Size-dependent predation by Dugesia lugubris (Turbellaria) on Physa acuta (Gastropoda): experiments and model

1. We investigated experimentally predation by the flatworm Dugesia lugubris on the snail Physa acuta in relation to predator body length and to prey morphology [shell length (SL) and aperture width (AW)]. 2. SL and AW correlate strongly in the field, but display significant and independent variance among populations. In the laboratory, predation by Dugesia resulted in large and significant selection differentials on both SL and AW. Analysis of partial effects suggests that selection on AW was indirect, and mediated through its strong correlation with SL. 3. The probability P(ij) for a snail of size category i (SL) to be preyed upon by a flatworm of size category j was fitted with a Poisson-probability distribution, the mean of which increased linearly with predator size (i). Despite the low number of parameters, the fit was excellent (r2 = 0.96). We offer brief biological interpretations of this relationship with reference to optimal foraging theory. 4. The largest size class of Dugesia (>2 cm) did not prey on snails larger than 7 mm shell length. This size threshold might offer Physa a refuge against flatworm predation and thereby allow coexistence in the field. 5. Our results are further discussed with respect to previous field and laboratory observations on P acuta life-history patterns, in particular its phenotypic variance in adult body size.

Type of prey influences biology and consumption rate of Orius insidiosus (Say) (Hemiptera, Anthocoridae)

Generalist predators are capable of consuming different types of prey, and as each prey may have distinct nutritional values, each may have a distinct impact on the biology of the predator. Therefore, the aim of this study was to determine how the consumption of different prey influences certain biological characteristics and the predatory capacity of Orius insidiosus (Say). The investigation was performed in climatic chamber at 25 ±1 ºC, RH 70 ± 10% and fotophase 12. Eggs of Anagasta kuehniella (Zeller), adults of Caliothrips phaseoli (Hood) and nymphs of Aphis gossypii Glover were used as prey and were provided daily ad libitum for all the mobile stages of the predator. The results showed that biological parameters of O. insidiosus are affected differently depending on the type of prey ingested. The development time of the nymphal stage was 13.1, 11.23 and 10.25 days for O. insidiosus feeding on eggs of A. kuehniella, nymphs of A. gossypii and adults of C. phaseoli, respectively. Longevity was five times larger for adults fed on eggs of A. kuehniella (56.25 days) compared to that of adults that preyed on nymphs of A. gossypii (11.44 days), and four times larger when the prey were adults of C. phaseoli (13.58 days). The consumption of eggs of A. kuehniella by predator females resulted in a shorter pre-oviposition period (3.2 days) and a longer oviposition period (44.4 days) when compared to the consumption of other types of prey. In addition, fecundity was increased with the consumption of eggs of A. kuehniella (195.25 eggs laid / female) when compared to feeding on the other prey, C. phaseoli (70.00 eggs laid / female) or A. gossypii (22.50 eggs laid / female). However, the consumption of aphids was larger (148.28 nymphs/ nymphal stage) than that of thrips (74.10 thrips / nymphal stage) or eggs of A. kuehniella (37.03 eggs /nymphal stage) for all of the nymphal stages of the predator. The results indicate that the eggs of A. kuehniella are the type of prey best suited for rearing this predator insect under laboratory conditions. Also fecundity was better with this prey even though the predator consumed during its nymphal stage a lesser quantity of eggs compared to the other prey.

Predation drives interpopulation differences in parental care expression.

Expressing parental care after oviposition or parturition is usually an obligate (evolved) trait within a species, despite evolutionary theory predicting that widespread species should vary in whether or not they express parental care according to local selection pressures. The lizard Eutropis longicaudata expresses maternal care only in a single population throughout its large geographical range, but why this pattern occurs is unknown. We used reciprocal translocation and predator exclusion experiments to test whether this intraspecific variation is a fixed trait within populations and whether predator abundance explains this perplexing pattern. Wild-caught female lizards that were reciprocally translocated consistently guarded or abandoned eggs in line with their population of origin. By contrast, most lizards raised in a common garden environment and subsequently released as adults adopted the maternal care strategy of the recipient population, even when the parents originated from a population lacking maternal care. Egg predation represents a significant fitness cost in the populations where females display egg-guarding behaviour, but guarding eggs outweighs this potential cost by increasing hatching success. These results imply that predators can be a driving force in the expression of parental care in instances where it is normally absent and that local selection pressure is sufficient to cause behavioural divergence in whether or not parental care is expressed.

