Species traits help explain butterfly habitat use in a tropical forest

1. When species can access all parts of the landscape, species-sorting metacommunity theory predicts that community composition depends on habitat choice and interactions with other species and the environment. These filtering processes can also depend on species' traits.
2. The authors investigated how traits mediate a species-sorting process in determining butterfly community composition in a naturally patchy landscape in the tropical Western Ghats, India. The authors asked, do traits mediate access to certain habitats and does seasonality affect these patterns? The authors surveyed 56 habitat patches in three habitat types: laterite plateau grasslands, ridge grassland, and moist-deciduous forest, in a 65-km² landscape.
3. Non-palatable butterflies showed similar occurrences across seasons and habitats, but palatable butterflies were less commonly encountered in open habitats in the dry season. Polyphagous butterflies occurred infrequently in the dry season in laterite habitats, potentially indicating emigration or diapause patterns are linked to diet breadth.
4. All species were present in all habitats, implying dispersal does not limit access to different habitat patches, consistent with the species-sorting metacommunity concept. Nevertheless, butterfly occurrence was strongly influenced by the interaction of mobility and habitat type with sedentary species occurring less often in low-resource open laterite patches than mobile species.
5. Species sorting is typically regarded as occurring directly through environmental filters, but here the authors suggest that the environmental filter acts through movement limitations. Studies integrating landscape heterogeneity and species characteristics will help us better understand metacommunities and species distributions in nature.

     

A community context for aggression? Multi‐species audience effects on territorial aggression in two species of Paridae

1. Territorial aggression in birds is widely observed and is commonly linked to sex, age, body size, physiology, seasonal cues, food resource, urbanization, and a variety of social contexts including conspecific audience effects. However, little is known about the heterospecific audience effects on territorial aggression.
2. Here, we address an emerging idea that heterospecific audience effects may be pervasive influences in the social lives of free‐living birds. We tested the hypothesis that the composition, number, and relative body size of heterospecific audiences observing an aggressive contest will influence the response probability and intensity of aggression displayed.
3. We subjected two Paridae species, tufted titmouse (TUTI, Baeolophus bicolor) and Carolina chickadee (CACH, Poecile carolinensis), to playbacks of aggressive calls during a breeding season in north‐central Florida. At widely spaced playback sites (N = 134) in woodland habitats, we characterized the makeup of heterospecific audiences, aggression type (intra vs. interspecific territoriality), local population density, and various environmental factors (tree density, wind speed, and noise level) that are likely to influence territorial aggression.
4. We found that the presence of heterospecific audiences increased TUTI aggression levels and that both parids were more likely to respond to playback stimuli when their audiences had higher heterospecific diversity (more heterospecific individuals and species). We also found TUTI were more likely to respond when CACH were present but not vice versa.
5. In conclusion, we found evidence that heterospecific audiences significantly influenced the metrics of territorial aggression of free‐living animals and we suggest that the definition of audience effects on the behavior of free‐living animals be expanded to incorporate heterospecific audiences.

     

A multi‐year dormancy strategy in a cabbage beetle population in southeastern China

The life cycle of the cabbage beetle Colaphellus bowringi in southeastern China is complex due to four options for adult development: summer diapause, winter diapause, prolonged diapsuse, and nondiapause. However, detailed information on the multi‐year emergence patterns of diapausing individuals in this beetle has not been documented. In this study, we monitored the adult emergence patterns of diapausing individuals and estimated the influence of the diapause‐inducing temperature and photoperiod on the incidence of prolonged diapause under seminatural conditions for several years. The duration of diapause for adults collected from the vegetable fields in different years varied from several months to 5 years. Approximately 25.9%–29.2% of individuals showed prolonged diapause (emergence more than 1 year after entering diapause) over the 5 years of observation. Furthermore, regardless of insect age, the emergence of diapausing adults from the soil always occurred between mid‐February and March in spring and between late August and mid‐October in autumn, when the host plants were available. The influence of diapause‐inducing temperatures (22, 25, and 28°C) combined with different photoperiods (L:D 12:12 h and L:D 14:10 h) on diapause duration was tested under seminatural conditions. Pairwise comparisons of diapause duration performed by the log‐rank test revealed that the low temperature of 22°C combined with the long photoperiod of L:D 14:10 h induced the longest diapause duration, whereas the low temperature of 22°C combined with the short photoperiod of L:D 12:12 h induced the highest proportion of prolonged diapause. This study indicates that C. bowringi adopts a multi‐year dormancy strategy to survive local environmental conditions and unpredictable risks.     

