Animal societies use nestmate recognition to protect against social cheaters and parasites. In most social insect societies individuals recognize and exclude any non-nestmates and the roles of cuticular hydrocarbons as recognition cues are well documented. Some ambrosia beetles live in cooperatively breeding societies with farmed fungus cultures that are challenging to establish, but of very high value once established. Hence, social cheaters that sneak into a nest without paying the costs of nest foundation may be selected. Therefore, nestmate recognition is also expected to exist in ambrosia beetles, but so far nobody has investigated this behavior and its underlying mechanisms. Here we studied the ability for nestmate recognition in the cooperatively breeding ambrosia beetle Xyleborinus saxesenii, combining behavioural observations and cuticular hydrocarbon analyses. Laboratory nests of X. saxesenii were exposed to foreign adult females from the same population, another population and another species. Survival as well as behaviours of the foreign female were observed. Behaviours of the receiving individuals were also observed. We expected that increasing genetic distance would cause increasing distance in chemical profiles and increasing levels of behavioural exclusion and possibly mortality. Chemical profiles differed between populations and appeared as variable as in other highly social insects. However, we found only very little evidence for behavioural exclusion of foreign individuals. Interpopulation donors left nests at a higher rate than control donors, but neither their behaviours nor the behaviours of receiver individuals within the nest showed any response to the foreign individual in either of the treatments. These results suggest that cuticular hydrocarbon profiles might be used for communication and nestmate recognition, but that behavioural exclusion of non-nestmates is either absent in X. saxesenii or agonistic encounters are so rare or subtle that they could not be detected by our method. Additional studies are needed to investigate this further.
Biologists increasingly rely on computer code to collect and analyze their data, reinforcing the importance of published code for transparency, reproducibility, training, and a basis for further work. Here we conduct a literature review examining temporal trends in code sharing in ecology and evolution publications since 2010, and test for an influence of code sharing on citation rate. We find that there is wide room for improvement in sharing code, as scientists are overwhelmingly (95%) failing to publish their code and that there has been no significant improvement over time. We also determined that there is a significant incentive to share, as we additionally find that code sharing can considerably improve citations, particularly when combined with open-access publication.
1. Prey metabarcoding has become a popular tool in molecular ecology for resolving trophic interactions at high resolution, from various sample types and animals. To date, most predator-prey studies of small-sized animals (<1 mm) have met the problem of overabundant predator DNA in dietary samples by adding blocking primers/peptide nucleic acids. These primers aim to limit the PCR amplification and detection of the predator DNA but may introduce bias to the prey composition identified by interacting with sequences that are similar to those of the predator. 2. Here we demonstrate the use of an alternative method to explore the prey of small marine copepods using whole-body DNA extracts and deep, brute force metabarcoding of an 18S rDNA fragment. 3. After processing and curating raw data from two sequencing runs of varying depth (0.4 and 5.4 billion raw reads), we isolated 1.3 and 52.2 million prey reads, with average depths of ~15 900 and ~120 000 prey reads per copepod individual, respectively. While data from both sequencing runs were sufficient to distinguish dietary compositions from disparate seasons, locations and copepod species, greater sequencing depth led to better separation of clusters. 4. As computation and sequencing are becoming ever more powerful and affordable, we expect the brute force approach to become a general standard for prey metabarcoding, as it offers a simple and affordable solution to consumers that are impractical to dissect or unknown to science.
Leucism, in which pigmentation is lost over part or the entire body of an animal, has a range of possible genetic causes. Here, we report leucism in an individual tiger keelback (Rhabdophis tigrinus) found on Jeung Island, Shinan-gun, Jeollanam-do, South Korea, during a survey of the distribution of reptiles in the area. The individual was observed sunbathing in the bushes next to a pond. This individual exhibited ecdysis, thus it considered that have normal feeding activity. Our report represents the first observation of leucism in R. tigrinus, and thus, further analysis is needed of this phenotype to more clearly understand its impact on the species and its natural history.
