Search

Group-living organisms offer a unique perspective on how environmental gradients influence geographic distributions, as not only the properties of individuals, but also those of their groups interact with the environment to determine a species range. In turn, the ranges of group-living organisms should provide insights on the conditions that favor group versus solitary living. Here we show that rain intensity and predation by ants, factors postulated to exclude subsocial Anelosimus spiders from the lowland tropical rainforest, are greater in this habitat than at higher elevations. We further show that experimentally excluding these factors increases the survival of subsocial Anelosimus colonies when transplanted to the lowland rainforest, but not at their native higher elevation range. While providing a rare experimental test of the simultaneous importance of abiotic and biotic gradients on species range limits, these results provide direct evidence that adverse environmental factors may prevent solitary living and require group living in certain environments. [ABSTRACT FROM AUTHOR]

Studies of venom variability have advanced from describing the mechanisms of action and relative potency of medically important toxins to understanding the ecological and evolutionary causes of the variability itself. While most studies have focused on differences in venoms among taxa, populations, or age-classes, there may be intersexual effects as well. Striped bark scorpions (Centruroides vittatus) provide a good model for examining sex differences in venom composition and efficacy, as this species exhibits dramatic sexual dimorphism in both size and defensive behavior; when threatened by an enemy, larger, slower females stand and fight while smaller, fleeter males prefer to run. We here add evidence suggesting that male and female C. vittatus indeed have different defensive propensities; when threatened via an electrical stimulus, females were more likely to sting than were males. We reasoned that intersexual differences in defensive phenotypes would select for venoms with different functions in the two sexes; female venoms should be effective at predator deterrence, whereas male venoms, less utilized defensively, might be better suited to capturing prey or courting females. This rationale led to our predictions that females would inject more venom and/or possess more painful venom than males. We were wrong. While females do inject more venom than males in a defensive sting, females are also larger; when adjusted for body size, male and female C. vittatus commit equal masses of venom in a sting to a potential enemy. Additionally, house mice (Mus musculus) find an injection of male venom more irritating than an equal amount of female venom, likely because male venom contains more of the toxins that induce pain. Taken together, our results suggest that identifying the ultimate causes of venom variability will, as we move beyond adaptive storytelling, be hard-won. [ABSTRACT FROM AUTHOR]

It is increasingly evident that cryptic stages of many parasites cause asymptomatic infections in a diversity of hosts. This review examines what may cause these infectious agents to persist as asymptomatic infections in invertebrates and how environmental change is linked with the subsequent development of overt infection and disease. In many systems, disease dynamics are closely associated with host condition which, in turn, is linked with environmental change. Symbionts (commensals and mutualists) display similar dynamics when environmental change causes them to exert negative effects on their hosts. Although such asymptomatic infections are demonstrated in a range of invertebrate hosts they are greatly undersampled because most invertebrate diseases are uninvestigated, infections are difficult to detect, and many parasite groups are poorly characterized. A better understanding of the diversity and distribution of parasites that cause asymptomatic infections and of their complex relationships with invertebrate hosts will enable a fuller appreciation of context-dependent host-parasite interactions and will address the biased focus on diseases of invertebrates of practical importance. The existence of such infections could underlie novel disease outbreaks that might otherwise be attributed to invasives while altered disease dynamics may provide an additional and complementary indicator of ecosystem change. [ABSTRACT FROM AUTHOR]