Modeling the demography of species providing extended parental care: A capture–recapture multievent model with a case study on polar bears (Ursus maritimus)

1. In species providing extended parental care, one or both parents care for altricial young over a period including more than one breeding season. We expect large parental investment and long‐term dependency within family units to cause high variability in life trajectories among individuals with complex consequences at the population level. So far, models for estimating demographic parameters in free‐ranging animal populations mostly ignore extended parental care, thereby limiting our understanding of its consequences on parents and offspring life histories.
2. We designed a capture–recapture multievent model for studying the demography of species providing extended parental care. It handles statistical multiple‐year dependency among individual demographic parameters grouped within family units, variable litter size, and uncertainty on the timing at offspring independence. It allows for the evaluation of trade‐offs among demographic parameters, the influence of past reproductive history on the caring parent''s survival status, breeding probability, and litter size probability, while accounting for imperfect detection of family units. We assess the model performance using simulated data and illustrate its use with a long‐term dataset collected on the Svalbard polar bears (Ursus maritimus).
3. Our model performed well in terms of bias and mean square error and in estimating demographic parameters in all simulated scenarios, both when offspring departure probability from the family unit occurred at a constant rate or varied during the field season depending on the date of capture. For the polar bear case study, we provide estimates of adult and dependent offspring survival rates, breeding probability, and litter size probability. Results showed that the outcome of the previous reproduction influenced breeding probability.
4. Overall, our results show the importance of accounting for i) the multiple‐year statistical dependency within family units, ii) uncertainty on the timing at offspring independence, and iii) past reproductive history of the caring parent. If ignored, estimates obtained for breeding probability, litter size, and survival can be biased. This is of interest in terms of conservation because species providing extended parental care are often long‐living mammals vulnerable or threatened with extinction.

     

Pliant pathogens: Estimating viral spread when confronted with new vector,host, and environmental conditions

1. Pathogen spread rates are determined, in part, by the performance of pathogens under altered environmental conditions and their ability to persist while switching among hosts and vectors.
2. To determine the effects of new conditions (host, vector, and nutrient) on pathogen spread rate, we introduced a vector‐borne viral plant pathogen, Barley Yellow Dwarf Virus PAV (BYDV‐PAV) into hosts, vectors, and host nutrient supplies that it had not encountered for thousands of viral generations. We quantified pathogen prevalence over the course of two serial inoculations under the new conditions. Using individual‐level transmission rates from this experiment, we parameterized a dynamical model of disease spread and projected spread across host populations through a growing season.
3. A change in nutrient conditions (increased supply of phosphorus) reduced viral transmission whereas shifting to a new vector or host species had no effect on infection prevalence. However, the reduction in the new nutrient environment was only temporary; infection prevalence recovered after the second inoculation.
4. Synthesis. These results highlight how robust the pathogen, BYDV‐PAV, is to changes in its biotic and abiotic environment. Our study also highlights the need to quantify longitudinal infection information beyond snapshot assessments to project disease risk for pathogens in new environments.

     

Brain architecture of the largest living land arthropod, the Giant Robber Crab Birgus latro (Crustacea, Anomura, Coenobitidae): evidence for a prominent central olfactory pathway?

Background

Several lineages within the Crustacea conquered land independently during evolution, thereby requiring physiological adaptations for a semi-terrestrial or even a fully terrestrial lifestyle. Birgus latro Linnaeus, 1767, the giant robber crab or coconut crab (Anomura, Coenobitidae), is the largest land-living arthropod and inhabits Indo-Pacific islands such as Christmas Island. B. latro has served as a model in numerous studies of physiological aspects related to the conquest of land by crustaceans. From an olfactory point of view, a transition from sea to land means that molecules need to be detected in gas phase instead of in water solution. Previous studies have provided physiological evidence that terrestrial hermit crabs (Coenobitidae) such as B. latro have a sensitive and well differentiated sense of smell. Here we analyze the brain, in particular the olfactory processing areas of B. latro, by morphological analysis followed by 3 D reconstruction and immunocytochemical studies of synaptic proteins and a neuropeptide.

