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Data from: Robust estimates of a high Ne/N ratio in a top marine predator, southern bluefin tuna
Genetic studies of several marine species with high fecundity have produced "tiny" estimates (≤10−3) of the ratio of effective population size (Ne) to adult census size (N), suggesting that even very large populations might be at genetic risk. A recent study using close-kin mark-recapture methods estimated adult abundance at N ≈ 2 × 106 for southern bluefin tuna (SBT), a highly fecund top predator that supports a lucrative (~$1 billion/year) fishery. We used the same genetic and life history data (almost 13,000 fish collected over 5 years) to generate genetic and demographic estimates of Ne per generation and Nb (effective number of breeders) per year and the Ne/N ratio. Demographic estimates, which accounted for age-specific vital rates, skip breeding, variation in fecundity at age, and persistent individual differences in reproductive success, suggest that Ne/N is >0.1 and perhaps about 0.5. The genetic estimates supported this conclusion. Simulations using true Ne = 5 × 105 (Ne/N = 0.25) produced results statistically consistent with the empirical genetic estimates, whereas simulations using Ne = 2 × 104 (Ne/N = 0.01) did not. Our results show that robust estimates of Ne and Ne/N can be obtained for large populations, provided sufficiently large numbers of individuals and genetic markers are used and temporal replication (here, 5 years of adult and juvenile samples) is sufficient to provide a distribution of estimates. The high estimated Ne/N ratio in SBT is encouraging and suggests that the species will not be compromised by a lack of genetic diversity in responding to environmental change and harvest.
Data from: Scale-dependent foraging ecology of a marine top predator modelled using passive acoustic data
1. Understanding which environmental factors drive foraging preferences is critical for the development of effective management measures, but resource use patterns may emerge from processes that occur at different spatial and temporal scales. Direct observations of foraging are also especially challenging in marine predators, but passive acoustic techniques provide opportunities to study the behavior of echolocating species over a range of scales. 2. We used an extensive passive acoustic dataset to investigate the distribution and temporal dynamics of foraging in bottlenose dolphins using the Moray Firth (Scotland, UK). Echolocation buzzes were identified with a mixture model of detected echolocation inter-click intervals, and used as a proxy of foraging activity. A robust modelling approach accounting for autocorrelation in the data was then used to evaluate which environmental factors were associated with the observed dynamics at two different spatial and temporal scales. 3. At a broad scale, foraging varied seasonally, and was also affected by sea-bed slope and shelf-sea fronts. At a finer scale, we identified variation in seasonal use and local interactions with tidal processes. Foraging was best predicted at a daily scale, accounting for site-specificity in the shape of the estimated relationships. 4. This study demonstrates how passive acoustic data can be used to understand foraging ecology in echolocating species, and provides a robust analytical procedure for describing spatio-temporal patterns. Associations between foraging and environmental characteristics varied according to spatial and temporal scale, highlighting the need for a multi-scale approach. Our results indicate that dolphins respond to coarser-scale temporal dynamics, but have a detailed understanding of finer-scale spatial distribution of resources.
Data from: Ecological opportunities and specializations shaped genetic divergence in a highly mobile marine top predator
Environmental conditions can shape genetic and morphological divergence. Release of new habitats during historical environmental changes was a major driver of evolutionary diversification. Here, forces shaping population structure and ecotype differentiation ('pelagic' and 'coastal') of bottlenose dolphins in the North-east Atlantic were investigated using complementary evolutionary and ecological approaches. Inference of population demographic history using approximate Bayesian computation indicated that coastal populations were likely founded by the Atlantic pelagic population after the Last Glacial Maxima probably as a result of newly available coastal ecological niches. Pelagic dolphins from the Atlantic and the Mediterranean Sea likely diverged during a period of high productivity in the Mediterranean Sea. Genetic differentiation between coastal and pelagic ecotypes may be maintained by niche specializations, as indicated by stable isotope and stomach content analyses, and social behaviour. The two ecotypes were only weakly morphologically segregated in contrast to other parts of the World Ocean. This may be linked to weak contrasts between coastal and pelagic habitats and/or a relatively recent divergence. We suggest that ecological opportunity to specialize is a major driver of genetic and morphological divergence. Combining genetic, ecological and morphological approaches is essential to understanding the population structure of mobile and cryptic species.
