The context and cause of adaptive radiations has been widely described and explored but why rapid evolutionary diversification does not occur in related evolutionary lineages has yet to be understood. One possible answer to this is simply that evolutionary diversification is provoked by environmental diversity, and that some lineages do not encounter the necessary environmental diversity. Three-spined stickleback on the Scottish island of North Uist show enormous diversification, which seems to be associated with the diversity of aquatic habitats. Stickleback on the neighbouring island of South Uist have not been reported to show the same level of evolutionary diversity, despite levels of environmental variation that we might expect to be similar to North Uist. In this study, we compared patterns of morphological and environmental diversity on North and South Uist. Ancestral anadromous stickleback from both islands exhibited similar morphology including size and bony ‘armour’. Resident stickleback showed significant variation in armour traits in relation to pH of water. However, North Uist stickleback exhibited greater diversity of morphological traits than South Uist and this was associated with greater diversity in pH of the waters of lochs on North Uist. Highly acidic and highly alkaline freshwater habitats are missing, or uncommon, on South Uist. Thus, pH appears to act as a causal factor driving the evolutionary diversification of stickleback in local adaptation in North and South Uist. This is consistent with diversification being more associated with ecological constraint than ecological opportunity.
The idea that populations are spatially structured has become a very powerful concept in ecology, raising interest in many research areas. However, despite dispersal being a core component of the concept, it typically does not consider the movement behavior underlying any dispersal. Using individual-based simulations in continuous space, we investigate the emergence of a spatially structured population in landscapes with spatially heterogeneous resource distribution and with organisms following simple area-concentrated search (ACS); individuals do not, however, perceive or respond to any habitat attributes per se but only to their foraging success. We investigated effects of different resource clustering pattern in landscapes (single large cluster vs. many small clusters) and different resource density on spatially structure of populations and movement between resource clusters of individuals. As results, we found that foraging success increased with increasing resource density and decreasing number of resource clusters. In a wide parameter space, the system exhibited attributes of a spatially structured populations with individuals concentrated in areas of high resource density, searching within areas of resources, and ‘dispersing’ in straight line between resource patches. ‘Emigration’ was more likely from patches that were small or of low quality (low resource density), but we observed an interaction effect between these two parameters. With the ACS implemented, individuals tended to move deeper into a resource cluster in scenarios with moderate resource density than in scenarios with high resource density. ‘Looping’ from patches was more likely if patches were large and of high quality. Our simulations demonstrate that spatial structure in populations may emerge if critical resources are heterogeneously distributed and if individuals follow simple movement rules (such as ACS). Neither the perception of habitat nor an explicit decision to emigrate from a patch on the side of acting individuals are necessary for the emergence of spatial structure.
Aim: North China leopard (Panthera pardus japonensis), is the most widespread subspecies of leopard and one of the rare and endangered species in China. It is currently confined to several isolated reserves, and little is known about its habitat network connectivity with land use changes. We proposed an approach for the evaluation of the impacts of land use changes on landscape connectivity for North China leopard. Location: The Great Taihang Region, in the north of China, covers the entire territory of Shanxi province, as well as some districts and counties in Beijing, Hebei and Henan provinces. Methods: We analysed multiple background layers affecting North China leopard movement patterns, including environmental and anthropogenic factors, and generated a landscape resistance surface. Then we used Circuit theory-based connectivity models to delineate pathways suitable for species movement, and evaluate the connectivity status of core areas and the impacts of land use changes on landscape connectivity. Results: We identified 33 least cos distance paths in 1990 and 34 paths in 2020, and four key barrier areas. The landscape connectivity has not been greatly improved with the land use changes, especially with the increase of forest land from 26.61 to 34.85%. Nevertheless, there is a decreasing trend on connectivity in some key movement barrier areas. Improving landscape connectivity at a broad spatial scale is as important as protecting the habitats (natural reserves) where the species lived. Main conclusions: Our study can serve as an example of how to explore the relationships between land use changes and landscape connectivity for species at broad spatial scales with limited movement patterns data. This information is proved to be critical for enhancing landscape connectivity for conservation concern of North China leopard and planning of natural reserves network.
