Aim: In theory, long-distance dispersal (LDD) outside a species’ range contributes to genetic divergence. However, previous studies have not discriminated this process from vicariant speciation in migratory bird species. We conducted an integrative phylogeographic approach to test the LDD hypothesis, which predicts that a Japanese migratory bird subspecies diverged from a population in the coastal region of the East China Sea (CRECS) via LDD over the East China Sea (ECS). Location: East Asia Taxon: Brown Shrike (Lanius cristatus) Methods: Both a haplotype network and a multi-locus gene network of its three subspecies were reconstructed to examine from which continental population the Japanese subspecies diverged. A species distribution model (SDM) for the Japanese subspecies was constructed using bioclimatic variables under the maximum entropy algorithm. It was projected to the climate of the last glacial maximum (LGM) to infer the candidate source area of colonisation. A migratory route of the Japanese subspecies, which possibly reflects a candidate past colonisation route, was tracked by light-level geolocators. Results: Molecular phylogenetic networks suggest that the Japanese subspecies diverged from a population in the CRECS. The SDM inferred that the emerged continental shelf of the ECS and the present CRECS were suitable breeding areas for the Japanese subspecies during the LGM. A major migratory route for the Japanese subspecies was inferred between the CRECS and the Japanese archipelago across the ECS. Main conclusions: Our integrative approach supported the LDD hypothesis for divergence of the Japanese subspecies of the Brown Shrike. Shrinkage and expansion of the ECS may have been responsible for successful colonisation and isolation of the new population. Vicariance was inferred for divergence of the subspecies in the northeast Asian continent from the Japanese population. Our framework provides a new phylogeographic scenario in this region, and discriminating LDD and vicariance models should improve our understanding of the phylogeographic histories of migratory species.
Comparisons of 3D shapes have recently been applied to diverse anatomical structures using landmarking techniques. However discerning evolutionary patterns can be challenging for structures lacking homologous landmarks. We used alpha shape analyses to quantify vaginal shape complexity in 40 marine mammal specimens including cetaceans, pinnipeds, and sirenians. We explored phylogenetic signal and the potential roles of natural and sexual selection on vaginal shape evolution. Complexity scores were consistent with qualitative observations. Cetaceans had a broad range of alpha complexities, while pinnipeds were comparatively simple and sirenians were complex. Intraspecific variation was found. Three-dimensional surface heat maps revealed that shape complexity was driven by invaginations and protrusions of the vaginal wall. Phylogenetic signal was weak and metrics of natural selection (relative neonate size) and sexual selection (relative testes size, sexual size dimorphism, and penis morphology) did not explain vaginal complexity patterns. Additional metrics, such as penile shape complexity, may yield interesting insights into marine mammal genital coevolution. We advocate for the use of alpha shapes to discern patterns of evolution that would otherwise not be possible in 3D anatomical structures lacking homologous landmarks.
1. Species distribution modelling, which allows users to predict the spatial distribution of species with the use of environmental covariates, has become increasingly popular, with many software platforms providing tools to fit species distribution models. However, the species observations used in species distribution models can have varying levels of quality and can have incomplete information, such as uncertain species identity. 2. In this paper, we develop two algorithms to reclassify observations with unknown species identities which simultaneously predict different species distributions using spatial point processes. We compare the performance of the different algorithms using different initializations and parameters with models fitted using only the observations with known species identity through simulations. 3. We show that performance varies with differences in correlation among species distributions, species abundance, and the proportion of observations with unknown species identities. Additionally, some of the methods developed here outperformed the models that didn't use the misspecified data. 4. These models represent an helpful and promising tool for opportunistic surveys where misidentification happens or for the distribution of species newly separated in their taxonomy.
