1. The structure, composition, and shape of teeth have been related to dietary specialization in many vertebrate species, except snakes. Yet, snakes have diverse dietary habits that may impact the shape of their teeth. We hypothesize that prey properties, such as hardness and shape, as well as feeding behavior, such as aquatic or arboreal predation, or holding vigorous prey, impose constraints on the evolution of tooth shape in snakes. 2. We compared the morphology of the dentary teeth of 63 species that cover the phylogenetic and dietary diversity of snakes, using 3D geometric morphometrics and linear measurements. 3. Our results show that prey hardness, foraging substrate and the main mechanical challenge are important drivers of tooth shape, size, and curvature. 4. Overall, long, slender, curved teeth with a thin layer of hard tissue are observed in species that need to maintain a grip on their prey. Short, stout, less curved teeth are associated with species that undergo high or repeated loads. 5. Our study demonstrates the diversity of tooth morphology in snakes and the need to investigate its underlying functional implications to better understand the evolution of teeth in vertebrates.
Recent declines in eastern wild turkeys (Meleagris gallopavo silvestris) has prompted increased interest in management and research of this important game species. However, the mechanisms underlying these declines are unclear, leaving uncertainty in how best to manage this species. Foundational to effective management of wildlife species is understanding the biotic and abiotic factors that influence demographic parameters and the contribution of vital rates to population growth. Our objectives for this study were to: 1) conduct a literature review to collect all published vital rates for eastern wild turkey over the last 50 years, 2) perform a scoping review of the biotic and abiotic factors that have been studied relative to wild turkey vital rates and highlight areas that require additional research, and 3) use the published vital rates to populate a life-stage simulation analysis (LSA) and identify the vital rates that make the greatest contribution to population growth. Based on published vital rates for eastern wild turkey, we estimated a mean asymptotic population growth rate (λ) of 0.91 (95% CI = 0.71, 1.12). Vital rates associated with after second year (ASY) females were most influential in determining population growth. Survival of ASY females had the greatest elasticity (0.53), while reproduction of ASY females had lower elasticity (0.21), but high process variance, causing it to explain a greater proportion of variance in λ. Our scoping review found that most research has focused on the effects of habitat characteristics at nest sites and the direct effects of harvest on adult survival, while research on topics such as disease, weather, predators, or anthropogenic activity on vital rates have received less attention. We recommend that future research take a more mechanistic approach to understanding variation in wild turkey vital rates as this will assist managers in determining the most appropriate management approach.
Seed dormancy contributes greatly to successful establishment and community stability and shows large variation over a continuous status scale in mountain ecosystems. Although empirical studies have shown that seed dormancy status (SDS) is shaped by elevation and phylogenetic history in mountain ecosystems, few studies have quantified their combined effects on SDS. Here, we collected mature seeds from 51 populations of 11 Impatiens species (Balsaminaceae) along an elevational gradient in the Gaoligong Mountains of southwest China and downloaded 19 bioclimatic variables from WorldClim v.2.1 for each Impatiens population. We used internal transcribed spacer (ITS), atpB-rbcL, and trnL-F molecular sequences from the GenBank nucleotide database to construct a phylogenetic tree of the 11 species of Impatiens. SDS was estimated using mean dormancy percentage of fresh seeds germinated at three constant temperatures (15, 20, and 25 °C). Logistic regression model analysis was performed to quantify the effects of phylogeny and environment on SDS. Results showed that there was a significant phylogenetic signal of SDS in the Impatiens species. Furthermore, elevation and phylogeny accounted for 63.629% of the total variation in SDS among the Impatiens populations. The logistic model indicated that climatic factors accounted for 20.832% of the total variation in SDS among the Impatiens species, and model residuals were significantly correlated with phylogeny, but not with elevation. Our results indicated that seed dormancy is phylogenetically conserved, and climate drives elevational patterns of SDS variation in mountain ecosystems. This study provides new insights into the response of seed plant diversity to climate change.