Climate change is increasing aridity in grassland and desert habitats across the southwestern United States, reducing available resources and drastically changing the breeding habitat of many bird species. Increases in aridity reduce sound propagation distances, potentially impacting habitat soundscapes, and leading to a breakdown of the avian soundscapes in the form of loss of vocal culture, reduced mating opportunities, and local population extinctions. We developed an agent-based model to examine how changes in aridity will affect both sound propagation and the ability of territorial birds to audibly contact their neighbors. We simulated vocal signal attenuation under a variety of environmental scenarios for the south central semi-arid prairies of the United States, ranging from contemporary weather conditions to predicted extremes under climate change. We also simulated how changes in physiological conditions, mainly evaporative water loss (EWL), would affect singing behavior. Under extreme climate change conditions, we found significantly fewer individuals successfully contacted all adjacent neighbors than did individuals in either the contemporary or mean climate change conditions. We also found that at higher sound frequencies and higher EWL, fewer individuals were able to successfully contact all of their neighbors, particularly in the extreme and extreme climate change conditions. These results indicate that climate change-mediated aridification may disrupt the avian soundscape, such that vocal communication no longer effectively functions for mate attraction or territorial defense. As climate change progresses increased aridity in current grasslands may favor shifts toward low frequency songs, colonial resource use, and altered songbird community compositions.
Phenotypic plasticity in reproductive behaviour can be a strong driver of individual fitness. For example, in species with high intra-sexual competition, changes in socio-sexual context can trigger quick adaptive plastic responses in males. In particular, a recent study in the vinegar fly (Drosophila melanogaster) shows that males respond adaptively to perception of female cues in a way that increases their reproductive success, but we ignore the underlying mechanisms of this phenomenon. Here, we aimed to fill this gap by investigating the short-term effects of female perception on male pre- and post-copulatory components of reproductive success: a) mating success, b) mating latency and duration, c) sperm competitiveness, and d) ejaculate effects on female receptivity and oviposition rate. We found that brief sexual perception increased mating duration, but had no effect on the main pre- or post-copulatory fitness proxies. These results tie up with previous findings to suggest that male adaptive responses to sexual perception are not due to a short-term advantage, but rather to fitness benefits that play out across the entire male lifespan.
Anthropogenic and climatic factors affect the survival of animal species. Chinese pangolins are a critically endangered species, and identifying which variables lead to local extinction events is essential for conservation management. Local chronicles in China serve as long-term monitoring data, providing a perspective to disentangle the roles of human impacts and climate changes in local extinctions. Through a generalized additive model, extinction risk assessment model and principal component analysis, we combined information from local chronicles over a period of three hundred years (1700-2000) and reconstructed environmental data to determine the causes of local extinctions of the Chinese pangolin in China. Our results showed that the extinction probability increased with population growth and climate warming. An extinction risk assessment indicated that the population and distribution range of Chinese pangolins has been persistently shrinking in response to highly intensive human activities (main cause) and climate warming. Overall, the factors that cause local extinction, intensive human interference and drastic climatic fluctuations induced by global warming, might increase the local extinction rate of Chinese pangolins. Approximately 25% of extant Chinese pangolins are confronted with a notable extinction risk (0.36≤extinction probability≤0.93), specifically those distributed in Southeast China, including Guangdong, Jiangxi, Zhejiang, Hunan, Fujian, Jiangsu and Taiwan Provinces. To rescue this endangered species, we suggest strengthening field investigations, identifying the exact distribution range and population density of Chinese pangolins and further optimizing the network of nature reserves to improve conservation coverage on the territory scale. Conservation practices that concentrate on the viability assessment of scattered populations could lead to the successful restoration of the Chinese pangolin population.
Sexual signals are important in speciation, but understanding their evolution is complex as these signals are often composed of multiple, genetically interdependent components. To understand how signals evolve, we thus need to consider selection responses in multiple components and account for the genetic correlations among components. One intriguing possibility is that selection changes the genetic covariance structure of a multicomponent signal in a way that facilitates a response to selection. However, this hypothesis remains largely untested empirically. In this study, we investigate the evolutionary response of the multicomponent female sex pheromone blend of the moth Heliothis subflexa to 10 generations of artificial selection. We observed a selection response of about 3/4s of a phenotypic standard deviation in the components under selection. Interestingly, other pheromone components that are biochemically and genetically linked to the components under selection did not change. We also found that after the onset of selection, the genetic covariance structure diverged, resulting in the disassociation of components under selection and components not under selection across the first two genetic principle components. Our findings provide rare empirical support for an intriguing mechanism by which a sexual signal can respond to selection without possible constraints from indirect selection responses.