Parentage analyses via molecular markers have revealed multiple paternity within the broods of polytocous species, reshaping our understanding of animal behavior, ecology, and evolution. In a meta-analysis of multiple paternity in bird and mammal species, we conducted a literature search and found 138 bird and 64 mammal populations with microsatellite DNA paternity results. Bird populations averaged 19.5% multiple paternity and mammals more than twice that level (46.1%). We used a Bayesian approach to construct a null model for how multiple paternity should behave at random among species, under the assumption that all mated males have equal likelihood of siring success, given mean brood size and mean number of sires. We compared the differences between the null model and actual probabilities of multiple paternity. While a few bird populations fell close to the null model, most did not, averaging 34.0-percentage points below null model predictions; mammals had an average probability of multiple paternity 13.6-percentage points below the null model. Differences between bird and mammal species were also subjected to comparative phylogenetic analyses that generally confirmed our analyses that did not adjust for estimated historical relationships. Birds exhibited extremely low probabilities of multiple paternity, not only compared to mammals, but relative to other major animal taxa. The generally low probability of multiple paternity in birds might be produced by a variety of factors, including behaviors that reflect sexual selection (extreme mate guarding or unifocal female choice) and sperm competition (e.g., precedence effects favoring fertilization by early or late matings).
Coat colour and pattern are a distinguished feature in mammalian carnivores, shaped by climatic cycles and habitat type. It can be expressed in various ways, such as gradients, polymorphisms, and rare colour variants. Although natural selection explains much of the phenotypic variation found in the wild, genetic drift and heterozygote deficiency, as prominent in small and fragmented populations, may also affect phenotypic variability through the fixation of recessive alleles. The aim of this study was to test whether rare colour variants in the wild could relate to a deficiency of heterozygotes, resulting from habitat fragmentation and small population size. We present an overview of all rare colour variants in the order Carnivora, and compiled demographic and genetic data of the populations where they did and did not occur, to test for significant correlations. We also tested how phylogeny and body weight influenced the presence of colour variants with phylogenetic generalized linear mixed models (PGLMMs). We found 40 colour-variable species and 59 rare colour variants. In 17 variable phenotypic populations for which genetic diversity was available, the average AR was 4.18, HO = 0.59, and HE = 0.66, and FIS = 0.086. We found that variable populations displayed a significant reduction in heterozygosity and allelic richness compared to non-variable populations across species. We also found a significant negative correlation between population size and inbreeding coefficients. Therefore, it is possible that small effective size had phenotypic consequences on the extant populations. The high frequency of the rare colour variants (averaging 20%) also implies that genetic drift is locally overruling natural selection in small effective populations. As such, rare colour variants could be added to the list of phenotypic consequences of inbreeding in the wild.
Herbarium specimens are increasingly being used as sources of information to understand the ecology and evolution of plants and their associated microbes. Most studies have used specimens as a source of genetic material using culture independent approaches. We demonstrate that herbarium specimens can also be used to culture nodule-associated bacteria, opening the possibility of using specimens to understand plant-microbe interactions at new spatiotemporal scales. We used historic and contemporary nodules of a common legume, Medicago lupulina, to create a culture collection. We were able to recover historic bacteria in 15 genera from three specimens (collected in 1950, 2004, and 2015). This work is the first of its kind to isolate historic bacteria from herbarium specimens. Future work should include inoculating plants with historic strains to see if they produce nodules and if they affect plant phenotype and fitness. Although we were unable to recover any Ensifer, the main symbiont of Medicago lupulina, we recovered some other potential nodulating species, as well as many putative growth-promoting bacteria.
