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A molecular phylogeny of historical and contemporary specimens of an under-studied micro-invertebrate group
<p>Resolution of relationships at lower taxonomic levels is crucial for answering many evolutionary questions, and as such, sufficiently varied species representation is vital. This latter goal is not always achievable with relatively fresh samples. To alleviate the difficulties in procuring rarer taxa, we have seen increasing utilization of historical specimens in building molecular phylogenies using high throughput sequencing. This effort, however, has mainly focused on large-bodied or well-studied groups, with small-bodied and under-studied taxa under-prioritized. Here, we utilize both historical and contemporary specimens, to increase the resolution of phylogenetic relationships among a group of under-studied and small-bodied metazoans, namely, cheilostome bryozoans. In this study, we pioneer sequencing of air-dried cheilostomes, utilizing a recent library preparation method for low DNA input. We evaluate a <i>de novo</i> mitogenome assembly and two iterative methods, using the sequenced target specimen as a reference for mapping, for our sequences. In doing so, we present mitochondrial and ribosomal RNA sequences of 43 cheilostomes representing 37 species, including 14 from historical samples ranging from 50 to 149 years old. The inferred phylogenetic relationships of these samples, analyzed together with publicly available sequence data, are shown in a statistically well-supported 65 taxa and 17 genes cheilostome tree, which is also the most broadly sampled and largest to date. The robust phylogenetic placement of historical samples whose contemporary conspecifics and or congenerics have been sequenced verify the appropriateness of our workflow and give confidence in the phylogenetic placement of those historical samples for which there are no close relatives sequenced. The success of our workflow is highlighted by the circularization of a total of 27 mitogenomes, seven from historical cheilostome samples. Our study highlights the potential of utilizing DNA from micro-invertebrate specimens stored in natural history collections for resolving phylogenetic relationships among species.</p>
Parentage analyses identify local dispersal events and sibling aggregations in a natural population of Millepora hydrocorals, a free-spawning marine invertebrate
<p><span><span><span><span><span><span><span><span><span><span><span>Dispersal is a critical process for the persistence and productivity of marine populations. For many reef species, there is increasing evidence that local demography and self-recruitment have major consequences on their genetic diversity and adaptation to environmental change. Yet empirical data of dispersal patterns in reef-building species remain scarce. Here, we document the first genetic estimates of self-recruitment and dispersal distances in a free-spawning marine invertebrate, the hydrocoral <i>Millepora platyphylla</i>. Using twelve microsatellite markers, we gathered genotypic information from 3,160 georeferenced colonies collected over 9,000 m<sup>2</sup> of a single reef in three adjacent habitats in Moorea, French Polynesia; the mid slope, upper slope, and back reef. Although the adult population was predominantly clonal (85% were clones), our parentage analysis revealed a moderate self-recruitment rate with 8 to 37% of sexual propagules produced locally. Assigned offspring often settled at less than 10 meters from their parents and dispersal events decrease with increasing geographic distance. There were no discrepancies between the dispersal distances of offspring assigned to parents belonging to clonal <i>versus</i> non-clonal genotypes. Inter-habitat dispersal events via cross-reef transport were also detected for sexual and asexual propagules. Sibship analysis showed that full siblings recruit together on the reef (more than 40% settled at < 30 m), resulting in sibling aggregations. Our findings highlight the importance of self-recruitment together with clonality in stabilizing population dynamics, which may ultimately enhance local sustainability and resilience to disturbance.</span></span></span></span></span></span></span></span></span></span></span></p>
Data from: Ocean warming affected faunal dynamics of benthic invertebrate assemblages across the Toarcian Oceanic Anoxic Event in the Iberian Basin (Spain)
