The effect of natal experience on habitat preferences

Local genetic structure on breeding grounds of a long-distance migrant passerine: the bluethroat (Luscinia svecica) in Spain

Breeding site fidelity can be determined by environmental features, which depending on their heterogeneous distribution may shape the genetic landscape of a population. We used 10 microsatellite loci to study the genetic variation of 83 bluethroats (Luscinia svecica azuricollis) across 14 localities within the Spanish breeding population and assess the relative influence of different habitat characteristics (physiography and vegetation) on genetic differentiation. Based on the genetic variation of this population, we identified 3 geographically consistent genetic clusters that on average showed a higher genetic differentiation than among other north European populations, even those belonging to different subspecies. The inferred genetic clusters occurred in geographic areas that significantly differed in elevation. The highest genetic differentiation was observed between sites at different mountain ranges, as well as between the highest altitude sites in the northeastern locale, whereas vegetation type did not explain a significant percentage of genetic variation. The lack of correlation between geographic and genetic distances suggests that this pattern of genetic structure cannot be explained as a consequence of isolation by distance. Finally, we discuss the importance of preserving areas encompassing high environmental and genetic variation as a means of preserving evolutionary processes and adaptive potential.

Effects of early visual experience on the background preference in juvenile cuttlefish Sepia pharaonis

Although cuttlefish are capable of showing diverse camouflage body patterns against a variety of background substrates, whether they show background preference when given a choice of substrates is not well known. In this study, we characterized the background choice of post-embryonic cuttlefish (Sepia pharaonis) and examined the effects of rearing visual environments on their background preferences. Different rearing backgrounds (enriched, uniformly grey and checkerboard) were used to raise cuttlefish from eggs or hatchlings, and four sets of two-background-choice experiments (differences in contrast, shape, size and side) were conducted at day 1 and weeks 4, 8 and 12 post-hatch. Cuttlefish reared in the enriched environment preferred high-contrast backgrounds at all post-embryonic stages. In comparison, those reared in the impoverished environments (uniformly grey and checkerboard) had either reversed or delayed high-contrast background preference. In addition, cuttlefish raised on the uniformly grey background, exposed to a checkerboard briefly (0.5 or 3 h) at week 4 and tested at week 8 showed increased high-contrast background preference. Interestingly, cuttlefish in the enriched group preferred an object size similar to their body size at day 1 and week 4, but changed this preference to smaller objects at week 12. These results suggest that high-contrast backgrounds may be more adaptive for juvenile cuttlefish, and visually enriched environments are important for the development of these background preference behaviours.

Dietary differentiation and the evolution of population genetic structure in a highly mobile carnivore

Recent studies on highly mobile carnivores revealed cryptic population genetic structures correlated to transitions in habitat types and prey species composition. This led to the hypothesis that natal-habitat-biased dispersal may be responsible for generating population genetic structure. However, direct evidence for the concordant ecological and genetic differentiation between populations of highly mobile mammals is rare. To address this we analyzed stable isotope profiles (δ¹³C and δ¹⁵N values) for Eastern European wolves (Canis lupus) as a quantifiable proxy measure of diet for individuals that had been genotyped in an earlier study (showing cryptic genetic structure), to provide a quantitative assessment of the relationship between individual foraging behavior and genotype. We found a significant correlation between genetic distances and dietary differentiation (explaining 46% of the variation) in both the marginal test and crucially, when geographic distance was accounted for as a co-variable. These results, interpreted in the context of other possible mechanisms such as allopatry and isolation by distance, reinforce earlier studies suggesting that diet and associated habitat choice are influencing the structuring of populations in highly mobile carnivores.

Pleistocene and ecological effects on continental-scale genetic differentiation in the bobcat (Lynx rufus)