Results

The primary and secondary olfactory centers dominate the brain of B. latro and together account for ca. 40% of the neuropil volume in its brain. The paired olfactory neuropils are tripartite and composed of more than 1,000 columnar olfactory glomeruli, which are radially arranged around the periphery of the olfactory neuropils. The glomeruli are innervated ca. 90,000 local interneurons and ca. 160,000 projection neurons per side. The secondary olfactory centers, the paired hemiellipsoid neuropils, are targeted by the axons of these olfactory projection neurons. The projection neuron axonal branches make contact to ca. 250.000 interneurons (per side) associated with the hemiellipsoid neuropils. The hemiellipsoid body neuropil is organized into parallel neuropil lamellae, a design that is quite unusual for decapod crustaceans. The architecture of the optic neuropils and areas associated with antenna two suggest that B. latro has visual and mechanosensory skills that are comparable to those of marine Crustacea.

Conclusions

In parallel to previous behavioral findings that B. latro has aerial olfaction, our results indicate that their central olfactory pathway is indeed most prominent. Similar findings from the closely related terrestrial hermit crab Coenobita clypeatus suggest that in Coenobitidae, olfaction is a major sensory modality processed by the brain, and that for these animals, exploring the olfactory landscape is vital for survival in their terrestrial habitat. Future studies on terrestrial members of other crustacean taxa such as Isopoda, Amphipoda, Astacida, and Brachyura will shed light on how frequently the establishment of an aerial sense of olfaction evolved in Crustacea during the transition from sea to land. Amounting to ca. 1,000,000, the numbers of interneurons that analyse the olfactory input in B. latro brains surpasses that in other terrestrial arthropods, as e.g. the honeybee Apis mellifera or the moth Manduca sexta, by two orders of magnitude suggesting that B. latro in fact is a land-living arthropod that has devoted a substantial amount of nervous tissue to the sense of smell.     

How do African elephants utilize the landscape during wet season? A habitat connectivity analysis for Sioma Ngwezi landscape in Zambia

1. The influence of environmental factors on the distribution and persistence of African elephants (Loxodonta africana) is pertinent to policy makers and managers to formulate balanced plans for different land‐use types.
2. The study focuses on movement of elephants and how they utilize foraging areas in Sioma Ngwezi landscape in Zambia by answering the following questions: (1) Which environmental variables and land‐cover class predict the movement of elephants during the wet season in Sioma Ngwezi landscape? (2) What is the wet season suitable habitat for elephants in Sioma Ngwezi landscape? (3) What are the major wet season movement corridors for elephants in Sioma Ngwezi landscape?
3. We used GPS telemetry data from the collared elephants to assess habitat connectivity. Maximum entropy (MaxEnt) and linkage mapper were the tools used to predict habitat suitability, movement corridors, and barriers in the landscape during the wet season.
4. The study identified elevation, land cover, and NDVI as the most important environmental predictors that modify the dispersal of elephants in the landscape during the wet season. Additionally, a total of 36 potential wet season corridors were identified connecting 15 core areas mainly used for foraging and protection from poachers in the landscape. Of these, 24 corridors were highly utilized and are suggested as priority corridors for elephant movement in the landscape.
5. The identified wet season habitats and functional corridors may help to combat elephant poaching by patrolling areas with high relative probability of elephant presence. The findings may also help abate human–elephant conflict such as crop‐raiding by managing identified corridors that run into agriculture zones in the game management area.

