During ontogeny, the increase in body size forces species to make trade-offs between their food requirements, the conditions necessary for growth and reproduction as well as the avoidance of predators. Ontogenetic changes are leading species to seek out habitats and food resources that meet their needs. These aspects are interesting to study in the case of deep pelagic fishes, as a significant part of the community migrates vertically at night to feed in the productive surface layer, while other species remain at depth. To this end, ontogenetic changes in nocturnal habitat (vertical use of the water column) and in the type of food resources (based on stable isotopes of nitrogen) were investigated in 12 species of deep pelagic fish from the Bay of Biscay in the Northeast Atlantic. Our results revealed the existence of major differences in the ontogenetic strategies employed by deep pelagic fishes. Some species showed ontogenetic changes in both vertical habitat use and food resources (e.g. Lampanyctus crocodilus and Melanostigma atlanticum). In contrast, other species showed no ontogenetic change (e.g. Searsia koefoedi and Notoscopelus kroyeri). Some species only changed food resources (e.g. Myctophum punctatum, Arctozenus risso, and Serrivomer beanii), while others seemed to be influenced more by depth than by trophic features (e.g. Xenodermichthys copei and Argyropelecus olfersii). These results suggest that to meet their increasing energy requirements during ontogeny, some species have adopted a strategy of shifting their food resources (larger prey or prey with a higher trophic level), while others seemed to maintain their food resources but are most likely increasing the quantity of prey ingested. In addition, some species opted for a habitat change to greater depths at adult age to limit the energy expenditure associated with migration, while others continued to feed at the surface at night.
Most parasite species infect multiple host species, and reciprocally, most hosts are infected by multiple parasites. This leads to complex webs of interactions that influence disease within the community, making it challenging to understand and predict disease spread within the community and epidemics. Here, we used network approaches to analyze a multi-year time series dataset that includes eight zooplankton host species (in the Daphnia and Ceriodaphnia genera) and seven microparasite species to examine patterns of cross-species transmission. These analyses suggest that parasite species varied in their ability to infect multiple host species and in which host species they most commonly infected. Three parasites (the bacteria Pasteuria ramosa and Spirobacillus cienkowskii and the oomycete Blastulidium paedophthorum) showed signatures of relatively high cross species transmission, while the others seemed more restricted. Even for the three common multihost parasites, our approach also revealed differences in patterns of potential cross species transmission. For P. ramosa, two host species, Daphnia dentifera and D. retrocurva, seem particularly likely to transmit across species; in contrast, for S. cienkowskii, no host species stands out as particularly important for cross species transmission. Additionally, these patterns matched those describing epidemic size, suggesting that infected host density may drive cross-species transmission. These results are based on observations of patterns of infection in natural communities, and therefore we cannot draw definitive conclusions about interspecific transmission in lakes. However, some of the patterns are supported by additional lines of evidence, and others point to interesting avenues for future research. Together, these findings provide additional evidence that network approaches can provide valuable insights into patterns of transmission in complex multihost-multiparasite communities in nature.
Male ornamentation is usually costly and may show trades-offs with other life-history traits such as paternal care, which can subsequently affect female preference. Studies on female mate choice have mostly examined how mate-choice cues differ in their expression or ability to be detected in different environmental contexts. However, less focus has been placed on examining how external forces affect female preferences. The purpose of this study was to explore how parental investment strategy and mate choice were mediated by ambient temperature. Specifically, we examined how male ornamentation characteristics and subsequent female incubation investment were impacted by ambient temperature in four plover populations that were breeding across an environmental gradient. We discovered that larger males had more ornamented plumage in warmer conditions, and they were favored by larger females who invested an elevated time into incubation. In contrast, in cooler conditions, males' body size and the color of their ornaments were inversely associated, and females showed weak preference for males with more colorful ornaments. These results imply that female preference for male ornament can change in response to ambient temperature and demonstrate that female preference for male ornamentation may be limited in harsher conditions with higher parental care expenses.
