the average population growth rate of the patches seen in isolation would predict otherwise. This phenomenon has generally been conceptualized and investigated through the movement of individuals among patches that each holds many individuals, as in metapopulation models. However, population persistence can likewise increase as the result of individuals moving among sites (e.g. breeding territories) within in a single patch. Here I examine the latter: individuals making small‐scale informed decisions with respect to where to breed can promote population persistence in poor environments. Based on a simple algebraic model, I demonstrate information thresholds, and predict that greater information use is required for population persistence under lower spatial heterogeneity in habitat quality, all else equal. Second, I implement an individual‐based model to explore prior experience and prospecting on conspecific success within a more complex, and spatially heterogeneous environment. Uniquely, I jointly examine the effects of simulated habitat loss, spatial heterogeneity prior to habitat, and variation in information gathering on population persistence. I find that habitat loss accelerates population quasi‐extinction risk; however, information use reduces extinction probabilities in proportion to the level of information gathering. Per capita reproductive success declines with number of breeding sites, suggesting that information‐mediated Allee effects may contribute to extinction risk. In conclusion, my study suggests that populations in a changing world may be increasingly vulnerable to extinction where patch size and spatial heterogeneity constrain the effectiveness of information‐use strategies.

Reproducing parents face the difficult challenge of trading-off investment in current reproduction against presumed future survival and reproduction. Glucocorticoids are supposed to mediate this trade-off because the adrenocortical response to stress disrupts normal reproductive behaviour in favour of self-maintenance and own survival. According to the brood-value hypothesis, individuals with a low survival probability until the next reproductive season have to invest in current reproduction, a process driven by a down-regulation of their adrenocortical response. If the adrenocortical response to stress effectively mediates the trade-off between current reproduction versus future survival and reproduction, we expect a negative relationship with reproductive success and a positive correlation of the adrenocortical stress response with survival. We studied the relationship between corticosterone secretion in parents and their current brood value, reproductive success and survival in a short-lived multi-brooded bird, the Eurasian hoopoe Upupa epops. The adrenocortical response to acute handling stress was correlated with the brood value within the individual (first and second broods of the year) and between individuals. Birds breeding late in the season mounted a lower total corticosterone response to acute stress than birds breeding earlier, while females showed lower levels than males. We observed a negative relationship between the adrenocortical stress response and rearing success or fledging success in females, as predicted by the brood-value hypothesis. However, we could not evidence a clear link between the adrenocortical stress response and survival. Future research testing the brood-value hypothesis and trade-offs between current reproduction and future survival should also measure free corticosterone and carefully differentiate between cross-sectional (i.e. between-individual) and individual-based experimental studies.

Spatial synchrony plays an important role in dictating the dynamics of spatial and stage-structured populations. Here we argue that, unlike the Moran effect where spatial synchrony is driven by exogenous factors, spatial correlation in intrinsic/local-scale processes can affect the level of spatial synchrony among distinct sub-populations, and therefore the persistence of the entire population. To explore this mechanism, we modelled the consequences of spatial heterogeneity in aquatic habitat quality, and that of temporal variation in local extinction probability, on the persistence of stage-structured mosquito populations. As a model system, we used two widely distributed mosquito species, Aedes albopictus and Culex pipiens, both key vectors of a range of infectious diseases. Spatial heterogeneity in aquatic habitat quality led to increased population persistence, and this pattern was more pronounced at intermediate dispersal rates, and in the long-dispersing species (C.pipiens). The highest regional persistence was obtained at high dispersal rates. This is probably because dispersal, in our model, did not carry any additional costs. Population persistence of both species was negatively correlated with increased temporal variation in local extinction probability. These differences were stronger in the short-dispersing species (A.albopictus), especially at intermediate dispersal rates. The dispersal of A.albopictus adults in each time step was limited to the nearest habitat patches, weakening the positive effect of spatial heterogeneity in aquatic habitat quality on population persistence. In contrast, C.pipiens adults could disperse into more remote sub-populations, resulting in much higher recolonization rates. Hence, the negative effect of temporal variation in local extinction probability on patch occupancy disappeared at intermediate dispersal rates. We suggest that effectively controlling these two mosquito species requires making few spatially synchronized control efforts (i.e., generating high temporal variation in local extinction probability), rather than many asynchronized local control efforts. Finally, our model can be easily fitted to other organisms characterized by complex life cycles, and it can be also used to examine alternative scenarios, including the effect of spatial configuration of local habitat patches and dispersal kernel shape on population persistence.

How does network structure and complexity in river systems affect population abundance and persistence?

