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.
Pine barren and sandplain ecosystems are unique, globally rare ecosystems whose open-canopied vegetation structure supports a unique assemblage of plants and animals. They occur almost exclusively on deep, sandy soils, and require periodic disturbances to prevent succession to forest. Though these ecosystems, and the unique species that live in them, are rare today, they once occupied a larger area of coastal and interior New York and New England. In order to better understand pine barren and sandplain distribution in the past, and the potential for restoring them in the future, we mapped the distribution of soils in New York State that can support these ecosystems. We quantified soil percent sand and soil depth of 156 known high quality remnant pine barren and sandplain ecosystems to calculate threshold soil characteristics. We then mapped all soils in the state that were at least as sandy and deep as the threshold values we calculated. The total area of our map of potential soil conditions was over 9,500 km2, made up of forested (57%), urban (26%), agricultural (13%) and open (4%) land cover. Nearly 7,000 km2 – almost 20 times the area of known, high quality remnant ecosystems – of land was forested, agricultural, or open land. Existing examples of pine barren and sandplain ecosystems were mostly embedded within much larger matrices of forest, agriculture, and urban land cover that shared the distinctive soil conditions. The presence of extensive soils in coastal and interior New York that, with the appropriate disturbance regime, have the potential to host pine barren and sandplain ecosystems offers a new perspective on these ecosystems’ distribution in the past – and about how to better align restoration and conservation to preserve the future.
Plant phenology is manifested in the seasonal timing of vegetative and reproductive processes, but also has ontogenetic aspects. The adaptive basis of seasonal phenology has been considered mainly in terms of climatic drivers. However, some biotic factors as likely evolutionary influences on plants’ phenology appear to have been under-researched. Several specific cases of putative biotic factors driving plant phenology are outlined, involving both herbivores and pathogens. These illustrate the diversity of likely interactions rather than any systematic coverage or review. Emphasis is on woody perennials, in which phenology is often most multi-faceted and complicated by the ontogenetic aspect. The complete seasonal leaf fall that characterises deciduous plants may be a very important defence against some pathogens. Whether biotic influences drive acquisition or long-term persistence of deciduousness is considered. In one case; of leaf rusts in poplars, countervailing influences of the rusts and climate suggest persistence. Often, however, biotic and environmental influences likely reinforce each other. The timing and duration of shoot flushing may in at least some cases contribute to defences against herbivores, largely through brief periods of ‘predator satiation’ when plant tissues have highest food value. Wide re-examination of plant phenology, accommodating the roles of biotic factors and their interplays with environments as additional adaptive drivers, is advocated, towards developing and applying hypotheses that are observationally or experimentally testable.
Climate change is affecting species and their mutualists and can lead to interaction weakening and loss. Through independent shifts in partner phenology and distribution, climatic stress can separate mutualists, leading to alterations in partner functional traits and fitness. Here, we explored the effects of drying soils and the loss of microbial mutualists via soil sterilization on legume germination success and phenology, focusing on how a loss of mutualisms with soil microbial species can alter legume early life traits. In particular, we assessed the effects of mutualism loss via soil sterilization, increased drought, or introduction to novel soils found beyond the current distributions of two focal legume species in subalpine environments. Through common garden experiments in controlled environments, we found evidence that soil sterilization (and consequent microbial absence) and dry soils caused phenological delays of 2-5 weeks in germination date, likely as a result of interaction loss between legumes and germination-promoting soil microbes, such as mutualistic rhizobia. Delays in germination caused by a mismatch between legumes and beneficial microbes could negatively affect legume fitness through increased plant-plant competition later in the season. Additionally, we found evidence of the presence of beneficial microbes beyond the current elevational range of our focal legumes which may allow for expansion of the leading edge, though harsh abiotic factors in the alpine may hinder this. Alterations in the strength of soil microbe-legume mutualisms may lead to reduced fitness and altered demography for both soil microbes and legumes.