Distinct genetic structure in populations of Chrysoperla externa (Hagen) (Neuroptera, Chrysopidae) shown by genetic markers ISSR and COI gene

Distinct genetic structure in populations of Chrysoperla externa (Hagen) (Neuroptera, Chrysopidae) shown by genetic markers ISSR and COI gene. Green lacewings are generalist predators, and the species Chrysoperla externa presents a great potential for use in biological control of agricultural pests due to its high predation and reproduction capacities, as well as its easy mass rearing in the laboratory. The adaptive success of a species is related to genetic variability, so that population genetic studies are extremely important in order to maximize success of the biological control. Thus, the present study used nuclear (Inter Simple Sequence Repeat - ISSR) and mitochondrial (Cytochrome Oxidase I - COI) molecular markers to estimate the genetic variability of 12 populations in the São Paulo State, Brazil, as well as the genetic relationships between populations. High levels of genetic diversity were observed for both markers, and the highest values of genetic diversity appear associated with municipalities that have the greatest areas of native vegetation. There was high haplotype sharing, and there was no correlation between the markers and the geographic distribution of the populations. The AMOVA indicated absence of genetic structure for the COI gene, suggesting that the sampled areas formed a single population unit. However, the great genetic differentiation among populations showed by ISSR demonstrates that these have been under differentiation after their expansion or may also reflect distinct dispersal behavior between males and females.

Note on predation of the brood of Mischocyttarus injucundus (de Saussure) by another social wasp in Caxiuanã, Pará, Brazil, with new records of species for the Ferreira Penna Research Station (Hymenoptera, Vespidae, Polistinae)

ABSTRACT Predation of the brood of Mischocyttarus injucundus by another polistine social wasp is reported from an Amazonian rainforest locality. This is the first report for the American tropics of naturally occurring predation by one social wasp on the brood of another. Three species are added to the list of the Ferreira Penna Research Station, raising known local richness to 81 species: Mischocyttarus filiformis (de Saussure, 1854), Mischocyttarus vaqueroi Zikán, 1949, and Parachartergus griseus (Fox, 1898).

Coexistence of specialist and generalist species is shaped by dispersal and environmental factors.

Disentangling the mechanisms mediating the coexistence of habitat specialists and generalists has been a long-standing subject of investigation. However, the roles of species traits and environmental and spatial factors have not been assessed in a unifying theoretical framework. Theory suggests that specialist species are more competitive in natural communities. However, empirical work has shown that specialist species are declining worldwide due to habitat loss and fragmentation. We addressed the question of the coexistence of specialist and generalist species with a spatially explicit metacommunity model in continuous and heterogeneous environments. We characterized how species' dispersal abilities, the number of interacting species, environmental spatial autocorrelation, and disturbance impact community composition. Our results demonstrated that species' dispersal ability and the number of interacting species had a drastic influence on the composition of metacommunities. More specialized species coexisted when species had large dispersal abilities and when the number of interacting species was high. Disturbance selected against highly specialized species, whereas environmental spatial autocorrelation had a marginal impact. Interestingly, species richness and niche breadth were mainly positively correlated at the community scale but were negatively correlated at the metacommunity scale. Numerous diversely specialized species can thus coexist, but both species' intrinsic traits and environmental factors interact to shape the specialization signatures of communities at both the local and global scales.