Echolocating bats use and adapt ultrasound pulses that vary in several parameters, one of them being the pulse’s source level, which is a measure of the emitted sound amplitude. This is a vital ecological parameter as it directly impacts the maximum distance over which bats can perceive targets in their environment, most importantly their prey. Different habitats present different sensing challenges for echolocation systems, and the quality and content of information derived from echolocation pulses reflect these environmental challenges. As such, echolocation pulses within or between species may vary from one habitat to the next due to variable selection pressure, resulting in local adaptation. Habitat is, therefore, a key component in shaping the evolution of echolocation. The Acoustic Adaptation Hypothesis (AAH) proposes that acoustic properties of the environment influence sound propagation and therefore the evolution of echolocation pulses. Here, we tested the AAH using multiple microphone arrays to measure the source levels of echolocation pulses of 14 bat species in bat assemblages across sites in six biomes in South Africa. Contrary to the AAH, our results revealed that bats in the same assemblage used different echolocation pulse source levels, frequencies, and duration resulting in different detection distances, which differ among bat assemblages occupying different sites. Furthermore, detection distance was species-specific and remained similar within species between assemblages; suggesting that species is a better predictor of detection distances compared to habitat as indicated by Miniopterus natalensis across all seven sites. KEYWORDS: adaptation, bat assemblages, detection distances, microphone arrays, selection pressure, source levels
Hatching plasticity allows fish and amphibians to initiate hatching in response to environmental cues including predation, flooding, and hypoxia. In species with terrestrial eggs, hatching plasticity often manifests as extended development of embryos when water is not available. Although these effects are taxonomically widespread, little attention has focused on differences in plasticity across closely related species with terrestrial and aquatic embryos. We propose that terrestrial embryonic environment that favors slower and extended development that, together, result in a more advanced stage at hatching than an aquatic embryonic environment. We test this hypothesis by comparing embryonic development between two fall-breeding mole salamanders, Ambystoma opacum and A. annulatum. Most Ambystoma lay eggs submerged in ponds but A. opacum lays its eggs on land, where hatching is triggered when eggs are submerged by rising pond levels. We compared embryonic development of A. opacum with A. annulatum, which lays eggs in water, in a common laboratory environment. Embryos of both species were reared in environments simulating either aquatic or terrestrial nests sites. We found that the A. opacum embryos exhibited slower development and took longer to hatch than A. annulatum embryos. We also found that A. opacum hatched at a more advanced stage, but only when reared in an environment that mimicked a terrestrial nest. This plasticity was absent in A. annulatum. Our results suggest that the terrestrial-laying A. opacum has evolved a developmental plasticity that allows its embryos to extend development when in terrestrial nests, while retaining the ability to hatch at a stage more typical of congeners when submerged in water.
Gamete traits can vary widely among species, populations and individuals, influencing fertilisation dynamics and overall reproductive fitness. Sexual selection can play an important role in determining the evolution of gamete traits with local environmental conditions determining the strength and direction of sexual selection. Here we test for signatures of post-mating selection on gamete traits in relation to population density, and possible interactive effects of population density and sperm concentration on sperm motility and fertilisation rates among natural populations of mussels. Our study shows that males from high density populations produce smaller sperm compared with males from low density populations, but we detected no effect of population origin on egg size. Our results also reveal that females from low density populations tended to exhibit lower fertilisation rates across a range of sperm concentrations, although this became less important as sperm concentration increased. Variances in fertilisation success were higher for females than males and the effect of gamete compatibility between males and females increases as sperm concentrations increase. These results suggest that local population density can influence gamete traits and fertilisation dynamics but also highlight the importance of phenotypic plasticity in governing sperm-egg interactions in a highly dynamic selective environment.
Quantitative evidence on tree space segregation among avian assemblages in temperate primeval forests is currently lacking. Therefore, our study aimed to determine the species composition of birds across different parts of trees. We investigated whether species richness differs between positions on a tree and how these positions influence the probability of occurrence of specific bird species. To achieve this, we observed birds within permanent plots in Białowieża National Park (BNP) and analyzed the distribution patterns of birds within six vertical and three horizontal sectors of trees. The compositional dissimilarity between tree sectors was assessed using detrended correspondence analysis. We employed generalized linear mixed-effects models to examine differences in species richness and the probability of occurrence for ten of the most frequently observed species across tree sectors. The majority of the BNP bird community was associated with the branches, while other birds occupied the tree crown trunks and the understory trunks. Species richness was the highest on branches in the crown part of trees, followed by lower species richness on trunks associated with crowns, and the lowest richness was observed on branches and trunks in the understory. These results indicate that branches in the middle and lower parts of the crown serve as avian diversity hotspots on trees, likely due to the abundance of various food sources. The differing patterns of tree usage by specific bird species may suggest the avoidance of interspecific competition for resources. Importantly, our study provides a pristine state for future investigations.