     

Age and social experience induced plasticity across brain regions of the paper wasp Polistes fuscatus

Developmental studies of brain volumes can reveal which portions of neural circuits are sensitive to environmental inputs. In social insects, differences in relative investment across brain regions emerge as behavioural repertoires change during ontogeny or as a result of experience. Here, we test the effects of maturation and social experience on morphological brain development in Polistes fuscatus paper wasps, focusing on brain regions involved in visual and olfactory processing. We find that mature wasps regardless of social experience have relatively larger brains than newly emerged wasps and this difference is driven by changes to mushroom body calyx and visual regions but not olfactory processing neuropils. Notably, social wasps invest more in the anterior optic tubercle (AOT), a visual glomerulus involved in colour and object processing in other taxa, relative to other visual integration centres the mushroom body calyces compared with aged socially naive wasps. Differences in developmental plasticity between visual and olfactory neuropil volumes are discussed in light of behavioural maturation in paper wasps, especially as it relates to social recognition. Previous research has shown that P. fuscatus need social experience to develop specialized visual processing of faces, which is used to individually recognize conspecifics. The present study suggests that the AOT is a candidate brain region that could mediate facial processing in this species.     

Linking behavioral states to landscape features for improved conservation management

1. A central theme for conservation is understanding how animals differentially use, and are affected by change in, the landscapes they inhabit. However, it has been challenging to develop conservation schemes for habitat‐specific behaviors.
2. Here we use behavioral change point analysis to identify behavioral states of golden eagles (Aquila chrysaetos) in the Sonoran and Mojave Deserts of the southwestern United States, and we identify, for each behavioral state, conservation‐relevant habitat associations.
3. We modeled behavior using 186,859 GPS points from 48 eagles and identified 2,851 distinct segments comprising four behavioral states. Altitude above ground level (AGL) best differentiated behavioral states, with two clusters of short‐distance movement behaviors characterized by low AGL (state 1 AGL = 14 m (median); state 2 AGL = 11 m) and two associated with longer‐distance movement behaviors and characterized by higher AGL (state 3 AGL = 108 m; state 4 AGL = 450 m).
4. Behaviors such as perching and low‐altitude hunting were associated with short‐distance movements in updraft‐poor environments, at higher elevations, and over steeper and more north‐facing terrain. In contrast, medium‐distance movements such as hunting and transiting were over gentle and south‐facing slopes. Long‐distance transiting occurred over the desert habitats that generate the best updraft.
5. This information can guide management of this species, and our approach provides a template for behavior‐specific habitat associations for other species of management concern.

     

The pollination of Habenaria rhodocheila (Orchidaceae) in South China: When butterflies take sides

Habenaria is one of the largest terrestrial genera in the family Orchidaceae. Most field studies on Habenaria species with greenish–white and nocturnal scented flowers are pollinated by nocturnal hawkmoths and settling moths. However, H. rhodocheila presents reddish flowers lacking a detectable scent and fails to fit the moth pollination syndrome. We investigated the pollinators, breeding system, and functional traits of H. rhodocheila in South China and found that two diurnal swallowtail butterflies Papilio helenus and Papilio nephelus (Papilionidae) were the effective pollinators. When butterflies foraged for nectar in the spur, the pollinia became attached between the palpi. A triangular projected median rostellar lobe was found at the entrance (sinus) of the spur of H. rhodocheila. This lobe divided the spur opening into two entrances forcing butterflies to enter their proboscides through the left or right side. When the projection of median rostellar lobe was removed, the site of pollinium attachment changed to the eyes of the butterflies, leading to a higher rate of pollinium removal but lower rate of pollinium deposition. Our quartz glass cylinder choice experiment suggested that visual rather than olfactory cues provided the major stimuli for butterflies to locate these flowers. Hand pollination experiments suggested this species was self‐compatible but pollinator‐dependent. However, the proportion of seeds with large embryos produced in self‐pollinated fruits was significantly lower than in cross‐pollinated fruits, indicating a significant inbreeding depression. Unlike many other orchid species, fruit set was higher than rates of pollinium removal, indicating a high level of pollination efficiency in a species with friable pollinia. Shifts from moth to butterfly pollination in the genus Habenaria parallel other orchid lineages providing insights into the potential for pollinator‐mediated floral trait selection.     