1. A time-consuming challenge faced by ecologists is the extraction of meaningful data from camera trap images to inform ecological management. Automated object detection solutions are increasingly, however, most are not sufficiently robust to be deployed on a large scale due to lack of location invariance across sites. This prevents optimal use of ecological data and results in significant resource expenditure to annotate and retrain object detectors. 2. In this study, we aimed to (a) assess the value of publicly available image datasets including FlickR and iNaturalist (FiN) when training deep learning models for camera trap object detection (b) develop a for training location invariant object detection models and (c) explore the use of small subsets of camera trap images for optimization training. 3. We collected and annotated 3 datasets of images of striped hyena, rhinoceros and pig, from FiN, and used transfer learning to train 3 object detection models in the task of animal detection. We compared the performance of these models to that of 3 models trained on the Wildlife Conservation Society and Camera CATalogue datasets, when tested on out of sample Snapshot Serengeti datasets. Furthermore, optimized the FiN models via infusion of small subsets of camera trap images to increase robustness for challenging detection cases. 4. In all experiments, the mean Average Precision (mAP) of the FiN models was significantly higher (82.33-88.59%) than that achieved by the models trained only on camera trap datasets (38.5-66.74%). The infusion of camera trap images into FiN training further improved mAP, with increases ranging from 1.78-32.08%. 5. Ecology researchers can use FiN images for training robust, location invariant, out-of-the-box, deep learning object detection solutions for camera trap image processing. This would allow AI technologies to be deployed on a large scale in ecological applications. Datasets and code related to this study are open source and available at: https://github.com/ashep29/infusion
For nearly all organisms, dispersal is a fundamental life history trait that can shape their ecology and evolution. Variation in dispersal capabilities within a species exists and can influence population genetic structure and ecological interactions. In fungus-gardening (attine) ants, co-dispersal of ants and mutualistic fungi is crucial to the success of this obligate symbiosis. Female-biased dispersal (and gene flow) may be favored in attines because virgin queens carry the responsibility of dispersing the fungi, but a paucity of research has made this conclusion difficult. Here, we investigate dispersal of the fungus-gardening ant Trachymyrmex septentrionalis using a combination of maternally- (mitochondrial DNA) and biparentally-inherited (microsatellites) markers. We found three distinct, spatially isolated mitochondrial DNA haplotypes. Two were found in the Florida panhandle and the other was found in the Florida peninsula. In contrast, biparental markers illustrated significant gene flow across this region and minimal spatial structure. The differential patterns uncovered from mitochondrial DNA and microsatellite markers suggest that most long-distance ant dispersal is male-biased and that females (and concomitantly the fungus) have more limited dispersal capabilities. Consequently, the limited female dispersal is likely an important bottleneck for the fungal symbiont. This bottleneck could slow fungal genetic diversification, which has significant implications for both ant hosts and fungal symbionts regarding population genetics, species distributions, adaptive responses to environmental change, and coevolutionary patterns.
We examined whether the presence or absence of different environmental stressors influenced the reproductive potential of a saltmarsh species - Plantago maritima. We focused on total seed output, seed quality and biomass of progeny. So far, there are no studies trying to answer the question of how different saltmarsh management affects the quality of seed in saltmarsh species. For the purposes of the study, plots subjected to light mowing, light or heavy grazing, trampling or rooting were designated in three nature reserves in Poland. On each plot, the abundance of infructescences per sq. metre was calculated. Mature infructascences were collected and their length and no of fruit capsules were measured. The seeds obtained from fruit capsules were weighted and sown in controlled conditions. The germination rate and the final germination percentage were calculated. A representative number of sprouts were grown. After a period of two months, the specimens were harvested and their total dry mass was measured. It was found that heavy grazing had the greatest effect on all of the studied characteristics. The presence of this factor resulted in shorter infructescences with a smaller number of fruit capsules. However, this phenomenon was compensated by the higher abundance of infructescences per sq. metre. At the same time seeds produced by grazed specimens were significantly lighter. Intensive trampling by people affected specimens in a similar way to heavy grazing, while mowing and rooting had less impact on the considered characteristics. Although a positive correlation between seed mass and germination success was found, the altogether lower seed mass had a negligible effect on germination parameters. Also, the differences in seed parameters did not affect dry mass of obtained progeny grown in lab conditions.
