Mutualisms are ubiquitous in nature, provide important ecosystem services, and involve many species of interest for conservation. Theoretical progress on the population dynamics of mutualistic interactions, however, comparatively lagged behind that of trophic and competitive interactions, leading to the impression that ecologists still lack a generalized framework to investigate the population dynamics of mutualisms. Yet, over the last 90 years, abundant theoretical work has accumulated, ranging from abstract to detailed. Here, we review and synthesize historical models of two-species mutualisms. We find that population dynamics of mutualisms are qualitatively robust across derivations, including levels of detail, types of benefit, and inspiring systems. Specifically, mutualisms tend to exhibit stable coexistence at high density and destabilizing thresholds at low density. These dynamics emerge when benefits of mutualism saturate, whether due to intrinsic or extrinsic density-dependence in intraspecific processes, interspecific processes, or both. We distinguish between thresholds resulting from Allee effects, low partner density, and high partner density, and their mathematical and conceptual causes. Our synthesis suggests that there exists a robust population dynamic theory of mutualism that can make general predictions.

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.

Allopreening occurs in many species of birds and is known for providing hygienic and social benefits. While this behavior has been studied between conspecifics, its occurrence among different species remains mysterious. Outside of captive environment, only a few records of interspecific allopreening exist. In this study, we describe our observations of Spot-necked Babbler (Stachyris strialata) preening Nonggang Babbler (Stachyris nonggangensis) in a non-captive environment in southern China. We provide three hypotheses (social dominance, cleaning mutualism, and hybridization) to explain the occurrence of this understudied behavior. We suggest that interspecific allopreening may not be as rare as we thought if we study this behavior under circumstances where it most frequently occurs. This study contributes to our understanding of not only the potential mechanism(s) for interspecific allopreening but also the behavioral ecology of the vulnerable Nonggang Babbler.

Tree functional traits together with processes such as forest regeneration, growth, and mortality affect forest and tree structure. Forest management inherently impacts these processes. Moreover, forest structure, biodiversity, resilience, and carbon uptake can be sustained and enhanced with forest management activities. To assess structural complexity of individual trees, comprehensive and quantitative measures are needed, and they are often lacking for current forest management practices. Here, we utilized 3D information from individual Scots pine (Pinus sylvestris L.) trees obtained with terrestrial laser scanning (TLS) to first, assess effects of forest management on structural complexity of individual trees, and second, understand relationship between several tree attributes and structural complexity. We studied structural complexity of individual trees represented by a single scale independent metric called “box dimension”. This study aimed at identifying drivers affecting structural complexity of individual Scots pine trees in boreal forest conditions. The results showed that thinning increased structural complexity of individual Scots pine trees. Furthermore, we found a relationship between structural complexity and stem and crown size and shape as well as tree growth. Thus, it can be concluded that forest management affected structural complexity of individual Scots pine trees in managed boreal forests, and stem, crown, and growth attributes were identified as drivers of it.

1. Describing and explaining patterns of individual animal behaviors in situ, and their repeatability over the annual cycle, is an emerging field in ecology owing largely to advances in tagging technology. 2. We describe individual movements of adult Sakhalin taimen Parahucho perryi, an endangered salmonid fish, in the headwaters of a river in northern Japan during the spring spawning season over two years. 3. Migration timing, separated into stages prior to, during, and following the spawning period, was found to be more consistent and repeatable for females than males. 4. We hypothesized that the observed coordinated movement within seasons, and repeatability in migration timing across seasons, could result from 1) individual-specific responsiveness resulting from endogenous, biological traits that are mediated by environmental factors, or 2) social interactions among comigrating individuals. 5. We found that water temperature and water level experienced by fish near the river mouth approximately a week before arrival at the spawning ground explained variability in run timing between years for females but not males. 6. We found no evidence of conspecific attraction or repulsion resulting from social interactions among the spawners and post-spawners. 7. We conclude that individual-specific responsiveness to environmental cues was the likely mechanism underpinning the observed migration timing and movement patterns. 8. Determining the importance of these environmental and social factors not only during spawning but also during non-breeding life-history stages would contribute to a more comprehensive understanding of migratory connectivity in this species.