Quantifying spatiotemporally explicit interactions within animal populations facilitates the understanding of social structure and its relationship with ecological processes. Data from animal tracking technologies (Global Positioning Systems [“GPS”]) can circumvent longstanding challenges in the estimation of spatiotemporally explicit interactions, but the discrete nature and coarse temporal resolution of data mean that ephemeral interactions that occur between consecutive GPS locations go undetected. Here, we developed a method to quantify individual and spatial patterns of interaction using continuous-time movement models (CTMMs) fit to GPS tracking data. We first applied CTMMs to infer the full movement trajectories at an arbitrarily fine temporal scale before estimating interactions, thus allowing inference of interactions occurring between observed GPS locations. Our framework then infers indirect interactions – individuals occurring at the same location, but at different times– while allowing the identification of indirect interactions to vary with ecological context based on CTMM outputs. We assessed the performance of our new method using simulations and illustrated its implementation by deriving disease-relevant interaction networks for two behaviorally differentiated species, wild pigs (Sus scrofa) that can host African Swine Fever and mule deer (Odocoileus hemionus) that can host Chronic Wasting Disease. Simulations showed that interactions derived from observed GPS data can be substantially underestimated when temporal resolution of movement data exceeds 30-minute intervals. Empirical application suggested that underestimation occurred in both interaction rates and their spatial distributions. CTMM-Interaction method, which can introduce uncertainties, recovered the majority of true interactions. Our method leverages advances in movement ecology to quantify fine-scale spatiotemporal interactions between individuals from lower temporal resolution GPS data. It can be leveraged to infer dynamic social networks, transmission potential in disease systems, consumer-resource interactions, information sharing, and beyond. The method also sets the stage for future predictive models linking observed spatiotemporal interaction patterns to environmental drivers.
Interactions between invaders and resource availability may explain variation in their success or management efficacy. For widespread invaders, regional variation in plant response to nutrients can reflect phenotypic plasticity of the invader, genetic structure of invading populations, or a combination of the two. The wetland weed Alternanthera philoxeroides (alligatorweed) is established throughout the southeastern USA and California, and has high genetic diversity despite primarily spreading clonally. Despite its history in the USA, the role of genetic variation for invasion and management success is only now being uncovered. To better understand how nutrients and genotype may influence A. philoxeroides invasion, we measured the response of plants from 26 A. philoxeroides populations (three cp haplotypes) to combinations of nitrogen (4 or 200 mg/L N) and phosphorus (0.4 or 40 mg/L P). We measured productivity (biomass accumulation and allocation), plant architecture (stem diameter and thickness, branching intensity) and foliar traits (toughness, dry matter content, percent N, percent P). A short-term developmental assay was also conducted by feeding a subset of plants from the nutrient experiment to the biological control agent Agasicles hygrophila, to determine whether increased availability of N or P to its host influenced agent performance, as has been previously suggested. A. philoxeroides haplotype Ap1 was more plastic than other haplotypes in response to nutrient amendments, producing more than double the biomass from low to high N and 50-68% higher shoot:root ratio than other haplotypes in the high N treatment. A. philoxeroides haplotypes differed in 7 of 10 variables in response to increased N. We found no differences in short-term A. hygrophila development between haplotypes but mass was 23% greater in high than low N treatments. This study is the first to explore the interplay between nutrient availability, genetic variation, and phenotypic plasticity in invasive characteristics of the global invader, A. philoxeroides.
Temperature is a key abiotic factor controlling population dynamics. In facultatively sexual animals inhabiting the temperate zone, temperature regulates the switch between asexual and sexual modes of reproduction, initiates growth or dormancy and acts together with photoperiod to mediate seasonal physiological transitions. Increasing temperature due to recent global warming is likely to disrupt population dynamics of facultatively sexual animals because of the strong temperature-dependence of multiple fitness components. However, the fitness consequences of warming in these animals are still poorly understood. This is unfortunate, since facultatively sexual animals – through their ability for asexual reproduction resulting in quick population growth and sexual reproduction enabling long-term persistence – are key components of freshwater ecosystems. Here, I studied the fitness effects of warming in Hydra oligactis, a freshwater cnidarian that reproduces asexually throughout most of the year but switches to sexual reproduction under decreasing temperatures. I exposed hydra polyps to simulated short summer heatwaves or long-term elevated winter temperatures. Since sexual development in this species is dependent on low temperature, I predicted reduced sexual investment (gonad production) and elevated asexual fitness (budding) in polyps exposed to higher temperatures. The results show a complex effect of warming on sexual fitness: while gonad number decreased in response to warming, polyps exposed to high winter temperature were capable of multiple rounds of gamete production. Asexual reproduction and survival rate, on the other hand, clearly increased in response to higher temperatures, especially in males. These results predict increased population growth of H. oligactis in temperate freshwater habitats, which will likely affect the population dynamics of its’ main prey (freshwater zooplankton), and through that, the whole food web.