The potential for widespread, mobile species to exhibit genetic structure without clear geographic barriers is a topic of growing interest. Yet the patterns and mechanisms of structure--particularly over broad spatial scales--remain largely unexplored for these species. Bobcats occur across North America and possess many characteristics expected to promote gene flow. To test whether historical, topographic or ecological factors have influenced genetic differentiation in this species, we analysed 1 kb mtDNA sequence and 15 microsatellite loci from over 1700 samples collected across its range. The primary signature in both marker types involved a longitudinal cline with a sharp transition, or suture zone, occurring along the Great Plains. Thus, the data distinguished bobcats in the eastern USA from those in the western half, with no obvious physical barrier to gene flow. Demographic analyses supported a scenario of expansion from separate Pleistocene refugia, with the Great Plains representing a zone of secondary contact. Substructure within the two main lineages likely reflected founder effects, ecological factors, anthropogenic/topographic effects or a combination of these forces. Two prominent topographic features, the Mississippi River and Rocky Mountains, were not supported as significant genetic barriers. Ecological regions and environmental correlates explained a small but significant proportion of genetic variation. Overall, results implicate historical processes as the primary cause of broad-scale genetic differentiation, but contemporary forces seem to also play a role in promoting and maintaining structure. Despite the bobcat's mobility and broad niche, large-scale landscape changes have contributed to significant and complex patterns of genetic structure.

The relative role of relatives in conspecific brood parasitism

Conspecific brood parasites lay their eggs in the nests of other females in the same population, leading to a fascinating array of possible ‘games’ among parasites and their hosts (Davies 2000; Lyon & Eadie 2008). Almost 30 years ago, Andersson & Eriksson (1982) first suggested that perhaps this form of parasitism was not what it seemed--indeed, perhaps it was not parasitism at all!Andersson & Eriksson (1982) observed that conspecific brood parasitism (CBP) was disproportionally common in waterfowl (Anatidae), a group of birds for which natal philopatry is female-biased rather than the more usual avian pattern of male-biased natal philopatry. Accordingly, Andersson (1984) reasoned (and demonstrated in an elegantly simple model) that relatedness among females might facilitate the evolution of CBP--prodding us to reconsider it as a kin-selected and possibly cooperative breeding system rather than a parasitic interaction. The idea was much cited but rarely tested empirically until recently--a number of new studies, empowered with a battery of molecular techniques, have now put Andersson’s hypothesis to the test (Table 1). The results are tantalizing, but also somewhat conflicting. Several studies, focusing on waterfowl, have found clear evidence that hosts and parasites are often related (Andersson & Åhlund 2000; Roy Nielsen et al. 2006; Andersson & Waldeck 2007; Waldeck et al. 2008; Jaatinen et al. 2009; Tiedemann et al. 2011). However, this is not always the case (Semel & Sherman 2001; Anderholm et al. 2009; and see Pöysa 2004). In a new study reported in this issue of Molecular Ecology, Jaatinen et al. (2011a) provide yet another twist to this story that might explain not only why such variable results have been obtained, but also suggests that the games between parasites and their hosts--and the role of kinship in these games--may be even more complex than Andersson (1984) imagined. Indeed, the role of kinship in CBP may be very much one of relative degree!

Host preference of cotton fleahopper, Pseudatomoscelis seriatus (Reuter) is not labile to geographic origin and prior experience

Several phytophagous insects exhibit distinct preference for their host plants. In widely distributed generalist insects, host preference can be influenced by geographic variation in host plant distribution and abundance as well as by prior experience. We have studied host preference of the cotton fleahopper, Pseudatomoscelis seriatus (Reuter), a pest of cotton in Texas and other neighboring states, by measuring olfactory orientation to horsemint (Monarda punctata L.) and cotton (Gossypium hirsutum L.). Horsemint is one of the primary, native, wild hosts of cotton fleahopper during late-spring and early summer in Texas, and it is commonly believed to be the main source of this pest in cotton. Although the abundance of horsemint, and therefore the fleahopper exposure to it, varies geographically, cotton fleahopper's preference for this native host-plant is maintained across two ecoregions in Texas, TX High Plains (Lubbock area) and Brazos Valley (College Station area). Similarly, preference for horsemint was retained regardless of prior experience with cotton throughout all the life stages of the insect. This fixed preference of cotton fleahopper to horsemint could be because of their ancestral insect-plant interaction, better fitness of cotton fleahopper on horsemint, and relatively low abundance of horsemint compared with cotton. Information gained from this study could be used to implement cultural control practices such as trap cropping, to develop attractants to monitor this pest, or both.