Data from: Patchy distribution and low effective population size raise concern for an at-risk top predator
Aim: Understanding carnivore distribution is important for management decisions that aim to restore naturally-regulated ecosystems and preserve biodiversity. Eastern Wolves, a species at risk in Canada, are centralized in Algonquin Provincial Park and their ability to disperse and establish themselves elsewhere is limited by human-caused mortality associated with hunting, trapping, and vehicle collisions. Here, we refine our understanding of Eastern Wolf distribution and provide the first estimates of their effective population size. Location: Southern Ontario and Gatineau Quebec. Methods: We used noninvasive samples, as well as blood samples archived from other research projects, collected between 2010 – 2014 to generate autosomal microsatellite genotypes at 12 loci for 98 Canis individuals. We utilized Bayesian and multivariate clustering analyses to identify Eastern Wolves in regions that were previously unsampled. Both linkage disequilibrium and temporal approaches were used to estimate effective population size of Eastern Wolves. Results: Assignment tests identified 34 individuals as Eastern Wolves, primarily in or near two provincial parks: Killarney and Queen Elizabeth II Wildlands. Eastern Coyotes were identified in Bon Echo Provincial Park, Frontenac Provincial Park, and Gatineau Park, whereas many of the samples were admixed among the different Canis types. Effective population size (Ne) estimates ranged from 24.3 – 122.1 with a harmonic mean of 45.6. Main Conclusions: The identification of Eastern Wolves in the regions of Killarney and Queen Elizabeth II Wildlands Provincial Parks extends the range of Eastern Wolves north of the French River and southward into previously unidentified regions. The effective population size is low and raises concerns for long-term persistence of this threatened carnivore; values are dangerously close to critical values recommended for short-term persistence. These results provide important information for upcoming Eastern Wolf recovery plans associated with federal and provincial endangered species legislation.
Data from: Longleaf pine proximity effects on air temperatures and hardwood top-kill from prescribed fire
Background Regulation of the dominance of sprouting understory hardwoods is a common objective for prescribed fire in open-canopy longleaf pine woodland of the southeastern USA. Nevertheless, little is known about the influence of individual pines on fire and hardwood mortality. We studied growing-season fires in stem-mapped stands in southwest Georgia USA which displayed large variation in structure due to cutting treatments applied 7 yr earlier. We measured air temperature and heating duration, and measured post-fire sprouting behavior of four guilds of understory hardwoods: mesic oaks, upland oaks, xeric oaks, and fleshy-fruited hardwoods. Mean air temperature (i.e., of flames, buoyant plume and smoldering combustion) and heating duration (time over 60°C) were analyzed with respect to fuel-bed conditions and neighboring tree density. Hardwood top-kill was analyzed with respect to neighboring tree density and hardwood height. Results Size of and distance to longleaf pines strongly affected time over 60°C, which increased linearly from a mean of 87 s to a mean of 234 s across a gradient of pine basal area from 0 to 30 m2 ha-1. Mean air temperature during prescribed fire was unaffected by pine density but increased linearly from a mean of 114°C to a mean of 148°C across a gradient of wiregrass cover from 0 to 100%. Neighborhood models showed that time over 60°C during the burns was longest at the base of pines and decreased by two-thirds at 3.3 m distance. Pines affected hardwood top-kill probability at a similar scale, the effect at 4.4 m decreasing by two-thirds compared to at the base of the pine. The four hardwood guilds were readily top-killed when ≤ 1 m tall, but at 2 m height upland and xeric oaks had become more resistant to top-kill than mesic oaks or fleshy fruited broadleaved trees. Conclusions The influence of individual pine trees on heating duration and top-kill power of prescribed fire drops by ⅔ of maximum within 3 to 4 m of a tree, compared to a maximum at the base of the tree. Neighborhood models provide a method to estimate tree effects on prescribed fire heating duration and top-kill probability, and thus a way of predicting stand structures that provide ecological benefits of openings while remaining below thresholds that trigger vigorous hardwood response.
