Keystone predators, by reducing the abundance of competitively superior prey, may have indirect positive effects on weak competitors, possibly increasing their abundance or preventing local competitive exclusion. By analogy to the Intermediate Disturbance Hypothesis, we would expect species diversity to peak at intermediate predator densities. In a replicated artificial pool experiment, we examined the relationships between density of the backswimmer Notonecta maculata (0, 1, 2, and 4 per 30 l pool) and invertebrate taxon diversity over an 11-week period of predator occupancy. Diversity reached high levels at high predator density sooner than at intermediate density. At the end of the experiment, taxon diversity was greatest at densities of 2 and 4 Notonecta per pool. While the overall predator density–diversity curve was in line with the intermediate disturbance hypothesis, the reduction in diversity from intermediate to high predator density was not statistically significant. Density of the preferred prey Daphnia magna decreased with Notonecta density, while densities of the smaller cladocerans Moina brachiata and Ceriodaphnia spp. increased. Suppression of Daphnia at high Notonecta densities may partially explain the increase in Moina and Ceriodaphnia densities. However, most of the relationship between Notonecta and the smaller cladocerans appears to be independent of Daphnia, suggesting complex interactions within the community. Our results suggest that keystone predation plays a strong role in structuring this community. Although diversity did not decrease significantly at the highest predator density as predicted, such a decrease may be more likely for pools with longer durations of predator occupancy or with higher predator densities.

Few papers have been published on “Turbellaria” in Israel, and of those, most concern “Turbellaria” from marine environments. In the present study, 22 freshwater species from Israel are reported. Ten of these species are new to Israel, and two are new to science. A detailed description of two species new to science from the family Typhloplanidae is given (Castrada multispina sp. nov. and Castradella biacantha sp. nov.). Typhloplanidae (Order Rhabdocoela) is the best represented family in this study with 16 species, compared to only 4 species from the family Dalyelliidae (Order Rhabdocoela) and the 2 Stenostomum-species. The faunal composition of the “microturbellarians” of Israel proved to be very similar to that of lentic environments in Europe, with the exception of the newly described species currently known only from Israel.

Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), was discovered on Tahiti Island in July 1996. Eradication programs were conducted from 1997 to 2001, but failed. From 1998 to 2006, B. dorsalis was recovered from 29 different host fruit from the five Society Islands: Tahiti, Moorea, Raiatea, Tahaa, and Huahine. Analysis of coinfestation patterns by B. dorsalis, Bactrocera tryoni (Froggatt), and Bactrocera kirki (Froggatt) suggested B. dorsalis had displaced these two species and become the most abundant fruit fly in coastal areas. To suppress B. dorsalis populations, a classical biological control program was initiated to introduce the natural enemy Fopius arisanus (Sonan) (Hymenoptera: Braconidae) into French Polynesia from Hawaii. Wasps were released and established on Tahiti, Moorea, Raiatea, Tahaa, and Huahine Islands. In guava, Psidium guajava L., collections for Tahiti, F. arisanus parasitism of fruit flies was 2.1, 31.8, 37.5, and 51.9% for fruit collected for 2003, 2004, 2005 and 2006, respectively. Based on guava collections in 2002 (before releases) and 2006 (after releases), there was a subsequent decrease in numbers of B. dorsalis, B. tryoni, and B. kirki fruit flies emerging (per kilogram of fruit) by 75.6, 79.3, and 97.9%, respectively. These increases in F. arisanus parasitism and decreases in infestation were similar for other host fruit. Establishment of F. arisanus is the most successful example of classical biological control of fruit flies in the Pacific area outside of Hawaii and serves as a model for introduction into South America, Africa, and China where species of the B. dorsalis complex are established.