The range of the Canada lynx (Lynx canadensis) has contracted substantially from its historical range prior to the 19th century. Using harvest records, we found that the southern range of the lynx in Ontario in the late 1940s collapsed and then in a short period of time increased to its largest extent in the mid-1960s where the lynx range spread south of the boreal forest for a decade. After this expansion the southern range contracted northwards beginning in the 1970s. Most recently, there has been a slight expansion between 2010-2017. We have attributed these dynamics on the southern range periphery to the fluctuation of the boreal lynx population in the core of the species’ range. In addition, connectivity to boreal lynx populations and snow depth seemed to condition whether the lynx expanded into an area. However, we did not find any evidence that would suggest that these changes were due to anthropogenic disturbances or competition. The boreal lynx population does not reach numbers as it once did, consequently we likely will not see large expansions of the southern lynx range as in the mid-1960s. Our results suggest that southern lynx range in Ontario have been driven by the magnitude of the boreal lynx population cycle, connectivity to the boreal forest and snow conditions. Therefore, it is quite unlikely that southern lynx population in the Great Lakes will ever recover, since the warming climate and forestry practices are causing a northward contraction of the boreal forest and likely with it the core lynx populations.
Third generation sequencing technologies, such as Oxford Nanopore Technologies (ONT) and Pacific Biosciences (PacBio), have gained popularity over the last years. These platforms can generate millions of long read sequences. This is not only advantageous for genome sequencing projects, but also for amplicon-based high-throughput sequencing experiments, such as DNA barcoding. However, the relatively high error rates associated with these technologies still pose challenges for generating high quality consensus sequences. Here we present NGSpeciesID, a program which can generate highly accurate consensus sequences from long-read amplicon sequencing technologies, including ONT and PacBio. The tool includes clustering of the reads to help filter out contaminants or reads with high error rates and employs polishing strategies specific to the appropriate sequencing platform. We show that NGSpeciesID produces consensus sequences with improved usability by minimizing preprocessing and software installation and scalability by enabling rapid processing of hundreds to thousands of samples, while maintaining similar consensus accuracy as current pipelines
Exploring vegetation distribution spatial patterns facilitates understanding how biodiversity addresses the potential threat of future climate variability, especially for highly diverse and threatened tropical plant communities, but few empirical studies have been performed over various environmental scales. In this study, we used species-based and phylogeny-based methods to analyze the α- and β-diversity pattern variation in Dacrydium pectinatum communities and its key drivers along elevation and geographical gradients across three national nature reserves in Bawangling, Diaoluoshan and Jianfengling. Our study indicates that the species and phylogenetic α-diversity patterns presented consistent decreasing with elevation, with the peak occurring at low elevations. Environmental filtering caused by decreases in limiting factors, such as temperature, precipitation, soil organic matter, soil phosphorus, and light, is the main reason for the decline in diversity at high elevations, whereas low-elevation areas are affected by various factors, such as environmental filtering and similarity limitations. Species and phylogenetic β-diversity changes are closely related to environmental filtering and dispersal limitation, but the latter is key in community assembly at the heterogeneous spatial scale. In conclusion, combining species-based and phylogeny-based methods to explore the biogeographic patterns of tropical plant communities helps provide convincing evidence and confirms that the relative contributions of niche and neutral theory in the assembly process vary along environmental gradients. Though the D. pectinatum community constitute a floristically integrated unit, the genetic relationships between species are relatively far, and co-evolution to promote species coexistence is difficult when faced with habitat pressure. Hence, we believe that species coexistence in tropical plant communities requires mild environmental conditions, and low temperatures, precipitation, soil nutrients and light will aggravate environmental filtering and species competition. We also recommend strengthening the construction and management of nature reserves and the exploration of biodiversity formation mechanisms, which are crucial for biodiversity conservation in endangered tropical plant communities.