Understanding the factors that regulate the functioning of our ecosystems in response to environmental changes can help to maintain the stable provisioning of ecosystem services to mankind. This is especially relevant given the increased variability of environmental conditions due to human activities. In particular, maintaining a stable production and plant biomass during the growing season (intra-annual stability) despite pervasive and directional changes in temperature and precipitation through time can help to secure food supply to wild animals, livestock, and humans. Here, we conducted a 29-year field observational study in a temperate grassland to explore how the intra-annual stability of primary productivity is influenced by biotic and abiotic variables through time. In particular, we analyzed the relationship of community biomass intra-annual stability with plant diversity and seasonal distribution patterns of temperature and precipitation. We found that lower accumulated precipitation between June and September during the 29-year investigated contributed to lower intra-annual community stability because of a decrease in compensatory mechanisms among species (species asynchrony). Additionally, higher precipitation in July contributed to higher intra-annual stability because higher species richness with higher precipitation led to higher average intra-annual stability of all species in the community (species stability). In contrast, we found no evidence that temperature influenced community intra-annual stability. Our results indicates that ongoing reduced seasonal precipitation leading to reduced intra-annual stability in the temperate grassland, which has important theoretical significance for us to take active measures to deal with climate change.
The non-breeding period represents a significant part of an Afro-Palearctic migratory bird’s annual cycle. Decisions such as whether to remain at a single site and whether to return to it across years have important effects on aspects such as survival, future breeding success, migratory connectivity, and conservation. During this study, we colour-ringed > 300 Common Whitethroats Curruca communis and undertook daily resightings to understand site persistence and the degree of site fidelity throughout three non-breeding periods (November – April) in Nigeria. The probability of detecting a colour-ringed Whitethroat when it was present, was 0.33. Site persistence varied widely across individuals (1 – 165 days) and did not differ significantly with sex or year, though first-year birds remained for significantly shorter periods than adults. We believe that shorter residencies are likely due to the use of multiple stationary non-breeding sites rather than low winter survival. A minimum of 19% of individuals returned to the study site the following year and shifted, on average, 300 meters, suggesting that Whitethroats have a relatively high degree of between-years site fidelity at a very fine scale. An individual’s previous residency duration did not seem to determine its residency duration the following year. We suggest that spatial fidelity is high and constant through years, but temporal fidelity is not, and individual residency patterns vary, probably according to yearly and seasonal conditions. Our results highlight the complexity of the annual cycle of a single species and the importance of carrying out in situ, small scale research throughout a migrant’s annual cycle over several years.
The maternally-inherited endosymbiont, Wolbachia, is known to alter the reproductive biology of its arthropod hosts for its benefit and can induce both positive and negative fitness effects in many hosts. Here we describe the effects of the maintenance of two distinct Wolbachia infections, one each from supergroups A and B, on the parasitoid host Nasonia vitripennis. We compare the effect of Wolbachia infections on various traits between the uninfected, single A infected, single B infected, and the double infected strains with their cured versions. Contrary to the previous reports, our results suggest that there is a significant cost associated with the maintenance of Wolbachia infections where traits like family size, fecundity, longevity, and rates of male copulation are compromised in Wolbachia infected strains. The double infected and supergroup B infection strains show higher Wolbachia titer than supergroup A. The double infected Wolbachia strain has the most detrimental impact on the host as compared to single infections. Moreover, there is a supergroup-specific negative impact on these wasps as the supergroup B infections elicit the most pronounced negative effects. These findings raise important questions on the mechanism of survival and maintenance of these reproductive parasites in arthropod hosts.
Growth and growth limitation are important indicators of density dependence and environmental limitation of populations. Estimating individual growth trajectories is therefore an important aspect of understanding and predicting the life history and dynamics of a population. Variation in individual growth trajectories arises due to variation in the environmental factors limiting individual growth. This environmental limitation can vary over time, between cohorts and between individuals within a cohort. For a complete and accurate understanding of individual growth in a population, it is important to include all these sources of variation. So far, statistical models only accounted for a subset of these factors or required an extensive growth history of individuals. Here we present a novel model describing the growth curves of cohorts in a population. This model is derived from a stochastic form of the Von Bertalanffy growth equation describing individual growth. The model is specifically tailored for use on length-at-age data in which the growth trajectory of an individual is unknown and every individual is only measured once. The presented method can also be used if growth limitation differs strongly between age or length classes. We demonstrate the use of the model for length-at-age data of North Sea plaice (Pleuronectes platessa) from the last thirty years. Fitting this model to length-at-age data can provide new insights in the dynamics of the environmental factors limiting individual growth and provides a useful tool for ecological research and management.