Habitat Choice and Speciation

The role of habitat choice in reproductive isolation and ecological speciation has often been overlooked, despite acknowledgement of its ability to facilitate local adaptation. It can form part of the speciation process through various evolutionary mechanisms, yet where habitat choice has been included in models of ecological speciation little thought has been given to these underlying mechanisms. Here, we propose and describe three independent criteria underlying ten different evolutionary scenarios in which habitat choice may promote or maintain local adaptation. The scenarios are the result of all possible combinations of the independent criteria, providing a conceptual framework in which to discuss examples which illustrate each scenario. These examples show that the different roles of habitat choice in ecological speciation have rarely been effectively distinguished. Making such distinctions is an important challenge for the future, allowing better experimental design, stronger inferences and more meaningful comparisons among systems. We show some of the practical difficulties involved by reviewing the current evidence for the role of habitat choice in local adaptation and reproductive isolation in the intertidal gastropodLittorina saxatilis, a model system for the study of ecological speciation, assessing whether any of the proposed scenarios can be reliably distinguished, given current research.

Underappreciated Consequences of Phenotypic Plasticity for Ecological Speciation

Phenotypic plasticity was once seen primarily as a constraint on adaptive evolution or merely a nuisance by geneticists. However, some biologists promote plasticity as a source of novelty and a factor in evolution on par with mutation, drift, gene flow, and selection. These claims are controversial and largely untested, but progress has been made on more modest questions about effects of plasticity on local adaptation (the first component of ecological speciation). Adaptive phenotypic plasticity can be a buffer against divergent selection. It can also facilitate colonization of new niches and rapid divergent evolution. The influence of non-adaptive plasticity has been underappreciated. Non-adaptive plasticity, too can interact with selection to promote or inhibit genetic differentiation. Finally, phenotypic plasticity of reproductive characters might directly influence evolution of reproductive isolation (the second component of ecological speciation). Plasticity can cause assortative mating, but its influence on gene flow ultimately depends on maintenance of environmental similarity between parents and offspring. Examples of plasticity influencing mating and habitat choice suggest that this, too, might be an underappreciated factor in speciation. Plasticity is an important consideration for studies of speciation in nature, and this topic promises fertile ground for integrating developmental biology with ecology and evolution.

Effects of natal habitat odour, reinforced by adult experience, on choice of oviposition site in the mosquito Aedes aegypti

The effects of natal experience on the oviposition behaviour of adult female mosquitoes were investigated in the laboratory using Aedes aegypti (L.) (Diptera: Culicidae). 'Treatment' mosquitoes were exposed to a dilute repellent (inducing stimulus) in their breeding water (aquatic stages) and/or in the air (adults) during various combinations of life stages [larval only (L regime); larval and pupal (LP regime); larval, pupal and emergent adult (LPE regime); larval, pupal, emergent adult and adult (LPEA regime); pupal, emergent adult and adult (PEA regime); adult only (A regime)]. 'Control' mosquitoes were raised in an identical manner, but were not exposed to the inducing stimulus. The oviposition behaviour of treatment and control females was assessed in an oviposition assay that presented a choice of water with or without the inducing stimulus. Of the 435 mosquitoes tested in the experiment, 176 were non-distributors (i.e. laid all of their eggs in only one of the choices). Treatment females (distributors plus non-distributors) reared in the presence of the inducing stimulus throughout their lives (LPEA regime) showed a significant preference for the oviposition option containing the inducing stimulus (24/36 females) compared with corresponding controls (5/39 females). Distributors reared under the LPEA and PEA regimes also showed this preference (6/6 treatment vs. 2/29 control females, and 13/18 treatment vs. 7/23 control females, respectively). Females that had been exposed to the inducing stimulus as either immatures or adults only showed no preference for, and some showed an aversion to, the treatment oviposition option. This is interpreted as evidence for a natal habitat preference induction (NHPI) in this species, albeit one that requires extensive reinforcement in the adult stage. This adult experience-reinforced NHPI (AER-NHPI) is discussed in terms of its adaptive significance for container breeders, the possible timing mechanism and sensory basis of induction and potential practical consequences.

