Caenorhabditis nematodes colonize ephemeral resource patches in neotropical forests.

Factors shaping the distribution and abundance of species include life-history traits, population structure, and stochastic colonization-extinction dynamics. Field studies of model species groups help reveal the roles of these factors. Species of Caenorhabditis nematodes are highly divergent at the sequence level but exhibit highly conserved morphological uniformity, and many of these species live in sympatry on microbe-rich patches of rotten material. Here, we use field experiments and large-scale opportunistic collections to investigate species composition, abundance, and colonization efficiency of Caenorhabditis in two of the world's best studied lowland tropical field sites: Barro Colorado Island in Panamá and La Selva in Sarapiquí, Costa Rica. We observed seven species of Caenorhabditis, four of them known only from these collections. While these localities contain species from many parts of the phylogeny, both localities were dominated by globally distributed androdiecious species. We found that Caenorhabditis were able to colonize baits accessible only by phoresy, preferring to colonize baits making direct contact with the ground. We estimate founder numbers per colonization event to be low.

Life history parameters and predation capacities of Nesidiocoris volucer: a new biological control agent for tomato crop

Whiteflies are one of the major pests of tomato under greenhouses, and their control partly relies on biocontrol strategies. Among those biocontrol agents, parasitoids or predators are widely used. However, the introduction of a biocontrol agent in a new area is not trivial. For that reason, we investigated the use of a tropical native mirid, Nesidiocoris volucer (Hemiptera: Miridae), for the biological control of whiteflies among other insect pests on tomato crops under greenhouses in the subtropical island of La Réunion, France. Nesidiocoris volucer life history traits and plant injury were examined. Nymphs developed and survived between 15 and 30°C and required on average 49.41 days at 15°C and on average 10.50 days at 30°C to develop (nymph survival >94%). At 25°C, each female produced on average 65 eggs. Nesidiocoris volucer was able to feed on several prey species, but performed better on whiteflies than on spider mites or thrips. No N. volucer feeding injury was observed on tomato. Nesidiocoris volucer has also been found in tropical countries of Africa, and we believe that the data presented on this natural enemy could be of great importance for the biocontrol of whiteflies in tropical areas.

Effects of larval diet on the life-history traits and phenotypic expression of pyrethroid resistance in the major malaria vector Anopheles gambiae s.s.

The success achieved in reducing malaria transmission by vector control is threatened by insecticide resistance. To strengthen the current vector control programmes, the non-genetic factors underlying the emergence of insecticide resistance in Anopheles vectors and its widespread need to be explored. This study aimed to assess the effects of larval diet on some life-history traits and pyrethroid-insecticide susceptibility of Anopheles gambiae s.s. Three (3) An. gambiae strains, namely Kisumu (insecticide susceptible), AcerKis (homozygous ace-1 R G119S resistant) and KisKdr (homozygous kdr R L1014F resistant) were fed with three different diets (low, medium, and high) of TetraMin ® Baby fish food. Pre-imaginal developmental time, larval mortality, adult emergence rate and female wing length were measured. Mosquito females were exposed to insecticide-treated net (ITN) PermaNet 2.0 and PermaNet 3.0. In the three An. gambiae strains, significant differences in adult emergence rates ( F = 1054.2; df = 2; p <0.01), mosquito wing length ( F = 970.5; df = 2; p <0.01) and adult survival post insecticide exposure ( χ2 = 173; df = 2; p <0.01), were noticed among the three larval diets. Larvae fed with the low food diets took more time to develop, were smaller at emergence and displayed a short lifespan, while the specimens fed with a high regime developed faster and into big adults. Although being fed with a high diet, none of An. gambiae strain harbouring the kdr R and ace-1 R allele survived 24 hours after exposure against PermaNet 3.0. This study showed that variation in the larval diet significantly impacts An. gambiae life-history traits such as larval mortality and developmental time, adult wing length, and female susceptibility to pyrethroid insecticides. Further investigations through field-based studies would allow an in-depth understanding of the implications of these non-genetic parameters on the physiological traits of malaria vectors and consequently improve resistance management.