<p>The Toarcian Oceanic Anoxic Event (TOAE; Early Jurassic, ca. 182 Ma ago) represents one of the major environmental disturbances of the Mesozoic and is associated with global warming, widespread anoxia, and a severe perturbation of the global carbon cycle. Warming-related dysoxia-anoxia has long been considered the main cause of elevated marine extinction rates, although extinctions have been recorded also in environments without evidence for deoxygenation. We addressed the role of warming and disturbance of the carbon cycle in an oxygenated habitat in the Iberian Basin, Spain, by correlating high resolution quantitative faunal occurrences of early Toarcian benthic marine invertebrates with geochemical proxy data (δ<sup>18</sup>O and δ<sup>13</sup>C). We find that temperature, as derived from the δ<sup>18</sup>O record of shells, is significantly correlated with taxonomic and functional diversity and ecological composition, whereas we find no evidence to link carbon cycle variations to the faunal patterns. The local faunal assemblages before and after the TOAE are taxonomically and ecologically distinct. Most ecological change occurred at the onset of the TOAE, synchronous with an increase in water temperatures, and involved declines in multiple diversity metrics, abundance, and biomass. The TOAE interval experienced a complete turnover of brachiopods and a predominance of opportunistic species, which underscores the generality of this pattern recorded elsewhere in the western Tethys Ocean. Ecological instability during the TOAE is indicated by distinct fluctuations in diversity and in the relative abundance of individual modes of life. Local recovery to ecologically stable and diverse post-TOAE faunal assemblages occurred rapidly at the end of the TOAE, synchronous with decreasing water temperatures. Because oxygen-depleted conditions prevailed in many other regions during the TOAE, this study demonstrates that multiple mechanisms can be operating simultaneously with different relative contributions in different parts of the ocean.</p>
Environmental DNA metabarcoding of cow dung reveals taxonomic and functional diversity of invertebrate assemblages
<p>Insects and other terrestrial invertebrates are declining in species richness and abundance. This includes the invertebrates associated with herbivore dung, which have been negatively affected by grazing abandonment and the progressive loss of large herbivores since the Late Pleistocene. Importantly, traditional monitoring of these invertebrates is time-consuming and requires considerable taxonomic expertise, which is becoming increasingly scarce. In this study, we investigated the potential of environmental DNA (eDNA) metabarcoding of cow dung samples for biomonitoring of dung-associated invertebrates. From eight cow pats we recovered eDNA from 12 orders, 29 families, and at least 54 species of invertebrates (mostly insects), representing several functional groups. Furthermore, species compositions differed between the three sampled habitats of dry grassland, meadow, and forest. These differences were in accordance with the species' ecology; for instance, several species known to be associated with humid conditions or lower temperatures were found only in the forest habitat. We discuss potential caveats of the method, as well as directions for future study and perspectives for implementation in research and monitoring.</p>
Data from: When does growth rate influence fitness in a colonial marine invertebrate?
<p>Growth rate affects body size, and larger body sizes are often associated with the capacity to produce more surviving offspring. However, the assumption that growth rate should positively relate to fitness is rarely tested, especially in colonial marine invertebrates where size and age can be decoupled. We measured growth, survival, and reproduction through repeated census of 97 colonies from two populations of a marine bryozoan in the field from settlement to the end of their reproductive season in the northern Gulf of Mexico. Despite large population differences in fitness when grown in a common garden setting, selection within populations on variation in relative growth rate prior to reproduction was similar. In both populations, colonies that grew faster early after settlement, hence were larger, did not consistently have higher fitness than colonies that grew slower after settlement. Instead, early juvenile growth was uncorrelated to later juvenile growth, and colonies that grew faster just prior to the onset of reproduction had higher fitness than colonies that grew slower during this time. Growth rates then declined with the onset of reproduction. Our results show that, rather than being a simple consequence of selection on body size, growth rate can directly affect variation in fitness in ways that are not directly attributable to juvenile size. Colony size and growth rate in modular animals are not always reliable surrogates for direct estimates of survival and reproduction, without identifying when and how growth affects fitness.</p>
MEDI: Macronutrient Extraction and Determination from Invertebrates, a rapid, cheap and streamlined protocol