A modified niche model for generating food webs with stage‐structured consumers: The stabilizing effects of life‐history stages on complex food webs

1. Almost all organisms grow in size during their lifetime and switch diets, trophic positions, and interacting partners as they grow. Such ontogenetic development introduces life‐history stages and flows of biomass between the stages through growth and reproduction. However, current research on complex food webs rarely considers life‐history stages. The few previously proposed methods do not take full advantage of the existing food web structural models that can produce realistic food web topologies.
2. We extended the niche model developed by Williams and Martinez (Nature, 2000, 404, 180–183) to generate food webs that included trophic species with a life‐history stage structure. Our method aggregated trophic species based on niche overlap to form a life‐history structured population; therefore, it largely preserved the topological structure of food webs generated by the niche model. We applied the theory of allometric predator–prey body mass ratio and parameterized an allometric bioenergetic model augmented with biomass flow between stages via growth and reproduction to study the effects of a stage structure on the stability of food webs.
3. When life‐history stages were linked via growth and reproduction, more food webs persisted, and persisting food webs tended to retain more trophic species. Topological differences between persisting linked and unlinked food webs were small to modest. The slopes of biomass spectra were lower, and weak interaction links were more prevalent in the linked food webs than the unlinked ones, suggesting that a life‐history stage structure promotes characteristics that can enhance stability of complex food webs.
4. Our results suggest a positive relationship between the complexity and stability of complex food webs. A life‐history stage structure in food webs may play important roles in dynamics of and diversity in food webs.

     

Spatial structure of reproductive success infers mechanisms of ungulate invasion in Nearctic boreal landscapes

1. Landscape change is a key driver of biodiversity declines due to habitat loss and fragmentation, but spatially shifting resources can also facilitate range expansion and invasion. Invasive populations are reproductively successful, and landscape change may buoy this success.
2. We show how modeling the spatial structure of reproductive success can elucidate the mechanisms of range shifts and sustained invasions for mammalian species with attendant young. We use an example of white‐tailed deer (deer; Odocoileus virginianus) expansion in the Nearctic boreal forest, a North American phenomenon implicated in severe declines of threatened woodland caribou (Rangifer tarandus).
3. We hypothesized that deer reproductive success is linked to forage subsidies provided by extensive landscape change via resource extraction. We measured deer occurrence using data from 62 camera traps in northern Alberta, Canada, over three years. We weighed support for multiple competing hypotheses about deer reproductive success using multistate occupancy models and generalized linear models in an AIC‐based model selection framework.
4. Spatial patterns of reproductive success were best explained by features associated with petroleum exploration and extraction, which offer early‐seral vegetation resource subsidies. Effect sizes of anthropogenic features eclipsed natural heterogeneity by two orders of magnitude. We conclude that anthropogenic early‐seral forage subsidies support high springtime reproductive success, mitigating or exceeding winter losses, maintaining populations.
5. Synthesis and Applications. Modeling spatial structuring in reproductive success can become a key goal of remote camera‐based global networks, yielding ecological insights into mechanisms of invasion and range shifts to inform effective decision‐making for global biodiversity conservation.

     

Age‐ and sex‐related dietary specialization facilitate seasonal resource partitioning in a migratory shorebird

1. Dietary specialization is common in animals and has important implications for individual fitness, inter‐ and intraspecific competition, and the adaptive potential of a species. Diet composition can be influenced by age‐ and sex‐related factors including an individual''s morphology, social status, and acquired skills; however, specialization may only be necessary when competition is intensified by high population densities or increased energetic demands.
2. To better understand the role of age‐ and sex‐related dietary specialization in facilitating seasonal resource partitioning, we inferred the contribution of biofilm, microphytobenthos, and benthic invertebrates to the diets of western sandpipers (Calidris mauri) from different demographic groups during mid‐winter (January/February) and at the onset of the breeding migration (April) using stable isotope mixing models. Western sandpipers are sexually dimorphic with females having significantly greater body mass and bill length than males.
3. Diet composition differed between seasons and among demographic groups. In winter, prey consumption was similar among demographic groups, but, in spring, diet composition differed with bill length and body mass explaining 31% of the total variation in diet composition. Epifaunal invertebrates made up a greater proportion of the diet in males which had lesser mass and shorter bills than females. Consumption of Polychaeta increased with increasing bill length and was greatest in adult females. In contrast, consumption of microphytobenthos, thought to be an important food source for migrating sandpipers, increased with decreasing bill length and was greatest in juvenile males.
4. Our results provide the first evidence that age‐ and sex‐related dietary specialization in western sandpipers facilitate seasonal resource partitioning that could reduce competition during spring at the onset of the breeding migration.
5. Our study underscores the importance of examining resource partitioning throughout the annual cycle to inform fitness and demographic models and facilitate conservation efforts.

