Field responses of stink bugs to the natural and synthetic pheromone of the Neotropical brown stink bug, Euschistus heros (Heteroptera: Pentatomidae)

Abstract.The synthetic racemic mixture of methyl 2,6,10‐trimethyltridecanoate, a component of the male produced pheromone of Euschistus heros (F.) (Heteroptera, Pentatomidae), was attractive to pentatomid species in a field test, using homemade pheromone trap designs. The pentatomid Piezodorus guildinii was caught in high numbers in field traps, during two field experiments, indicating a consistent response of this species to the E. heros pheromone. A correlation was found between the range of insects caught in the pheromone‐baited traps and a random sampling method. The synthetic stereoisomeric mixture of methyl 2,6,10‐trimethyldodecanoate, a minor component of E. heros pheromone, was also field tested and caught no pentatomids. Egg parasitoids were caught in traps baited with E. heros pheromone, indicating that this pheromone can be exploited as a kairomone. A synchrony in the periodicity of trap catch, between the egg parasitoids and their host, was also recorded.     

Seasonal abundance of the neotropical brown stink bug, Euschistus heros, in overwintering sites, and the breaking of dormancy

The seasonal abundance of the neotropical brown stink bug, Euschistus heros (Heteroptera: Pentatomidae), in overwintering sites in northern Paraná state, Brazil (latitude 23°11 S, longitude 51°11 W) was monitored from September 1994 to August 1995. The breaking of dormancy (oligopause) was studied in the laboratory by comparing the feeding activity and reproduction of adults collected in the field under different physiological conditions (i.e., dormant and non-dormant). No bugs were found in overwintering sites during the summer (December to February) and during early autumn (March). From mid-autumn to winter (April – August), the number of E. heros captured in these sites gradually increased, decreasing thereafter with the start of spring in September. Dormant and non-dormant E. heros taken to the laboratory and maintained at 25 ± 1 °C , 65± 5% r.h., and L14: D10 photoperiod, and given suitable food (soybean pods or seeds), began feeding immediately. The number of stylet sheaths deposited/day on the food was greater for non-dormant than for dormant adults. Feeding activity was greater on immature pods than on mature seeds of soybean. Dormant females placed under suitable biotic and abiotic conditions took ca. 2 weeks to start reproduction, in contrast to non-dormant females, which reproduced immediately.     

Performance and seasonal abundance of the neotropical brown stink bug, shape Euschistus heros nymphs and adults on a novel food plant (pigeonpea) and soybean

Pigeonpea, Cajanus cajan (L.) Millsp. (Leguminosae) was found as a novel food plant of the neotropical brown stink bug, Euschistus heros (F.), in Paraná State, Brazil. Laboratory studies indicated nymphs performing better when fed on immature pods of soybean, Glycine max (L.) Merrill (Leguminosae), than on immature pods of pigeonpea. Female nymphs required 1.7 d less to complete development and tended to have a lower mortality on soybean (17.5%) than on pigeonpea (25.0%). At emergence, fresh body weight was greater on soybean than on pigeonpea. Adult E. heros performed better on soybean than on pigeonpea. After 120 d, 35% of adults were alive on soybean and 30% on pigeonpea; 93.3% of females oviposited on soybean, and 73.3% on pigeonpea, with an oviposition delay of 17 days on pigeonpea compared to soybean. Fecundity was 63% greater on soybean than on pigeonpea, and adult body weight gain for females and males at different ages was 6–36% greater on soybean than on pigeonpea. E. heros colonized soybean during January–March, from the pod-setting and filling stages (R3–R6) to maturity (R7–R8), and pigeonpea during April–June. These results indicate that E. heros has expanded its host range to pigeonpea in Brazil; pods of this plant are suitable food, and can support the insect during autumn-early winter, after soybean harvest, and before it enters into partial hibernation.     

Induced volatiles in soybean and pigeon pea plants artificially infested with the neotropical brown stink bug, Euschistus heros, and their effect on the egg parasitoid, Telenomus podisi