Strong theory exists regarding population sex ratio evolution that predicts equal sex ratio (when parental investment is equal). In most animals, sex chromosomes determine the sex of offspring, and this fixed genotype for sex has made theory difficult to test since genotypic variance for the trait (sex) is lacking. It has long been argued that the genotype has become fixed in most animals due to the strong selection for equal sex ratios. The marine copepod Tigriopus californicus has no sex chromosomes, multiple genes affecting female brood sex ratio and a brood sex ratio that responds to selection. The species thus provides an opportune system in which to test established sex ratio theory. In this paper we further our exploration on the possibility that T. californicus has polygenic sex determination using an incomplete diallel crossing design and the “animal model” for analysis of the variance components of sex determination in the species. Our data confirm the presence of extra-binomial variance for sex, further confirming that sex is not determined through simple Mendelian trait inheritance. In addition, our crosses and backcrosses of isofemale lines selected for biased brood sex ratios show intermediate phenotypic means, as expected if sex is a threshold trait determined by an underlying “liability” trait controlled by many genes of small effects. Finally, we estimate heritability of an individual to be male or female on the observed binary scale as 0.09 (95% CI: 0.034-0.14). This work furthers our accumulating evidence for polygenic sex determination in T. californicus.
Current ecological research and ecosystem management call for improved understanding of the abiotic drivers of community dynamics, including temperature effects on species interactions and biomass accumulation. Allometric trophic network (ATN) models provide an attractive framework to study consumer-resource interactions from organisms to ecosystems, but they rarely consider changes in some key abiotic drivers that affect e.g. consumer metabolism and producer growth. Here we investigate how seasonal changes in carrying capacity and light-dependent growth rate of producers and temperature-dependent mass-specific metabolic rate of consumers affect ATN model dynamics, namely seasonal biomass accumulation, productivity and standing stock biomass of different trophic guilds, including age-structured fish communities. Our simulations of the complex Lake Constance (LC) food web indicated marked effects of seasonal abiotic drivers on seasonal biomass accumulation of different guild groups, particularly among the lowest trophic levels (autotrophs and invertebrates). While the adjustment of irradiance level had minor effect, increasing metabolic rate associated with 1–2˚C temperature increase lead to a marked decline of larval (0-year age) fish biomass, but to a substantial biomass increase of 2- and 3-year-old fish that were not predated by ≥4-year-old perch. A gradual temperature increase of 0.037˚C year–1 observed in LC increased the productivity of highest trophic levels (i.e., juvenile and adult fish) by ca. 40–50% over the 100-year simulation period. However, when looking at biomass distribution and transfer between trophic guilds in the LC food web, inclusion of seasonal abiotic drivers caused only minor changes in average standing stock biomasses and productivity of different trophic guild groups. Our results demonstrate the potential of introducing seasonal variation in abiotic ATN model parameters to simulate within-year fluctuations in community dynamics, as well as to assess potential future community-level responses to ongoing environmental changes.
