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Data from: Disentangling species limits in the Vauquelinia corymbosa complex (Pyreae, Rosaceae)
Vauquelinia corymbosa (Pyreae, Rosaceae) is a shrubby sclerophyllous species largely restricted to the Chihuahuan Desert, distributed from Texas, Coahuila, and along the Sierra Madre Oriental to Hidalgo. According to a previous taxonomic revision, it comprises six subspecies. Vauquelinia corymbosa has noteworthy morphological variation, mostly in leaf characters, and the majority of its subspecies are restricted to certain areas of the desert. In this study, based on 16 morphometric characters and four anatomical characters collected from 201 specimens of the six subspecies throughout their distribution range,we ran a number of uni-, multivariate, and phylogenetic analyses to determine how many species can be recognized in this species complex. We also analyzed the gaps in morphology across geography to identify whether gaps in morphometric characters are indeed useful to separate species or if they are the result of variation related to geography. The results of the analyses coincided in recognizing that subsp. angustifolia should be considered a separate species and that the remaining subspecies are part of Vauquelinia corymbosa with remarkable morphological variation. Vauquelinia angustifolia has diagnostic characters such as very narrow leaves (0.4–0.6 cm at the middle and 0.2–0.4 cm at the base) and short petioles (1–1.5 cm) and it is restricted to the northeastern region of the Chihuahuan Desert.
Data from: Predator-dependent functional response in wolves: from food limitation to surplus killing
The functional response of a predator describes the change in per capita kill rate to changes in prey density. This response can be influenced by predator densities, giving a predator-dependent functional response. In social carnivores which defend a territory, kill rates also depend on the individual energetic requirements of group members and their contribution to the kill rate. This study aims to provide empirical data for the functional response of wolves Canis lupus to the highly managed moose Alces alces population in Scandinavia. We explored prey and predator dependence, and how the functional response relates to the energetic requirements of wolf packs. Winter kill rates of GPS-collared wolves and densities of cervids were estimated for a total of 22 study periods in 15 wolf territories. The adult wolves were identified as the individuals responsible for providing kills to the wolf pack, while pups could be described as inept hunters. The predator-dependent, asymptotic functional response models (i.e. Hassell-Varley type II and Crowley-Martin) performed best among a set of 23 competing linear, asymptotic and sigmoid models. Small wolf packs acquired > 3 times as much moose biomass as required to sustain their field metabolic rate (FMR), even at relatively low moose abundances. Large packs (6 - 9 wolves) acquired less biomass than required in territories with low moose abundance. We suggest the surplus-killing by small packs is a result of an optimal foraging strategy to consume only the most nutritious parts of easy accessible prey while avoiding the risk of being detected by humans. Food limitation may have a stabilizing effect on pack size in wolves, as supported by the observed negative relationship between body weight of pups and pack size.
Data from: Soil nutrients and dispersal limitation shape compositional variation in secondary tropical forests across multiple scales
1. Soil resource partitioning and dispersal limitation have been shown to shape the tree community structure of mature tropical forests, but are poorly studied in the context of forest succession. We examined the relative contributions of both ecological processes to the variation in the species composition of young tropical secondary forests at different spatial scales, and if the relative importance of these two ecological processes changed during succession. At the species level, we examined if the association between species abundances and soil fertility differed between early and late successional species and/or changed over the course of succession. 2. We used vegetation and soil data from 47 secondary forest sites with two plots each in a tropical agricultural landscape. A distance-based redundancy analysis and variation partition were employed to examine the relative importance of spatial distance (proxy for dispersal limitation) and heterogeneity in soil nutrients (proxy for soil nutrient partitioning) at the landscape scale, and a linear regression to test their effects at the local scale. We examined interspecific variation in species' responses to successional age and soil nutrients with a joint species distribution model. 3. Dispersal limitation and soil niche partitioning drove considerable variation in the composition of plant communities at local and landscape scales. The relative contribution of these two ecological processes changed with scale (local versus landscape), topography (lower slope versus upper slope plots). At the species level, significant abundance-soil fertility associations were mostly positive. Most species became less responsive to soil nutrients over the first few decades of tropical forest succession, probably because light became the main limiting resource in older forests. 4. Synthesis. Our key finding is that spatial heterogeneity in soil resources and spatial distance jointly drive compositional variation within and across early successional forests. Our results highlight that a network of forest fragments enhances the resilience of ecological processes and the potential of secondary forests to restore and preserve biodiversity in human-modified landscapes. To advance our understanding of ecological succession, we need to move beyond single-factor and local-scale studies and examine the effects of multiple variables on succession at multiple spatial scales.