Herbivory is known to increase the emission of volatiles, which attract natural enemies to herbivore‐damaged plants in laboratory and agricultural systems. We report on signalling through volatiles induced by Euschistus heros (F.) (Heteroptera: Pentatomidae) in two legumes that influence the attraction and retention of the egg parasitoid Telenomus podisi (Ashmead) (Hymenoptera: Scelionidae). Air‐borne extracts obtained from two host plants of E. heros, soybean, Glycine max, and pigeon pea, Cajanus cajan (Leguminosae), produce a different blend of emitted volatiles when attacked by adult males or females and nymphs of the pest species, compared with the undamaged plants. The same results were obtained when the plants were treated with extracted saliva of E. heros which had been mechanically introduced into the plants. This indicates that some substance in the saliva contributed to the release of the volatiles. Bioassays in a Y‐tube olfactometer with female T. podisi and treated plants confirmed the significant preference of the egg parasitoid for plants attacked by either males, females, or fourth instar nymphs of the pest species. On the other hand, volatile extracts obtained from soybean subjected to the velvetbean caterpillar, Anticarsia gemmatalis, a non‐host species for T. podisi, showed a different blend of volatiles compared to those obtained from plants subjected to E. heros. Additionally, the volatiles obtained from this plant–host complex were not attractive to T. podisi. These results indicate that E. heros causes an increase in the emission of specific plant volatiles, and that the induction is possibly caused by an elicitor present in the pest saliva. The possibility that these plant volatiles play an important role in the attraction and retention of the egg parasitoid T. podisi is discussed.     

Reduced‐risk insecticides in Neotropical stingless bee species: impact on survival and activity

As honeybees are the main pollinator subject to an intense research regarding effects of pesticides, other ecologically important native bee pollinators have received little attention in ecotoxicology and risk assessment of pesticides in general, and insecticides in particular, some of which are perceived as reduced‐risk compounds. Here, the impact of three reduced‐risk insecticides – azadirachtin, spinosad and chlorantraniliprole – was assessed in two species of stingless bees, Partamona helleri and Scaptotrigona xanthotrica, which are important native pollinators in Neotropical America. The neonicotinoid imidacloprid was used as a positive control. Spinosad exhibited high oral and contact toxicities in adult workers of both species at the recommended label rates, with median survival times (LT₅₀s) ranging from 1 to 4 h, whereas these estimates were below 15 min for imidacloprid. Azadirachtin and chlorantraniliprole exhibited low toxicity at the recommended label rates, with negligible mortality that did not allow LT₅₀ estimation. Sublethal behavioural assessments of these two insecticides indicated that neither one of them affected the overall group activity of workers of the two species. However, both azadirachtin and chlorantraniliprole impaired individual flight take‐off of P. helleri and S. xanthotrica worker bees, which may compromise foraging activity, potentially leading to reduced colony survival. These findings challenge the common perception of non‐target safety of reduced‐risk insecticides and bioinsecticides, particularly regarding native pollinator species.     

三种杀虫剂对褐飞虱海藻糖含量和海藻糖酶活性的影响

为了解农药处理导致褐飞虱Nilaparvata lugens (Stål）飞行能力增强的生理机制, 本文采用蒽酮法和酶促反应终止法, 研究了吡虫啉、 三唑磷和溴氰菊酯3种杀虫剂亚致死剂量对褐飞虱3龄、 5龄若虫及长、 短翅型雌雄成虫体内海藻糖含量和海藻糖酶活性的影响。结果表明： 杀虫剂处理的褐飞虱3龄若虫海藻糖含量和海藻糖酶活性与对照相比没有显著差异（P>0.05）。40 mg/L三唑磷处理的褐飞虱5龄若虫体内海藻糖含量显著低于对照（P<0.05）, 比对照降低了24%; 而20和40 mg/L三唑磷处理的褐飞虱5龄若虫海藻糖酶活性显著高于对照（P<0.05）, 分别比对照高出了100%和129%。10 mg/L吡虫啉, 20 和40 mg/L三唑磷以及3和6 mg/L溴氰菊酯处理的褐飞虱短翅雌成虫和雄成虫体内海藻糖含量显著低于对照（P<0.05）, 雌成虫体内海藻糖含量比对照分别降低了36%, 53%, 67%, 58%和69%, 雄成虫体内海藻糖含量比对照分别降低了59%, 71%, 65%, 70%和77%; 而40 mg/L三唑磷以及3和6 mg/L溴氰菊酯处理的褐飞虱短翅型雌成虫和雄成虫体内海藻糖酶活性显著高于对照（P<0.05）, 雌成虫体内海藻糖酶活性比对照分别高出了124%, 100%和88%, 雄成虫体内海藻糖酶活性比对照分别高出了146%, 132%和118%。10 mg/L吡虫啉, 40 mg/L三唑磷和3 mg/L溴氰菊酯处理的褐飞虱长翅型雌成虫和雄成虫海藻糖含量显著低于对照（P<0.05）, 雌成虫海藻糖含量比对照分别降低了44%, 34%和37%, 雄成虫体内海藻糖含量比对照降低了48%, 54%和43%; 而5和10 mg/L吡虫啉处理的长翅型雌成虫和雄成虫海藻糖酶活性显著高于对照（P<0.05）, 雌成虫体内海藻糖酶活性比对照分别高出了317%和300%, 雄成虫体内海藻糖酶活性比对照分别高出了170%和97%。这些结果说明这3种杀虫剂亚致死剂量处理可以增强褐飞虱体内海藻糖酶活性, 并导致海藻糖含量下降。本研究结果对深入阐明农药诱导褐飞虱再猖獗及杀虫剂处理增强其飞行能力的生理机制具有一定的科学价值。     