Animals show among-individual variation in behaviours, including migration behaviours, which are often repeatable across time periods and contexts, commonly termed “personality”. These behaviours can be correlated, forming a behavioural syndrome. In this study, we assessed the repeatability and correlation of different behavioural traits i.e., boldness, exploration and sociality and the link to migration patterns in Atlantic cod juveniles. To do so, we collected repeated measurements within two short-term (three days) and two long-term (two months) intervals of these traits and genotypes of the Pan I locus, which is indirectly correlated to feeding migration patterns in this species. We found that mainly exploration behaviour was repeatable in the short- and long-term intervals, and a trend for the relationship between exploration and the Pan I locus. Boldness and sociality were only repeatable in the second short-term interval indicating a possible development of stability over time and did not show a relation with the Pan I locus. We found no indication of behavioural syndromes among the studied traits. Although we were unable to identify the existence of a migration syndrome for the migratory genotype (Pan IBB), this study is the first one to highlight the existence of a possible link between the personality trait exploration and the migration-linked Pan I locus. This supports the need for further research that should focus on the effect of exploration tendency and other personality traits on cod movement, including the migratory (frontal) ecotype, to develop management strategies based on behavioural units, rather than treating the population as a single homogeneous stock.
Ant societies are primarily composed of females, whereby labor is divided into reproductive and non-reproductive, worker, castes. Workers and reproductive queens can differ greatly in behavior, longevity, physiology, and morphology, but their differences are usually modest relative to the differences relative to males. Males are short-lived, typically do not provide the colony with labor, often look like a different species, and only occur seasonally. It is these differences that have historically led to their neglect in social insect research, but also why they may facilitate novel phenotypic variation – by increasing the phenotypic variability that is available for selection. In this study, worker variation along a size-shape axis corresponded with variation in male-queen size and shape. As worker variation increased within species, so did sexual variation. Across species in two independent genera, sexual size dimorphism correlated with worker polymorphism regardless of whether the ancestral condition was large or small worker/sexual dimorphism. These results, along with mounting molecular data showing that process of queen-worker caste determination has co-opted many genes/pathways from sex determination, lead to the hypothesis that sexual selection and selection on colony-level traits are non-independent and that sexual dimorphism may even have facilitated the evolution of the distinct worker caste.
In the Flora of China account (Pan et al. 2001) of Saxifraga mengtzeana Engl. & Irmsch., eight synonyms were attributed to it and one variant, recognised as S. epiphylla Gornall & Ohba, was split from it. This study re-evaluates the taxonomic status of some of the synonyms and of the segregated species in the light of new evidence presented here. Morphological and molecular evidence demonstrate that populations from north-western Yunnan and Sichuan are genetically differentiated from those in south-eastern Yunnan and neighbouring Guangxi. Observations in the field and in cultivation show that the peltate petiole attachment diagnostic of S. mengtzeana var. peltifolia Engl. & Irmsch. is developmentally labile. Similar observations combined with molecular data show that viviparous phenotypes, formerly treated as S. epiphylla, although largely under genetic control, occur sporadically throughout the ranges of both northern and southern taxa. Populations from north-western Yunnan and Sichuan are best recognised as S. geifolia Balf.f., whereas those from south-eastern Yunnan and neighbouring Guangxi are S. mengtzeana. Peltate-leaved variants of the latter are given no status and are relegated to complete synonymy. Viviparous phenotypes of S. mengtzeana are demoted to the rank of forma, as f. epiphylla; analogous phenotypes of S. geifolia are newly described as f. vivipara. Keywords China, Saxifragaceae, Phylogeny, Morphology, Taxonomy
Increased access to genome-wide data provides new opportunities for plant conservation. However, information on neutral genetic diversity in a small number of marker loci can still be valuable because genomic data are not available to most rare plant species. In the hope of bridging the gap between conservation science and practice, we outline how conservation practitioners can more efficiently employ population genetic information in plant conservation. We first review the current knowledge about the within-population genetic variation and among-population differentiation in neutral genetic variation (NGV) and adaptive genetic variation (AGV) in seed plants. We then introduce the estimates of among-population genetic differentiation in quantitative traits (QST) and neutral markers (FST) to plant biology and summarize conservation applications derived from QST–FST comparisons, particularly on how to capture most AGV and NGV on both in-situ and ex-situ programs. Based on a review of published studies, we found that, on average, two and four populations would be needed for woody perennials (n = 18) to capture 99% of neutral and adaptive genetic variation, respectively, whereas four populations would be needed in case of herbaceous perennials (n = 14). On average, QST is about 3.6, 1.5, and 1.1 times greater than FST in woody plants, annuals, and herbaceous perennials, respectively. We suggest using maximum QST rather than average QST among trait comparisons. Hence, conservation and management policies or suggestions based solely on inference on FST could be misleading, particularly in woody species. We recommend conservation managers and practitioners consider this when formulating further conservation and restoration plans for plant species, and for woody species in particular.