Natal experience and conspecifics influence the settling behaviour of the juvenile terrestrial isopod Armadillidium vulgare

Cues used by dispersing juveniles to assess habitat quality can be based on public information available to all individuals or on private information obtained from experience in the natal habitat. The presence of conspecifics (public information) and natal habitat quality (private information) have been shown to influence habitat preferences in many species, but the relative importance of these two cue types is seldom investigated. We examined whether habitat quality relative to the natal habitat had a stronger influence on the settling decisions of the juvenile terrestrial isopod Armadillidium vulgare (Latreille, 1804), than sign of conspecifics. We raised juvenile A. vulgare in either high- or low-quality habitats and then observed how the presence of conspecific sign influenced their preference for each of these habitats. When conspecific sign was absent, juveniles preferred high-quality habitat, regardless of their natal habitat. When the low-quality habitat was treated with conspecific sign, juveniles born on low-quality habitat continued to prefer the high-quality habitat, but juveniles raised on high-quality habitat displayed no preference. This suggests juvenile isopods respond to these cues hierarchically: they first search for habitats higher in quality than their natal habitat and then cue into conspecific sign when the preferred habitat is unavailable.

Social learning in birds and its role in shaping a foraging niche

We briefly review the literature on social learning in birds, concluding that strong evidence exists mainly for predator recognition, song, mate choice and foraging. The mechanism of local enhancement may be more important than imitation for birds learning to forage, but the former mechanism may be sufficient for faithful transmission depending on the ecological circumstances. To date, most insights have been gained from birds in captivity. We present a study of social learning of foraging in two passerine birds in the wild, where we cross-fostered eggs between nests of blue tits, Cyanistes caeruleus and great tits, Parus major. Early learning causes a shift in the foraging sites used by the tits in the direction of the foster species. The shift in foraging niches was consistent across seasons, as showed by an analysis of prey items, and the effect lasted for life. The fact that young birds learn from their foster parents, and use this experience later when subsequently feeding their own offspring, suggests that foraging behaviour can be culturally transmitted over generations in the wild. It may therefore have both ecological and evolutionary consequences, some of which are discussed.

Adaptation and habitat selection in the eco-evolutionary process

The struggle for existence occurs through the vital rates of population growth. This basic fact demonstrates the tight connection between ecology and evolution that defines the emerging field of eco-evolutionary dynamics. An effective synthesis of the interdependencies between ecology and evolution is grounded in six principles. The mechanics of evolution specifies the origin and rules governing traits and evolutionary strategies. Traits and evolutionary strategies achieve their selective value through their functional relationships with fitness. Function depends on the underlying structure of variation and the temporal, spatial and organizational scales of evolution. An understanding of how changes in traits and strategies occur requires conjoining ecological and evolutionary dynamics. Adaptation merges these five pillars to achieve a comprehensive understanding of ecological and evolutionary change. I demonstrate the value of this world-view with reference to the theory and practice of habitat selection. The theory allows us to assess evolutionarily stable strategies and states of habitat selection, and to draw the adaptive landscapes for habitat-selecting species. The landscapes can then be used to forecast future evolution under a variety of climate change and other scenarios.

Effects of early stress on behavioral syndromes: an integrated adaptive perspective

This paper presents a behavioral ecologist's view on adaptive responses to early stress. I first summarize two approaches to this topic drawn from other papers in this Special Issue: the 'inoculation model' and the 'adaptive calibration model'. I then describe three relevant modeling approaches from behavioral and evolutionary ecology: models of adaptive plasticity, models of adaptive prey behavior under uncertainty about risk, and models of state-dependent adaptive behavioral syndromes. These models generate some novel predictions on factors that explain variation in how organisms might respond adaptively to early stress. In particular, the state-dependent models of adaptive behavioral syndromes emphasize the importance of feedback loops between behavior and state variables in explaining the long-term persistence of effects of early experiences. State variables can include aspects of physiology, morphology or life history, differences among individuals in information state or skill, or even in social state (e.g., social rank). The feedbacks between behavior and individual state suggest a framework for an integrative approach to understanding responses to stress. The behavioral syndrome approach also emphasizes the importance of understanding stress carryovers - e.g., situations where effects of one kind of stressor (e.g., early social stress) carry over to influence other stress responses (e.g., response to danger) later in life. Finally, I discuss how responses to early stress might relate to variation in the ability of animals to cope well with novel conditions associated with human-induced rapid environmental change, a ubiquitous problem that animals face in the modern world.