Female‐biased size dimorphism in a diapausing caddisfly,Mesophylax aspersus: effect of fecundity and natural and sexual selection

1. The effect of mating success, female fecundity and survival probability associated with intra‐sex variation in body size was studied in Mesophylax aspersus, a caddisfly species with female‐biased sexual size dimorphism, which inhabits temporary streams and aestivates in caves. Adults of this species do not feed and females have to mature eggs during aestivation. 2. Thus, females of larger size should have a fitness advantage because they can harbour more energy reserves that could influence fecundity and probability of survival until reproduction. In contrast, males of smaller size might have competitive advantages over others in mating success. 3. These hypotheses were tested by comparing the sex ratio and body size of individuals captured before and after the aestivation period. The associations between body size and female fecundity, and between mating success and body size of males, were explored under laboratory conditions. 4. During the aestivation period, the sex ratio changed from 1 : 1 to male biased (4 : 1), and a directional selection on body size was detected for females but not for males. Moreover, larger clutches were laid by females of larger size. Finally, differences in mating success between small and large males were not detected. These results suggest that natural selection (i.e. the differential mortality of females associated with body size) together with possible fecundity advantages, are important factors responsible of the sexual size dimorphism of M. aspersus. 5. These results highlight the importance of taking into account mechanisms other than those traditionally used to explain sexual dimorphism. Natural selection acting on sources of variation, such as survival, may be as important as fecundity and sexual selection in driving the evolution of sexual size dimorphism.     

Dissecting insect responses to climate warming: overwintering and post‐diapause performance in the southern green stink bug,Nezara viridula,under simulated climate‐change conditions

The effect of simulated climate change on overwintering and post‐diapause reproductive performance is studied in Nezara viridula (L.) (Heteroptera: Pentatomidae) close to the species' northern range limit in Japan. Insects are reared from October to June under quasi‐natural (i.e. ambient outdoor) conditions and in a transparent incubator, in which climate warming is simulated by adding 2.5°C to the ambient temperatures. Despite the earlier assumption that females of N. viridula overwinter in diapause, whereas males do so in quiescence, regular dissections show that the two sexes overwinter in a state of true diapause. During winter, both sexes are dark‐coloured and have undeveloped reproductive organs. Resumption of development does not start until late March. During winter, the effect of simulated warming on the dynamics and timing of physiological processes appears to be limited. However, the warming significantly enhances winter survival (from 27–31% to 47–70%), which is a key factor in range expansion of N. viridula. In spring, the effect of simulated warming is complex. It advances the post‐diapause colour change and transition from dormancy to reproduction. The earlier resumption of development is more pronounced in females: in April, significantly more females are already in a reproductive state under the simulated warming than under quasi‐natural conditions. In males, the tendency is similar, although the difference is not significant. Warming significantly enhances spring survival and percentage of copulating adults, although not the percentage of ovipositing females and fecundity. The results suggest that, under the expected climate‐warming conditions, N. viridula will likely benefit mostly as a result of increased winter and spring survival and advanced post‐diapause reproduction. Further warming is likely to allow more adults to survive the critical cold season and contribute (both numerically and by increasing heterogeneity) to the post‐overwintering population growth, thus promoting the establishment of this species in newly‐colonized areas.     

Production and sex‐pheromonal activity of alkaloid‐derived androconial compounds in the danaine butterfly,Parantica sita (Lepidoptera: Nymphalidae: Danainae)