Conversion of the North American prairies to cropland remains a prominent threat to grassland bird populations. Yet, a few species nest in these vastly modified systems. The thick-billed longspur (Rhynchophanes mccownii) is an obligate grassland bird whose populations have declined 4% annually during the past 50 years. Thick-billed longspurs historically nested in recently disturbed or sparsely vegetated patches within native mixed-grass prairie, but observations of longspurs in crop fields during the breeding season suggest such fields also provide cues for habitat selection. Maladaptive selection for poor quality habitat may contribute to ongoing declines in longspur populations, but information on thick-billed longspur breeding ecology in crop fields is lacking. We hypothesized that crop fields may function as ecological traps; specifically, we expected that crop fields may provide cues for territory selection but frequent human disturbance and increased exposure to weather and predators would have negative consequences for reproduction. To address this hypothesis, we compared measures of habitat selection (settlement patterns and trends in abundance) and productivity (nest density, nest survival, and number of young fledged) between crop fields and native sites in northeastern Montana, USA. Settlement patterns were similar across site types and occupancy ranged from 0.52 ± 0.17SE to 0.99 ± 0.01 on April 7 and 30, respectively. Early season abundance differed by year and changes in abundance during the breeding season were associated with precipitation-driven vegetation conditions, rather than habitat type. Standardized nest density (0.19 ± 0.27SD nests/plot/hour), the number of young fledged per successful nest (2.9 ± 0.18SE), and nest survival (0.24 ± 0.03 SE; n=222 nests) were similar for crop and native sites. Collectively, the data did not support our hypothesis that crop fields are ecological traps: longspurs did not exhibit a clear preference for cropland and reproductive output was not significantly reduced. Our results indicate that crop fields provide alternative breeding habitat within a human-dominated landscape.
Wolf spiders are typically the most common group of arthropod predators on both lake and marine shorelines, because of the high prey availability in these habitats. However, shores are also harsh environments due to flooding and, in proximity to marine waters, to toxic salinity levels. Here, we describe the spider community, prey availabilities and spider diets between shoreline sites with different salinities, albeit with comparatively small differences (5 vs. 7‰). Despite the small environmental differences, spider communities between low and higher saline sites showed an almost complete species turnover. At the same time, differences in prey availability or spider gut contents did not match changes in spider species composition but rather changed with habitat characteristics within region, where spiders collected at sites with thick wrack beds had a different diet than sites with little wrack. These data suggest that shifts in spider communities are due to habitat characteristics rather than prey availabilities, and the most likely candidate restricting species in high salinity would be saline sensitivity. At the same time, species absences from low-saline habitats remain unresolved.
Aim: To test whether the occupancy of shorebirds has changed in the eastern Canadian Arctic, and whether these changes could indicate that shorebird distributions are shifting in response to long-term climate change Location: Foxe Basin and Rasmussen Lowlands, Nunavut, Canada Methods: We used a unique set of observations, made 25 years apart, using general linear models to test if there was a relationship between changes in shorebird species’ occupancy and their Species Temperature Index, a simple version of a species climate envelope. Results: Changes in occupancy and density varied widely across species, with some increasing and some decreasing. This is despite that overall population trends are known to be negative for all of these species, based on surveys during migration. The changes in occupancy that we observed were positively related to the Species Temperature Index, such that the warmer-breeding species appear to be moving into these regions, while colder-breeding species appear to be shifting out of the regions, likely northwards. Main Conclusions: Our results suggest that we should be concerned about declining breeding habitat availability for bird species whose current breeding ranges are centred on higher and colder latitudes.