Fish communities of streams and rivers might substantially be subsidized by terrestrial insects that fall into the water. Although such animal-mediated fluxes are increasingly recognized, little is known on how anthropogenic perturbations may influence the strength of such exchanges. Intense land-use, such as lignite mining may impact a river ecosystem due to the flocculation of iron (III) oxides, and thus altering food web dynamics. We compared sections of the Spree River in North-East Germany that were greatly influenced by iron oxides with sections located downstream of a dam where passive remediation technologies are applied. Compared to locations downstream of the dam, the abundance of benthic macroinvertebrates at locations of high iron concentrations upstream of the dam was significantly reduced. Similarly, catch per unit effort of all fishes was significantly higher in locations downstream of the dam compared to locations upstream of the dam and condition of juvenile and adult piscivorous pike Esox lucius were significantly lower in size in sections of high iron concentrations. Using an estimate of short-term (i.e., metabarcoding of the gut content) as well as longer-term (i.e., hydrogen stable isotopes) resource use, we could demonstrate that two of the three most abundant fish species, perch Perca fluviatilis, and bleak Alburnus alburnus, received higher contributions of terrestrial insects to their diet at locations of high iron concentration. In summary, lotic food webs upstream and downstream of the dam greatly differed in the overall structure with respect to the energy available for the highest tropic levels and the contribution of terrestrial insects to the diet of omnivorous fish. Therefore, human-induced environmental perturbation such as river damming and mining activities represent strong pressures that can alter the flow of energy between aquatic and terrestrial systems, indicating a broad impact on the landscape level.
Personality variation, defined as among-individual differences in behaviour that are repeatable across time and context, is widely reported across animal taxa. From an evolutionary perspective, characterising the amount and structure of this variation is useful since differences among individuals are the raw material for adaptive behavioural evolution. However, behavioural variation among-individuals also has implications for more applied areas of evolution and ecology – from invasion biology, to ecotoxicology, and selective breeding in captive systems. Here, we investigate the structure of personality variation in the red cherry shrimp, Neocaridina heteropoda, a popular ornamental species that is readily kept and bred under lab conditions and is emerging as a decapod crustacean model across these fields, but for which basic biological, ecological, and behavioural data is limited. Using two assays and a repeated measures approach, we quantify behaviours putatively indicative of shy-bold variation and test for sexual dimorphism and/or size-dependent behaviours (as predicted by some state-dependent models of personality). We find moderate to high behavioural repeatabilities across traits. Although strong individual-level correlations across behaviours are consistent with a major personality axis underlying these observed traits, the multivariate structure of personality variation does not fully match a priori expectations of a shy-bold axis. This may reflect our ecological naivety with respect to what really constitutes bolder, more risk prone, behaviour in this species. We find no evidence for sexual dimorphism and only weak support size-dependent behaviour. Our study contributes to the growing literature describing behavioural variation in aquatic invertebrates. Furthermore, it lays a foundation for further studies harnessing the potential of this emerging model system. In particular, this existing behavioural variation could be functionally linked to life-history traits, invasive success, and serve as target of artificial selection or bioassays. It thus holds significant promise in applied research across ecotoxicology, aquaculture, and invasion biology.