Insects perform the greatest part of pollination services (Winfree et al., 2011) and insects native to a given habitat can play an irreplaceable ecological role in food webs and plant reproduction (Travis & Kohn, 2023; Pelmyr, et al., 1996; Suarez, et al.,2000). With precipitous declines in insect species over the last decades, it is urgent to document insect assemblages in native plant communities to support conservation efforts. Identifying pollinators and their pollination activity is challenging; emerging methods involve the use of camera traps (Droissart, et al., 2021). In this study, we compare the accuracy of two different methods of monitoring to produce insect assemblage of Encinitas Baccharis (Baccharis vanessae): focal observations and video recordings from camera traps. B. vanessae is a rare, endemic species found in Coastal Sage Scrub communities in San Diego County (U.S. Fish and Wildlife Service, 2021). This federally listed species is threatened by habitat loss and fragmentation, which may also be affecting the availability of its insect pollinators (U.S. Fish and Wildlife Service, 2011). Preliminary results indicate that B. vanessae supports a variety of flower-visiting insect guilds and is in turn supported by diverse pollinators. While focal observations underreported insect activity by approximately half, the proportions of common diurnal visitors were similar with both methods. Camera traps were unable to provide sufficient detail to discern visually similar guilds, but were able to record nocturnal insect activity, which was dominated by moths (Lepidoptera, 82%). While collection protocol in this study did not record the time an insect spent interacting with a flower, moths spent notably longer periods in contact with flowers than most diurnal insects. This study has implications for the effective monitoring of endangered plant species and their affiliated pollinators.
In root-nodule symbioses (RNS) between nitrogen (N) fixing bacteria and plants, bacterial symbionts cycle between nodule-inhabiting and soil-inhabiting niches that exert differential selection pressures on bacterial traits. Little is known about how the resulting evolutionary tension between host plants and symbiotic bacteria structures naturally occurring bacterial assemblages in soils. We used DNA cloning to examine soil-dwelling assemblages of the actinorhizal symbiont Frankia in sites with long-term stable assemblages in Alnus incana ssp. tenuifolia nodules. We compared: 1) phylogenetic diversity of Frankia in soil vs. nodules, 2) change in Frankia assemblages in soil vs. nodules in response to environmental variation: both across succession, and in response to long-term fertilization with N and phosphorus, and 3) soil assemblages in the presence and absence of host plants. Phylogenetic diversity was much greater in soil-dwelling than nodule-dwelling assemblages, and fell into two large clades not previously observed. Presence of host plants was associated with enhanced representation of genotypes specific to A. tenuifolia, and decreased representation of genotypes specific to a second Alnus species. The relative proportion of symbiotic sequence groups across a primary chronosequence was similar in both soil and nodule assemblages. Contrary to expectations, both N and P enhanced symbiotic genotypes relative to non-symbiotic ones. Our results provide a rare set of field observations against which predictions from theoretical and experimental work in the evolutionary ecology of RNS can be compared.
Colour polymorphism can be maintained by colour morph-specific benefits across environmental conditions. Currently, the amount and duration of snow cover during winter decreases especially in northern latitudes, which can alter the potential for camouflage of animals with light and dark morphs. Tawny owls, Strix aluco, are colour polymorphic avian predators with dark (brown) and light (grey) colour morphs, where the grey morph is presumed to enjoy camouflage benefits under snowy conditions. We studied the two tawny owls’ morphs’ camouflage potential using passerines’ probability to detect and mob in the wild during spring, autumn, and winter with and without snow. We find that grey tawny owls are both less likely to be detected and have a lower probability of being mobbed compared to brown tawny owls only during snowy winters. The two colour morphs therefore experience differential benefits across snow conditions, which may help to maintain colour morphs in the population, although further warming of winter climate will reduce the potential for camouflage for grey tawny owls in northern latitudes.
Acoustic communication in animals can be affected by multiple biotic (intra and interspecific) and abiotic (e.g., wind and rain) natural noises. In addition, human beings produce additional novel sources of noise, which can reduce or inhibit the reception of acoustic signals by conspecifics, leading to behavioral changes. In this study, we investigated whether sound of conspecifics and road noise additively affect the acoustic parameters of the advertisement call of males of a Yellow Heart-tongued Frog (Phyllodytes luteolus). We hypothesized that males that vocalize in larger choruses (many males) and in areas close to highways (anthropic noise) will increase their temporal and spectral acoustic parameters, respectively, to avoid acoustic signal masking. We recorded the vocalizations of 38 males in environments close (N=18) to and distant (N=20) from highways in different social contexts (many or few individuals in the chorus). Contrary to our expectation, the results indicated that individuals exposed to road noise had lower dominant frequency calls than those from natural areas, and that the density of males in the chorus had no influence on the acoustic parameters. Furthermore, we found a positive relationship between body size and intensity, indicating that larger individuals can emit calls that can reach greater distances. The advertisement call of Phyllodytes luteolus has a high dominant frequency, with little overlap with the frequency of anthropic noises (roads), which may explain its presence and reproductive success of this species in bromeliads from urbanized areas.