Satyrium is an endangered and rare genus of plant that has various pharmacodynamic functions. In this study, MaxEnt default parameters were adjusted by the ENMeval package. Optimized MaxEnt models were used in analyzing potential geographical distributions under current and future climatic conditions (the 2050s and 2070s) and dominant environmental variables influencing their geographic distribution. The results provided reference for implementation of long-term conservation and management approaches for the species. The results showed the area of the total suitable habitat for S. ciliatum in China is 32.51 × 104 km2, the total suitable habitat area for S. nepalense in China is 61.76 × 104 km2, and the area of the total suitable habitat for S. yunnanense in China is 89.73 × 104 km2 under current climatic conditions. The potential suitable habitat of Satyrium is mainly distributed in Southwest China. The major environmental variables influencing the geographical distribution of S. ciliatum were isothermality (bio3), temperature seasonality (bio4), and mean temperature of coldest quarter (bio11). Environmental variables such as isothermality (bio3), temperature seasonality (bio4), and precipitation of coldest quarter (bio19) affected the geographical distribution of S. nepalense; and environmental variables such as isothermality (bio3), temperature seasonality (bio4), and lower temperature of coldest month (bio6) affected the geographical distribution of S. yunnanense. The distribution range of Satyrium was extended as global warming increased, showing emissions of greenhouse gases with lower concentration (SSP1-2.6) and higher concentration (SSP5-8.5). According to the study, the distribution of suitable habitat will shift with a change to higher elevation areas and higher latitude areas in the future.
Aim Determine seasonal, annual and decadal patterns of abundance in reptile populations and assemblages occupying an isolated urban bushland remnant Location Bold Park (~338 ha), Perth, Southwestern Australia Time period 1986-2021 Major taxa studied: Squamate reptiles Methods Fenced pitfall trapping in four sampling sites representing different habitats and fire history over the primary reptile activity period and 35 consecutive years; trapping regime was modified for the last 28 years. Results The location occurs in one of 35 global biodiversity hotspots and has a Mediterranean climate experiencing a 15% decline from the century average rainfall over the last 50 years. Twenty-nine species were recorded, with 16 captured in 32 or more years and accounting for nearly 97% of all captures; the six most common for 81%. Three taxa became locally extinct. Activity predominates in warmer and dryer months (October to April), peaking in November December. Species richness remained relatively constant between years with around 73% of known taxa captured annually. Assemblage structure didn’t change when analysing presence/absence data but shifted through five statistically significantly assemblages analysing relative abundance data. Over the last 28 years relative abundance was significantly and positively correlated with annual rainfall residuals for the three years preceding annual sampling, resulting in significant changes in total assemblage structure and significantly similar patterns in four sample sites; presence/absence data indicated minor assemblage structure changes. Main conclusions Annual species number remained relatively constant but relative abundance illustrated significant temporal changes in assemblage structure over decades; presence/absence did not. The modeled relationship between relative abundance and annual rainfall residuals for the three years preceding annual sampling is supported by known ecological responses and reptile demographics within this Mediterranean climate. Maintenance of urban biodiversity should consider impacts of a significantly drying climate exacerbating the extinction debt already inherent in isolated bushland populations.
Abiotic and biotic factors structure species assembly in ecosystems both horizontally and vertically. However, the way community composition changes along comparable horizontal and vertical distances in complex three-dimensional habitats, and the factors driving these patterns, remain poorly understood. By sampling ant assemblages at comparable vertical and horizontal spatial scales in a tropical rain forest, we compared observed patterns with those predicted according to environmental filtering by microclimate and microhabitat structure. We found that although dissimilarity between ant assemblages increased with vertical distance, the dissimilarity was higher horizontally but was independent of distance. The pronounced horizontal and vertical structuring of ant assemblages across short distances is likely explained by a combination of microclimate and microhabitat connectivity. Our results demonstrate the importance of considering three-dimensional spatial variation in local assemblages and reveal how highly diverse communities can be supported by complex habitats.
Understanding the extent to which predators engage in active search for prey versus incidentally encountering them is important because active search can exert a stabilizing force on prey populations by alleviating predation pressure on low-density prey and increasing it for high-density prey. Parturition of many large herbivores occurs during a short and predictable temporal window in which young are highly vulnerable to predation. Our study aims to determine how a suite of carnivores responds to the seasonal pulse of newborn ungulates using contemporaneous GPS locations of four species of predators and two species of prey. We used step-selection functions to assess whether coyotes, cougars, black bears, and bobcats actively searched for parturient females in a low-density population of mule deer and a high-density population of elk. We then assessed whether searching carnivores shifted their habitat use toward areas exhibiting a high probability of encountering neonates. None of the four carnivore species encountered parturient mule deer more often than expected by chance suggesting that predation of young resulted from incidental encounters. By contrast, we determined that cougar and male bear movements positioned them in proximity of parturient elk more often than expected by chance which is evidence of searching behavior. Although both male bears and cougars searched for neonates, only male bears used elk parturition habitat in a way that dynamically tracked the phenology of the elk birth pulse suggesting that maximizing encounters with juvenile elk was a motivation when selecting resources. Our results support the existence of a stabilizing mechanism to prey populations through active search behavior by predators because carnivores in our study searched for the high-density prey species (elk) but ignored the low-density species (mule deer). We conclude that prey density must be high enough to warrant active search, and that there is high interspecific and intersexual variability in foraging strategies among large mammalian predators and their prey.