Data from: Evolutionary divergence of adult body size and juvenile growth in sympatric subpopulations of a top predator in aquatic ecosystems
Evolutionary theory predicts that different selective regimes may contribute to divergent evolution of body size and growth rate among populations, but most studies have focused on allopatric populations. Here, we studied five sympatric subpopulations of anadromous northern pike (Esox lucius) in the Baltic Sea subjected to allopatric habitats for a short period of their life cycle due to homing behavior. We report differences in adult body size among subpopulations that were in part due to variation in growth rate. Body size of emigrating juveniles also differed among subpopulations, and differences remained when individuals were reared in a common environment, thus indicating evolutionary divergence among subpopulations. Furthermore, a QST-FST comparison indicated that differences had evolved due to divergent selection rather than genetic drift, possibly in response to differences in selective mortality among spawning habitats during the allopatric life stage. Adult and juvenile size were negatively correlated across subpopulations, and reconstruction of growth trajectories of adult fishes suggested that body size differences developed gradually and became accentuated throughout the first years of life. These results represent rare evidence that sympatric subpopulations can evolve differences in key life-history traits despite being subjected to allopatric habitats during only a very short fraction of their life.
Data from: Variable sea-ice conditions influence trophic dynamics in an Arctic community of marine top predators
Sea‐ice coverage is a key abiotic driver of annual environmental conditions in Arctic marine ecosystems and could be a major factor affecting seabird trophic dynamics. Using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in eggs of thick‐billed murres (Uria lomvia), northern fulmars (Fulmarus glacialis), glaucous gulls (Larus hyperboreus), and black‐legged kittiwakes (Rissa tridactyla), we investigated the trophic ecology of prebreeding seabirds nesting at Prince Leopold Island, Nunavut, and its relationship with sea‐ice conditions. The seabird community of Prince Leopold Island had a broader isotopic niche during lower sea‐ice conditions, thus having a more divergent diet, while the opposite was observed during years with more extensive sea‐ice conditions. Species' trophic position was influenced by sea ice; in years of lower sea‐ice concentration, gulls and kittiwakes foraged at higher trophic levels while the opposite was observed for murres and fulmars. For murres and fulmars over a longer time series, there was no evidence of the effect of sea‐ice concentration on species' isotopic niche. Results suggest a high degree of adaptation in populations of high Arctic species that cope with harsh and unpredictable conditions. Such different responses of the community isotopic niche also show that the effect of variable sea‐ice conditions, despite being subtle at the species level, might have larger implications when considering the trophic ecology of the larger seabird community. Species‐specific responses in foraging patterns, in particular trophic position in relation to sea ice, are critical to understanding effects of ecosystem change predicted for a changing climate.
Data from: Landscape genetics of a top neotropical predator
Habitat loss and fragmentation as a consequence of human activities is a worldwide phenomenon and one of the major threats to global biodiversity. Habitat loss and fragmentation is particularly a concern in the biodiverse tropics, where deforestation is occurring at unprecedented rates. Although insects are one of the most diverse and functionally important groups in tropical ecosystems, the quantitative effect of landscape features on their gene flow remains unknown. Here, we used a robust landscape genetics approach to quantify the effect of ten landscape features (deforestation, mature forests, other forest types, the River Chagres, streams, stream banks, roads, sea, lakes and swamps) and interactions between them, on the gene flow of a neotropical forest keystone species, the army ant Eciton burchellii. The influence of landscape on E. burchellii's gene flow reflected the different dispersal capability of its sexes; aerial for males and pedestrian for females, and the different depths of population history inferred from microsatellites and mitochondrial DNA. In contrast to the gene flow-facilitating effect of mature forests, deforested areas were found to be strong barriers for E. burchellii's gene flow. Other forest types were found to be gene flow facilitators but only when interacting with mature secondary forests, therefore indicating the importance of mature forests for the survival of E. burchelii and its associate species. The River Chagres was identified as a major historical gene flow barrier for E. burchellii, suggesting that an important loss of connectivity may occur because of large artificial waterways such as the Panama Canal.