Wildlife monitoring is a crucial component of conservation management, with reliable field surveys being important for trend analysis and population viability modelling. Unoccupied aircraft systems (UAS), also known as drones, are rapidly supplanting manned aircraft for aerial wildlife counts. Here we investigated and compared the impacts of drone presence on two large terrestrial mammals from Tasmania, Australia—Bennett’s wallaby (Notamacropus rufogriseus), and Forester kangaroo (Macropus giganteus tasmaniensis) —using a commercial quadcopter model: DJI Phantom 4 Pro. Further, a ground bird, the domestic chicken (Gallus gallus domesticus), was used as a model organism to further investigate behavioural responses of ‘aerial aware’ species to drones. We found that M. giganteus tasmaniensis and N. rufogriseus started to exhibit noticeable changes in behaviour, including evasion, when the drone motor sound exceeded ~50 decibels (dB) as heard from the ground (at flight altitudes of 30 – 50 m). At lower sound levels (48 dB and below, above 50 m), the animal’s response was minimal. The response of G. gallus domesticus to the drone was remarkably similar to that of the Macropus species, despite the species generally being more susceptible to, and instinctively vigilant against drone-sized aerial predators such as raptors. This study has established the baseline information required to understand the limits of drone operations, in terms of target disturbance, for macropod surveys.
Fallback foods (FBF), classified into staple and filler types, are low-quality food resources chosen by animals due to a shortage of preferred food during a specific period. The selection of lichens as FBF for Yunnan snub-nosed monkeys (Rhinopithecus bieti) represents a unique ecological adaptation and evolutionary development in the animal kingdom. This study investigates the yearly dietary selection of five R. bieti groups to address the issues and elucidate the nutritional value and ecological selection of lichens for this monkey species, which resides at the highest altitude among nonhuman primates. The results indicate that the consumed lichens serve as the staple FBF. Two main lichen species taken by the monkeys are Bryoria spp. and Usnea longissimi, with Bryoria spp. being the primary choice (67.25 ± 12.20% compared to 15.79 ± 11.66% from U. longissimi). Bryoria spp. provides a higher level of digestible fiber (NDF) and a lower level of tannin, fat, ADF, and energy compared to U. longissimi, which offers higher availability. Lichens are the dominant food and nutritional resource for the monkey species during the dry season, while they serve as a primary food source rather than a nutritional resource during the wet season. Therefore, they compensate for nutrients from other food types, such as fruits, seeds, and leaves. Compared to other Asian colobine counterparts, this species consumes the highest amount of lichens but the lowest proportions of leaves, flowers, and seeds. This dietary pattern demonstrates a specific type of ecological selection and evolutionary development during the Quaternary. The biomass of lichens in the monkeys’ habitat has significantly decreased due to environmental degradation. This study also provides evidence and information to develop or amend conservation strategies and guidelines for the dietary management of captive Yunnan snub-nosed monkeys.
Many symbionts are sexually transmitted and impact their host’s development, ecology, and evolution. While the significance of symbionts that cause sexually transmitted diseases (STDs) is relatively well understood, the prevalence and potential significance of the sexual transmission of beneficial symbionts remain elusive. Here, we study the effects of sexually transmitted mutualist nematodes on their dung beetle hosts. Symbiotic Diplogastrellus monhysteroides nematodes are present on the genitalia of male and female Onthophagus beetles and are horizontally transmitted during mating and vertically passed on to offspring during oviposition. A previous study indicates that the presence of nematodes benefits larval development and life history in a single host species, Onthophagus taurus. However, Diplogastrellus nematodes can be found in association with a variety of beetle species. Here, we replicate these previous experiments, assess whether the beneficial effects extend to other host species, and test whether nematode-mediated effects differ between male and female hosts. Rearing three distantly related dung beetle species with and without nematodes, we find that the presence of nematodes benefits body size, but not development time or survival across all three species. Likewise, we found no difference in the benefit of nematodes to male compared to female beetles. These findings highlight the role of sexually transmitted mutualists in the evolution and ecology of dung beetles. Furthermore, these results suggest a potential new avenue through which environmental pollution with veterinary deworming agents may affect dung beetles and their ecosystem services.