Kleptoparasitism, disturbance and predation of yellow-legged gulls on Audouin's gulls in three colonies of the western Mediterranean

The impact of yellow-legged gulls on Audouin´s gulls was studied by means of observations from a blind, at the Ebro Delta, the Chafarinas Islands and the Columbretes Islands colonies, during different stages of Audouin´s Gulls breeding cycle. The rates of predation (upon eggs and chicks) and kleptoparasitism (aerial and on courtship and chick-feeding regurgitates) were recorded to evaluate this impact. Kleptoparasitism and predation rates recorded at the three colonies may be considered low when compared with similar studies dealing with other gull species. It seems that interactions did not represent a threat to the population dynamics of Audouin´s Gulls in any of the three colonies. The highest rates of aerial kleptoparasitism, courtship feeding and chick mortality were recorded at the Columbretes Islands, and the lowest at the Ebro Delta. The ratio of the number of yellow-legged gulls to the number of Audouin´s gulls seems to influence the rate of disturbances. Food availability was also likely to play an important role in the number of interactions, which increased when food was in shorter supply. The study at the Ebro Delta and Chafarinas Islands was restricted to some subcolonies and hence results may not be necessarily representative of the entire colonies. The existence of some yellow-legged gull individuals specialised as predators was recorded. Finally, we discuss the suitability of several conservation measures commonly applied in colonies where both species breed syntopically.

Sea Urchins Predation Facilitates Coral Invasion in a Marine Reserve

Macroalgae is the dominant trophic group on Mediterranean infralittoral rocky bottoms, whereas zooxanthellate corals are extremely rare. However, in recent years, the invasive coral Oculina patagonica appears to be increasing its abundance through unknown means. Here we examine the pattern of variation of this species at a marine reserve between 2002 and 2010 and contribute to the understanding of the mechanisms that allow its current increase. Because indirect interactions between species can play a relevant role in the establishment of species, a parallel assessment of the sea urchin Paracentrotus lividus, the main herbivorous invertebrate in this habitat and thus a key species, was conducted. O. patagonica has shown a 3-fold increase in abundance over the last 8 years and has become the most abundant invertebrate in the shallow waters of the marine reserve, matching some dominant erect macroalgae in abundance. High recruitment played an important role in this increasing coral abundance. The results from this study provide compelling evidence that the increase in sea urchin abundance may be one of the main drivers of the observed increase in coral abundance. Sea urchins overgraze macroalgae and create barren patches in the space-limited macroalgal community that subsequently facilitate coral recruitment. This study indicates that trophic interactions contributed to the success of an invasive coral in the Mediterranean because sea urchins grazing activity indirectly facilitated expansion of the coral. Current coral abundance at the marine reserve has ended the monopolization of algae in rocky infralittoral assemblages, an event that could greatly modify both the underwater seascape and the sources of primary production in the ecosystem.

A conserved transcript pattern in response to a specialist and a generalist herbivore.

Transcript patterns elicited in response to attack reveal, at the molecular level, how plants respond to aggressors. These patterns are fashioned both by inflicted physical damage as well as by biological components displayed or released by the attacker. Different types of attacking organisms might therefore be expected to elicit different transcription programs in the host. Using a large-scale DNA microarray, we characterized gene expression in damaged as well as in distal Arabidopsis thaliana leaves in response to the specialist insect, Pieris rapae. More than 100 insect-responsive genes potentially involved in defense were identified, including genes involved in pathogenesis, indole glucosinolate metabolism, detoxification and cell survival, and signal transduction. Of these 114 genes, 111 were induced in Pieris feeding, and only three were repressed. Expression patterns in distal leaves were markedly similar to those of local leaves. Analysis of wild-type and jasmonate mutant plants, coupled with jasmonate treatment, showed that between 67 and 84% of Pieris-regulated gene expression was controlled, totally or in part, by the jasmonate pathway. This was correlated with increased larval performance on the coronatine insensitive1 glabrous1 (coi1-1 gl1) mutant. Independent mutations in COI1 and GL1 led to a faster larval weight gain, but the gl1 mutation had relatively little effect on the expression of the insect-responsive genes examined. Finally, we compared transcript patterns in Arabidopis in response to larvae of the specialist P. rapae and to a generalist insect, Spodoptera littoralis. Surprisingly, given the complex nature of insect salivary components and reported differences between species, almost identical transcript profiles were observed. This study also provides a robustly characterized gene set for the further investigation of plant-insect interaction.