The mechanisms of forest seed dispersal and regeneration of various altered forest ecosystems are complemented by the action of carnivores. The objective of this study was to evaluate the role of endozoochoric and diploendozoochoric mammals in the dispersal, scarification, and germination of seeds in two different forest ecosystems: temperate forest (TF) and dry tropical forest (DTF). A direct search and scat collection were carried out to determine dispersing agents and the abundance and richness of seeds in the Protected Natural Area, Sierra Fría, Aguascalientes, Mexico. Viability was evaluated by means of X-rays and a germination test using an optical densitometry. In addition, thickness measurements and observations were made on the surfaces of the testas by a scanning electron microscopy. In the TF, four plant species were dispersed, mainly Arctostaphylos pungens (P < 0.05), by four mammals, where the gray fox dispersed the highest average (66.8 ± 68.2; P < 0.05) and diploendozoochory was detected in bobcat scats associated with rabbit hair (Sylvilagus floridanus). The DTF presented higher abundance and richness of species, where Myrtillocactus geometrizans had the highest abundance (2680 ± 4423) and the coati (P < 0.05) dispersed the highest number of seeds (8639 ± 12203). In both types of forest, endozoochory and diploendozoochory did not affect the viability, the thickness of the testas, or the germination of any species of seeds. These results suggest that dispersing carnivores adapt to the abundance and richness of seeds in the forests they inhabit, thus developing an important ecological function by dispersing, scarifying and promoting the selective germination of seeds with thick testas in TF and thin testas in DTF.
Diapause is an adaptive dormancy strategy by which arthropods endure extended periods of adverse climatic conditions. Seasonal variation in larval diapause initiation and duration in Ostrinia furnacalis influences adult mating generation number (voltinism) across different local environments. The degree of mating period overlap between sympatric voltine ecotypes influence hybridization level, but impacts on O. furnacalis population genetic structure and evolution of divergent adaptive phenotypes remains uncertain. Genetic differentiation was estimated between voltine ecotypes collected from 8 locations. Mitochondrial haplotypes were significantly different between historically allopatric univoltine and bivoltine locations. Haplotypes from sympatric locations were clustered more-closely to bivoltine locations, but influenced by local demographics. Additionally, analyses of single nucleotide polymorphism (SNP) genotypes implicate voltinism, as opposed to geographic distance, as contributing to low, but significant levels of variation among voltine ecotypes. Regardless, only 11 of 257 SNP loci were predicted to be under selection, suggesting population genetic homogenization except at loci proximal to factors putatively responsible for locally adaptive or voltinism-specific traits. These findings provide evidence that divergent voltine ecotypes may be maintained in allopatric and sympatric areas despite relatively high rates of nuclear gene flow, yet influence of voltinism on maintenance of observed haplotype divergence remains unresolved.
1. Species are not genetically homogeneous, as the genetic structure among populations is related to the degree of isolation amongst them, such as isolation-by-distance, isolation-by-barrier and isolation-by-environment. 2. To decipher the isolation processes that drive population structuring in Jenynsia lineata we analyzed 221 sequences of the mitochondrial cytochrome c oxidase I gene (COI), which came from 19 localities. Jenynsia lineata is a small viviparous fish that inhabits a wide range of habitats in South America. Then, we examined the influence of the three most common types of isolation to explain the genetic variation found in this species. 3. Our results revealed a marked structuration, with three groups: i) La Plata/Desaguadero Rivers (sampling sites across Argentina, Uruguay, and Southern Brazil), ii) Central Argentina, and iii) Northern Argentina. A distance-based redundancy analysis including the explanatory variables geographical distances, altitude, latitude, basin, was able to explain up to 65% of the genetic structure. A variance partitioning analysis showed that the two most important variables underlying the structuration in J. lineata were altitude (isolation-by-environment) and type of basin (isolation-by-barrier). 4. Our results show that in this species, the processes of population diversification are complex and are not limited to a single mechanism. Population-structuring may lead to population reproductive isolation and ultimately to speciation. 5. This study demonstrated that the process of diversification of populations is complex and is not limited to a single mechanism. The processes that play a prominent role in this study could explain the high rate of diversity that characterizes freshwater fish species. And these processes in turn are the basis for possible speciation events.