Abstract: Sensitivity to bitter tastes provides animals with an important means of interacting with their environment and thus, influences their dietary preferences. Genetic variants encoding functionally distinct receptor types contribute to variation in bitter taste sensitivity. Our previous study showed that two nonsynonymous sites, A52V and Q296H, in the TAS2R20 gene are directionally selected in giant pandas from the Qinling Mountains, which are speculated to be the causative base-pair changes of Qinling pandas for the higher preference for bamboo leaves in comparison with other pandas. Here, we used functional expression in engineered cells to identify agonists of pTAS2R20 (i.e. giant panda’s TAS2R20) and interrogated the differences in perception in the in vitro responses of pTAS2R20 variants to the agonists. Our results show that pTAS2R20 is specifically activated by quercitrin and that pTAS2R20 variants exhibit differences in the sensitivity of their response to the agonist. Compared to pTAS2R20 in pandas from other areas, the receptor variant with A52V and Q296H, which is most commonly found in Qinling pandas, confers a significantly decreased sensitivity to quercitrin. We subsequently quantified the quercitrin content of the leaves of bamboo distributed in the Qinling Mountains, which was found to be significantly higher than that of the leaves of bamboo from panda habitats in other areas. Our results suggest that the decreased sensitivity to quercitrin in Qinling pandas results in higher-quercitrin-containing bamboo leaves to be tasting less bitter to them and thus, influences their dietary preference. This study illustrates the genetic adaptation of Qinling pandas to their environments and provides a fine example of the functional effects of directional selection in the giant panda.

Investigating diversity gradients helps to understand biodiversity drivers and threats. However, one diversity gradient is seldomly assessed, namely how plant species distribute along the depth gradient of lakes. Here, we provide the first in-depth characterization of depth diversity gradients (DDG) of submerged macrophytes across different lakes. We characterize the DDG for additive richness components (alpha, beta, gamma), assess environmental drivers and address temporal change over recent years. We take advantage of yet the largest dataset of macrophyte occurrence along lake depth (274 depth transects across 28 deep lakes) as well as of physio-chemical measurements (12 deep lakes from 2006 to 2017 across Bavaria), provided publicly online by the Bavarian State Office for the Environment. We found a high variability in DDG shapes across the study lakes. The DDG for alpha and gamma richness are predominantly hump-shaped, while beta richness shows a decreasing DDG. Generalized additive mixed-effect models indicate that the maximum alpha richness within the depth transect (Rmax) is significantly influenced by lake area only, whereas for the corresponding depth (Dmax) are influenced by light quality, light quantity and layering depth. Most observed DDGs seem generally stable over recent years. However, for single lakes we found significant linear trends for Rmax and Dmax going into different directions. The observed hump-shaped DDGs agree with three competing hypotheses: the mid-domain effect, the mean-disturbance hypothesis, and the mean-productivity hypothesis. The DDG amplitude seems driven by lake area (thus following known species-area relationships), whereas skewness depended on physio-chemical factors, mainly water transparency and layering depth. Our results provide insights for conservation strategies and for mechanistic frameworks to disentangle competing explanatory hypotheses for the DDG.

Once widespread throughout the tropical forests of the Indian Subcontinent, the sloth bears have suffered a rapid range collapse and local extirpations in the recent decades. A significant portion of their current distribution range is situated outside of the protected areas (PAs). These unprotected sloth bear populations are under tremendous human pressures, but little is known about the patterns and determinants of their occurrence in most of these regions. The situation is more prevalent in Nepal where virtually no systematic information is available for sloth bears living outside of the PAs. We undertook a sign survey-based single-season occupancy study intending to overcome this information gap for the sloth bear populations residing in the Trijuga forest of southeast Nepal. Sloth bear sign detection/non-detection data and field-based covariates data were collected at the 74 randomly chosen 4-km2 grid cells using a varying number of 400m long transects in each grid cell. From our results, the model-averaged estimate of site use probability (ψ ± SE) was estimated to be 0.432 ± 0.039, which is a 13% increase from the naïve estimate (0.297) not accounting for imperfect detections of sloth bear signs. The presence of termite mounds and the distance to the nearest water source were the most important variables affecting the habitat use probability of sloth bears. The average site-level detectability (p ± SE) of sloth bear signs was estimated to be 0.195 ± 0.003 and was significantly determined by the index of human disturbances. We recommend considering the importance of fine-scale ecological and anthropogenic factors in predicting the sloth bear-habitat relationships across their range in the Churia habitat of Nepal.