Data from: Genetic correlations and little genetic variance for reaction norms may limit potential for adaptation to pollution by ionic and nanoparticulate silver in a whitefish (Salmonidae)
For natural populations to adapt to anthropogenic threats, heritable variation must persist in tolerance traits. Silver nanoparticles, the most widely used engineered nanoparticles, are expected to increase in concentrations in freshwaters. Little is known about how these particles affect wild populations, and whether genetic variation persists in tolerance to permit rapid evolutionary responses. We sampled wild adult whitefish and crossed them in vitro full factorially. In total, 2896 singly raised embryos of 48 families were exposed to two concentrations (0.5 μg/L; 100 μg/L) of differently sized silver nanoparticles or ions (silver nitrate). These doses were not lethal; yet higher concentrations prompted embryos to hatch earlier and at a smaller size. The induced hatching did not vary with nanoparticle size and was stronger in the silver nitrate group. Additive genetic variation for hatching time was significant across all treatments, with no apparent environmental dependencies. No genetic variation was found for hatching plasticity. We found some treatment-dependent heritable variation for larval length and yolk volume, and one instance of additive genetic variation for the reaction norm on length at hatching. Our assessment suggests that the effects of silver exposure on additive genetic variation vary according to trait and silver source. While the long-term fitness consequences of low-level silver exposure on whitefish embryos must be further investigated to determine whether it is, in fact, detrimental, our results suggest that the evolutionary potential for adaptation to these types of pollutants may be low.
Data from: Co-occurrence of related asexual, but not sexual, lineages suggests that reproductive interference limits coexistence
We used randomizations to analyse patterns of co-occurrence of sexual and apomictic (asexual) members of the North American Crepis agamic complex (Asteraceae). We expect strong asymmetry in reproductive interactions in Crepis: apomicts produce clonal seeds with no need for pollination and are not subject to reproductive interference from co-occurring relatives. However, because they still produce some viable pollen, apomicts can reduce reproductive success of nearby sexual relatives, potentially leading to eventual local exclusion of sexuals. Consistent with this, randomizations reveal that sexuals are over-represented in isolated sites, while apomicts freely co-occur. Incorporation of taxonomic and phylogenetic evidence indicates that this pattern is not driven by local origins of asexuals. Our evidence that patterns of local co-occurrence are structured by reproductive interference suggests an underappreciated role for these interactions in community assembly, and highlights the need for explicit tests of the relative contributions of ecological and reproductive interactions in generating patterns of limiting similarity.
Data from: Gape-limited predators as agents of selection on the defensive morphology of an invasive invertebrate
Invasive species have widespread and pronounced effects on ecosystems and adaptive evolution of invaders is often considered responsible for their success. Despite the potential importance of adaptation to invasion, we still have limited knowledge of the agents of natural selection on invasive species. Bythotrephes longimanus, a cladoceran zooplankton, invaded multiple Canadian Shield lakes over the past several decades. Bythotrephes have a conspicuous caudal process (tail spine) that provides a morphological defense against fish predation. We measured viability selection on the longest component of the Bythotrephes spine, the distal spine segment, through a comparison of the lengths of first and second instar Bythotrephes collected from lakes differing in the dominance of gape-limited predation (GLP) and non-gape-limited predation (NGLP) by fish. We found that natural selection varied by predator gape-limitation, with strong selection (selection intensity: 0.20-0.79) for increased distal spine length in lakes dominated by GLP, and no significant selection in lakes dominated by NGLP. Further, distal spine length was 17% longer in lakes dominated by GLP, suggesting the possibility of local adaptation. As all study lakes were invaded less than twenty years prior to our collections, our results suggest rapid divergence in defensive morphology in response to selection from fish predators.