Abstract The braconid parasitoid Fopius arisanus (Sonan) (Hymenoptera: Braconidae) is a candidate for augmentative biological control of tephritid fruit flies. In the Puna district of Hawaii Island, F. arisanus parasitized 41–72% of oriental fruit flies, Bactrocera dorsalis (Hendel), in wild common guava, Psidium guajava L.; strawberry guava, Psidium cattleianum Sabine; and tropical almond, Terminalia catappa L. In commercial papaya, Carica papaya L., in the same region, parasitism was only 22% in tree-collected fruit and 3% in ground-collected fruit. The low level of parasitism in papaya suggests that wild parasitoids may not track the host flies well in commercial fruit and that augmentative parasitoid releases could potentially increase parasitism and thus suppress host fly populations in this habitat. The very low parasitism in ground-collected papaya suggests that F. arisanus may avoid foraging on ground fruit. Field cage experiments support this hypothesis. Numbers of females observed on tree fruit were two-fold higher than on ground fruit in small cages and 4–6-fold higher in large cages. In an experiment conducted in a papaya orchard, sentinel fruit was placed within the canopy, on the trunk, or on the ground. Parasitism was significantly higher in the canopy-placed fruit in only one of three trials. This variable response to ground fruit in the field suggests that augmentative parasitoid releases may have a significant, albeit reduced, effect on host populations under conditions of poor sanitation.

Gene flow between populations of Culex pipiens L. is relevant to observed differences in disease transmission, insecticide resistance, behavior, and physiology. Intracellular Wolbachia bacteria have been hypothesized to affect gene flow in insects. Specifically, Wolbachia cause a form of embryonic mortality known as cytoplasmic incompatibility (CI) in crosses between individuals with different Wolbachia types. Incompatibility in Culex is exceptional in that it represents the most complex CI pattern known, and yet Culex populations are not infected with divergent Wolbachia strains. This has led to the hypothesis that extrachromosomal factors such as phages or mobile genetic elements may be involved in determining CI phenotype. Recent molecular characterization of Culex laboratory strains has identified variation in the orf7 locus of the Wolbachia-associated bacteriophage WO. Here, crosses between eight Culex strains differing in their orf7 type were conducted to examine for the hypothesized involvement of bacteriophage WO in determining CI in Culex. Although crossing results show examples of compatibility, partial compatibility, and incompatibility, the results fail to show a correlation between the CI phenotypes and orf7 type. Specific examples include high egg hatch resulting in crosses between Culex strains that differ significantly in their orf7 type and low egg hatch resulting in crosses between Culex strains with similar orf7 types. Thus, the phage orf7 locus alone cannot predict CI type in the Culex strains examined in this study. However, rejection of the hypothesized role of WO phage in Culex CI will require the characterization of additional phage loci.

Priority effects, i.e., effects of an early cohort on the performance of a later cohort, are generally studied between, and not within, species. The paucity of intraspecific assessments does not reflect a lack of ecological importance, but the technical problem associated with differentiating between conspecific cohorts. Here, we examine priority and density-dependent effects on larval Salamandra salamandra infraimmaculata. Larvae deposited by their mother early in the season have increased risk of desiccation, as rains at the beginning of the season are less frequent and unpredictable. However, breeding later may incur a high cost through conspecific priority effects, including cannibalism and competition. In an outdoor artificial pool experiment, we established densities of 0, 1, 2, 4 or 6 newly born larvae per pool (∼30 l), and 40 days later, added a second cohort of three newly born larvae to each pool. We differentiated between cohorts using natural individual-specific markings. For the early cohort, increasing density decreased survival and size at metamorphosis, and increased time to metamorphosis. For the late cohort, survival was 100% in pools without early-cohort larvae, but ranged between 13 and 33% in the presence of early-cohort larvae. Time to metamorphosis was significantly longer in the presence of low vs high densities of early-cohort larvae. Results suggest that early-cohort larvae are mainly subjected to exploitative competition and cannibalism mediated by food limitation, and that late-cohort larvae are subjected to cannibalism and interference due to size asymmetry between cohorts. The strong priority effects suggest that Salamandra females could increase their fitness by adjusting the number of larvae they deposit in specific pools to avoid cannibalism and intraspecific competition.