Data from: Mesoscale activity facilitates energy gain in a top predator
How animal movement decisions interact with the distribution of resources to shape individual performance is a key question in ecology. However, links between spatial and behavioural ecology and fitness consequences are poorly understood because the outcomes of individual resource selection decisions, such as energy intake, are rarely measured. In the open ocean, mesoscale features (~10-100 km) such as fronts and eddies can aggregate prey and thereby drive the distribution of foraging vertebrates through bottom-up biophysical coupling. These productive features are known to attract predators, yet their role in facilitating energy transfer to top predators is opaque. We investigated the use of mesoscale features by migrating northern elephant seals and quantified the corresponding energetic gains from the seals' foraging patterns at a daily resolution. Migrating elephant seals modified their diving behaviour and selected for mesoscale features when foraging. Daily energy gain increased significantly with increasing mesoscale activity, indicating that the physical environment can influence predator fitness at fine temporal scales. Results show that areas of high mesoscale activity not only attract top predators as foraging hotspots, but also lead to increased energy transfer across trophic levels. Our study provides evidence that the physical environment is an important factor in controlling energy flow to top predators by setting the stage for variation in resource availability. Such understanding is critical for assessing how changes in the environment and resource distribution will affect individual fitness and food web dynamics.
Data from: Combined bottom-up and top-down pressures drive catastrophic population declines of Arctic skuas in Scotland
1. Understanding drivers of population change is critical for effective species conservation. In the northeast Atlantic Ocean, recent changes amongst seabird communities are linked to human and climate change impacts on foodwebs. Many species have declined severely, with food shortages and increased predation reducing productivity. Arctic skua Stercorarius parasiticus, a kleptoparasite of other seabirds, is one such species. 2. The aim of the study was to determine relative effects of bottom-up and top-down pressures on Arctic skuas across multiple colonies in a rapidly declining national population. 3. Long-term monitoring data were used to quantify changes in population size and productivity of Arctic skuas, their hosts (black-legged kittiwake Rissa tridactyla, common guillemot Uria aalge, Atlantic puffin Fratercula arctica, Arctic tern Sterna paradisaea), and an apex predator (great skua Stercorarius skua) over 24 years (1992–2015) in Scotland. We used digital mapping and statistical models to determine relative effects of bottom-up (host productivity) and top-down (great skua density) pressures on Arctic skuas across 33 colonies, and assess variation between three colony types classified by host abundance. 4. Arctic skuas declined by 81% and their hosts by 42–92%, whereas at most colonies great skuas increased. Annual productivity declined in Arctic skuas and their hosts, and reduced Arctic skua breeding success was a driver of the species' population decline. Arctic skua productivity was positively associated with annual breeding success of hosts, and negatively with great skua density. Inter-colony variation suggested Arctic skua trends and productivity were most sensitive to top-down pressures at smaller colonies of host species where great skuas had increased most, whereas bottom-up pressures dominated at large colonies of host species. 5. Scotland's Arctic skua population is declining rapidly, with bottom-up and top-down pressures simultaneously reducing breeding success to unsustainably low levels. Marine food web alterations, strongly influenced by fisheries management and climate change, are driving the decline, and this study demonstrates severe vulnerability of seabirds to rapid change in human-modified ecosystems. Potential but untested conservation solutions for Arctic skuas include Marine Protected Areas, supplementary feeding within colonies, and management of great skuas.