Climate change impacts are driving forest fires worldwide and reducing snowfall in temperate countries. Whether these impacts result in a significant alteration of winter soil respiration (Rs) rates and temperature in the postfire and the undisturbed black pine (Pinus nigra) forests remain poorly understood. A field experiment was conducted in the postfire and the undisturbed black pine forests during a winter period in Türkiye to quantify Rs rates as affected by lack of snow and snow cover. Four treatments were applied: snow-exclusion postfire (SEPF), snow postfire (SPF), snow-exclusion undisturbed forest (SEUF), and snow-undisturbed forest (SUF). The SEPF exhibited the significantly lowest mean Rs rates (0.71 µmol m-2 s-1) compared to the SPF (1.02 µmol m-2 s-1), SEUF (1.44 µmol m-2 s-1, and SUF (1.48 µmol m-2 s-1). The Rs also showed significant variations with time (p <.0001). However, treatments and time exhibited no statistically significant interaction effects (p = 0.6801). Total amounts of winter Rs (January to March) ranged from 4.92 to 5.07 Mt CO2 ha-1 in the undisturbed forest and 2.53 to 3.51 Mt CO2 ha-2 in the postfire site. The Rs showed a significantly positive relationship (p <.0001) with the soil (0.59) and air (0.46) temperatures and a significantly negative relationship (p = 0.0017) with the soil moisture (-0.20) at the 5 cm depth. In contrast, the Rs showed a negative, but not statistically significant relationship (p = 0.0932) with the soil moisture (-0.16) at the 10 cm soil depth. The combined effects of lack of snow and forest fire resulted in a significant decrease of Rs. In contrast, a warmer winter significantly increased Rs rates in the undisturbed forest, suggesting that a warmer winter could potentially accelerate soil organic carbon losses in naturally growing undisturbed forest ecosystems, thus, providing positive feed backs to climate change.
Maternal provisioning and the developmental environment are fundamental determinants of offspring traits, particularly in oviparous species. However, the extent to which embryonic responses to these factors differ across populations to drive phenotypic variation is not well understood. Here, we examine the contributions of maternal provisioning and incubation temperature to variation in hatchling morphological and metabolic traits across four populations of the American alligator (Alligator mississippiensis), encompassing a large portion of the species’ latitudinal range. Our results show that whereas the influence of egg mass is generally consistent across populations, responses to incubation temperature show extensive population-level variation in several fitness-related traits, including mass, head length, head width and residual yolk mass. Additionally, the influence of incubation temperature on developmental rate is greater at northern populations, while the allocation of maternal resources towards fat body mass is greater at southern populations. Overall, our results suggest that responses to incubation temperature, relative to maternal provisioning, are a larger source of interpopulation phenotypic variation and may contribute to the local adaptation of populations.
Winter, the most challenging season for animals, is usually accompanied by extremely cold temperatures and limited food resources. Harsh winter conditions force birds to develop behavioral and physiological adaptations to reduce mortality. Birds might select for sexual segregation to reduce conflict between different social hierarchies at the population level. They can also adjust their body conditioning via fat reserve to balance the trade-off between starvation and predation at the individual level. Using mist-netting surveys and bird banding, we traced 61 orange-flanked bush-robin (Tarsiger cyanurus), an abundant and easily-observed long-distance migratory bird exhibiting delayed plumage maturation, to better understand the winter adaptation of these songbirds. We found that the number of 2yr+ adult males with bright-blue plumage was significantly lower than the number of males with olive-brown plumage. However, the sex-ratio was only slightly skewed to males with olive-brown plumage, suggesting that habitat-type influences sexual segregation. This robin tends to become heavier and store more fat over the course of winter, as they can fine-tune their fat reserve in response to changes in weather (including temperature, humidity, and snowfall) and food abundance. Interestingly, capturing the birds may also have a significant positive effect on their fat reserve. Overall, these results improved our understanding of the flexibility in adaptation of small passerine birds wintering in a subtropical forest and provided vision for considering the inevitable influence by ornithology field methods.
All animals and plants respond to changes in the environment during their life cycle. This flexibility is known as phenotypic plasticity and allows organisms to cope with variable environments. A common source of environmental variation is predation risk, which describes the likelihood of being attacked and killed by a predator. Some species can respond to the level of predation risk by producing morphological defences against predation. A classic example is the production of pedestals and head spikes in the water flea, Daphnia pulex, which defend against predation from Chaoborus midge larvae. Previous studies of these defences have focussed on changes in pedestal size and the number of spikes along a gradient of predation risk. Although these studies have provided a model for continuous plasticity, they do not capture the whole-organism shape response to predation risk. In contrast, studies in fish and amphibians focus on shape as a complex, multi-faceted trait made up of different variables. In this study, we analyse how multiple aspects of shape change in D. pulex along a gradient of predation risk from C. flavicans. These changes are dominated by the inducible morphological defence, but there are also changes in the size and shape of the head and the body. We detected change in specific modules of the body plan and a level of integration among modules. These results are indicative of a complex, multi-faceted response to predation and provide insight into how predation risk drives variation in shape and size at the level of the whole organism.