Major aridification events in Australia during the Pliocene may have had significant impact on the distribution and structure of widespread species. To explore the potential impact of Pliocene and Pleistocene climate oscillations we estimated the timing of population fragmentation and past connectivity of the currently isolated but morphologically similar subspecies of the widespread brushtail possum (Trichosurus vulpecula). We use ecological niche modelling (ENM) with the current fragmented distribution of brushtail possum to estimate the environmental envelope of this marsupial. We projected the ENM on models of past climatic conditions in Australia to infer the potential distribution of brushtail possums over six million years. D-loop haplotypes were used to describe population structure. From shotgun sequencing we assembled whole mitochondrial DNA genomes and estimated timing of intraspecific divergence. Our projections of ENMs suggest current possum populations were unlikely to have been in contact during the Pleistocene. Although lowered sea level during glacial periods enabled colonisation of Tasmania, climate fluctuation during this time would not have facilitated gene flow. The most recent common ancestor of sampled intraspecific diversity dates to the early Pliocene when continental aridification caused significant changes to Australian ecology and Trichosurus vulpecula distribution was likely fragmented. Phylogenetic analysis revealed that the subspecies T. v. hypoleucus (koomal; southwest), T. v. arnhemensis (langkurr; north) and T. v. vulpecula (bilda; southeast) correspond to distinct mitochondrial lineages. Despite little phenotypic differentiation, Trichosurus vulpecula populations probably experienced little gene flow with one another since the Pliocene, supporting the recognition of several subspecies and explaining their adaptations to the regional plant assemblages on which they feed.
Quantifying space use and segregation, as well as the extrinsic and intrinsic factors affecting them, is crucial to increase our knowledge of species-specific movement ecology and to design effective management and conservation measures. This is particularly relevant in the case of species that are highly mobile and dependent on sparse and unpredictable trophic resources, such as vultures. Here, we used the GPS-tagged data of 127 adult Griffon Vultures Gyps fulvus captured at five different breeding regions in Spain to describe the movement patterns (home-range size and fidelity, and monthly cumulative distance). We also examined how individual sex, season and breeding region determined the cumulative distance travelled and the size and overlap between consecutive monthly home-ranges. Overall, Griffon Vultures exhibited very large annual home-range sizes of 5,027 ± 2,123 km2, mean monthly cumulative distances of 1,776 ± 1,497 km, and showed a monthly home-range fidelity of 67.8 ± 25.5 %. However, individuals from northern breeding regions showed smaller home-ranges and travelled shorter monthly distances than those from southern ones. In all cases, home-ranges were larger in spring and summer than in winter and autumn. Moreover, females showed larger home-ranges and less monthly fidelity than males, indicating that the latter tended to use the similar areas throughout the year. Overall, our results indicate that both extrinsic and intrinsic factors modulate the home-range the social Griffon Vulture and that spatial segregation depend on sex and season at the individual level, without relevant differences between breeding regions in individual site fidelity.
A combination of short-read paired-end and mate-pair libraries of large insert sizes is used as a standard method to generate genome assemblies with high contiguity. The third-generation sequencing techniques also are used to improve the quality of assembled genomes. However, both mate-pair libraries and the third-generation libraries require high-molecular-weight DNA, making the use of these libraries inappropriate for samples with only degraded DNA. An in silico method that generates mate-pair libraries using a reference genome was devised for the task of assembling target genomes. Although the contiguity and completeness of assembled genomes were significantly improved by this method, a high level of errors manifested in the assembly, further to which the methods for using reference genomes were not optimized. Here, we tested different strategies for using reference genomes to generate in silico mate-pairs. The results showed that using a closely related reference genome from the same genus was more effective than using divergent references. Conservation of in silico mate-pairs by comparing two references and using those to guide genome assembly reduced the number of misassemblies (18.6% – 46.1%) and increased the contiguity of assembled genomes (9.7% – 70.7%), while maintaining gene completeness at a level that was either similar or marginally lower than that obtained via the current method. Finally, we developed a pipeline of optimized method and compared it with another reference-guided assembler, Ragtag. We found that Ragtag produced longer scaffolds (17.8 Mbp vs. 3.0 Mbp), but resulted in a much higher misassembly rate (85.68%) than our optimized in silico mate-pair method. This optimized in silico pipeline developed in this study should facilitate further studies on genomics, population genetics and conservation of endangered species.