     

Intraspecific trait variability and community assembly in hawkmoths (Lepidoptera: Sphingidae) across an elevational gradient in the eastern Himalayas,India

1. We investigated some aspects of hawkmoth community assembly at 13 elevations along a 200‐ to 2770‐m transect in the eastern Himalayas, a little studied biodiversity hot spot of global importance. We measured the morphological traits of body mass, wing loading, and wing aspect ratio of 3,301 free‐ranging individuals of 76 species without having to collect or even constrain them. We used these trait measurements and T‐statistic metrics to assess the strength of intracommunity (“internal") and extra‐community (“external”) filters which determine the composition of communities vis‐a‐vis the regional pool of species.
2. The trait distribution of constituent species turned out to be nonrandom subsets of the community‐trait distribution, providing strong evidence for internal filtering in all elevational communities. The external filter metric was more ambiguous. However, the elevational dependence of many metrics including that of the internal filter provided evidence for external (i.e., environmental) filtering. On average, a species occupied as much as 50%–75% of the total community‐trait space, yet the T‐statistic metric for internal filter was sufficiently sensitive to detect a strong nonrandom structure in the trait distribution.
3. We suggest that the change in T‐statistic metrics along the environmental gradient may provide more clues to the process of community assembly than previously envisaged. A large, smoothly varying and well‐sampled environmental span would make it easier to discern them. Developing T‐statistics for combined analysis of multiple traits will perhaps provide a more accurate picture of internal/filtering and niche complementarity. Moths are a hyperdiverse taxon and a very important component of many ecosystems. Our technique for accurately measuring body and wing dimensions of free‐ranging moths can generate trait database for a large number of individuals in a time‐ and resource‐efficient manner for a variety of community assembly studies using this important taxon.

     

Temporal patterns in the social network of core units in Rwenzori Angolan colobus monkeys: Effects of food availability and interunit dispersal

1. Multi‐level societies are complex, nested social systems where basic social groups (i.e., core units) associate in a hierarchical manner, allowing animals to adjust their group sizes in response to variables such as food availability, predation, or conspecific threat. These pressures fluctuate over time and examining the extent to which this variation affects the clustering of core units into different tiers may be instrumental in understanding the evolution of multi‐level societies.
2. The goal of our study was to determine the degree of temporal variability in interunit associations in a multi‐level society of Rwenzori Angolan colobus monkey (Colobus angolensis ruwenzorii), and to determine the social and ecological factors that underlie association patterns. The C. a. ruwenzorii multi‐level society consists of at least three tiers, with core units clustering into clans that share a home range in a band tier.
3. We performed social network analyses on 21 months of association data from 13 core units (totaling 139 identifiable individuals) at Lake Nabugabo, Uganda. We described the patterns of variation in core‐unit associations over time and investigated how changes in rainfall, food availability, and interunit dispersals were correlated with these associations over the short‐term (month to month) and long‐term (year to year).
4. Although clans were relatively stable, larger‐scale changes in association patterns included the formation of an all‐male unit and the transfer of one core unit between clans (within the band tier). Seasonally, core units associated significantly more when fruit, their preferred food source, was abundant (i.e., social networks were denser and more clustered) and there was no direct effect of rainfall seasonality or young leaf availability. Male dispersals also occurred more during periods of high fruit availability, suggesting that greater band cohesion allowed males to prospect and transfer between core units. Once males transferred, their previous and new units associated significantly more with one another than with other core units for 1–2 months postdispersal. The dispersal of five males from one core unit to another in a different clan co‐occurred with this core unit switching its clan affiliation.
5. By examining temporal shifts in social network structure among core units, this study shows the interconnected roles that food availability and dispersal have in shaping the C. a. ruwenzorii multi‐level social system. Our findings highlight how ecological conditions can drive association patterns, impact interunit relationships, and influence social organization.