Population size is a central parameter for conservation, however monitoring abundance is often problematic for threatened marine species. Despite substantial investment in research, many marine species remain data-poor resulting in uncertain population forecasts and restricting the evaluation of past and present conservation actions. Such is the case for the white shark (Carcharodon carcharias), a highly mobile apex predator for whom population monitoring is a conservation priority following substantial declines recorded through the 20th century. Here, we estimate the effective number of breeders that successfully contribute offspring in one reproductive cycle (Nb) providing a snapshot of recent reproductive effort in an east-Australian New Zealand population of white shark. Nb was estimated over four consecutive age cohorts (2010, 2011, 2012, 2013) using two genetic estimators (linkage-disequilibrium; LD and sibship assignment; SA) based on genetic data derived from two types of genetic markers (single-nucleotide-polymorphisms; SNPs and microsatellite loci). While estimates of Nb using different marker types produced comparable estimates, microsatellite loci were the least precise. The LD and SA estimates of Nb within cohorts using SNPs were comparable, for example the 2013 age-cohort Nb(SA) was 289 (95%CI 200-461) and Nb(LD) was 208.5 (95%CI 116.4-712.7). We show that over the time period studied Nb was stable and ranged between 206.1(±45.9) and 252.0(±46.7) per year using a combined estimate of Nb(SA+LD) from SNP loci, and a simulation approach showed that in this population effective population size (Ne) per generation can be expected to be larger than Nb per reproductive cycle. This study demonstrates how breeding population size can be monitored over time to provide insight into the effectiveness of recovery and conservation measures for the white shark, where the methods described here may be applicable to other data-poor species of conservation concern.
1. The Cormack-Jolly-Seber (CJS) model and its extensions have been widely applied to the study of animal survival rates in open populations. The model assumes that individuals within the population of interest have independent fates. It is, however, highly unlikely that a pair of animals which have formed a long-term pairing have dissociated fates. 2. We examine a model extension which allows animals who have formed a pair-bond to have correlated survival and recapture fates. Using the proposed extension to generate data, we conduct a simulation study exploring the impact that correlated fate data has on inference from the CJS model. We compute Monte Carlo estimates for the bias, range, and standard errors of the parameters of the CJS model for data with varying degrees of survival correlation between mates. Furthermore, we study the likelihood ratio test of gender effects within the CJS model by simulating densities of the deviance. Finally, we estimate the variance inflation factor for CJS models that incorporate sex-specific heterogeneity. 3. Our study shows that correlated fates between mated animals may result in underestimated standard errors for parsimonious models, significantly deflated likelihood ratio test statistics, and underestimated values of the variance inflation factor for models taking sex-specific effects into account. 4. Underestimated standard errors can result in lowered coverage of confidence intervals. Moreover, deflated test statistics will provide overly conservative test results. Finally, underestimated variance inflation factors can lead researchers to make incorrect conclusions about the level of extra-binomial variation present in their data.
1. Landscape change is a key driver of biodiversity declines due to habitat loss and fragmentation, but spatially shifting resources can also facilitate range expansion and invasion. Invasive populations are reproductively successful, and landscape change may buoy this success. 2. We show how modelling the spatial structure of reproductive success can elucidate the mechanisms of range shifts and sustained invasions for mammalian species with attendant young. We use an example of white-tailed deer (deer; Odocoileus virginianus) expansion in the Nearctic boreal forest, a North American phenomenon implicated in severe declines of threatened woodland caribou (Rangifer tarandus). 3. We hypothesized that deer reproductive success is linked to forage subsidies provided by extensive landscape change via resource extraction. We measured deer occurrence using data from 62 camera-traps in northern Alberta, Canada, over three years. We weighed support for multiple competing hypotheses about deer reproductive success using multi-state occupancy models and generalized linear models in an AIC-based model selection framework. 4. Spatial patterns of reproductive success were best explained by features associated with petroleum exploration and extraction, which offer early seral vegetation resource subsidies. Effect sizes of anthropogenic features eclipsed natural heterogeneity by two orders of magnitude. We conclude that deer populations are likely buffered from overwinter mortality by landscape change, wherein early seral forage subsidies support high springtime reproductive success to offset or exceed winter losses. 5. Synthesis and Applications. Modelling spatial structuring in reproductive success can become a key goal of remote camera-based global networks, yielding ecological insights into mechanisms of invasion and range shifts to inform effective decision-making for global biodiversity conservation.