The evolution of insect visual opsin genes with specific consideration of the influence of ocelli and life history traits

Background Visual opsins are expressed in the compound eyes and ocelli of insects and enable light detection. Three distinct phylogenetic groups of visual opsins are found in insects, named long (LW), short (SW) and ultraviolet (UV) wavelength sensitive opsins. Recently, the LW group was found to be duplicated into the LW2b and the LW2a opsins. The expression of LW2b opsins is ocelli specific in some insects (e.g., bees, cricket, scorpion flies), but the gene was not found in other orders possessing three or less ocelli (e.g., dragonflies, beetles, moths, bugs). In flies, two LW2b homologs have been characterised, with one expressed in the ocelli and the other in the compound eyes. To date, it remains unclear which evolutionary forces have driven gains and losses of LW opsins in insects. Here we take advantage of the recent rapid increase in available sequence data (i.e., from insect genomes, targeted PCR amplification, RNAseq) to characterize the phylogenetic relationships of 1000 opsin sequences in 18 orders of Insects. The resulting phylogeny discriminates between four main groups of opsins, and onto this phylogeny we mapped relevant morphological and life history traits. Results Our results demonstrate a conserved LW2b opsin only present in insects with three ocelli. Only two groups (Brachycera and Odonata) possess more than one LW2b opsin, likely linked to their life history. In flies, we hypothesize that the duplication of the LW2b opsin occurred after the transition from aquatic to terrestrial larvae. During this transition, higher flies (Brachycera) lost a copy of the LW2a opsin, still expressed and duplicated in the compound eyes of lower flies (Nematocera). In higher flies, the LW2b opsin has been duplicated and expressed in the compound eyes while the ocelli and the LW2b opsin were lost in lower flies. In dragonflies, specialisation of flight capabilities likely drove the diversification of the LW2b visual opsins. Conclusion The presence of the LW2b opsin in insects possessing three ocelli suggests a role in specific flight capabilities (e.g., stationary flight). This study provides the most complete view of the evolution of visual opsin genes in insects yet, and provides new insight into the influence of ocelli and life history traits on opsin evolution in insects.

Echoes of the hunt? An inter-continental comparison of patterns of growth and determinants of size of brown bears in Canada and Sweden.

Comparing life history traits among populations that have been separated genetically for several hundred thousand years, but live in similar habitats on different continents, may help us understand how ecological and anthropomorphic factors shape life histories. We compared patterns of growth in body length and mass, and the influence of population density, habitat quality (NDVI), and reproduction on age-specific length and mass of male and female brown bears between Alberta, Canada, and Sweden. We found that Swedish females were significantly smaller in both length and mass than Alberta females. Swedish females also reached primiparity earlier and at a smaller mass and length. However, there were no continental differences in the patterns of growth in males. We found strong positive effects of NDVI, but only weak negative effects of population density on female mass and length in both areas. Generally, especially mass of Alberta females was more strongly affected by NDVI and density than for Swedish females. Reproduction had stronger negative effects on female mass in Alberta than in Sweden. We found no effects of NDVI and population density on male mass and body length in both areas. The larger variation in female growth and size between the areas, in contrast to males, may be related to differences in female reproductive investment due to differences in population trends, i.e., earlier reproduction in increasing populations or populations below carrying capacity, or to different selection pressures in the past, potentially due to human persecution. Swedish females exhibited characteristics typical of increasing populations, whereas Alberta females exhibited characteristics typical of stable or decreasing populations. The difference in reproduction investment means that Swedish bears can be harvested at higher rates, whereas Alberta bears must be managed more conservatively.

Secondary Seed Ingestion in Snakes: Germination Frequency and Rate, Seedling Viability, and Implications for Dispersal in Nature

The importance of vertebrate animals as seed dispersers (zoochory) has received increasing attention from researchers over the past 20 years, yet one category in particular, diploendozoochory, remains understudied. As the term implies, this is a two-phase seed dispersal system whereby a secondary seed predator (carnivorous vertebrate) consumes a primary seed predator or granivore (rodent and bird) with undamaged seeds in their digestive tract (mouth, cheek pouch, crop, stomach, or other organ), which are subsequently eliminated with feces. Surprisingly, although snakes are among the most abundant predators of granivorous vertebrates, they are the least studied group insofar as our knowledge of seed rescue and secondary dispersal in a diploendozoochorous system. Here, using live snake subjects of the Sonoran Desert (one viperid and two colubrid species) and seeds of the Foothill Palo Verde (Parkinsonia microphylla), a dominant tree of the same region, we experimentally tested germination frequency and rate, and seedling viability. Specifically, to mimic rodents with seed-laden cheek pouches, we tested whether wild-collected P. microphylla seeds placed in the abdomen of thawed laboratory mice and ingested by the snakes would retain their germination viability. Second, we examined whether seeds exposed to gut transit germinated at a greater frequency and rate than the controls. While we found strong statistical support for our first hypothesis, both aspects of the second one were not significant. Accordingly, we provide an explanation for these results based on specific life-history traits (dormant and non-dormant seeds) of P. microphylla. Our study provides support for the role of snakes as important agents of seed rescue and dispersal in nature, their potential as ecosystem engineers, and crucial evidence for the investment of field-based studies on diploendozoochorous systems in deserts and other ecosystems.