Phenotypic variation among individuals and species is a fundamental principle of natural selection. In this review, we focus on numerous experiments involving the model species Daphnia (Crustacea) and categorize the factors, especially secondary ones, affecting intraspecific variations in inducible defense. Primary factors, such as predator type and density, determine the degree to which inducible defense expresses and increases or decreases. Secondary factors, on the other hand, act together with primary factors to inducible defense, or without primary factors on inducible defense. The secondary factors increase intra-species variation in inducible defense, and thus the level of adaptation of organisms varies within species. Future research will explore the potential for new secondary factors, as well as the relative importance between factors needs to be clarified.

Capture-mark-recapture (CMR) studies have been used extensively in ecology and evolution. While it is feasible to apply CMR in some animals, it is considerably more challenging in small fast-moving species such as insects. In these groups, low recapture rates can bias estimates of demographic parameters, thereby, handicapping effective management of wild populations. Here we use high-speed videos (HSV) of the adults of two large dragonfly species that rarely land and, thus, are particularly challenging for CMR studies. We specifically test whether HSV, compared to conventional eye observations, increases the “resighting” rates and improves the certainty of the estimates of survival rate, and the effects of demographic covariates on survival rates. We show that the use of HSV increases the number of resights substantially. HSV improved our estimates of resighting and survival probability which were either under- or overestimated with the conventional observations. HSV increased the accuracy of the estimates of effect sizes of important covariates (age and body size). Integrating HSV in CMR of highly mobile animals is valuable because it is easy, non-invasive, and has the potential to improve demographic estimates. Hence, it opens the door for a wide range of research possibilities on species that are traditionally difficult to monitor, including within insects, birds, and mammals.

Animals are expected to select a breeding habitat using cues that should reflect, directly or not, the fitness outcome of the different habitat options. However, human-induced environmental changes can alter the relationship between habitat characteristics and their fitness consequences, leading to a maladaptive habitat choice. The most severe case of such nonideal habitat selection is the ecological trap, which occurs when individuals prefer to settle in poor-quality habitats while better ones are available. Here we studied the adaptiveness of nest box selection in a tree swallow (Tachycineta bicolor) population breeding over a 10-year period in a network of 400 nest boxes distributed along a gradient of agricultural intensification in southern Québec, Canada. We first examined the effects of multiple environmental and social habitat characteristics on nest box preference to identify potential settlement cues. We then assessed the links between those cues and habitat quality as defined by the reproductive performance of individuals that settled early or late in nest boxes. We found that tree swallows preferred nesting in open habitats with high cover of perennial forage crops, high spring insect biomass, and high density of house sparrows, their main competitors for nest sites. They also preferred nesting where the density of breeders and their mean number of fledglings during the previous year were high. Additionally, we detected mismatches between preference and habitat quality for several environmental variables. The density of competitors and conspecific social information showed severe mismatches, as their relationships to preference and breeding success went in opposite direction under certain circumstances. Spring food availability and agricultural landscape context, while related to preferences, were not related to breeding success. Overall, our study emphasizes the complexity of habitat selection behavior and provides evidence that multiple mechanisms may potentially lead to an ecological trap in farmlands.