Freshwater ecosystems are increasingly affected by rising annual mean temperatures and extreme heatwaves. While heatwaves are expected to have more immediate effects than mean temperature increases on local communities, comparative experimental studies are largely lacking. We conducted a one-month mesocosm experiment to test the effect of different warming scenarios, constantly raised temperatures (+3°C), and recurring heatwaves (+6°C) on plankton communities. We specifically tested how shifts in zooplankton trait composition and functional groups are reflected in ecosystem functioning (top-down control on primary producers). We found that heatwaves had a stronger and more immediate effect on trait and functional group compositions. Heatwaves were associated with larger body sizes, and the decrease in micrograzers resulted in weaker top-down control, leading to elevated algal biomass. Altogether, our results highlight the importance of the indirect effects of heatwaves via inducing shifts in zooplankton functional groups and trait composition which may foster periodic algal blooms.
Species richness has been shown to decrease, and elevational range increase (the Rapoport effect), with elevation as a consequence of biotic and abiotic factors, but patterns are inconsistent across taxonomic groups. Despite being an important indicator taxon and component of local communities, Orthoptera distributions at higher elevations in Europe remain unclear. We investigated the relationship of Orthoptera species richness and elevational range with elevation by conducting field studies at 28 sites across three study areas in the Pyrenees mountains, Europe. We found that species richness declined with elevation. Study area and the site-specific factors of sampling effort, topography (slope) and vegetation structure (density and cover) were also important predictors of species richness. We did not observe a Rapoport effect, with elevational range peaking at mid-elevation instead. Smaller elevational ranges found at high elevations may be due to a combination of sampling over a restricted elevational range and the presence of specialist high-elevation species. We also explored the composition of Orthoptera assemblages using multivariate methods, finding no clear effect of elevation, slope or vegetation structure on these communities, although study area somewhat influenced assemblages. To our knowledge, this is the first study of the Rapoport effect along an elevational gradient using insects as a study system in Europe. We argue that our findings are useful for understanding species distributions with elevation at the interface between local and regional scales. Clarifying the biotic and abiotic predictors of species distribution is important for informing conservation efforts and predicting consequences of climate change.
Fish play vital roles in river ecosystems; however, traditional investigations of fish usually cause certain ecological damage. Extracting DNA from aquatic environments and identifying DNA sequences offers an alternative, non-invasive approach for detecting fish species. In this study, environmental DNA (eDNA), coupled with PCR and next-generation sequencing, and electrofishing were used to compare their effects in identifying fish community characteristics. In three subtropical rivers of southern China, fish specimens and eDNA in water were collected from headwaters to estuaries. Both eDNA OTU richness and individual abundance (including number and biomass) could group 38 sampling sites into eight spatial zones with significant differences in local fish community composition. Compared with the order-/family-level grouping, the genus-/species-level grouping could more accurately recognize the differences between upstream zones I − III, midstream zones IV − V, and downstream zones VI – VIII. From headwaters to estuary, two environmental gradients significantly influenced the longitudinal distribution of fish species, including the first gradient composed of habitat and physical water parameters and the second gradient composed of chemical water parameters. The high regression coefficient of alpha diversity between eDNA and electrofishing methods as well as the accurate recognition of dominant, alien, and biomarker species at each spatial zone indicated that eDNA could characterize fish community attributes at a similar level of traditional approach. Generally, our results demonstrated that eDNA metabarcoding can be used as an effective tool in revealing fish composition and diversity, which is important for using the eDNA technique in aquatic field monitoring.
Root system architecture is limited by phylogenetic relationships and ultimately affect the biomass allocation of resource acquisition organs. However, many studies have only focused on the impact of environmental driven trait variation and biomass allocation on root system architecture, neglecting the impact of phylogenetic relationships. Therefore, biomass allocation and phylogenetic relationship affect the root system architecture and its variation patterns were investigated in annual ephemerals. We found that the interspecific variation of root tissue density (RTD) was the highest (51.63%), and the topological index (TI) was the lowest (5.92%). Moreover, the range of intraspecific variation for specific root length (SRL) and specific surface area (SRA) is high, and the TI is low. This convergence and divergence of root traits reflect the Phenotypic plasticity of roots and their adaptation to environmental filtering and interspecific competition. Maximum root depth (MRD) was detected significantly and weakly phylogenetic signal (0