Learning the Hard Way: Imprinting Can Enhance Enforced Shifts in Habitat Choice

We investigated the potential importance of learning in habitat choice within a young hybrid zone of two closely related species of birds. Pied flycatchers (Ficedula hypoleuca) are being excluded from deciduous habitats into a mixed forest type by collared flycatchers (F. albicollis). We investigated whether this enforced habitat shift influenced reproductive isolation between the two species, and, by cross-fostering nestlings, we tested whether learning may lead to a corresponding shift in habitat choice in consecutive generations. Our results show that the majority of the recruits, even if translocated across different habitat types, return to breed in the area where they were fostered. As male pied flycatchers were more likely to hybridize in the originally preferred habitat, we argue that early imprinting on an alternate habitat can play an important role in increasing reproductive isolation and facilitate regional coexistence between species experiencing secondary contact.

Cultural inheritance drives site fidelity and migratory connectivity in a long-distance migrant

Cultural transmission is thought to be a mechanism by which migratory animals settle into habitats, but little evidence exists in wild populations because of the difficulty of following individuals over successive generations and wide geographical distances. Cultural inheritance of migration routes represents a mechanism whereby geographical isolation can arise between separate groups and could constrain individuals to potentially suboptimal sites within their range. Conversely, adopting the parental migratory route in adult life, rather than dispersing randomly, may increase an individual's reproductive success because that strategy has already been proven to allow successful breeding. We combined a pedigree of related light-bellied Brent geese (Branta bernicla hrota) with 6 years of observations of marked birds to calculate the dispersal distances of adult offspring from their parents in both Ireland and Iceland. In both countries, the majority of offspring were found to recruit into or near their parental sites, indicating migratory connectivity in the flyway. Despite this kin structure, we found no evidence of genetic differentiation using genotype data from 1127 individuals across 15 microsatellite loci. We suggest that the existence of migratory connectivity of subpopulations is far more common than previous research indicates and that cultural information may play an important role in structuring reproductive isolation among them.

Innate recognition of water bodies in echolocating bats

In the course of their lives, most animals must find different specific habitat and microhabitat types for survival and reproduction. Yet, in vertebrates, little is known about the sensory cues that mediate habitat recognition. In free flying bats the echolocation of insect-sized point targets is well understood, whereas how they recognize and classify spatially extended echo targets is currently unknown. In this study, we show how echolocating bats recognize ponds or other water bodies that are crucial for foraging, drinking and orientation. With wild bats of 15 different species (seven genera from three phylogenetically distant, large bat families), we found that bats perceived any extended, echo-acoustically smooth surface to be water, even in the presence of conflicting information from other sensory modalities. In addition, naive juvenile bats that had never before encountered a water body showed spontaneous drinking responses from smooth plates. This provides the first evidence for innate recognition of a habitat cue in a mammal.

Little is known about the way bats recognize large objects, such as trees, buildings or a lake. Greif and Siemers show that bodies of water are recognized solely by echolocation, and that this ability is innate, thus smooth surfaces are recognized as water by naive juvenile bats.

The conservation-welfare nexus in reintroduction programmes: a role for sensory ecology

Since reintroduction programmes involve moving animals from captive or wild environments and releasing them into novel environments, there are sure to be a number of challenges to the welfare of the individuals involved. Behavioural theory can help us develop reintroductions that are better for both the welfare of the individual and the conservation of populations. In addition to modifying captive environments to prepare animals for release to the wild, it is possible to modify the animals’ experience in the post-release environment. For releases to be more successful, they need to better accommodate the ecological and psychological needs of individuals. A better understanding of sensory ecology — how animals acquire and respond to information in their environment — is needed to develop new, more successful management strategies for reintroductions. Sensory ecology integrates ecological and psychological processes, calling for better synergy among researchers with divergent backgrounds in conservation and animal welfare science. This integrative approach leads to new topics of investigation in reintroduction biology, including more careful consideration of post-release stress and the role of social support. Reintroductions are essentially exercises in ‘forced’ dispersal; thus, an especially promising avenue of research is the role of proximate mechanisms governing dispersal and habitat selection decisions. Reintroduction biologists have much to gain from the study of mechanism because mechanisms, unlike function or adaptive value, can be manipulated to enhance conservation and welfare goals.