Arsenic (As) can play an important role in the contamination of soils, waters, and air. The toxicity of As to most organisms is well established, but little is known about the interactions between environmental As and terrestrial invertebrates and the fate of As through trophic levels. Pteris vittata L. (Polypodiales: Pteridaceae), a fern that hyperaccumulates arsenic, serves as a potential mechanism to facilitate interactions between environmental arsenic and other biota. We compared invertebrate arsenic concentrations (hereafter as [As]) and bioaccumulation factors associated with soil and fern [As] to elucidate relationships between invertebrate and environmental As exposure. We collected invertebrates in pitfall traps from field sites associated with P. vittata, and identified them to order for whole body arsenic analysis and subsequently family for classification into functional feeding groups. We found that overall [As] in invertebrates increased with soil [As], but not with fern [As]. The absence of a relationship between fern [As] and invertebrate [As] may indicate invertebrates are avoiding the fern. Individual taxonomic groups significantly differed in whole body [As], and individual taxa also varied in their relationship between whole body [As] relative to soil and fern [As]. Overall invertebrate abundance decreased as invertebrate [As] load increased but varied across taxa. One particular herbivore, Callopistria floridensis (Florida fern caterpillar), associated with relatively low environmental As exposure contained over 4,000mg kg-1 As. Our results show that As bioaccumulates into higher trophic levels and invertebrate body [As] covary with exposure to naturally occurring environmental [As] associated with P. vittata. [ABSTRACT FROM AUTHOR]

We examined how leaf litter of alien invasive honeysuckle (Lonicera maackii Rupr.) either alone or in combination with leaf litter of one of two native tree species, sugar maple (Acer saccharum Marshall) and northern red oak (Quercus rubra L.), affects the ecology of Culex restuans Theobald, Ochlerotatus triseriatus Say, and Ochlerotatus japonicus Theobald. Experimental mesocosms containing single species litter or a mixture of honeysuckle and one of two native tree species litter were established at South Farms and TreleaseWoods study sites in Urbana, IL, and examined for their effect on 1) oviposition site selection by the three mosquito species, and 2) adult production and body size of Oc. triseriatus and Oc. japonicus. There were no significant effects of study site and leaf treatment on Oc. japonicus and Oc. triseriatus oviposition preference and adult production. In contrast, significantly more Cx. restuans eggs rafts were collected at South Farms relative to Trelease Woods and in honeysuckle litter relative to native tree species litter. Significantly larger adult females of Oc. japonicus and Oc. triseriatus were collected at South Farms relative to TreleaseWoods and in honeysuckle litter relative to native tree species litter. Combining honeysuckle litter with native tree species litter had additive effects on Cx. restuans oviposition preference and Oc. japonicus and Oc. triseriatus body size, with the exception of honeysuckle and northern red oak litter combination, which had antagonistic effects on Oc. triseriatus body size. We conclude that input of honeysuckle litter into container aquatic habitats may alter the life history traits of vector mosquito species. [ABSTRACT FROM AUTHOR]

Caves are long-known examples of evolutionary replications where similar morphologies (troglomorphies) evolve independently as the result of strong natural selection of the extreme environment. Recently, this paradigm has been challenged based on observations that troglomorphies are inconsistent across taxa and different subterranean habitats. We investigated the degree of replicated phenotypic change in two independent cave invasions by the freshwater isopod Asellus aquaticus; the first in a sulphidic aquifer in Romania, the second in a sinking river in the Dinaric Karst in Slovenia. Both ancestral surface populations still live alongside the subterranean ones. Phylogenetic analyses show independence of the two colonization events, and microsatellite analysis shows no evidence of ongoing genetic exchange between surface and subterranean ecomorphs. The overall morphology has changed dramatically at both sites (50 of 62 morphometric traits). The amount of phenotypic change did not reflect differences in genetic diversity between the two ancestral populations. Multivariate analyses revealed divergent evolution in caves, not parallel or convergent as predicted by the current paradigm. Still, 18 traits changed in a parallel fashion, including eye and pigment loss and antennal elongation. These changes might be a consequence of darkness as the only common ecological feature, because Romanian caves are chemoautotrophic and rich in food, whereas Slovenian caves are not. Overall, these results show that morphologically alike surface populations can diverge after invading different subterranean habitats, and that only about one-third of all changing traits behave as troglomorphies in the traditional sense. [ABSTRACT FROM AUTHOR]