Data from: Life at the top: lake ecotype influences the foraging patterns, metabolic costs and life history of an apex fish predator
1.We used acoustic telemetry and acceleration sensors to compare population-specific measures of the metabolic costs of an apex fish predator living in four separate lakes. We chose our study species and populations to provide a strong test of recent theoretical predictions that optimal foraging by an apex fish predator in a typical aquatic environment would be consistent with feeding to satiation rather than continuous feeding. We chose four populations where the primary prey type differed along a body size gradient (from small invertebrates to large planktivorous fish) and along a thermal accessibility gradient (from easily accessible coldwater pelagic prey to less accessible warmwater epilimnetic and littoral prey). We expected that these gradients in prey type would evoke distinctly different activity gradients depending on whether predators fed to satiation (e.g. less frequent 'rest' detections where primary prey are smaller/less accessible) or fed continuously (e.g. fixed level of 'rest' detections under all prey conditions). 2. Our study organism was a fall spawning, coldwater visual apex predator (lake trout). Therefore, we focused our study on diel (early night, dawn, day, dusk, late night) changes in metabolic costs associated with summer feeding behaviour. The duration (~20 days) and fine temporal scale (~30 minutes) of our behavioural data provided a uniquely detailed picture of intra- and inter-population differences in activity patterns over a critical period in the annual growing season. 3. In all populations, diel shifts in activity were qualitatively consistent with that expected of a visual predator (e.g. resting state detections were most frequent at night). 4. Between-lake differences in daytime thermal experience were qualitatively consistent with between-lake differences in the location of primary prey (e.g. excursions to warm habitats were common in lakes with epilimnetic/littoral fish as primary prey and relatively rare in lakes with pelagic coldwater invertebrates/fish as primary prey). 5. Daytime activity patterns were consistent with feeding to satiation rather than continuous feeding: (a) individuals in all four populations exhibited clearly delineated bouts of resting behaviour and active behaviour; (b) the frequency of resting bouts and the resultant overall cost of daily activity were strongly associated with the size and accessibility of prey – in lakes with smaller and/or less accessible prey, predators rested less frequently, exhibited marginally higher costs when active and had higher overall daytime activity costs. Within each lake, similar changes in activity occurred concurrently with diel changes in prey accessibility/relative density.
Data from: Bottom-up effects of host-plant species diversity and top-down effects of ants interactively increase plant performance
While plant diversity is well known to increase primary productivity, whether these bottom-up effects are enhanced by reciprocal top-down effects from the third trophic level is unknown. We studied whether pine tree species diversity, aphid-tending ants and their interaction determined plant performance and arthropod community structure. Plant diversity had a positive effect on aphids, but only in the presence of mutualistic ants, leading to threefold greater number of both groups in the tri-specific cultures than in monocultures. Plant diversity increased ant abundance not only by increasing aphid number, but also by increasing ant recruitment per aphid. The positive effect of diversity on ants in turn cascaded down to increase plant performance; diversity increased plant growth (but not biomass), and this effect was stronger in the presence of ants. Consequently, bottom-up effects of diversity within the same genus and guild of plants and top-down effects from the third trophic level (predatory ants) interactively increased plant performance.
Data from: Avian top predator and the landscape of fear: responses of mammalian mesopredators to risk imposed by the golden eagle
Top predators may induce extensive cascading effects on lower trophic levels, for example, through intraguild predation (IGP). The impacts of both mammalian and avian top predators on species of the same class have been extensively studied, but the effects of the latter upon mammalian mesopredators are not yet as well known. We examined the impact of the predation risk imposed by a large avian predator, the golden eagle (Aquila chrysaetos, L.), on its potential mammalian mesopredator prey, the red fox (Vulpes vulpes, L.), and the pine marten (Martes martes, L.). The study combined 23 years of countrywide data from nesting records of eagles and wildlife track counts of mesopredators in Finland, northern Europe. The predation risk of the golden eagle was modeled as a function of territory density, density of fledglings produced, and distance to nearest active eagle territory, with the expectation that a high predation risk would reduce the abundances of smaller sized pine martens in particular. Red foxes appeared not to suffer from eagle predation, being in fact most numerous close to eagle nests and in areas with more eagle territories. This is likely due to similar prey preferences of the two predators and the larger size of foxes enabling them to escape eagle predation risk. Somewhat contrary to our prediction, the abundance of pine martens increased from low to intermediate territory density and at close proximity to eagle nests, possibly because of similar habitat preferences of martens and eagles. We found a slightly decreasing trend of marten abundance at high territory density, which could indicate that the response in marten populations is dependent on eagle density. However, more research is needed to better establish whether mesopredators are intimidated or predated by golden eagles, and whether such effects could in turn cascade to lower trophic levels, benefitting herbivorous species.