Data from: Phosphorus amendment mitigates nitrogen addition-induced phosphorus limitation in two plant species in a desert steppe, China
Background and aims: The increasing deposition of atmospheric nitrogen (N) due to anthropogenic activities has significantly enhanced N inputs to ecosystems, resulting in an imbalance in the N: phosphorus (P) ratios in plants and soils. This study aimed to determine whether, and to what extent, P addition alleviates N-induced P limitation in a desert steppe ecosystem. Methods: We conducted a multi-level N:P supply experiment (i.e., constant N with varied P-addition levels) for a grass species, Pennisetum centrasiaticum, and a N-fixing species, Glycyrrhiza uralensis. Results: With increasing amounts of P addition (thereby decreasing the N:P ratio), green-leaf P concentrations of the two species studied tended to increase, while P-resorption proficiency and efficiency tended to decrease. There were no consistent trends in green-leaf N concentrations in response to P addition. However, both species exhibited high N-resorption proficiency, especially in G. uralensis, with high P addition. Generally, the carbon (C):P and N:P ratios both in soils and in green leaves had positive relationships with green-leaf N concentration and P-resorption proficiency of P. centrasiaticum as well as P-resorption traits of G. uralensis, but negative relationships with green-leaf P concentrations in both species. Conclusions: Our study indicates that P addition can alter P-conservation strategy and thereby releasing plant species from the N-induced imbalance of N:P ratios. However, large amounts of P addition could overcompensate and pose a risk of N limitation in desert steppe ecosystems.
Data from: Numbers and distribution of the Great Cormorant in Iceland: limitation at the regional and metapopulation level
We studied a metapopulation of great cormorant (Phalacrocorax carbo) in Iceland, using complete aerial censuses of nests in 25 years during 1975–2015. Age composition was estimated in 1998–2014 by ground surveys in September and February. Brood size was estimated from aerial photographs in 2007–2015. Weather, food, breeding habitat, and density were considered as explanatory variables when examining numerical and distributional changes in the cormorant metapopulation. In 1975–1990 total nest numbers changed little, very low numbers about 1992 were followed by an annual increase of 3.5% in 1994–2015. Total nest numbers were positively correlated with estimates of spawning stocks of cod and saithe and inversely related to the subpolar gyre index (SPG‐I). During the increase in 1994–2015, average colony size at first increased and then declined. Habitat use also changed: the proportion of nests on small rocky islets (skerries) at first declined, from 69% to 44% in 1995–2003 and then increased again to about 58% in 2012–2014. Habitat changes were probably a response to changed patterns of human disturbance. Breeding density, as nests per km2 sea <20 m deep, was rather uniform among five defined regions in 1975–1996. Thereafter, densities became much higher in two sheltered regions with kelp forests and in one mostly exposed region. A second exposed region remained low and in the third nest numbers declined markedly. Thus, carrying capacity was higher in sheltered regions where cormorant breeding had historically been depressed by human disturbance. Brood size varied little among regions but declined with the years from about 2.5 to 1.8. The proportion of juveniles in September (fecundity) declined in 1998–2015 from over 0.4 to 0.3 and was inversely correlated with year and nest numbers, if outlier years were excluded, suggesting resource limitation. Survival of juvenile cormorants in September–February was estimated at 0.471 ± 0.066 SE. Commercial fish stocks and climate indices were not correlated with the proportion of juveniles. Annual survival of adults (breeding and nonbreeding) was estimated from nest counts and age composition 1999–2014, as 0.850 ± 0.026 SE and showed no trend in 1998–2014. We conclude that the metapopulation of cormorants in Iceland was resource‐limited at two levels: fecundity at the regional and winter survival at the total level.
Data from: Limitation of seedling growth by potassium and magnesium supply for two ectomycorrhizal tree species of a Central African rain forest and its implication for their recruitment
In the ectomycorrhizal caesalpiniaceous groves of southern Korup National Park, the dominant tree species, Microberlinia bisulcata, displays very poor in situ recruitment compared with its codominant, Tetraberlinia bifoliolata. The reported ex situ experiment tested whether availabilities of soil potassium and magnesium play a role. Seedlings of the two species received applications of K and Mg fertilizer in potted native soil in a local shade house, and their responses in terms of growth and nutrient concentrations were recorded over 2 years. Amended soil concentrations were also determined. Microberlinia responded strongly and positively in its growth to Mg, but less to K; Tetraberlinia responded weakly to both. Added Mg led to strongly increased Mg concentration for Microberlinia while added K changed that concentration only slightly; Tetraberlinia strongly increased its concentration of K with added K, but only somewhat its Mg concentration with added Mg. Additions of Mg and K had small but important antagonistic effects. Microberlinia is Mg-demanding and apparently Mg-limited in Korup soil; Tetraberlinia, whilst K-demanding, appeared not to be K-limited (for growth). Added K enhanced plant P concentrations of both species. Extra applied Mg may also be alleviating soil aluminum toxicity, and hence improving growth indirectly and especially to the benefit of Microberlinia. Mg appears to be essential for Microberlinia seedling growth and its low soil availability in grove soils at Korup may be an important contributing factor to its poor recruitment. Microberlinia is highly shade-intolerant and strongly light-responding, whilst Tetraberlinia is more shade-tolerant and moderately light-responding, which affords an interesting contrast with respect to their differing responses to Mg supply. The study revealed novel aspects of functional traits and likely niche-partitioning among ectomycorrhizal caesalps in African rain forests. Identifying the direct and interacting indirect effects of essential elements on tropical tree seedling growth presents a considerable challenge due the complex nexus of causes involved.