Freshwater habitats and organisms are among the most threatened on Earth, and freshwater ecosystems have been subject to large biodiversity losses. We developed a Climate Change Sensitivity (CCS) indicator based on trait information for a selection of stream- and lake-dwelling Ephemeroptera, Plecoptera and Trichoptera taxa. We calculated the CCS scores based on ten species traits identified as sensitive to global climate change. We then assessed climate change sensitivity between the six main ecoregions of Sweden as well as the three Swedish regions based on Illies. This was done using biological data from 1,382 stream and lake sites where we compared large-scale (ecoregional) patterns in climate change sensitivity with potential future exposure of these ecosystems to increased temperatures using ensemble-modelled future changes in air temperature. Current (1961~1990) measured temperature and ensemble-modelled future (2100) temperature showed an increase from the northernmost towards the southern ecoregions, whereas the predicted temperature change increased from south to north. The CCS indicator scores were highest in the two northernmost boreal ecoregions where we also can expect the largest global climate change-induced increase in temperature, indicating an unfortunate congruence of exposure and sensitivity to climate change. These results are of vital importance when planning and implementing management and conservation strategies in freshwater ecosystems, e.g., to mitigate increased temperatures using riparian buffer strips. We conclude that traits information on taxa specialization, e.g., in terms of feeding specialism or taxa having a preference for high altitudes as well as sensitivity to changes in temperature are important when assessing the risk from future global climate change to freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Pollutant dynamics and bioavailability greatly differ in soil and aquatic systems. Therefore, specific approaches and models are needed to assess the impact of soil contamination to terrestrial ecosystems. Earthworms among other soil invertebrates have received more attention because of their ecological importance. They represent a dominant part of the soil biomass and are soil engineers regulating important soil processes, notably fertilization. The release in soils of pollutants known for their persistence and/or their toxicity is a concern. Exposure of terrestrial species to pollutants that may alter genomic function has become an increasing topic of research in the last decade. Indeed, genome disturbances due to genetic and epigenetic mechanisms may impair growth, as well as reproduction and population dynamics in the long term. Despite their importance in gene expression, epigenetic mechanisms are not yet understood in soil invertebrates. Until now, pollutant-induced changes in genome expression in natural biota are still being studied through structural alteration of DNA. The first biomarker relating to genotoxicant exposure in earthworms from multi-contaminated soils reported is DNA adducts measurements. It has been replaced by DNA breakage measured by the Comet assay, now more commonly used. Functional genomic changes are now being explored owing to molecular "omic" technologies. Approaches, objectives and results are overviewed herein. The focus is on studies dealing with genotoxicity and populational effects established from environmentally-relevant experiments and in situ studies. [ABSTRACT FROM AUTHOR]

Aims: The aim of this study was to characterise and identify vibrios isolated from the haemolymph of apparently healthy adult spider crabs ( Maja brachydactyla) wild-caught in the Spanish localities of Galician coast and in the Canary Islands and also from captive animals held at IRTA’s facilities in the Ebro Delta of Catalonia, north-west Spanish Mediterranean coast. Methods and Results: A total of 277 bacterial isolates were obtained, and of these, 171 were characterised with rep-PCR, resulting electrophoretic bands were analysed and clusters formed. Identification of representative strains of each cluster was made by sequencing the 16S rRNA. Samples from animals caught in Galicia and captive at IRTA (around 15–18°C) rendered mostly species belonging to the Splendidus clade (72·2 and 76·6% respectively), commonly found in cold waters (below 20°C). Higher species diversity was found in the haemolymph of the captive animals. In the warmer Canary Islands waters (around 21°C), the diversity of vibrios is dominated by three clades, Harveyi ( Vibrio core group, 39·3%), Orientalis (23·2%) and Splendidus (21·4%) with a species diversity that equals that of the colder captive animals. Conclusions: Differences in the vibrios populations were found in the haemolymph extracted from animals collected from the three localities. Potential new species were found, and their description is under way. Significance and Impact of Study: As with other invertebrates, spider crabs also contain a diverse population of vibrios. These findings should help researchers to diagnose when a crab is infected. [ABSTRACT FROM AUTHOR]