     

Current and time‐lagged effects of climate on innate immunity in two sympatric snake species

1. Changing environments result in alterations at all levels of biological organization, from genetics to physiology to demography. The increasing frequency of droughts worldwide is associated with higher temperatures and reduced precipitation that can impact population persistence via effects on individual immune function and survival.
2. We examined the effects of annual climate variation on immunity in two sympatric species of garter snakes from four populations in California over a seven‐year period that included the record‐breaking drought.
3. We examined three indices of innate immunity: bactericidal competence (BC), natural antibodies (NABs), and complement‐mediated lysis (CL).
4. Precipitation was the only climatic variable explaining variation in immune function: spring precipitation of the current year was positively correlated to Thamnophis sirtalis BC and NABs, whereas spring precipitation of the previous year was positively correlated to T. elegans BC and NABs. This suggests that T. elegans experiences a physiological time‐lag in response to reduced precipitation, which may reflect lack of capital for investment in immunity in the year following a dry year.
5. In general, our findings demonstrate compelling evidence that climate can influence wild populations through effects on physiological processes, suggesting that physiological indices such as these may offer valuable opportunities for monitoring the effects of climate.

     

Variation in the life cycle of monogonont rotifers: Commitment to sex and emergence from diapause

1. A review of research on life-cycle events in field and laboratory populations of monogonont rotifers shows that there is great variation at multiple levels: (1) degree of sexual dimorphism; (2) occurrence and timing of sex; (3) propensity for sex during sexual periods; (4) factors controlling initiation of sex; and (5) timing and extent of emergence from diapause. There is no regular pattern where: (1) fertilised resting eggs hatch to start the growing season; (2) populations develop via female parthenogenesis during favourable conditions; and then (3) bisexual reproduction with resting-egg production occurs during later, unfavourable conditions.
2. Sexual reproduction in natural populations can occur throughout much of the growing season, be restricted to some period(s) during the growing season, or be completely absent. During sexual reproduction in both natural and laboratory populations, only some fraction of females produces males or resting eggs. This bet-hedging strategy can prevent a population crash and permits future population growth via female parthenogenesis. Selection against sexual reproduction, and rapid loss of sex, can occur.
3. Laboratory experiments with pond-dwelling species have identified specific environmental factors that induce sex in different species: (1) increasing population density; (2) dietary tocopherol (vitamin E) and (3) long photoperiods. These factors generally are associated with favourable conditions for population growth and production of energy-rich resting eggs: (1) large population size; (2) high probability of contacts between males and fertilisable females; and (3) nutritious diets. Endogenous factors can inhibit responses to these environmental inducers, and thus favour female parthenogenesis.
4. The timing of resting-egg hatching depends on: (1) occurrence of specific environmental conditions; (2) the minimum duration of obligate diapause; and (3) the genotype and physiology of females producing resting eggs. Hatching may occur shortly after oviposition, after a long diapause before or at the start of a new growing season, or throughout the growing season. Hatching can be massive and contribute substantially to population growth and genetic diversity.
5. Areas for future research include: (1) determining the timing and extent of sex and resting-egg hatching in more natural populations, especially those that are marine, benthic, sessile, and interstitial; and (2) identifying environmental and physiological factors controlling these events.

     

Phenotypic plasticity, seasonal climate and the population biology of Bicyclus butterflies (Satyridae) in Malawi

Abstract.

• 1 Seasonal polyphenism is studied in a community of five African butterflies of the genus Bicyclus at the transition between a wet and a dry season from May to July.
• 2 Butterflies characterized by large eyespots and, especially in B.sufitza (Hewitson), a pale band (the wet season form) are replaced over this period by butterflies lacking conspicuous wing markings (the dry season form, dsf). The latter butterflies also tend to be larger, but more variable in size. Butterflies of an intermediate phenotype are recruited over a comparatively short interim period.
• 3 This turnover coincides with a period of declining temperature and drying of the habitat, including the grasses on which larvae feed. Butterflies are progressively more likely to rest on brown leaf litter rather than on green herbage.
• 4 A relationship with temperature is supported by laboratory experiments with B.saJitza and B.anynana (Butler) showing that increasingly extreme dsf butterflies develop with decreasing rearing temperature in the final larval instar.
• 5 Some differences in behaviour and activity were observed between the seasonal forms. Butterflies of the dsf develop ovarian dormancy and fat bodies. They can survive to reproduce at the beginning of the rains in November.
• 6 Capture-recapture experiments showed that the adult butterflies have a comparatively long life expectancy and are quite sedentary.
• 7 The results are discussed in relation to a hypothesis linking the polyphenism to seasonal changes in resting background and selection for crypsis.