<p>Macronutrients, comprising carbohydrates, proteins and lipids, underpin many ecological processes, but their quantification in ecological studies is often inaccurate and laborious, requiring large investments of time and bulk samples, which make individual-level studies impossible. This study presents MEDI (Macronutrient Extraction and Determination from Invertebrates), a protocol for the direct, rapid and relatively low-cost determination of macronutrient content from single small macroinvertebrates.</p> <p>Macronutrients were extracted by a sequential process of soaking in 1:12 chloroform:methanol solution to remove lipid and then solubilizing tissue in 0.1 M NaOH. Proteins, carbohydrates and lipids were determined by colorimetric assays from the same individual specimens.</p> <p>The limits of detection of MEDI with the equipment and conditions used were 0.067 mg ml-1, 0.065 mg ml-1 and 0.006 mg ml-1 for proteins, carbohydrates and lipids, respectively. Adjusting the volume of reagents used for extraction and determination can broaden the range of concentrations that can be detected. MEDI successfully identified taxonomic differences in macronutrient content between five insect species.</p> <p>MEDI can directly and rapidly determine macronutrient content in tiny (dry mass ~3 mg) and much larger individual invertebrates. Using MEDI, the total macronutrient content of over 50 macroinvertebrates can be determined within around three days of collection at a cost of ~$1.35 per sample.</p>
Stochastic processes and ecological connectivity drive stream invertebrate community responses to short-term drought
1. Community responses to and recovery from disturbances depend on local (e.g. presence of refuges) and regional (connectivity to recolonization sources) factors. Droughts are becoming more frequent in boreal regions, and are likely to constitute a severe disturbance for boreal stream communities where organisms largely lack adaptations to such hydrological extremes. 2. We conducted an experiment in 24 seminatural stream flumes to assess the effects of local and regional factors on the responses of benthic invertebrate communities to a short-term drought. We manipulated flow (drought vs. constant-flow), spatial arrangement of leaf litter patches (aggregated vs. evenly distributed) and colonization from regional species pool (enhanced vs. ambient connectivity) to test the combined effects of disturbance, connectivity, and resource arrangement on the structural and functional responses of benthic invertebrate communities. 3. We found that a drought as short as one week reduced invertebrate richness and abundances, mainly through stochastic extinctions. Such changes in richness were not reflected in functional diversity. This suggests that communities were characterized by a high degree of functional redundancy, which allowed maintenance of functional diversity despite species losses. Feeding groups responded differently to drought, with organic matter decomposers responding more than scrapers and predators. 4. Three weeks was insufficient for a complete invertebrate community recovery from the drought. However, recovery was greater in channels subjected to enhanced connectivity, which increased taxonomic diversity and abundance of certain taxa. Spatial configuration of resources explained the least variation in our response variables, having a significant effect only on invertebrate abundance and evenness (both sampling occasions) and species richness (end of recovery period). 5. Even a short drought, if occurring late to the season, may not allow communities to recover before the onset of winter, thus having a potentially long-lasting effect on stream communities. For boreal headwaters, extreme dewatering poses a novel disturbance regime that may trigger substantial and potentially irreversible changes. An improved understanding of such changes is needed to underpin adaptive management strategies in these increasingly fragmented and disturbed ecosystems. 18-Dec-2020
Supplementary material 1 from: Weigand AM, Desquiotz N, Weigand H, Szucsich N (2021) Application of propylene glycol in DNA-based studies of invertebrates. Metabarcoding and Metagenomics 5: e57278. https://doi.org/10.3897/mbmg.5.57278
Overview of DNA-based studies of invertebrates applying propylene glycol, sorted by year and taxonomic group
Data from: Abundance data applied to a novel model invertebrate host sheds new light on parasite community assembly in nature