Gene flow between populations of Culex pipiens L. is relevant to observed differences in disease transmission, insecticide resistance, behavior, and physiology. Intracellular Wolbachia bacteria have been hypothesized to affect gene flow in insects. Specifically, Wolbachia cause a form of embryonic mortality known as cytoplasmic incompatibility (CI) in crosses between individuals with different Wolbachia types. Incompatibility in Culex is exceptional in that it represents the most complex CI pattern known, and yet Culex populations are not infected with divergent Wolbachia strains. This has led to the hypothesis that extrachromosomal factors such as phages or mobile genetic elements may be involved in determining CI phenotype. Recent molecular characterization of Culex laboratory strains has identified variation in the orf7 locus of the Wolbachia-associated bacteriophage WO. Here, crosses between eight Culex strains differing in their orf7 type were conducted to examine for the hypothesized involvement of bacteriophage WO in determining CI in Culex. Although crossing results show examples of compatibility, partial compatibility, and incompatibility, the results fail to show a correlation between the CI phenotypes and orf7 type. Specific examples include high egg hatch resulting in crosses between Culex strains that differ significantly in their orf7 type and low egg hatch resulting in crosses between Culex strains with similar orf7 types. Thus, the phage orf7 locus alone cannot predict CI type in the Culex strains examined in this study. However, rejection of the hypothesized role of WO phage in Culex CI will require the characterization of additional phage loci.

We examined species richness separately for cladocerans and ostracods in 52 temporary pools in a small geographical area, relating species richness with habitat traits using multiple regressions. Habitat traits considered included surface area, water depth, permanence and sediment depth. Permanence was an important predictor of species richness of both cladocerans and ostracods. Additionally, variation in ostracod species richness was significantly explained by water depth (negative relationship) and sediment depth (positive relationship). Surface area was not a statistically significant factor in any of our analyses. The importance of permanence supports the hypothesis that extinction due to pool drying is a major driving force behind the structuring of microcrustacean communities in temporary pools.

Natural selection should favor females that avoid ovipositing where risk of predation is high for their progeny. Despite the large consequences of such oviposition behavior for individual fitness, population dynamics, and community structure, relatively few studies have tested for this behavior. Moreover, these studies have rarely assessed the mode of detection of predators, compared responses in prey species that vary in vulnerability to predators, or tested for the behavior in natural habitats. In an outdoor artificial pool experiment, we tested the oviposition responses of two dipteran species, Culiseta longiareolata (mosquito) and Chironomus riparius (midge), to the hemipteran predator, Notonecta maculata. Both dipteran species have similar life history characteristics, but Culiseta longiareolata larvae are highly vulnerable to predation by Notonecta, while Chironomus riparius larvae are not. As their vulnerabilities would suggest, Culiseta longiareolata, but not Chironomus riparius, strongly avoided ovipositing in pools containing Notonecta. An experiment in natural rock pools assessing oviposition by Culiseta longiareolata in response to Notonecta maculata yielded an oviposition pattern highly consistent with that of the artificial pool experiment. We also demonstrated that the cue for oviposition avoidance by Culiseta longiareolata was a predator-released chemical: Notonecta water (without Notonecta replenishment) repelled oviposition for 8 days. Oviposition avoidance and mode of detection of the predator have important implications for how to assess the true impact of predators and for the use of commercially produced kairomones for mosquito control.

Some species of mosquitoes can detect the presence of predatory notonectid bugs and avoid oviposition in predator pools. The oviposition response of two mosquito species, Culiseta longiareolata Macquart and Culex laticinctus Edwards (Diptera: Culicidae), to a range of densities of the predator, Notonecta maculata Fabricius (Heteroptera: Notonectidae), was tested here. Densities of 0, 1, 2 or 4 Notonecta were established in 30-L artificial pools. Both mosquito species oviposited less in predator pools, but the response was unrelated to predator density, whereas vulnerability of Culiseta immatures to predation was density-dependent. Thus, although mosquitoes can detect Notonecta at any density within the range tested, they may be unable to discriminate among predator densities. The avoidance of predator pools by Culiseta, as well as its vulnerability to predation, occurred to a lesser degree than in earlier studies. This may have been due to the mitigating effects of components of the biotic community.