1. The gut microbiota of rodents is essential for survival and adaptation, and has been shown to be susceptible to a variety of factors, ranging from environmental conditions to genetic predispositions. Nevertheless, few comparative studies have considered the contribution of species identity and geographic spatial distance to the variation in gut microbiota. 2. Here, we investigated the gut microbial communities of four wild rodent species (Rattus norvegicus, Apodemus agrarius, Cricetulus barabensis, and Tscherskia triton) at five sites in northern China’s farming-pastoral transition zone. By performing a cross-factorial comparison, we are able to test whether belonging to the same species, or instead, being in the same capture site dominates in determining gut microbiota composition. 3. Our analysis found that the Amplicon Sequence Variants (ASVs) showed a partial overlap with the species identity and the geographic capture sites, which did not reveal a ‘phylosymbiosis’ pattern. 4. The gut microbiota of these four rodent species adhered to typical mammalian characteristics, predominantly characterised by the Firmicutes and Bacteroidetes phyla. As the geographic distance between populations increased, the shared microbial taxa among conspecific populations decreased. We observed that within a relatively small geographical range, even different species exhibit convergent α-diversity due to their inhabitation within the same environmental microbial pool. In contrast, the composition and structure of the intestinal microbiota in allopatric populations of A. agrarius showed marked differences, as well as C. barabensis. Additionally, geographical environmental elements, exhibited significant correlations with diversity indices. Conversely, host-related factors had minimal influence on microbial abundance. 5. These findings illuminated that the similarity of the microbial compositions was not determined primarily by the host species, the location of the sampling explained a greater amount of variation in the microbial composition, indicating that the local environment played a crucial role in shaping the microbial composition.
“Coexistence frontiers”, or regions where human infrastructure and activity are increasing rapidly or newly appearing, constitute novel environments where wildlife must learn to navigate and coexist with people. It is widely recognized that behaviorally flexible species are more likely to persist in these human-dominated landscapes. Nevertheless, we do not fully understand how these animals navigate landscapes shaped by infrastructure, human activity, and human tolerance. As a widely reviled and behaviorally plastic apex predator, the spotted hyena (Crocuta crocuta) is a model species for understanding how wide-ranging large carnivores navigate social-ecological landscapes in an urbanizing world. Using high-resolution (minimum 5-min fix rates) GPS collar data and supplemental camera trap imagery, we applied resource selection and step selection functions to assess spotted hyena landscape navigation and fine-scale movement decisions in relation to social-ecological features in Lake Nakuru National Park and Soysambu Conservancy, Kenya. Second, we used camera traps and barrier behavior analysis (BaBA) to further examine hyena interactions with barriers. Our results show that environmental covariates—including NDVI, terrain, and proximity to water—were the best predictors of landscape-scale resource selection by hyenas, while human infrastructure and the likelihood of conflict with humans or livestock predicted fine-scale hyena movement decisions. We also found that hyena selection for these characteristics changed seasonally and across land management types. Camera traps documented an exceptionally high number of individual spotted hyenas (234) approaching the national park fence at 16 sites during the study period, and BaBA results suggested that hyenas perceive protected area boundaries’ electric fences as risky but may cross them out of necessity. Our results highlight that wildlife adaptability in coexistence frontiers may be expressed differently depending on context and scale. These results also point to the need to incorporate societal factors into multiscale analyses of carnivore movement to effectively plan for human-carnivore coexistence.
Damselfishes (Pomacentridae) are one of the most behaviourally diverse, colourful and species rich reef fish families. One remarkable characteristic of damselfishes is that they communicate in ultraviolet (UV) light. Not only are they sensitive to UV they are also prone to have UV-reflective colours and patterns enabling social signalling. Using more than 50 species, we aimed to uncover the evolutionary history of UV colour and UV vision in damselfishes. We find that all damselfishes had UV-transmitting lenses, expressed the UV-sensitive SWS1 opsin gene, and most displayed UV-reflective patterns and colours. We find evidence for several tuning events across the radiation, and while SWS1 gene duplications are generally very rare amongst teleosts, our phylogenetic reconstructions uncovered two independent duplication events, one close to the base of the most species-rich clade in the subfamily Pomacentrinae, and one in an individual Chromis species. Using amino acid comparisons, we found that known spectral tuning sites were altered several times in parallel across the damselfish radiation (through sequence change and duplication followed by sequence change), causing repeated shifts in peak spectral absorbance of around 10 nm. Pomacentrine damselfishes expressed either one or both copies of SWS1, likely to further finetune UV-signal detection and differentiation. This highly advanced and modified UV vision among damselfishes, in particular the duplication of SWS1 among Pomacentrinae, might be seen as a key evolutionary innovation that facilitated the evolution of the exuberant variety of UV reflectance traits and possibly the diversification of this coral reef fish lineage.