Data from: Unusually limited pollen dispersal and connectivity of Pedunculate oak (Quercus robur) refugial populations at the species' southern range margin
Low-latitudinal range margins of temperate and boreal plant species typically consist of scattered populations that persist locally in microrefugia. It remains poorly understood how their refugial habitats affect patterns of gene flow and connectivity, key components for their long-term viability and evolution. We examine landscape-scale patterns of historical and contemporary gene flow in refugial populations of the widespread European forest tree Pedunculate oak (Quercus robur) at the species' southwestern range margin. We sampled all adult trees (n = 135) growing in a 20 km long valley and genotyped 724 acorns from 72 mother trees at 17 microsatellite loci. The ten oak stands that we identified were highly differentiated and formed four distinct genetic clusters, despite sporadic historical dispersal being detectable. By far most contemporary pollination occurred within stands, either between local mates (85.6%) or through selfing (6.8%). Pollen exchange between stands (2.6%) was remarkably rare given their relative proximity and was complemented by long-distance pollen immigration (4.4%) and hybridization with the locally abundant Quercus pyrenaica (0.6%). The frequency of between-stand mating events decreased with increasing size and spatial isolation of stands. Overall, our results reveal outstandingly little long-distance gene flow for a wind-pollinated tree species. We argue that the distinct landscape characteristics of oaks' refugial habitats, with a combination of a rugged topography, dense vegetation and humid microclimate, are likely to increase plant survival but to hamper effective long-distance pollen dispersal. Moreover, local mating might be favoured by high tree compatibility resulting from genetic purging in these long-term relict populations.
Data from: Small volume plasma exchange for Guillain-Barré syndrome in resource-limited settings: a phase II safety and feasibility study
OBJECTIVE: To assess the safety and feasibility of small volume plasma exchange (SVPE) as an alternative to standard plasma exchange (PE) or intravenous immunoglobulin (IVIg) for Guillain-Barré syndrome (GBS) patients. DESIGN: Non-randomized, single arm, interventional trial. SETTING: National Institute of Neurosciences and Hospital, Dhaka, Bangladesh. PARTICIPANTS: Twenty adult (>18 years) patients with GBS presented within 2 weeks of onset of weakness who were unable to walk unaided for more than 10 meters. INTERVENTIONS: SVPE involves blood cell sedimentation in a blood bag and removal of supernatant plasma after blood cells are re-transfused. This procedure was repeated three to six times a day, for eight consecutive days. OUTCOME MEASURES: Serious adverse events (SAE) were defined as severe sepsis and deep venous thrombosis related to the central vein catheter (CVC) used during SVPE. SVPE was considered safe if less than 5/20 patients experienced a SAE, and feasible if 8 L plasma could be removed within 8 days in at least 15/20 patients. RESULTS Median patient age 33 years (IQR 23-46; range 18-55); 13 (65%) were male. Median MRC sum score was 20 (IQR 0-29; range 0-36); three (15%) patients required mechanical ventilation. One patient developed SAE (severe sepsis, possibly related to CVC). Minor adverse effects were transient hypotension in 10 (50%) patients; CVC-associated bleeding in 10 (50%); transfusion reaction to fresh frozen plasma in 4 (20%); and hypo-albuminemia, anaemia or electrolyte imbalance in 4 (20%). Removal of 8 L plasma was possible in 15 (75%) patients. GBS disability score improved by at least one grade in 14 (70%) patients four weeks after SVPE started. No patients died. CONCLUSION: SVPE seems a safe and feasible alternative treatment to standard PE or IVIg for GBS; further studies of clinical efficacy in low-resource developing countries are warranted. TRIAL REGISTRATION: Clinicaltrials.gov NCT02780570 on May 23, 2016. Strength and limitations of the study: 1. The strength of this study underlies the novel and simple technique of SVPE, which is much less expensive than conventional immunotherapies (plasma exchange and intravenous immunoglobulin). 2. SVPE is corroborated as safe and feasible for the first time in a prospective and standardized cohort of patients with Guillain-Barré syndrome (GBS). 3. The intrinsic limitations of this study are its non-randomized, single arm nature, which is conducted in a single center with a limited sample size of GBS patients. 4. Clinical efficacy of SVPE on patients with GBS was a secondary end-point assessment and therefore deserves a randomized controlled trial in future to assess the clinical efficacy of SVPE for the patients with GBS.