Predation and infanticide influence ideal free choice by a parrot occupying heterogeneous tropical habitats

The ideal free distribution (IFD) predicts that organisms will disperse to sites that maximize their fitness based on availability of resources. Habitat heterogeneity underlies resource variation and influences spatial variation in demography and the distribution of populations. We relate nest site productivity at multiple scales measured over a decade to habitat quality in a box-nesting population of Forpus passerinus (green-rumped parrotlets) in Venezuela to examine critical IFD assumptions. Variation in reproductive success at the local population and neighborhood scales had a much larger influence on productivity (fledglings per nest box per year) than nest site or female identity. Habitat features were reliable cues of nest site quality. Nest sites with less vegetative cover produced greater numbers of fledglings than sites with more cover. However, there was also a competitive cost to nesting in high-quality, low-vegetative cover nest boxes, as these sites experienced the most infanticide events. In the lowland local population, water depth and cover surrounding nest sites were related with F. passerinus productivity. Low vegetative cover and deeper water were associated with lower predation rates, suggesting that predation could be a primary factor driving habitat selection patterns. Parrotlets also demonstrated directional dispersal. Pairs that changed nest sites were more likely to disperse from poor-quality nest sites to high-quality nest sites rather than vice versa, and juveniles were more likely to disperse to, or remain in, the more productive of the two local populations. Parrotlets exhibited three characteristics fundamental to the IFD: habitat heterogeneity within and between local populations, reliable habitat cues to productivity, and active dispersal to sites of higher fitness.

How different types of natal experience affect habitat preference

In many animals, exposure to cues in a natal habitat increases disperser preferences for those cues (natal habitat preference induction [NHPI]), but the proximate and ultimate bases for this phenomenon are obscure. We developed a Bayesian model to study how different types of experience in the natal habitat and survival to the age/stage of dispersal interact to affect a disperser's estimate of the quality of new natal-type habitats. The model predicts that the types of experience a disperser had before leaving its natal habitat will affect the attractiveness of cues from new natal-type habitats and that favorable experiences will increase the level of preference for natal-type habitats more than unfavorable experiences will decrease it. An experimental study of NHPI in Drosophila melanogaster provided with "good" and "bad" experiences in their natal habitats supports these predictions while also indicating that the effects of different types of natal experience on NHPI vary across genotypes. If habitat preferences are modulated by an individual's experience before dispersal as described in this study, then NHPI may have stronger effects on sympatric speciation, metapopulation dynamics, conservation biology, and pest management than previously supposed.

Phenotype-dependent native habitat preference facilitates divergence between parapatric lake and stream stickleback

Adaptive divergence between adjoining populations reflects a balance between the diversifying effect of divergent selection and the potentially homogenizing effect of gene flow. In most models of migration-selection balance, gene flow is assumed to reflect individuals' inherent capacity to disperse, without regard to the match between individuals' phenotypes and the available habitats. However, habitat preferences can reduce dispersal between contrasting habitats, thereby alleviating migration load and facilitating adaptive divergence. We tested whether habitat preferences contribute to adaptive divergence in a classic example of migration-selection balance: parapatric lake and stream populations of three-spine stickleback (Gasterosteus aculeatus). Using a mark-transplant-recapture experiment on morphologically divergent parapatric populations, we showed that 90% of lake and stream stickleback returned to their native habitat, reducing migration between habitats by 76%. Furthermore, we found that dispersal into a nonnative habitat was phenotype dependent. Stream fish moving into the lake were morphologically more lake-like than those returning to the stream (and the converse for lake fish entering the stream). The strong native habitat preference documented here increases the extent of adaptive divergence between populations two- to fivefold relative to expectations with random movement. These results illustrate the potential importance of adaptive habitat choice in driving parapatric divergence.

Using genetics to understand the dynamics of wild primate populations

While much can be learned about primates by means of observation, the slow life history of many primates means that even decades of dedicated effort cannot illuminate long-term evolutionary processes. For example, while the size of a contemporary population can be estimated from field censuses, it is often desirable to know whether a population has been constant or changing in size over a time frame of hundreds or thousands of years. Even the nature of "a population" is open to question, and the extent to which individuals successfully disperse among defined populations is also difficult to estimate by using observational methods alone. Researchers have thus turned to genetic methods to examine the size, structure, and evolutionary histories of primate populations. Many results have been gained by study of sequence variation of maternally inherited mitochondrial DNA, but in recent years researchers have been increasingly focusing on analysis of short, highly variable microsatellite segments in the autosomal genome for a high-resolution view of evolutionary processes involving both sexes. In this review we describe some of the insights thus gained, and discuss the likely impact on this field of new technologies such as high-throughput DNA sequencing.