The estimation of demographic parameters is a key component of evolutionary demography and conservation biology. Capture-mark-recapture methods have served as a fundamental tool for estimating demographic parameters. The accurate estimation of demographic parameters in capture-mark-recapture studies depends on accurate modeling of the observation process. Classic capture-mark-recapture models typically model the observation process as a Bernoulli or categorical trial with some detection probability conditional on a marked individual’s availability for detection (e.g., alive, or alive and present in a study area). Alternatives to this approach are underused, but may have great utility in capture-recapture studies. In this paper we explore a simple concept: in the same way that counts contain more information about abundance than simple detection/non-detection data, the number of encounters of individuals during observation occasions contain more information about the observation process than detection/non-detection data for individuals during the same occasion. Rather than using Bernoulli or categorical distributions to estimate detection probability, we demonstrate the application of zero-inflated Poisson and gamma-Poisson distributions. This allows for inference on availability for encounter (i.e., temporary emigration), as well as a wide variety of parameterizations for heterogeneity in the observation process. We demonstrate that this approach can accurately recover demographic and observation parameters in the presence of individual heterogeneity in detection probability, and discuss some potential future extensions of this method.
1. Non-native ungulate grazing has negatively impacted native species across the globe, leading to massive loss of biodiversity and ecosystem services. Despite their pervasiveness, interactions between grazers and native species are not fully understood. We often observe declines in demography or survival of these native species, but lack understanding about the mechanisms underlying these declines. Physiological stress represents one mechanism of (mal)adaptation but data are sparse. 2. We investigated glucocorticoid levels in a native avian herbivore exposed to different intensities of non-native grazing in the cold desert Great Basin ecosystem, USA. We measured corticosterone, a glucocorticoid in birds, in feathers for a large sample (n = 280) of female Greater Sage-grouse (Centrocercus urophasianus) from three study areas in Northern Nevada and Southern Oregon with different grazing regimes of livestock and feral horses. 3. We found greater feral horse density was associated with higher corticosterone levels, and this effect was exacerbated by drought conditions. Livestock grazing produced similar results; however there was more model uncertainty about the livestock effect. Subsequent nesting success was lower with increased feather corticosterone, but corticosterone levels were not predictive of other vital rates. 4. Our results indicate a physiological response by sage-grouse to grazing pressure from non-native grazers. We found substantial among-individual variation in the strength of the response. These adverse effects were intensified during unfavorable weather events, highlighting the need to reevaluate management strategies in the face of climate change.
Marine heatwaves (MHWs) emerge as a severe stressor in marine ecosystems. Extreme warm sea surface temperatures during MHWs are often beyond the optimal thermal range and beyond one generation of tropical coastal zooplankton. However, it is relatively unknown whether transgenerational MHW effect may shape the offspring fitness, particularly in an ecologically relevant context with biotic interactions such as predation stress. We addressed these novel research questions by quantifying the reproductive success, grazing, and survival of copepod Pseudodiaptomus incisus exposed to MHW and fish predator cues (FPC) for two generations (F1 and F2). There were four F1 treatments [(control or F1-MHW) × (no FPC or F1-FPC)] and 16 F2 treatments [(control or F1-MHW) × (no F1-FPC or F1-FPC)] × [(control or F2-MHW × no F2-FPC or F2-FPC)]. In both generations, P. incisus performance was substantially lowered in MHW, but slightly higher in FPC, particularly in control temperature. F2 reproductive success and cumulative faecals were reduced by 20-30% in F1-MHW, but increased by ~2% in F1-FPC. Strikingly, direct MHW exposure strongly reduced survival, but transgenerational MHW exposure ameliorated its lethal effect and was independent of FPC. The increased survival came with a cost of reduced reproductive success, constrained by reduced grazing. The rapid transgenerational MHW acclimation and its associated costs are likely widespread and crucial mechanisms underlying the resilience of coastal tropical zooplankton to MHWs under high predation pressure in the tropical coastal marine ecosystems.