Data from: Sensory limitations and the maintenance of color polymorphisms: viewing the 'alba' female polymorphism through the visual system of male Colias butterflies
Although color polymorphisms are a widespread and conspicuous component of extant biodiversity, the selective pressures that act to maintain multiple morphs within populations remain poorly understood in most cases. In particular, the role that visual system limitations may play in maintaining multiple color morphs is not well explored. We used a female-limited color polymorphism common to the butterfly genus Colias, called the 'alba' polymorphism, to investigate the hypotheses that mate-searching males may struggle to discriminate pale 'alba' females from co-occurring heterospecific white butterflies and/or heterospecific 'alba' females, or that 'alba' females may be more difficult to detect than non-'alba' females in natural scenes. Such perceptual limitations may influence the relative mating rates of 'alba' versus non-'alba' females, contributing to the evolutionary persistence of both morphs. Based on receptor-noise-limited modeling of the male Colias visual system, we find that 'alba' females exhibit chromatic and luminance contrasts against background foliage that are most similar to the 'alba' females of other co-occurring Colias species and females of the co-occurring white butterfly Pieris rapae. When compared to other co-flying butterflies including non-'alba' females, 'alba' females are consistently lower in chromatic contrast against background, but higher in luminance contrast. When viewed side-by-side, we estimate that male Colias should be able to discriminate 'alba' females from other co-occurring heterospecific butterflies, including heterospecific 'albas'. However, under field conditions that involve larger distances in space or time, males are likely to face challenges discriminating between conspecific 'alba' females and co-occurring heterospecific white butterflies, particularly heterospecific 'alba' females. Our results suggest that constraints arising from male visual function may be involved in the maintenance of this color polymorphism, particularly in populations that co-occur with other 'alba'-polymorphic Colias species. We argue that such visual system constraints may play a larger role in the maintenance of color polymorphism than has been empirically appreciated to date.
Data from: Do respiratory limitations affect metabolism of insect larvae before moulting: an empirical test at the individual level
Recent data suggest that oxygen limitation may induce moulting in larval insects. This oxygen dependent induction of moulting (ODIM) hypothesis stems from the fact that the tracheal respiratory system of insects grows primarily at moults, whereas tissue mass increases massively between moults. This may result in a mismatch between oxygen supply and demand at the end of each larval instar because oxygen demand of growing tissues exceeds the relatively fixed supply capacity of the respiratory system. The ODIM hypothesis predicts that, within larval instars, respiration and metabolic rates of an individual larva first increase with increasing body mass but eventually level off once the supply capacity of the tracheal system starts to constrain metabolism. Here, we provide the first individual-level test of this key prediction of the ODIM hypothesis. We use a novel methodology where we repeatedly measure respiration and metabolic rates throughout the penultimate- and final-instar larvae in the butterfly Pieris napi. In the penultimate instar, respiration and metabolic rates gradually decelerated along with growth, supporting the ODIM hypothesis. However, respiration and metabolic rates increased linearly during growth in the final instar, contradicting the prediction. Moreover, our data suggest considerable variation among individuals in the association between respiration rate and mass in the final instar. Overall, the results provide partial support for the ODIM hypothesis and suggest that oxygen limitation may emerge gradually within a larval instar. The results also suggest that there may be different moult induction mechanisms in larva-to-larva moults compared to the final metamorphic moult.