<ol> <li>Understanding how environmental drivers influence the assembly of parasite communities, in addition to how parasites may interact at an infracommunity level, are fundamental requirements for the study of parasite ecology. Knowledge of how parasite communities are assembled will help to predict the risk of parasitism for hosts, and model how parasite communities may change under variable conditions. However, studies frequently rely on presence-absence data and examine multiple host species or sites, metrics which may be too coarse to characterise nuanced within-host patterns.</li> <li>We utilised a novel host system, the freshwater mussel <i>Anodonta anatina</i>, to investigate the drivers of community structure and explore parasite interactions. In addition, we aimed to highlight consistencies and inconsistencies between presence-absence and abundance data.</li> <li>Our analysis incorporated 14 parasite taxa and 720 replicate infracommunities. Using redundancy analysis, a joint species distribution model and a Markov random fields approach, we modelled the impact of both host-level and environment-level characteristics on parasite structure, as well as parasite-parasite correlations after accounting for all other factors. This approach was repeated for both the presence and abundance of all parasites.</li> <li>We demonstrated that the regional species pool, individual host characteristics (mussel length and gravidity) and predicted parasite-parasite interactions are all important but to varying degrees across parasite species, suggesting that applying generalities to parasite community construction is too simplistic. Further, we showed that presence-absence data fails to capture important density-dependent effects of parasite load for parasites with high abundance, and in general performs poorly for high-intensity parasites.</li> <li>Host and parasite traits, as well as broader environmental factors, all contribute to parasite community structure, emphasising that an integrated approach is required to study community assembly. However, care must be taken with the data used to infer patterns, as presence-absence data may lead to incorrect ecological inference.</li> </ol>
Data from: Complex indirect effects of epiphytic bromeliads on the invertebrate food webs of their support tree
Ecosystem engineers are species that affect others through the provision of habitat rather than consumptive resources. The extent to which ecosystem engineers can indirectly affect entire food webs, however, is poorly understood. Epiphytic tank bromeliads (Bromeliaceae) are ecosystem engineers that are common throughout the Neotropics, and are associated with a variety of predatory arthropods. Here, we examine if bromeliads, by increasing predator densities, indirectly benefit their support tree through reduction in herbivorous insects and leaf damage. We observed and manipulated bromeliad densities in Costa Rican orange orchards, and measured impacts on leaf damage and arboreal and bromeliad invertebrate communities in two different seasons. Our results show that bromeliads are associated with predatory and herbivorous invertebrates but not leaf damage. Bromeliads were correlated with increased densities of their associated predators, especially ants and hunting spiders, but we could not confirm a causal link. Associations with bromeliads changed over time, with seasonal shifts interfering with responses to our manipulations. Bromeliads had a reduced association with predators in the dry season. Moreover, a null association between bromeliads and herbivorous invertebrates in the dry season unexpectedly became positive in the wet season. In summary, we have only limited evidence that bromeliads indirectly promote the top-down control of arboreal herbivores; instead, our manipulations suggest that bromeliads increase herbivore densities in the wet season. This research suggests that although bromeliads may act as ecosystem engineers, indirectly influencing the invertebrate food web on support trees, their effects are trophically complex and seasonally dependent.
Data from: Individual marking of soft-bodied subtidal invertebrates in situ - a novel staining technique applied to the giant plumose anemone Metridium farcimen (Tilesius, 1809)
The ability to recognize individuals and track growth over time is crucial to population dynamics research as well as studies of animal behavior. Invertebrates are particularly difficult to track as they often molt, have regenerative capabilities, or lack hard parts to attach markers. We tested, in laboratory and field studies, a new way of marking sea anemones (order Actiniaria) by injection of three vital stains (i.e., neutral red, methylene blue, and fluorescein). Neutral red and methylene blue did not affect growth or survival, but fluorescein was lethal at high concentrations. Marked individuals could be identified up to seven months after injection with neutral red, six weeks with methylene blue, and three days with low concentrations of fluorescein. Neutral red could be used for long-term monitoring of growth and survival in the field, and in combination with methylene blue could be used to mark individuals in distinguishable patterns for short-term studies such as examining predator-prey interactions, movement of individuals, and recruitment survival.