     

Age‐specific habitat preference,carrying capacity,and landscape structure determine the response of population spatial variability to fishing‐driven age truncation

1. Understanding the mechanisms underlying spatial variability of exploited fish is critical for the sustainable management of fish stocks. Empirical studies suggest that size‐selective fishing can elevate fish population spatial variability (i.e., more heterogeneous distribution) through age truncation, making the population less resilient to changing environment. However, species differ in how their spatial variability responds to age truncation and the underlying mechanisms remain unclear.
2. We hypothesize that age‐specific habitat preference, together with environmental carrying capacity and landscape structure, determines the response of population spatial variability to fishing‐induced age truncation. To test these hypotheses, we design an individual‐based model of an age‐structured fish population on a two‐dimensional landscape under size‐selective fishing. Individual fish reproduces and survives, and moves between habitats according to age‐specific habitat preference and density‐dependent habitat selection.
3. Population spatial variability elevates with increasing age truncation, and the response is stronger for populations with stronger age‐specific habitat preference. On a gradient landscape, reducing carrying capacity elevates the relative importance of density dependence in habitat selection, which weakens the response of spatial variability to age truncation for populations with strong age‐specific habitat preference. On a fragmented landscape, both populations with strong and weak age‐specific habitat preferences are restricted at local optimal habitats, and reducing carrying capacity weakens the responses of spatial variability to age truncation for both populations.
4. Synthesis and applications. We demonstrate that to track and predict the changes in population spatial variability under exploitation, it is essential to consider the interactive effects of age‐specific habitat preference, carrying capacity, and landscape structure. To improve spatial management in fisheries, it is crucial to enhance empirical and theoretical developments in the methodology to quantify age‐specific habitat preference of marine fish, and to understand how climatic change influences carrying capacity and landscape continuity.

     

Integrating omics to characterize eco‐physiological adaptations: How moose diet and metabolism differ across biogeographic zones

1. With accelerated land conversion and global heating at northern latitudes, it becomes crucial to understand, how life histories of animals in extreme environments adapt to these changes. Animals may either adapt by adjusting foraging behavior or through physiological responses, including adjusting their energy metabolism or both. Until now, it has been difficult to study such adaptations in free‐ranging animals due to methodological constraints that prevent extensive spatiotemporal coverage of ecological and physiological data.
2. Through a novel approach of combining DNA‐metabarcoding and nuclear magnetic resonance (NMR)‐based metabolomics, we aim to elucidate the links between diets and metabolism in Scandinavian moose Alces alces over three biogeographic zones using a unique dataset of 265 marked individuals.
3. Based on 17 diet items, we identified four different classes of diet types that match browse species availability in respective ecoregions in northern Sweden. Individuals in the boreal zone consumed predominantly pine and had the least diverse diets, while individuals with highest diet diversity occurred in the coastal areas. Males exhibited lower average diet diversity than females.
4. We identified several molecular markers indicating metabolic constraints linked to diet constraints in terms of food availability during winter. While animals consuming pine had higher lipid, phospocholine, and glycerophosphocholine concentrations in their serum than other diet types, birch‐ and willow/aspen‐rich diets exhibit elevated concentrations of several amino acids. The individuals with highest diet diversity had increased levels of ketone bodies, indicating extensive periods of starvation for these individuals.
5. Our results show how the adaptive capacity of moose at the eco‐physiological level varies over a large eco‐geographic scale and how it responds to land use pressures. In light of extensive ongoing climate and land use changes, these findings pave the way for future scenario building for animal adaptive capacity.