Data from: Migratory constraints on yolk precursors limit yolk androgen deposition and underlie a brood reduction strategy in rockhopper penguins
Hormonally mediated maternal effects link maternal phenotype and environmental conditions to offspring phenotype. The production of lipid-rich maternal yolk precursors may provide a mechanism by which lipophilic steroid hormones can be transported to developing yolks, thus predicting a positive correlation between yolk precursors in mothers and androgen levels in eggs. Using rockhopper penguins (Eudyptes chrysocome), which produce a two-egg clutch characterized by extreme egg-size dimorphism, reversed hatching asynchrony and brood-reduction, we examined correlations between circulating concentrations of the primary yolk-precursor vitellogenin (VTG) and levels of yolk androgens. Previous work in Eudyptes penguins has shown that egg-size dimorphism is the product of migratory constraints on yolk precursor production. We predicted that if yolk precursors are constrained, androgen transport to developing yolks would be similarly constrained. We reveal positive linear relationships between maternal VTG and androgens in small A-eggs but not larger B-eggs, which is consistent with a migratory constraint operating on the A-egg. Results suggest that intra-clutch variation in total yolk androgen levels depends on the production and uptake of yolk precursors. The brood reduction strategy common to Eudyptes might thus be best described as the result of a migratory constraint.
Data from: Evidence for inbreeding depression in a species with limited opportunity for maternal effects
It is often assumed that mating with close relatives reduces offspring fitness. In such cases, reduced offspring fitness may arise from inbreeding depression (i.e., genetic effects of elevated homozygosity) or from post-mating maternal investment. This can be due to a reduction in female investment after mating with genetically incompatible males ("differential allocation") or compensation for incompatibility ("reproductive compensation"). Here, we looked at the effects of mating with relatives on offspring fitness in mosquitofish, Gambusia holbrooki. In this species, females are assumed to be nonplacental and to allocate resources to eggs before fertilization, limiting differential allocation. We looked at the effects of mating with a brother or with an unrelated male on brood size, offspring size, gestation period, and early offspring growth. Mating with a relative reduced the number of offspring at birth, but there was no difference in the likelihood of breeding, gestation time, nor in the size or growth of these offspring. We suggest that due to limited potential for maternal effects to influence these traits that any reduction in offspring fitness, or lack thereof, can be explained by inbreeding depression rather than by maternal effects. We highlight the importance of considering the potential role of maternal effects when studying inbreeding depression and encourage further studies in other Poeciliid species with different degrees of placentation to test whether maternal effects mask or amplify any genetic effects of mating with relatives.
Data from: Herbivory and pollen limitation at the upper elevational range limit of two forest understory plants of eastern North America
Studies of species' range limits focus most often on abiotic factors, although the strength of biotic interactions might also vary along environmental gradients and have strong demographic effects. For example, pollinator abundance might decrease at range limits due to harsh environmental conditions, and reduced plant density can reduce attractiveness to pollinators and increase or decrease herbivory. We tested for variation in the strength of pollen limitation and herbivory by ungulates along a gradient leading to the upper elevational range limits of Trillium erectum (Melanthiaceae) and Erythronium americanum (Liliaceae) in Mont-Mégantic National Park, Québec, Canada. In T. erectum, pollen limitation was higher at the range limit, but seed set decreased only slightly with elevation and only in one of two years. In contrast, herbivory of T. erectum increased from <10% at low elevations to >60% at the upper elevational range limit. In E. americanum, we found no evidence of pollen limitation despite a significant decrease in seed set with elevation, and herbivory was low across the entire gradient. Overall, our results demonstrate the potential for relatively strong negative interactions (herbivory) and weak positive interactions (pollination) at plant range edges, although this was clearly species-specific. To the extent that these interactions have important demographic consequences – highly likely for herbivory on Trillium, based on previous studies – such interactions might play a role in determining plant species' range limits along putatively climatic gradients.
Data from: The scaling of parasite biomass with host biomass in lake ecosystems: are parasites limited by host resources?