Data from: The role of flow velocity combined with habitat complexity as a top–down regulator in seagrass meadows
Large‐scale losses of seagrass areas have been associated with eutrophication events, which have led to an overproduction of photosynthetic organisms including epiphytes. Grazers that feed on epiphytes can exert a significant top–down control in the system, but the effects of physical factors on grazing activity and feeding behaviour have been rarely examined. We addressed the combination of hydrodynamic regime and seagrass shoot density can alter the feeding and foraging behaviours of mesograzers. A full factorial experiment, with flow velocity (high, medium and low) and shoot density (high versus low) as main factors, was conducted in a racetrack flume using artificial seagrass plots. The results showed that when high flow velocity conditions were combined with low shoot density, consumption of epiphytes by mesograzers was strongly reduced. In contrast, when flow velocity was low or shoot density was high, mesograzers exhibited high feeding rates and vigorous swimming behaviour. These results clearly indicate that hydrodynamic stress reduces the time that mesograzers can spend feeding, since it inhibits their swimming behaviour, and thus indirectly affecting to the density of epiphytes. Therefore, the triggering of trophic cascade effects in seagrass communities under these experimental conditions depended on the interrelationship and feedbacks among shoot density, abiotic (flow velocity) and biotic (epiphytes and mesograzers) compartments, with flow velocity exerting a top–down control on seagrass ecosystems.
Data from: The changing contribution of top-down and bottom-up limitation of mesopredators during 220 years of land use and climate change
Apex predators may buffer bottom-up driven ecosystem change, as top-down suppression may dampen herbivore and mesopredator responses to increased resource availability. However, theory suggests that for this buffering capacity to be realized, the equilibrium abundance of apex predators must increase. This raises the question: will apex predators maintain herbivore/mesopredator limitation, if bottom-up change relaxes resource constraints? Here, we explore changes in mesopredator (red fox Vulpes vulpes) abundance over 220 years in response to eradication and recovery of an apex predator (Eurasian lynx Lynx lynx), and changes in land use and climate which are linked to resource availability. A three-step approach was used. First, recent data from Finland and Sweden were modelled to estimate linear effects of lynx density, land use and winter temperature on fox density. Second, lynx density, land use and winter temperature was estimated in a 22 650 km2 focal area in boreal and boreo-nemoral Sweden in the years 1830, 1920, 2010 and 2050. Third, the models and estimates were used to project historic and future fox densities in the focal area. Projected fox density was lowest in 1830 when lynx density was high, winters cold and the proportion of cropland low. Fox density peaked in 1920 due to lynx eradication, a mesopredator release boosted by favourable bottom-up changes - milder winters and cropland expansion. By 2010, lynx recolonization had reduced fox density, but it remained higher than in 1830, partly due to the bottom-up changes. Comparing 1830 to 2010, the contribution of top-down limitation decreased, while environment enrichment relaxed bottom-up limitation. Future scenarios indicated that by 2050, lynx density would have to increase by 79% to compensate for a projected climate driven increase in fox density. We highlight that although top-down limitation in theory can buffer bottom-up change, this requires compensatory changes in apex predator abundance. Hence apex predator recolonization/recovery to historical levels would not be sufficient to compensate for widespread changes in climate and land use, which have relaxed the resource constraints for many herbivores and mesopredators. Variation in bottom-up conditions may also contribute to context dependence in apex predator effects.