Birds are known to act as potential vectors for the exogenous dispersal of bryophyte diaspores. Given the totipotency of vegetative tissue of many bryophytes, birds could also contribute to endozoochorous bryophyte dispersal. Research has shown that fecal samples of the upland goose (Chloephaga picta) and white-bellied seedsnipe (Attagis malouinus) contain bryophyte fragments. Although few fragments from bird feces have been known to regenerate, the evidence for the viability of diaspores following passage through the bird intestinal tract remains ambiguous. We evaluated the role of endozoochory in these same herbivorous and sympatric bird species in sub-Antarctic Chile. We hypothesized that fragments of bryophyte gametophytes retrieved from their feces are viable and capable of regenerating new plant tissue. Eleven feces disc samples containing undetermined moss fragments from C. picta (N=6) and A. malouinus (N=5) and six moss fragment samples from wild collected mosses (Conostomum tetragonum, Syntrichia robusta, and Polytrichum strictum) were grown ex situ in peat soil and in vitro using a agar-Gamborg medium. After 91 days, 20% of fragments from A. malouinus feces, 50% of fragments from C. picta feces, and 67% of propagules from wild mosses produced new growth. The fact that moss diaspores remained viable and can regenerate under experimental conditions following the passage through the intestinal tracts of these robust fliers and altitudinal and latitudinal migrants, suggests that sub-Antarctic birds may play a critical role in bryophyte dispersal. This relationship may have important implications in the way bryophytes disperse and colonize habitats facing climate change. Keywords: birds, bryophyte dispersal, endozoochory, mosses, sub-Antarctic

Barriers to fieldwork exist for many reasons such as physical ability, financial cost, and time availability. Unfortunately, these barriers disproportionately affect minority communities and create a disparity in access to fieldwork experience in the natural science community. Travel restrictions and the global lockdown has extended this barrier to fieldwork across the community and led to increased anxiety about gaps in productivity, especially for graduate students and early-career researchers. In this paper, we discuss Agent-Based Modeling as an open-source, accessible, and inclusive resource to substitute for lost fieldwork during COVID-19 and future scenarios of travel restrictions such as climate change. We detail the process of model development with a plethora of examples from the literature on how Agent-Based Models can be applied broadly across life-science research. We aim to amplify awareness and adoption of this technique to broaden the diversity and size of the Agent-Based Modeling community in ecology and evolutionary research. We also describe the benefits of Agent-Based models as a teaching and training resource for students across education levels. Finally, we discuss the current challenges facing Agent-Based Modeling and discuss how the field of quantitative ecology can work in tandem with traditional field ecology to improve both methods.

Monitoring the effect of ecosystem restoration can be difficult and time consuming. Autonomous sensors, such as acoustic recorders, can aid monitoring across long time scales. This project successfully developed, tested and implemented call recognisers for eight species of frog in the Murray-Darling Basin. Recognisers for all but one species performed well and substantially better than many species recognisers reported in the literature. We achieved this through a comprehensive development phase, which carefully considered and refined the representativeness of training data, as well as the construction (amplitude cut-off) and the similarity thresholds (score cut-offs) of each call template used. Recogniser performance was high for almost all species examined. Recognisers for C. signifera, L. fletcherii, L. dumerilii, L. peronii, and C. parinsignifera all performed well, with most templates having ROC values (the proportion of true positive and true negatives) over 0.7, and some much higher. Recognisers for L. peronii, L. fletcherii and L. dumerilii performed particularly well in the training dataset, which allowed for responses to environmental watering events, a restoration activity, to be clearly observed. While slightly more involved than building recognisers using commercial packages, the workflows ensure that a high quality recogniser can be built and the performance fine-tuned using multiple parameters. Using the same framework, recognisers can be improved in future iterations. We believe that multi-species recognisers are a highly effective and precise way to detect the effects of ecosystem restoration.

Turtles have been prominent subjects of analyses of sexual size dimorphism (SSD) owing to their mating system and habitat diversity. In prior studies, marine turtles were grouped with non-marine aquatic turtles (NMAT). This is odd because it is well-established that the marine environment imposes a distinct selective milieu on body form of vagile vertebrates, driven by convergent adaptations for energy-efficient propulsion and drag reduction. We generated a comprehensive database of adult marine turtle body size (38,569 observations across all species), which we then used to evaluate both the magnitude of SSD in marine turtles and how it compares to SSD in NMAT. We find that marine turtles are not sexually size dimorphic, whereas NMAT typically exhibit female-biased SSD. We argue that the reason for this difference is the sustained long-distance swimming that characterises marine turtle ecology, which entails significant energetic costs incurred by both sexes. Hence, the ability of either sex to allocate proportionately more to growth than the other is likely constrained, meaning that sexual differences in growth and resultant body size are not possible. Consequently, lumping marine turtles with NMAT dilutes the statistical signature of different kinds of selection on SSD and should be avoided in future studies.