The standing crop biomass of different populations or trophic levels reflects patterns of energy flow through an ecosystem. The contribution of parasites to total biomass is often considered negligible; recent evidence suggests otherwise, although it comes from a narrow range of natural systems. Quantifying how local parasite biomass, whether that of a single species or an assemblage of species sharing the same host, varies across localities with host population biomass, is critical to determine what constrains parasite populations. We use an extensive dataset on all free-living and parasitic metazoan species from multiple sites in New Zealand lakes to measure parasite biomass and test how it covaries with host biomass. In all lakes, trematodes had the highest combined biomass among parasite taxa, ranging from about 0.01 to 0.25 g m−2, surpassing the biomass of minor free-living taxa. Unlike findings from other studies, the life stage contributing the most to total trematode biomass was the metacercarial stage in the second intermediate host, and not sporocysts or rediae within snail first intermediate hosts, possibly due to low prevalence and small snail sizes. For populations of single parasite species, we found no relationship between host and parasite biomass for either juvenile or adult nematodes. In contrast, all life stages of trematodes had local biomasses that correlated positively with those of their hosts. For assemblages of parasite species sharing the same host, we found strong relationships between local host population biomass and the total biomass of parasites supported. In these host–parasite biomass relationships, the scaling factor (slope in log-log space) suggests that parasites may not be making full use of available host resources. Host populations appear capable of supporting a little more parasite biomass, and may be open to expansion of existing parasites or invasion by new ones.
Data from: Tracing coco de mer's reproductive history: pollen and nutrient limitation reduce fecundity
Habitat degradation can reduce or even prevent the reproduction of previously abundant plant species. To develop appropriate management strategies, we need to understand the reasons for reduced recruitment in degraded ecosystems. The dioecious coco de mer palm (Lodoicea maldivica) produces by far the largest seeds of any plant. It is a keystone species in an ancient palm forest that occurs only on two small islands in the Seychelles, yet contemporary rates of seed production are low, especially in fragmented populations. We developed a method to infer the recent reproductive history of female trees from morphological evidence present on their inflorescences. We then investigated the effects of habitat disturbance and soil nutrient conditions on flower and fruit production. The 57 female trees in our sample showed a 19.5-fold variation in flower production among individuals over a seven-year period. Only 77.2% of trees bore developing fruits (or had recently shed fruits), with the number per tree ranging from zero to 43. Flower production was positively correlated with concentrations of available soil nitrogen and potassium, and did not differ significantly between closed and degraded habitat. Fruiting success was positively correlated with pollen availability, as measured by numbers and distance of neighbouring male trees. Fruit-set was lower in degraded habitat than in closed forest, while the proportion of abnormal fruits that failed to develop was higher in degraded habitat. Seed size recorded for a large sample of seeds varied widely, with fresh weights ranging from 1 to 18 kg. Shortages of both nutrients and pollen appear to limit seed production of Lodoicea in its natural habitat, with these factors affecting different stages of the reproductive process. Flower production varies widely amongst trees, while seed production is especially low in degraded habitat. The size of seeds is also very variable. We discuss the implications of these findings for managing this ecologically and economically important species.
Data from: Variation in life-history traits among Daphnia and its relationship to species-level responses to phosphorus limitation
Currently organisms are experiencing changes in their environment at an unprecedented rate. Therefore the study of the contributions to and responses in traits linked to fitness is crucial, as they have direct consequences on a population's success in persisting under such change. Daphnia is used as a model organism as the genus contains keystone primary consumers in aquatic food webs. A life-history table experiment (LHTE) using four species of Daphnia was conducted to compare variation in life-history traits among species across two different environmental conditions (high and low phosphorous availability). Results indicate that the food quality environment had the most impact on life-history traits, while genetic contributions to traits were higher at the species-level than clonal-level. Higher trait variation and species-level responses to P-limitation was more evident in reproductive traits, while growth traits were found to be less affected by food quality and had less variation. Exploring trait variation and potential plasticity in organisms is increasingly important to consider as a potential mechanism for population persistence given the fluctuations in environmental stressors we are currently experiencing.
Data from: Habitat filtering not dispersal limitation shapes oceanic island floras: species assembly of the Galápagos archipelago
Remote locations, such as oceanic islands, typically harbour relatively few species, some of which go on to generate endemic radiations. Species colonising these locations tend to be a non-random subset from source communities, which is thought to reflect dispersal limitation. However, non-random colonisation could also result from habitat filtering, whereby only a few continental species can become established. We evaluate the imprints of these processes on the Galápagos flora by analysing a comprehensive regional phylogeny for ~ 39 000 species alongside information on dispersal strategies and climatic suitability. We found that habitat filtering was more important than dispersal limitation in determining species composition. This finding may help explain why adaptive radiation is common on oceanic archipelagoes – because colonising species can be relatively poor dispersers with specific niche requirements. We suggest that the standard assumption that plant communities in remote locations are primarily shaped by dispersal limitation deserves reconsideration.
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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.