Data from: Warming advances top-down control and reduces producer biomass in a freshwater plankton community
Global warming has been shown to affect ecosystems worldwide. Warming may, for instance, disrupt plant herbivore synchrony and bird phenology in terrestrial systems, reduce primary production in oceans, and promote toxic cyanobacterial blooms in freshwater lakes. Responses of communities will not only depend on direct species-specific temperature effects, but also on indirect effects related to bottom-up and top-down processes. Here, we investigated the impact of warming on freshwater phytoplankton community dynamics, and assessed the relative contribution of nutrient availability, fungal parasitism, and grazing therein. For this purpose, we performed an indoor mesocosm experiment following seasonal temperature dynamics of temperate lakes and a warmed (+4°C) scenario from early spring to late summer. We assessed phytoplankton biomass, C:N:P stoichiometry and community composition, dissolved nutrient availabilities, fungal parasite (i.e., chytrid) prevalence, and zooplankton abundance. Warming led to an overall reduction in phytoplankton biomass as well as lower C:P and N:P ratios, while phytoplankton community composition remained largely unaltered. Warming resulted in an earlier termination of the diatom spring bloom, and an epidemic of its fungal parasite ended earlier as well. Furthermore, warming advanced zooplankton phenology, leading to an earlier top-down control on phytoplankton in the period after the spring bloom. Linear model analysis showed that most of the observed variance in phytoplankton biomass was related to seasonal temperature dynamics in combination with zooplankton abundance. Our findings showed that warming advanced grazer phenology and reduced phytoplankton biomass, thereby demonstrating how bottom-up and top-down related processes may shape future phytoplankton dynamics.
Detection of prey odors underpins dietary specialization in a Neotropical top-predator: how army ants find their ant prey
<p>1. Deciphering the mechanisms that underpin dietary specialization and niche partitioning is crucial to understanding the maintenance of biodiversity. New world army ants live in species-rich assemblages throughout the Neotropics and are voracious predators of other arthropods. They are therefore an important and potentially informative group for addressing how diverse predator assemblages partition available prey resources. 2. New World army ants are largely specialist predators of other ants, with each species specializing on different ant genera. However, the mechanisms of prey choice are unknown. In this study, we addressed whether the army ant Eciton hamatum: 1) can detect potential prey odors, 2) can distinguish between odors of prey and non-prey, and 3) can differentiate between different types of odors associated with its prey. 3. Using field experiments, we tested the response of army ants to the following four odor treatments: alarm odors, dead ants, live ants, and nest material. Each treatment had a unique combination of odor sources and included some movement in two of the treatments (alarm and live ants). Odor treatments were tested for both prey and non-prey ants. These data were used to determine the degree to which E. hamatum are using specific prey stimuli to detect potential prey and direct their foraging. 4. Army ants responded strongly to odors derived from prey ants, which triggered both increased localized recruitment and slowed advancement of the raid as they targeted the odor source. Odors from non-prey ants were largely ignored. Additionally, the army ants had the strongest response to the nest material of their preferred prey, with progressively weaker responses across the live ant, dead ant, and alarm odors treatments, respectively. 5. This study reveals that the detection of prey odors, and especially the most persistent odors related to the prey's nest, provides a mechanism for dietary specialization in army ants. If ubiquitous across the Neotropical army ants, then this olfaction-based ecological specialization may facilitate patterns of resource partitioning and coexistence in these diverse predator communities. 08-Jan-2020</p>
Data from: Size, sex, and individual-level behavior drive intra-population variation in cross-ecosystem foraging of a top-predator
1. Large-bodied, top-predators are often highly mobile, with the potential to provide important linkages between spatially distinct food webs. What biological factors contribute to variation in cross-ecosystem movements, however, have rarely been examined. 2. Here, we investigated how ontogeny (body size), sex, and individual-level behavior impacts intra-population variation in cross-ecosystem foraging (i.e., between freshwater and marine systems), by the top-predator Alligator mississippiensis. 3. Field surveys revealed A. mississippiensis uses marine ecosystems regularly and are abundant in estuarine tidal creeks (from 0.3–6.3 individuals/km of creek, n = 45 surveys). Alligator mississippiensis captured in marine/estuarine habitats were significantly larger than individuals captured in freshwater and intermediate habitats. 4. Stomach content analysis showed that small juveniles consumed marine/estuarine prey less frequently (6.7% of individuals) than did large juveniles (57.8%), sub-adult (73%), and adult (78%) size classes. Isotopic mixing model analysis (SIAR) also suggests substantial variation in use of marine/estuarine prey resources with differences among and within size classes between sexes and individuals (range of median estimates for marine/estuarine diet contribution = 0.05–0.76). 5. These results demonstrate the importance of intra-population characteristics (body size, sex, and individual specialization) as key determinants of the strength of predator-driven ecosystem connectivity resulting from cross-ecosystem foraging behaviors. Understanding the factors which contribute to variation in cross-ecosystem foraging behaviors will improve our predictive understanding of the effects of top-predators on community structure and ecosystem function.