Data from: Invertebrate biodiversity in cold groundwater fissures in Iceland
Iceland has an abundance of fissures that are parallel to the Mid-Atlantic ridge where bedrock cracks as a result of continental rifting. Some fissures penetrate the aquifer and expose the groundwater within the bedrock, becoming springs. As such, groundwater fissures have uniform and constant physical and chemical environment but they can differ greatly in morphology. In addition, there is often great variation in depth within fissures and substrate types contrast between vertical rock wall and more heterogenous horizontal bottom. The variation in morphological environment may create dissimilar habitats with unique characteristics and/or influence distribution of resources. Our objective was to study macrozoobenthos communities in cold groundwater fissures in Iceland in relation to physical habitat by comparing invertebrate diversity and density both between fissures with different morphological characteristics as well as between substrate types and depths within fissures. Samples were collected in two fissures in SW Iceland, Silfra and Flosagjá. Assemblages were similar between fissures except for higher densities of cladocerans in Flosagjá fissure. Within fissures, there was significant difference in Shannon diversity between substrate types in Flosgjá and ostracods were found in significantly higher densities on bottom. The distribution of all other taxa groups was homogenous in both fissures regardless of depth gradient and substrate. Invertebrates were found to be living within and around a biofilm that covered the entire substrate. These biofilm mats are made from Cyanobacteria and benthic diatoms, which are successful under low light conditions and may minimize any effect of the heterogeneous habitat creating a uniform and suitable microhabitat for invertebrates regardless of depth and substrate type.
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: A parallel population genomic and hydrodynamic approach to fishery management of highly-dispersive marine invertebrates: the case of the Fijian black-lip pearl oyster Pinctada margaritifera
Fishery management and conservation of marine species increasingly relies on genetic data to delineate biologically relevant stock boundaries. Unfortunately for high gene flow species which may display low, but statistically significant population structure, there is no clear consensus on the level of differentiation required to resolve distinct stocks. The use of fine-scale neutral and adaptive variation, considered together with environmental data can offer additional insights to this problem. Genome-wide genetic data (4,123 SNPs), together with an independent hydrodynamic particle dispersal model were used to inform farm and fishery management in the Fijian black-lip pearl oyster Pinctada margaritifera, where comprehensive fishery management is lacking, and the sustainability of exploitation uncertain. Weak fine-scale patterns of population structure were detected, indicative of broad-scale panmixia among wild oysters, while a hatchery-sourced farmed population exhibited a higher degree of genetic divergence (Fst = 0.0850–0.102). This hatchery-produced population had also experienced a bottleneck (NeLD = 5.1; 95% C.I. = [5.1–5.3]); compared to infinite NeLD estimates for all wild oysters. Simulation of larval transport pathways confirmed the existence of broad-scale mixture by surface ocean currents, correlating well with fine-scale patterns of population structuring. Fst outlier tests failed to detect large numbers of loci supportive of selection, with 2–5 directional outlier SNPs identified (average Fst = 0.116). The lack of biologically significant population genetic structure, absence of evidence for local adaptation and larval dispersal simulation, all indicate the existence of a single genetic stock of P. margaritifera in the Fiji Islands. This approach using independent genomic and oceanographic tools has allowed fundamental insights into stock structure in this species, with transferability to other highly-dispersive marine taxa for their conservation and management.
Data from: Travelling at a slug's pace: possible invertebrate vectors of Caenorhabditis nematodes
Background: How do very small animals with limited long-distance dispersal abilities move between locations, especially if they prefer ephemeral micro-habitats that are only available for short periods of time? The free-living model nematode Caenorhabditis elegans and several congeneric taxa appear to be common in such short-lived environments, for example decomposing fruits or other rotting plant material. Dispersal is usually assumed to depend on animal vectors, yet all current data is based on only a limited number of studies. In our project we performed three comprehensive field surveys on possible invertebrate vectors in North German locations containing populations of C. elegans and two related species, especially C. remanei, and combined these screens with an experimental analysis of persistence in one of the vector taxa. Results: Our field survey revealed that Caenorhabditis nematodes are commonly found in slugs, isopods, and chilopods, but are not present in the remaining taxonomic groups examined. Surprisingly, the nematodes were frequently isolated from the intestines of slugs, even if slugs were not collected in close association with suitable substrates for Caenorhabditis proliferation. This suggests that the nematodes are able to enter the slug intestines and persist for certain periods of time. Our experimental analysis confirmed the ability of C. elegans to invade slug intestines and subsequently be excreted alive with the slug feces, although only for short time periods under laboratory conditions. Conclusions: We conclude that three invertebrate taxonomic groups represent potential vectors of Caenorhabditis nematodes. The nematodes appear to have evolved specific adaptations to enter and persist in the harsh environment of slug intestines, possibly indicating first steps towards a parasitic life-style.