Invertebrates are the main source of protein for many small-to-medium sized monkeys. Prey vary in size, mobility, degree of protective covering, and use of the forest, i.e. canopy height, and whether they are exposed or embed themselves in substrates. Sex-differentiation in foraging patterns is well documented for some monkey species and recent studies find that color vision phenotype can also affect invertebrate foraging. Since vision phenotype is polymorphic and sex-linked in most New World monkeys - males have dichromatic vision and females have either dichromatic or trichromatic vision - this raises the possibility that sex differences are linked to visual ecology. We tested predicted sex differences for invertebrate foraging in white-faced capuchins Cebus capucinus and conducted 12 months of study on four free-ranging groups between January 2007 and September 2008. We found both sex and color vision effects. Sex: Males spent more time foraging for invertebrates on the ground. Females spent more time consuming embedded, colonial invertebrates, ate relatively more "soft" sedentary invertebrates, and devoted more of their activity budget to invertebrate foraging. Color Vision: Dichromatic monkeys had a higher capture efficiency of exposed invertebrates and spent less time visually foraging. Trichromats ate relatively more "hard" sedentary invertebrates. We conclude that some variation in invertebrate foraging reflects differences between the sexes that may be due to disparities in size, strength, reproductive demands or niche preferences. However, other intraspecific variation in invertebrate foraging that might be mistakenly attributed to sex differences actually reflects differences in color vision. [ABSTRACT FROM AUTHOR]

Feeding invertebrate larvae may be food limited while developing in the ocean. If they are, then their time in the plankton is prolonged, which likely increases mortality. Food limitation could be due to the quantity and/or quality of the food available. In an effort to answer how food type influences larval nutrition, we compared growth, development and lipid deposition for Dendraster excentricus larvae reared in natural seawater from two depths (1 and 20 m) and in filtered seawater on a monoculture laboratory diet of 6 cells ?L?1 of the green alga Dunaliella tertiolecta (Butcher). Five days post-fertilization, larvae reared on the laboratory diet had developed to the latest stage, were the largest and had lipid deposits. Larvae reared on natural surface water were intermediate in size and developmental stage, and larvae reared in the water from 20 m depth were the smallest and developed the slowest. This trend continued at 8 days post-fertilization when surface water diet larvae were similar in size to laboratory diet larvae, but their juvenile rudiments were significantly smaller. To assess food availability in each food treatment, we compared the concentration of chlorophyll (Chl) a, b and c in natural seawater from each depth and in D. tertiolecta culture in filtered seawater. Natural seawater collected from the surface had the highest concentration of Chl a and c, whereas Chl b was not significantly different between treatments. Increased Chl concentrations in the surface water are likely due to higher concentrations of diatoms and dinoflagellates, which are typically not high-quality food items for echinoid larvae. Our results support a hypothesis that echinoid larvae in the water column may be limited by food quality. [ABSTRACT FROM AUTHOR]

Earthworms have profound impact on soil-based ecosystems. Although theoretical considerations suggest that most microbes in the earthworm gut are likely ingested and transient, the non-responsiveness of soil microbes to a specific high value gut nutrient and anoxia has made it difficult to demonstrate that responsive gut fermenters are derived from soil. Therefore, soil and gut content of the model earthworm Lumbricus terrestris were examined for their fermentative capabilities. In unsupplemented anoxic microcosms, fermentation was negligible with soil but rapid with gut content. However, both soil and gut content facilitated robust fermentations when challenged with complex nutrients indicative of those released from gizzard-disrupted cells. Based on the relative abundances of 16S rRNA and 16S rRNA gene sequences, the responsive fermentative taxa in unsupplemented gut content treatments were negligible in unsupplemented soil treatments. In contrast, the responsive fermentative taxa in soil and gut content treatments supplemented with complex nutrients displayed marked similarities, with numerous Proteobacteria - and Firmicutes -affiliated phylotypes being dominant. These findings indicated that detectable differences between the fermentative taxa in soil and gut contents are due in part to the nutrient-dependent metabolic status of community members and reinforce the likelihood that ingested transient microbes contribute to fermentation in the alimentary canal. [ABSTRACT FROM AUTHOR]