Diversification rates and evolutionary trajectories are known to be influenced by phenotypic traits and the geographic history of the landscapes that organisms inhabit. One of the most conspicuous traits in butterflies is their wing color pattern, which has been shown to be important in speciation. The evolution of many taxa in the Neotropics has also been influenced by the closure of the Panama Isthmus and the dynamic uplift of the Andes. Using a dated, species-level molecular phylogenetic hypothesis for Preponini, a colorful Neotropical butterfly tribe, we evaluated if diversification rates were constant or varied through time, and if they were dependent on color patterns or biogeographic events. We also estimated the rate of forewing color evolution and ancestral geographic ranges. We found that Preponini originated approximately 28 million years ago and that diversification has increased through time dependent on Andean uplift. Even though some clades show evolutionarily rapid transitions in coloration, these traits seem decoupled from diversification regimes. Preponini apparently originated within South America and range evolution has since been dynamic, congruent with Andean geologic activity, closure of the Panama Isthmus and Miocene climate variability. The potential involvement in mimicry rings with other butterfly groups might explain rapid changes in dorsal color patterns in this tribe.

Abstract Aim: The invasion process is a complex, context-dependent phenomenon; nevertheless, it can be described using the PAB framework. This framework encompasses the joint effect of propagule pressure (P), abiotic characteristics of the environment (A), and biotic characteristics of both the invader and recipient vegetation (B). We analyzed the effectiveness of proxies of PAB factors to explain the spatial pattern of Solidago canadensis and S. gigantea invasion using invasive species distribution models. Location: Carpathian Mountains and their foreground, Central Europe. Methods: The data on species presence or absence were from an atlas of neophyte distribution based on a 2 × 2 km grid, covering approximately 31,200 km2 (7752 grid cells). Proxies of PAB factors, along with data on historical distribution of invaders were used as explanatory variables in Boosted Regression Trees models to explain the distribution of invasive Solidago. The areas with potentially lower sampling effort were excluded from analysis based on a target species approach. Results: Proxies of the PAB factors helped to explain the distribution of both S. canadensis and S. gigantea. Distributions of both species were limited climatically because a mountain climate is not conducive to their growth; however, the S. canadensis distribution pattern was correlated with proxies of human pressure, whereas S. gigantea distribution was connected with environmental characteristics. The varied responses of species with regard to distance from their historical distribution sites indicated differences in their invasion drivers. Main conclusions: Proxies of PAB are helpful in the choice of explanatory variables as well as the ecological interpretation of species distribution models. The results underline that human activity can cause variation in the invasion of ecologically similar species.

Polyandry, when females mate with more than one male, is theorised to play an important role in successful colonisation of new habitats. In addition to possible benefits from sexual selection, even mild polyandry could facilitate colonisation by protecting against inbreeding and reducing the costs of mating with incompatible or infertile males. Here, we measure the importance of mild polyandry for population viability and reproductive fitness following experimental founder events into a higher temperature regime. Using colonisation experiments with the model beetle Tribolium castaneum, in which females can produce offspring for up to 140 days following a single mating, we founded more than 100 replicate populations using single females that had been given the opportunity to mate with either one or two males, and then tracked their subsequent population dynamics. Following population viability and fitness across ten generations, we found that extinction rates were significantly lower in populations founded by females given polyandrous opportunities to mate with two males (9%) compared to populations founded by monogamous females (34%). In addition, populations founded by females that had been provided with opportunities to store sperm from two different males showed double the median productivity following colonisation compared to monogamous-founded populations. Notably, we identified short-term and longer-term benefits to post-colonisation populations from double-mating, with results suggesting that polyandry acts to both protect against mating with incompatible males through the founder event, and reduce inbreeding depression as the colonisation proceeds for ten generations. Our results therefore show that even mild polyandry provides both reproductive and genetic benefits for colonising populations.