Data from: DNA-based analysis of regurgitates: a noninvasive approach to examine the diet of invertebrate consumers
DNA-based gut content analysis has become an important tool for unravelling feeding interactions in invertebrate communities under natural conditions. It usually implies killing of the consumer and extracting the DNA from its food, either using the whole animal or its dissected gut. This post-mortem approach, however, is not suitable for investigating the diet of rare or protected species and also prohibits tracking individual dietary preferences as each consumer can provide trophic information only once. Moreover, removing large numbers of consumers from a habitat for analysis might critically change population densities and affect species interactions. Here, we present DNA-based analysis of invertebrate regurgitates, a novel approach to overcome these limitations. Conducting feeding experiments where adult Poecilus cupreus (Coleoptera: Carabidae) were fed with larvae of Amphimallon solstitiale (Coleoptera: Scarabaeidae), we show that detection success in regurgitates compared to samples prepared from whole beetles was similar or significantly enhanced for small/medium and large prey DNA fragments, respectively. Prey DNA detection success remained high in regurgitates stored in ethanol for 21 months at room temperature prior to DNA extraction. We conclude that in those invertebrates where regurgitates can be obtained, examination of food DNA in regurgitates offers many advantages over conventional post-mortem gut content analysis.
Data from: A multispecies approach reveals hot-spots and cold-spots of diversity and connectivity in invertebrate species with contrasting dispersal modes
Genetic diversity is crucial for species' maintenance and persistence, yet is often overlooked in conservation studies. Species diversity is more often reported due to practical constraints, but it is unknown if these measures of diversity are correlated. In marine invertebrates, adults are often sessile or sedentary and populations exchange genes via dispersal of gametes and larvae. Species with a larval period are expected to have more connected populations than those without larval dispersal. We assessed the relationship between measures of species and genetic diversity, and between dispersal ability and connectivity. We compiled data on genetic patterns and life history traits in nine species across five phyla. Sampling sites spanned 600 km in the northwest Mediterranean Sea and focused on a 50 km area near Marseilles, France. Comparative population genetic approaches yielded three main results. (1) Species without larvae showed higher levels of genetic structure than species with free-living larvae but the role of larval type (lecithotrophic or planktotrophic) was negligible. (2) A narrow area around Marseilles, subject to offshore advection, limited genetic connectivity in most species. (3) We identified sites with significant positive contributions to overall genetic diversity across all species, corresponding with areas near low human population densities. In contrast, high levels of human activity corresponded with a negative contribution to overall genetic diversity. Genetic diversity within species was positively and significantly linearly related with local species diversity. Our study suggests that local contribution to overall genetic diversity should be taken into account for future conservation strategies.