The subfamily Typhlocybinae is a ubiquitous, highly diverse group of mostly tiny, delicate leafhoppers. The tribal classification has long been controversial and phylogenetic methods have only recently begun to test the phylogenetic status and relationships of tribes. To shed light on the evolution of Typhlocybinae, we performed phylogenetic analyses based on 28 newly sequenced and 19 previously sequenced mitochondrial genomes representing all currently recognized tribes. The results support the monophyly of the subfamily and its sister group relationship to Mileewinae. The tribe Zyginellini is polyphyletic with some included genera derived independently within Typhlocybini. Ancestral character state reconstruction suggests that some morphological characters traditionally considered important for diagnosing tribes (presence/absence of ocelli, development of hind wing submarginal vein) are homoplastic. Divergence time estimates indicate that the subfamily arose during the Middle Cretaceous and that the extant tribes arose during the Late Cretaceous. Phylogenetic results support establishment of a new genus, Subtilissimia Yan & Yang gen. nov., with two new species, Subtilissimia fulva Yan & Yang sp. nov. and Subtilissimia pellicula Yan & Yang sp. nov. (Typhlocybinae: Typhlocybini); but indicate that two previously recognized species of Farynala distinguished only by the direction of curvature of the processes of the aedeagus are synonyms, i.e., Farynala dextra Yan & Yang, 2017 equals Farynala sinistra Yan & Yang, 2017 syn. nov. A key to tribes of Typhlocybinae is provided.
Gobbling activity of Eastern wild turkeys (Meleagris gallopavo silvestris; hereafter, turkeys) has been widely studied, focusing on drivers of daily variation. Weather variables are widely believed to influence gobbling activity, but results across studies are contradictory and often equivocal, leading to uncertainty in the relative contribution of weather variables to daily fluctuations in gobbling activity. Previous works relied on road-based auditory surveys to collect gobbling data which limits data consistency, duration, and quantity due to logistical difficulties associated with human observers and restricted sampling frames. Development of new methods using autonomous recording units (ARUs) allows researchers to collect continuous data in more locations for longer periods of time, providing the opportunity to delve into factors influencing daily gobbling activity. We used ARUs from 1 March to 31 May to detail gobbling activity across multiple study sites in the southeastern United States during 2014 – 2018. We used state-space modeling to investigate the effects of weather variables on daily gobbling activity. Our findings suggest rainfall, greater wind speeds, and greater temperatures negatively affected gobbling activity, whereas increasing barometric pressure positively affected gobbling activity. Therefore, when using daily gobbling activity to make inferences relative to gobbling chronology, reproductive phenology, and hunting season frameworks stakeholders should recognize and consider the potential influences of extended periods of inclement weather.
The Tanzania-Zambia (TANZAM) Highway traversing Mikumi National Park (MINAPA) has been a concern for wildlife managers since it was first paved in 1973-74. After its upgrade in 1989-90, researchers have documented increasing traffic resulting in considerable animal injuries and mortalities. Yellow baboons in MINAPA are known to use the road as their bridge to and from foraging areas, therefore in addition to the risk of mortality; road use could potentially have significant influence on their feeding behaviour. However, knowledge on the influences of the TANZAM highway in the feeding behaviour of the baboons is sparse. Using focal animal sampling techniques, we collected data on feeding and foraging behaviour of two habituated troops of yellow baboons to examine to what extent the TANZAM highway is important in their feeding and foraging behaviour. Results showed that in relation to habitat availability, visitation to habitat types reflect actual habitat choice of baboons. In general, baboons less frequently visit and spent less time in the highway compared to natural habitats. Whenever they were on the highway, adult females and subadult males engage more into feeding, resting and socializing, while adult males were more vigilant. The major dietary compositions were fruits, seeds, leaves, sap and invertebrates, almost exclusively collected from natural habitats, foods from the highway were opportunistically consumed. This study provides empirical evidence and concludes that yellow baboons do not directly depend on the highway for food, rather they use the TANZAM highway as normal part of their home range. The TANZAM highway is used because it improves visibility and reduces the perceived predation risk compared to natural habitats. However, its location near sleeping sites may have significant impact on baboons’ activity budget. With these findings, we recommend strict implementation of rules against park littering and animal feeding in protected areas traversed by highways.