The geographic distribution of three braconid parasitoids of the Caribbean fruit fly, Anastrepha suspensa (Loew), was determined by collecting host fruit throughout central and southern Florida. Diachasmimorpha longicaudata (Ashmead) was most abundant in southern Florida, occurring at higher latitudes along the Atlantic and Gulf coasts. Distribution of this species was negatively related to variance of monthly temperatures. This suggests that D. longicaudata may be dependent on a relatively constant supply of hosts. Doryctobracon areolatus (Szepligeti) was the dominant species at the majority of interior locations, but it was uncommon or absent along both coasts. Utetes anastrephae (Viereck) was widespread but usually less common than the other species. Parasitism levels of both D. areolatus and D. longicaudata were positively related to density of common guava, Psidium guajava L., trees. Parasitism levels of both D. longicaudata and U. anastrephae were positively related to numbers of A. suspensa captured in McPhail traps. Abundance of D. areolatus was inversely related to that of both D. longicaudata and U. anastraphae. The absence of D. areolatus in southeastern Florida, where it was originally established, suggests that a process of competitive displacement may have occurred. Parasitoid distribution is consistent with the hypothesis that D. areolatus is a superior searcher and D. longicaudata is a superior intrinsic competitor.

Temporary water bodies exhibit a high level of biodiversity,much of which is unique tothese habitats.Studies of microturbellarian community ecology in temporary pools are scarce,eventhough turbellarians are potentially important in organizing community structure.Moreover,therehas been virtually no documentation of microturbellarians from Israel.We examined the re-lationships between several pool properties (surface area,water depth,permanence and sedimentdepth)and microturbellarian species richness among 52 temporary pools at a single site.A total of17 taxa of microturbellarians were identi ed,of which 14 were determined to genus or species level.Richness was positively related with surface area and with maximal sediment depth,togetherexplaining 54%of the variance.In more intensive sampling of a subset of 18 pools,surface areawas the only signi cant predictor,explaining 76%of the variance.Community dissimilarity waspositively related with di erences in both surface area and permanence.We identi ed three cate-gories of pool size,each characterized by di erent turbellarian species:large pools were dominatedbyCastrada viridis andGieysztoria cuspidata ,intermediate pools byDochmiotrema limicola ,and many of the small pools byGieysztoria ornata andOlisthanella obtusa .Large pools contributed themost to regional diversity,with 11 of the 17 observed taxa.However,some species were unique tosmall pools.Thus,in order to maintain maximal regional diversity of temporary water turbellar-ians,it is important to conserve habitats containing pools of various sizes.

Summary Freshwater temporary pools constitute insular habitats that can vary extensively in the richness of their macro‐invertebrate fauna, even within small spatial scales. While strictly statistical analyses may identify variables that account partially for this variation, they do not address explicitly the mechanisms that generate it. Here we show how a simple island‐biogeographical model explains 62% of the variation in local species richness of 47 neighbouring pools, based solely on pool size and permanence. A regression of the observed richness on that predicted by the model did not indicate any systematic biases, and left residuals that were distributed according to the expected. The model provides a robust working hypothesis, to which we apply a novel approach of quantifying the relative impact of local and regional factors on the species richness of individual pools. Using elasticity analysis of model parameters and invoking elasticity as a measure of parameter ‘importance’ we show, for example, that the impact of regional species richness on the richness of noninteractive communities should always exceed that of the probability of local extinction. The analysis exposes potential difficulties in generalizing which factor – local or regional – has the greater relative importance, and to what extent, as the answer can depend on: (i) the specific factors being compared, and (ii) particular habitat characteristics of individual localities.