Data from: Evolution and conservation on top of the world: Phylogeography of the Marbled Water Frog (Telmatobius marmoratus species complex; Anura, Telmatobiidae) in protected areas of Chile
The Andean Altiplano has served as a complex setting throughout its history, driving dynamic processes of diversification in several taxa. We investigated phylogeographic processes in the Telmatobius marmoratus species complex occurring in this region by studying the geographic patterns of genetic variability, genealogies, and historical migration, using the cytochrome b (cyt-b) gene as a marker. DNA sequences from Telmatobius gigas and Telmatobius culeus, Bolivian species with an uncertain taxonomic status, were also included. Additionally, we evaluated the phylogenetic diversity (PD) represented within Chilean protected areas and the complementary contribution from unprotected populations. Phylogenetic reconstructions from 148 cyt-b sequences revealed 4 main clades, one of which corresponded to T. culeus. T. gigas was part of T. marmoratus clade indicating paraphyletic relationships. Haplotypes from Chilean and Bolivian sites were not reciprocally monophyletic. Geographic distribution of lineages, spatial Bayesian analysis, and migration patterns indicated that T. marmoratus displays a weaker geographic structure than expected based on habitat distribution and physiological requirements. Demographic and statistical phylogeography analyses pointed out to a scenario of recent population expansion and high connectivity events of a more recent age than the post Last Glacial Maximum, probably associated to more humid events in Altiplano. PD of T. marmoratus populations within protected areas represents 55.6% of the total estimated PD. The unprotected populations that would contribute the most to PD are Caquena and Quebe (21%). Recent evolutionary processes and paleoclimatic changes, potentially driving shifts in habitat connectivity levels and population sizes, could explain the phylogeographic patterns recovered herein.
Data from: Pulsing hydrology determines top-down control of basal resources in a tropical river-floodplain ecosystem
Variable hydrology of rivers strongly affects biophysical factors that influence primary production and population densities, thereby affecting the relative influence of bottom-up and top-down processes in trophic networks. Many tropical floodplain rivers have sustained seasonal flood pulses driven by precipitation patterns of the Intertropical Convergence Zone. These changes in flow alter concentrations of dissolved nutrients, aquatic primary productivity, and per-unit-area densities of aquatic organisms. Therefore, one would predict that the strength of top-down effects of animals on basal resources should shift as the annual flood pulse progresses. We conducted a series of field experiments in a Neotropical lowland river to test for effects of hydrologic phase, habitat (in-channel vs. floodplain aquatic habitat), and benthic feeding fish and meiofauna on particulate organic matter, chlorophyll, and benthic microalgae. Net ecosystem productivity of this oligotrophic river is higher during the low phase of the annual flood cycle, which is also when resident fishes are at highest densities and there is a seasonal influx of migratory benthic feeding fish. We therefore hypothesized that top-down effects of benthic-feeding fish would fluctuate temporally, with strongest effects during low water levels. We found that fish controlled the abundance of particulate organic matter and algae on solid substrates, but not on sand, during falling- and low-water phases within both channel and floodplain habitats. Except for diatom assemblages, which responded to fish exclusion, the taxonomic structure of algal and meiofauna assemblages was not significantly influenced by fish exclusion treatments, but varied in relation to habitat type and hydrologic phase. Meiofauna densities were highest during the low-water period; experimental exclusion of meiofauna during this period had a significant effect on accumulation of particulate organic matter in sand. By controlling abundance of important basal resources, fishes and meiofauna have large potential to influence other components of this tropical ecosystem. Our findings emphasize the predictable, gradual, changes in consumer-resource interactions associated with the seasonal flood pulse in tropical river systems.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.