Data from: Using survival models to estimate invertebrate prey identification times in a generalist stream fish
Estimates of predator feeding rates are important for understanding trophic dynamics. One common method for quantifying feeding rates in fishes combine mass-based diet data with gastric evacuation times to estimate prey mass consumed per predator. An alternative approach is to estimate rates of prey individuals consumed using prey identification times − the time period over which prey remain identifiable in a predator's stomach. One challenge with the analysis of prey identification times, however, is that the response variable is likely to be censored because the 'true' prey identification time cannot be observed directly. Here, we applied survival analysis that can incorporate censored data to estimate the effects of predator body size, water temperature, and prey characteristics (type, count and body size) on identification times in reticulate sculpin (Cottus perplexus). We focused on seven types of prey that are common in this generalist predator's diet: mayflies (Ephemeroptera), caddisflies (Trichoptera), stoneflies (Plecoptera), flies (Diptera), beetles (Coleoptera), worms (Annelida), and sculpin eggs. An information-theoretic model comparison approach indicated that an accelerated failure-time Weibull model with all five covariates provided the best relative fit to the full dataset. Prey type had a strong effect on prey identification times, with annelid worms having the shortest times (< 1 hr) and caddisflies having the longest times (> 15 hrs). Water temperature decreased prey identification times (7.5% per 1°C increase), whereas prey count (i.e. meal size) increased prey identification times (15.5% per additional prey item). Sculpin body size had a weak negative effect on prey identification times (0.04% per 1 mm increase). Body sizes of some taxa, including mayflies, caddisflies, and stoneflies, increased prey identification times, leading to an interaction between prey type and prey size. Our study highlights the utility of survival analysis to quantify variation in prey identification times in the diets of generalist predators.
Data from: Climate-driven hydrological variability determines inter-annual changes in stream invertebrate community assembly
Although flow regime is one of the major drivers of riverine communities, not much is known about how inter-annual variability and extremes of flow influence community assembly mechanisms. We used data on benthic macroinvertebrates and modelled flow regimes in 23 near-pristine boreal streams to assess how community assembly mechanisms and species occupancy varied in response to inter-annual variability in flow conditions across 11 successive years encompassing extreme (both low and high) flow events. A null model approach was used to test whether deterministic or stochastic processes dominated community assembly and how much regional (among-stream) flow variability contributed to community variability (β-diversity). Mean daily flow and the greatest rate of flow rise were the strongest flow-related descriptors of invertebrate community composition. Communities were differentially assembled depending on the direction of change in flow magnitude: in high-flow years, communities were more similar than expected by chance, while at low flows they tended to be more dissimilar than expected. Beta-diversity of macroinvertebrate communities was related to among-stream flow variability only at high flows. Common species correlated strongly with flow variability and contributed most to variation in β-diversity, suggesting that changes in assembly mechanisms are mainly driven by common species. While homogenization of communities in high-flow years reflected increased species occupancies and environmental sorting, increased turnover during low flows likely resulted from stochastic extinctions and dispersal limitation. Our findings suggest that extreme hydrological events exert a strong control over stream invertebrate community assembly, and their effect may be even more profound in the future as high and low-flow spells are expected to occur more frequently, not allowing time for communities to recover.
Data from: Inbreeding shapes the evolution of marine invertebrates
<p>Inbreeding is a potent evolutionary force shaping the distribution of genetic variation within and among populations of plants and animals. Yet, our understanding of the forces shaping the expression and evolution of non-random mating in general, and inbreeding in particular, remains remarkably incomplete. Most research on plant mating systems focuses on self-fertilization and its consequences for automatic selection, inbreeding depression, purging, and reproductive assurance, whereas studies of animal mating systems have often assumed that inbreeding is rare, and that natural selection favors traits that promote outbreeding. Given that many sessile and sedentary marine invertebrates and marine macroalgae share key life-history features with seed plants (<i>e.g</i>., low mobility, modular construction, and the release of gametes into the environment), their mating systems may be similar. Here, we show that published estimates of inbreeding coefficients (<i>F<sub>IS</sub></i>) for sessile and sedentary marine organisms are similar and at least as high as noted in terrestrial seed plants. We also found that variation in <i>F<sub>IS</sub></i> within invertebrates is related to the potential to self-fertilize, disperse, and choose mates. The similarity of <i>F<sub>IS</sub> </i>for these organismal groups suggests that inbreeding could play a larger role in the evolution of sessile and sedentary marine organisms than is currently recognized. Specifically, associations between traits of marine invertebrates and <i>F<sub>IS</sub></i> suggest that inbreeding could drive evolutionary transitions between hermaphroditism and separate sexes, direct development and multiphasic life cycles, and external and internal fertilization.</p>
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Annotated Behaviour and Observability Dataset (ABODe)
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