Fine-scale spatial variation in genetic relatedness and inbreeding occur across continuous distributions of several populations of vertebrates; however, the basis of observed variation is often left untested. Here we test the hypothesis that prior observations of spatial patterns in genetics for an island population of feral horses (Sable Island, Canada) were the result of spatial variation in population dynamics, itself based in spatial heterogeneity in underlying habitat quality. In order to assess how genetic and population structuring related to habitat, we used hierarchical cluster analysis of water sources and an indicator analysis of the availability of important forage species to identify a longitudinal gradient in habitat quality along the length of Sable Island. We quantify a west-east gradient in access to fresh water and availability of two important food species to horses: sandwort, Honckenya peploides, and beach pea, Lathyrus japonicas. Accordingly, the population clusters into three groups that occupy different island segments (west, central, and east) that vary markedly in their local dynamics. Density, body condition, and survival and reproduction of adult females were highest in the west, followed by central and east areas. These results mirror a previous analysis of genetics, which showed that inbreeding levels are highest in the west (with outbreeding in the east), and that there are significant differences in fixation indices among groups of horses along the length of Sable Island. Our results suggest that inbreeding depression is not an important limiting factor to the horse population. We conclude that where habitat gradients exist, we can anticipate fine-scale heterogeneity in population dynamics and hence genetics.

A central question in ecology is explaining spatial variation in the abundance of species. Patterns of spatial variation in abundance can often be explained by spatial variation in the environment, including resource availability, climatic variables, and other factors that influence a species’ reproduction and survival. We show that spatial patterns in abundance may also be driven by temporal environmental variation, in the absence of any fixed spatial environmental variation. To illustrate this, we build on work by J. H. Brown, D. W. Mehlman, and G. C. Stevens, who demonstrated spatial patterns in bird abundances that can be explained by fixed spatial variation in the environment. Using a pair of simple stochastic models of bird population dynamics, we show that similar patterns can be generated through temporal environmental variation that has no fixed spatial component. This occurs when population dynamics are characterized by very weak density dependence, so that population densities exhibit near-random-walk behavior. Because similar patterns of spatial variation in species’ abundances can be produced by either fixed spatial environmental variation or spatiotemporal environmental variation, we argue that interpreting spatial variation in abundance may sometimes require understanding temporal variation in abundance.

Temporal variation in food availability may generate changes in the feeding strategies and trophic preferences of animals. We studied the temporal variation in feeding behavior, diet composition, and prey availability of the Black-faced Ibis (Theristicus melanopis) in pastures of southern Chile between May 1999 and January 2000. Soil core samples showed that hypogeous invertebrates such as, earthworms (Lumbricus spp.), black cutworm larvae (Agrotis spp.), black pasture caterpillars (Dalaca spp.), and southern green chafers (Hylamorpha elegans) were the most abundant prey in the pastures and that their populations experienced pronounced seasonal variations. Insect larvae were the main prey of the Black-faced Ibis and were consumed in greater proportion than expected by chance. The diet composition (based on feces) and trophic preferences coincided with variations in prey availability. During periods of reduced prey abundance Black-faced Ibises foraged on more different types of prey and their consumption rate diminished. At the same time, the abundance of Black-faced Ibises decreased in the study area. These variations were most evident in late spring and summer, when prey abundance in the pastures was lower than in the other seasons. Our results suggest that the life cycle of the prey is the main causal factor that influences the feeding ecology of the Black-faced Ibis in pastures of southern Chile.

The spatial and temporal variation in the availability of suitable habitat within metapopulations determines colonization-extinction events, regulates local population sizes and eventually affects local population and metapopulation stability. Insights into the impact of such a spatiotemporal variation on the local population and metapopulation dynamics are principally derived from classical metapopulation theory and have not been experimentally validated. By manipulating spatial structure in artificial metapopulations of the spider mite Tetranychus urticae, we test to which degree spatial (mainland-island metapopulations) and spatiotemporal variation (classical metapopulations) in habitat availability affects the dynamics of the metapopulations relative to systems where habitat is constantly available in time and space (patchy metapopulations). Our experiment demonstrates that (i) spatial variation in habitat availability decreases variance in metapopulation size and decreases density-dependent dispersal at the metapopulation level, while (ii) spatiotemporal variation in habitat availability increases patch extinction rates, decreases local population and metapopulation sizes and decreases density dependence in population growth rates. We found dispersal to be negatively density dependent and overall low in the spatial variable mainland-island metapopulation. This demographic variation subsequently impacts local and regional population dynamics and determines patterns of metapopulation stability. Both local and metapopulation-level variabilities are minimized in mainland-island metapopulations relative to classical and patchy ones.

Investing in the current reproduction requires diverting energy resources from other metabolic functions, which may compromise future reproduction and lifespan. To solve this trade-off, an individual may consider its labile state to decide how much to invest in current reproduction. We tested experimentally whether the “state quality” of male rock lizards influences their reproductive strategies. To improve the nutritional status of males before the mating season, we captured and supplemented experimental males (N = 20) with dietary vitamin D3 (an essential nutrient for lizards) and had a control group of males (N = 20). Then, we released all these males and females (N = 31) in a large semi-natural outdoor enclosure where lizards could interact and mate freely during the mating period. Activity levels of males did not vary between treatments, but supplemented males started fewer intrasexual agonistic interactions and made fewer mating advances to females. When the mating season ended, we incubated eggs laid by females to obtain the offspring and estimated the paternity of males using DNA microsatellites. Supplemented males sired fewer offspring than control males. These results suggest that vitamin D3 supplemented males used a low risk/less costly mating strategy to protect their assets (i.e., vitamin D reserves), but that still resulted in “some” current reproductive success, while likely increasing longevity and the expected future total reproductive success.