Effects of survival on the attractiveness of cues to natal dispersers

Habitat selection by natal dispersers is one of several contexts in which preexisting biases interact with experience to affect the attractiveness of cues from biologically significant items. Here we use a Bayesian approach to explore the conditions that favor this phenomenon. We demonstrate that the simplest possible type of natal experience--namely, survival to the age/stage of dispersal--can increase the attractiveness of cues from an individual's natal habitat relative to the attractiveness of those same cues to naive individuals. The effects of survivorship on cue attractiveness are strongest when the quality of the habitat that produces that cue varies widely across large spatial or temporal scales, when that type of habitat is rarely of high quality, and when offspring survivorship provides a reliable indication of the quality of that type of habitat at the current time and locality. More generally, the framework outlined here may also apply to other situations in which extended exposure to cues early in life increases the attractiveness of those cues later in life.

Females shape the genetic structure of a gorilla population

Dispersal, one of the key life-history features of a species, influences gene flow and, consequently, the genetic structuring of populations. Landscape characteristics such as rivers, mountains, or habitat fragmentation affect dispersal and result in broad-scale genetic structuring of various mammalian species [1-5]. However, less attention has been paid to studying how dispersal is influenced by finer-scale microgeographic variation in a continuous habitat. Here we investigate the genetic structure of a closed population of approximately 300 endangered mountain gorillas living in multiple groups in a small (331 km(2)) forest in southwestern Uganda. In a species in which both sexes routinely disperse, population genetic structure in females was influenced by distance, altitude, and plant community composition, whereas males were not geographically structured. The effect of distance fits the observed tendency of females to transfer to neighboring groups, whereas the effects of altitude and vegetation reflect the changing species composition of locally available food resources. These results suggest that individual dietary preferences are important even in a highly mobile species living amid abundant food, and we propose that preference for natal habitats will influence dispersal decisions in many other vertebrate taxa.

Coral reef fish smell leaves to find island homes

Recent studies have shown that some coral reef fish larvae return to natal reefs, while others disperse to distant reefs. However, the sensory mechanisms used to find settlement sites are poorly understood. One hypothesis is that larvae use olfactory cues to navigate home or find other suitable reef habitats. Here we show a strong association between the clownfish Amphiprion percula and coral reefs surrounding offshore islands in Papua New Guinea. Host anemones and A. percula are particularly abundant in shallow water beneath overhanging rainforest vegetation. A series of experiments were carried out using paired-choice flumes to evaluate the potential role of water-borne olfactory cues in finding islands. Recently settled A. percula exhibited strong preferences for: (i) water from reefs with islands over water from reefs without islands; (ii) water collected near islands over water collected offshore; and (iii) water treated with either anemones or leaves from rainforest vegetation. Laboratory reared-juveniles exhibited the same positive response to anemones and rainforest vegetation, suggesting that olfactory preferences are innate rather than learned. We hypothesize that A. percula use a suite of olfactory stimuli to locate vegetated islands, which may explain the high levels of self-recruitment on island reefs. This previously unrecognized link between coral reefs and island vegetation argues for the integrated management of these pristine tropical habitats.

Informed dispersal, heterogeneity in animal dispersal syndromes and the dynamics of spatially structured populations

There is accumulating evidence that individuals leave their natal area and select a breeding habitat non-randomly by relying upon information about their natal and future breeding environments. This variation in dispersal is not only based on external information (condition dependence) but also depends upon the internal state of individuals (phenotype dependence). As a consequence, not all dispersers are of the same quality or search for the same habitats. In addition, the individual's state is characterized by morphological, physiological or behavioural attributes that might themselves serve as a cue altering the habitat choice of conspecifics. These combined effects of internal and external information have the potential to generate complex movement patterns and could influence population dynamics and colonization processes. Here, we highlight three particular processes that link condition-dependent dispersal, phenotype-dependent dispersal and habitat choice strategies: (1) the relationship between the cause of departure and the dispersers' phenotype; (2) the relationship between the cause of departure and the settlement behaviour and (3) the concept of informed dispersal, where individuals gather and transfer information before and during their movements through the landscape. We review the empirical evidence for these processes with a special emphasis on vertebrate and arthropod model systems, and present case studies that have quantified the impacts of these processes on spatially structured population dynamics. We also discuss recent literature providing strong evidence that individual variation in dispersal has an important impact on both reinforcement and colonization success and therefore must be taken into account when predicting ecological responses to global warming and habitat fragmentation.