Does the generalist parasitic plant Cuscuta campestris selectively forage in heterogeneous plant communities?

Cuscuta spp. are holoparasitic plants that can simultaneously parasitise several host plants. It has been suggested that Cuscuta has evolved a foraging strategy based on a positive relationship between preuptake investment and subsequent reward on different host species. Here we establish reliable parasite size measures and show that parasitism on individuals of different host species alters the biomass of C. campestris but that within host species size and age also contributes to the heterogeneous resource landscape. We then performed two additional experiments to test whether C. campestris achieves greater resource acquisition by parasitising two host species rather than one and whether C. campestris forages in communities of hosts offering different rewards (a choice experiment). There was no evidence in either experiment for direct benefits of a mixed host diet. Cuscuta campestris foraged by parasitising the most rewarding hosts the fastest and then investing the most on them. We conclude that our data present strong evidence for foraging in the parasitic plant C. campestris.

2013 Update in addiction medicine for the generalist.

Increasingly, patients with unhealthy alcohol and other drug use are being seen in primary care and other non-specialty addiction settings. Primary care providers are well positioned to screen, assess, and treat patients with alcohol and other drug use because this use, and substance use disorders, may contribute to a host of medical and mental health harms. We sought to identify and examine important recent advances in addiction medicine in the medical literature that have implications for the care of patients in primary care or other generalist settings. To accomplish this aim, we selected articles in the field of addiction medicine, critically appraised and summarized the manuscripts, and highlighted their implications for generalist practice. During an initial review, we identified articles through an electronic Medline search (limited to human studies and in English) using search terms for alcohol and other drugs of abuse published from January 2010 to January 2012. After this initial review, we searched for other literature in web-based or journal resources for potential articles of interest. From the list of articles identified in these initial reviews, each of the six authors independently selected articles for more intensive review and identified the ones they found to have a potential impact on generalist practice. The identified articles were then ranked by the number of authors who selected each article. Through a consensus process over 4 meetings, the authors reached agreement on the articles with implications for practice for generalist clinicians that warranted inclusion for discussion. The authors then grouped the articles into five categories: 1) screening and brief interventions in outpatient settings, 2) identification and management of substance use among inpatients, 3) medical complications of substance use, 4) use of pharmacotherapy for addiction treatment in primary care and its complications, and 5) integration of addiction treatment and medical care. The authors discuss each selected articles' merits, limitations, conclusions, and implication to advancing addiction screening, assessment, and treatment of addiction in generalist physician practice environments.

Generalist hydrocarbon-degrading bacterial communities in the oil-polluted water column of the North Sea.

The aim of this work was to determine the effect of light crude oil on bacterial communities during an experimental oil spill in the North Sea and in mesocosms (simulating a heavy, enclosed oil spill), and to isolate and characterize hydrocarbon-degrading bacteria from the water column. No oil-induced changes in bacterial community (3 m below the sea surface) were observed 32 h after the experimental spill at sea. In contrast, there was a decrease in the dominant SAR11 phylotype and an increase in Pseudoalteromonas spp. in the oiled mesocosms (investigated by 16S rRNA gene analysis using denaturing gradient gel electrophoresis), as a consequence of the longer incubation, closer proximity of the samples to oil, and the lack of replenishment with seawater. A total of 216 strains were isolated from hydrocarbon enrichment cultures, predominantly belonging to the genus Pseudoaltero monas; most strains grew on PAHs, branched and straight-chain alkanes, as well as many other carbon sources. No obligate hydrocarbonoclastic bacteria were isolated or detected, highlighting the potential importance of cosmopolitan marine generalists like Pseudoalteromonas spp. in degrading hydrocarbons in the water column beneath an oil slick, and revealing the susceptibility to oil pollution of SAR11, the most abundant bacterial clade in the surface ocean.