It is generally believed that there is only one species, Nectogale elegans in the genus Nectogale. However, the validity of the species status of Nectogale sikhimensis has been controversial, and the phylogenetic relationship of this genus has not been well resolved. In this study, the mitochondrial cytochrome b gene and eight nuclear genes were used to infer the molecular phylogenetic relationship of the genus. The results of phylogenetic trees indicated that Nectogale was divided into two large lineages—Group A from Tibet and Group B from Sichuan and Yunnan. The divergence time between the two groups was estimated to be 5.76 million years. The genetic distance of K2P between the two groups was over 14%. Some morphological differences were also found in Groups A and B, including the skull size, shape of the second upper molar (M2), first lower unicuspid (a1), and palatal suture. In consideration of the large genetic distance, divergence time, and morphological differences, we recover the species status of N. sikhimensis and support that Nectogale consists of two species.
Robust estimates of demographic parameters are critical for effective wildlife conservation and management, but are difficult to obtain for elusive species. We estimated the breeding and adult population sizes, as well as the minimum population size, in a high-density brown bear population on the Shiretoko Peninsula, in Hokkaido, Japan, using DNA-based pedigree reconstruction. A total of 1,288 individuals, collected in and around the Shiretoko Peninsula between 1998 and 2020, were genotyped at 21 microsatellite loci. Among them, 499 individuals were identified by intensive genetic sampling conducted in two consecutive years (2019 and 2020) mainly by noninvasive methods (e.g., hair and fecal DNA). Among them, both parents were assigned for 330 bears, and either maternity or paternity was assigned to 47 and 76 individuals, respectively. The subsequent pedigree reconstruction indicated a range of breeding and adult (≥4 years old) population sizes: 128–173 for female breeders and 66–91 male breeders, and 155–200 for female adults and 84–109 male adults. The minimum population size was estimated to be 449 (252 females and 197 males) in 2019. Long-term continuous genetic sampling prior to a short-term intensive survey would enable parentage to be identified in a population with a high probability, thus enabling reliable estimates of breeding population size for elusive species.
Metabolic rate is a trait that may evolve in response to the direct and indirect effects of predator-induced mortality. Predators may indirectly alter selection by lowering prey densities and increasing resource availability or by intensifying resource limitation through changes in prey behaviour (e.g. use of less productive areas). In the current study we quantify evolution of metabolic rate in the zooplankton Daphnia pulicaria following an invasive event by the predator Bythotrephes longimanus in Lake Mendota, Wisconsin, US. This invasion has been shown to dramatically impact D. pulicaria, causing a ~60% decline in their biomass. Using a resurrection ecology approach, we compared the metabolic rate of D. pulicaria clones originating from prior to the Bythotrephes invasion with that of clones having evolved in the presence of Bythotrephes. We observed a 7.4% reduction in metabolic rate among post-invasive clones compared to pre-invasive clones, and discuss the potential roles of direct and indirect selection in driving this change.
It is widely acknowledged that population structure can have a substantial impact on evolutionary trajectories. In social animals, this structure is strongly influenced by relationships among the population members, so studies of differences in social structure between diverging populations or nascent species are of prime interest. Ideal models for such a study are two house mouse subspecies, Mus musculus musculus and M. m. domesticus, meeting in Europe along a secondary contact zone. Though the latter subspecies has usually been supposed to form tighter and more isolated social units than the former, the evidence is still inconclusive. Here, we carried out a series of radio-frequency identification experiments in semi-natural enclosures to gather large longitudinal datasets on individual mouse movements. The data were summarised in the form of uni- and multi-layer social networks. Within them, we could delimit and describe the social units (‘modules’). While the number of estimated units was similar in both subspecies, domesticus revealed a more ‘modular’ structure. This subspecies also showed more intramodular social interactions, higher spatial module separation, higher intramodular persistence of parent-offspring contacts, and lower multiple paternity, suggesting more effective control of dominant males over reproduction. We also demonstrate that long-lasting modules can be identified with basic reproductive units or demes. We thus provide the first robust evidence that the two subspecies differ in their social structure and dynamics of the structure formation.