The structure of Apteryx’s eggshell has generated much debate over the decades because it does not fit well with most allometric predictions. Apteryx eggshells are unusually thin and have been reported to be 60% less porous than expected. It has been suggested that these adaptations are compensations for a very long incubation period. Most studies so far have been carried out in what has been reported as Apteryx australis, and using infertile eggs or eggs laid in captivity. However, A. australis once comprised all kiwi with brown plumage, now separated into three distinct species: Brown Kiwi (A.mantelli), Rowi (A.rowi), and Tokoeka (A.australis). These three species use different habitats and live at different latitudes and altitudes. In addition, captive eggs are much smaller than wild laid eggs. These confounding factors make necessary to revise the assumptions made for Apteryx in the past. In this study, we analysed the physical characteristics of the Apteryx eggshells making a comparison between the three species of brown coloured kiwi and for some of the analysis we included some specimens of Roroa (A. haastii, Great Spotted Kiwi). We found that shell characteristics are different between the different species studied. The pore area of Apteryx eggshells was higher than previously suggested, and the water vapour conductance was much closer to what is expected for an egg that size. We found several new features such as triangular mineral particles composing the cuticle, only reported for a cretaceous Theropod, and the presence of plugs and caps on the eggshell pores. We suggest that the characteristics of the eggshells of the different species relate to the mating system of each species in addition to environmental variables, particularly pluviosity. We also suggest that the erosion of the cuticle during incubation is an adaptation to a long incubation period in a burrow.
Understanding trade-offs in wild populations is difficult, but important if we are to understand the evolution of life histories and the impact of ecological variables upon them. Markers that reflect physiological state and predict future survival would be of considerable benefit to unravelling such trade-offs and could provide insight into individual variation in senescence. However, currently used markers often yield inconsistent results. One underutilised measure is haematocrit, the proportional of blood comprising of erythrocytes, which relates to the blood’s oxygen-carrying capacity and viscosity, and to individual endurance. Haematocrit has been shown to decline with age in cross-sectional studies (which may be confounded by selective appearance/disappearance). However, few studies have tested whether haematocrit declines within-individuals or whether low haematocrit impacts survival in wild taxa. Using longitudinal data from the Seychelles warbler (Acrocephalus sechellensis), we demonstrated that haematocrit increases with age in young individuals (<1.5 years) but decreases with age in older individuals (1.5–13 years). In breeders, haematocrit was higher in males than females and varied relative to breeding stage. High haematocrit was associated with lower survival in young individuals, but not older individuals. Thus, while we did not find support for haematocrit as a marker of senescence, high haematocrit is indicative of poor condition in younger individuals. Possible explanations are that these individuals were experiencing dehydration and/or high endurance demands prior to capture, which warrants further investigation. Our study demonstrates that haematocrit can be an informative metric for life-history studies investigating trade-offs between survival, longevity and reproduction.
Understanding the processes that enable species coexistence has important implications for assessing how ecological systems will respond to global change. Morphology and functional similarity increase the potential for competition, and therefore, co-occurring morphologically similar but genetically unique species are a good model system for testing coexistence mechanisms. We used DNA metabarcoding and High Throughput Sequencing to characterise for first time the trophic ecology of two recently-described cryptic bat species with parapatric ranges, Myotis escalerai and Myotis crypticus. We collected faecal samples from allopatric and sympatric regions and locations to describe the diet both taxonomically and functionally and compare prey consumption with prey availability. The two bat species had similar diets characterised by high arthropod diversity, particularly Lepidoptera, Diptera and Araneae, and a high proportion of prey that is not volant at night, which points to extensive use of gleaning. Diet overlap at the prey-item level was lower in locally sympatric than allopatric locations, supporting trophic shift under fine-scale sympatry. Furthermore, locally sympatric samples of M. escalerai had a marginally lower proportion of not nocturnally volant prey, suggesting that the shift in diet may be driven by a change in foraging mode. Our findings suggest that fine-scale coexistence mechanisms can have implications for maintaining broad-scale diversity patterns. This study highlights the importance of including both allopatric and sympatric populations and choosing meaningful spatial scales for detecting ecological patterns. We conclude that a combination of high taxonomic resolution with a functional approach helps identify patterns of niche shift.