Rangelands and semi-arid ecosystems are subject to increasing changes in ecologic makeup from a collection of factors. In much of the northern Great Basin, rangelands invaded by exotic annual grasses such as cheatgrass (Broumus tectorum) and medusahead (Taeniatherum caput-medusae) are experiencing an increasingly short fire cycle which is compounding and persistent. Improving and expanding ground-based field methods for measuring above-ground biomass (AGB) may enable more sample collections across a landscape and over succession regimes, and better harmonize with other remote sensing techniques. Developments and increased adoption of uncrewed aerial vehicles and instrumentation for vegetation monitoring are enabling greater understanding of vegetation in many ecosystems. Research towards understanding the relationship of traditional field measurements with newer aerial platforms in rangeland environments is growing rapidly, and there is increasing interest in exploring the potential use both to quantify AGB and fine fuel load at pasture scales. Our study here uses relatively inexpensive handheld photography with custom sampling frames to collect and automatically reconstruct 3D-models of the vegetation within 0.2 m2 quatrats (n = 288). Next, we examine the relationship between volumetric estimates of vegetation to compare with biomass. We found that volumes calculated with 0.5 cm voxel sizes (0.125 cm3) most closely represented the range of biomass weights. We further develop methods to classify ground points, finding a 2% reduction in predictive ability compared to using the true ground surface. Overall, our reconstruction workflow had an R2 of 0.42, further emphasizing the importance of high-resolution imagery and reconstruction techniques. Ultimately, we conclude that more work is needed of increasing extents (such as from UAS) to better understand and constrain uncertainties in volumetric estimations of biomass in ecosystems with high amounts of invasive annual grasses and fine fuel litter.
The Arctic archipelago of Svalbard is a hotspot of global warming and many fjords experience a continuous increase in seawater temperature and glacial melt while sea-ice cover declines. In 1996/98 and 2012-14 macroalgal biomass and species diversity were quantified at the study site Hansneset, Kongsfjorden (W-Spitsbergen) in order to identify potential changes over time. In 2021, we repeated the earlier studies by stratified random sampling (1x1 m2, n=3) along a sublittoral depth transect (0, 2.5, 5, 10 and 15m) and investigated the lower depth limits of dominant brown algae between 2-20m. The fresh weight maximum was 11.5 kg m-2 at 2.5m and kelp blades stored 277g carbon m-2 and 18g nitrogen m-2 at this depth. Although biomass did not significantly change since 2012/13, the ‘Digitate Kelps’ community (Laminaria digitata/Hedophyllum nigripes) changed to an Alaria esculenta dominated kelp forest in 2021 and a balanced age structure of kelps (juveniles plus many older kelp individuals) was only apparent at 2.5m. In addition, the abundances and lower depth limits of all dominant brown algae declined noticeably over the last 25 years while the deep red algae flora remained stable. As we revealed that biomass allocation to blades, stipes and holdfasts as well as the ability to store blade carbon and nitrogen was kelp species-specific, a pronounced shift in the functionality of the kelp forest had occurred over time. We propose that the observed changes in the macroalgal community are mainly driven by alterations in underwater light climate as in situ data confirmed increasing turbidity and decreasing irradiance since 2012 and 2017, respectively. As a consequence, the overall retreat of the kelp forest to lower depth levels seems to be a result of strong glacial melt and will possibly continue in future with unforeseen consequences for Arctic coasts and their socio-ecological fjord systems.