Doryetobracon areolatus (Szepligeti) (Hymenoptera: Braconidae) is a common parasitoid of Anastrepha spp. (Diptera: Tephritidae). An efficient method of laboratory rearing incorporates chemicals from pear fruits into oviposition units. Production for the F-1 and F-2 generations was 12.1 and 9.3 progeny per female, respectively. Mean daily progeny production by F-2 females was between 1-2 progeny per female for almost all ages from 9 to 22 days. A bioassay was designed to determine the source of chemical cues used for host location. Parasitoids were given a choice between two oviposition units: a positive control containing all possible cues, and a treatment unit with cues derived from either the host fly, host fruit, both, or none. The number of females active on each oviposition unit was recorded. This experiment demonstrated that chemical cues derived from the host fruit, probably the peel, are involved in host location.

We investigated the effects of the predatory backswimmer, Anisops sardea, on oviposition habitat selection of mosquitoes and other dipterans, and on community structure in experimental pools. We predicted that those dipteran species whose larvae were shown to be highly vulnerable to predation by Anisops would avoid Anisops pools when choosing an oviposition site. We established the following treatments in plastic tubs: (1) Control (without Anisops); (2) Free Anisops (ten Anisops within pool but not caged); (3) Caged Anisops (ten Anisops in cage). The pools were open to colonization by insects. We added resting stages of crustaceans and first instar larvae of the mosquitoes Culiseta longiareolata and Culex laticinctus. Among the dipteran species, Culiseta longiareolata, Culex laticinctus, Chironomus riparius (Chironomidae) and Forcipomyia sp. (Ceratopogonidae), only Culisetalarvae were highly vulnerable to predation. As predicted, based on larval vulnerability, Culiseta, but not the other species, avoided Anisops pools when ovipositing. Free Anisops reduced taxon richness. This reduction resulted largely from the elimination of the cladoceran Ceriodaphniasp. and Culiseta in most free Anisops pools. Thus, Anisops sardea structures the community, both by a behavioral response of prey to its presence and by consumption of prey.

Parasierola swirskiana Argaman (Hymenoptera: Bethylidae) is a parasitoid of the moth Batrachedra amydraula Meyrick, a pest of unripe fruits of the date palm, Phoenix dactylifera L. The parasitoid is most commonly found in the field on second-generation host ,larvae. Its biological characteristics were studied in the laboratory. Adult longevity averaged 34.9 and 20.5 days for females and males, respectively. Clutch size ranged between 1 and 13 eggs per host, and was positively correlated with host weight. Females laid an average of 60.4 eggs on 11.6 hosts, with a maximum of 152 eggs on 29 hosts in 53 days. Parasitoids were observed standing motionless upon 52% of the paralyzed hosts, and active brood defense was occasionally observed. Immature development is described. Total development time from egg to adult averaged 13.6 days at 26 ± 2°C and 30-50% r.h. The potential for utilizing P. swirskiana for biological control of B. amydraula is discussed.

Two species of Braconidae, Diachasmimorpha longicaudata (Ashmead) and Doryctobracon areolatus (Szepligeti), commonly attack the Caribbean fruit fly, Anastrepha suspensa (Loew), in central Florida. There are temporal changes in the relative abundance of the 2 parasitoids, with a tendency for D. longicaudata to become more common as the fruiting periods of various host trees progress. An exception occurs when D. longicaudata declines relative to D. areolatus during the late-autumn and winter fruiting of the citrus fruit calamundin, χ Citrofortuella mitis J. Ingram & H. E. Moore. During the year there is a spring rise and then an autumn decline in the relative abundance of D. longicaudata . This pattern is not explained by any within-tree changes in fruit size or host larval densities. Many changes in relative abundance are consistent with D. areolatus being superior to D. longicaudata in finding host patches, but inferior at exploiting hosts (counter-balanced competition). Seasonal changes in maximum temperatures are also correlated to changes in the relative abundance of D. longicaudata to D. areolatus . It appears that the outcome of the competition between the 2 species is influenced by climatic conditions.