Close associations of certain lepidopteran taxa with pyrrolizidine alkaloids (PAs), a typical class of plant secondary metabolites, have been well documented from the perspective of evolutionary ecology. Male danaine butterflies are thought to utilize PAs as precursors for the production of dihydropyrrolizines [e.g. danaidone (DO) and hydroxydanaidal (HD)] in their two distinct androconial organs, viz. alar scent organs (sex brands) and abdominal hairpencils. However, little is known about the quantitative profiles of these compounds in danaines, the mechanism for their formation in the androconial organs, or their biological functions, particularly in mating behaviour. The present study addressed these unanswered questions posed for males of the danaine butterfly, Parantica sita. Chemical analyses of androconial extracts revealed considerable seasonal/regional and individual variations of the amounts of DO (the major dihydropyrrolizine produced) and 7R‐HD (the 7R‐enantiomer of HD detected in this study) found in the two organs. These variations seemed to depend primarily on the age of the male and the phenological traits of PA‐containing plants available. Males were found to acquire an adequate capability to produce DO ~1 week after eclosion. DO was shown to be produced exclusively in the sex brand and subsequently physically transferred to the hairpencil through a contact behaviour between the two organs, here termed ‘perfuming behaviour’. The results of behavioural experiments with PA‐fed and PA‐unfed males that were allowed to compete for mates, combined with the positive electroantennographic (EAG) responses of the female, to both DO and 7R‐HD, led to the conclusion that either or both of these compounds can act as the sex pheromone. Oral administration of PAs to males indicated that DO can be biosynthesized from various PA precursors, while 7R‐HD, unlike in arctiid moths, is derived only from PAs with the 7R‐configuration. The putative biosynthetic pathways of DO and 7R‐HD, and the evolutionary provenance of the binate androconial system in the Danainae are also discussed.     

Cytogenetic relationships,polyploid origin and taxonomic issues in Paspalum species: inter‐ and intraspecific hybrids between a sexual synthetic autotetraploid and five wild apomictic tetraploid species

• Paspalum is a noteworthy grass genus due to the forage quality of most species, with approximately 330 species, and the high proportion of those that reproduce via apomixis. Harnessing apomictic reproduction and widening knowledge about the cytogenetic relationships among species are essential tools for plant breeding.
• We conducted cytogenetic analyses of inter‐ and intraspecific hybridisations involving a sexual, colchicine‐induced autotetraploid plant of P. plicatulum Michx. and five indigenous apomictic tetraploid (2n = 40) species: P. compressifolium Swallen, P. lenticulare Kunth, two accessions of P. nicorae Parodi, P. rojasii Hack. and two accessions of P. plicatulum. Fertility of the hybrids was investigated and their reproductive system was analysed considering the relative embryo:endosperm DNA content from flow cytometry. Morphological, nomenclatural and taxonomic issues were also analysed.
• Cytogenetic analysis suggested that all indigenous tetraploid accessions of five apomictic species are autotetraploid or segmental allotetraploid. If segmental allotetraploids, they probably originated through autoploidy followed by diploidisation processes. Autosyndetic male chromosome pairing observed in all hybrid families supported this assertion. Allosyndetic chromosome associations were also observed in all hybrid families. In the hybrids, the proportion of male parent chromosomes involved in allosyndesis per pollen mother cell varied from 5.5% to 35.0% and the maximum was between 25% and 60%. The apomictic condition of the indigenous male parents segregated in the hybrids.
• These results confirm a strong association between autoploidy and apomixis in Paspalum, and the existence of cytogenetic relationships between different species of the Plicatula group. Allosyndetic chromosome pairing and seed fertility of the hybrids suggest the feasibility of gene transfer among species.

     

Description of a new species of the genus Resseliella (Diptera: Cecidomyiidae), a pollinator of Kadsura longipedunculata (Schisandraceae) in China,with comments on its flower‐visiting habit

A gall midge pollinating flowers of Kadsura longipedunculata is described as Resseliella kadsurae sp. nov. based on adult specimens collected in 2006 from Langshan, Xinning County, Hunan Province, China. The new species is distinguishable from other known congeners in the combination of the following characteristics: gynecoid male flagellomeres, mottled wings, simple claws on all legs; male hypoproct with a transverse bridge‐like structure ventrally connecting both sides of hypoproct. In particular, the gynecoid male flagellomeres and transverse bridge‐like structure are unique to the new species. Partial sequencing of the cytochrome oxidase subunit I mitochondrial gene indicates that R. kadsurae is grouped with the R. theobardi + R. yagoi clade, but this clade and the monophyly of the genus Resseliella are not statistically supported. The new species is nocturnal, and mating occurs at dusk. At the time of mating, males and females hang on opposite sides of non‐sticky old spider webs in a venter‐to‐venter position. Immature stages and the life history of R. kadsurae are unknown. The flower‐visiting habit of R. kadsurae is contrasted with that of other flower‐visiting gall midges and the probability that this behavior exists in other congeners is discussed.     

Land‐use Change Dynamics,Soil Type and Species Forming Mono‐dominant Patches: the Case of Pteridium aquilinum in a Neotropical Rain Forest Region

Deforestation and agricultural land degradation in tropical regions can create conditions for growth of perennial plant species forming mono‐dominated patches (MDP). Such species might limit forest regeneration, and their proliferation forces the abandonment of fields and subsequent deforestation to establish new fields. Therefore, identifying factors fostering MDP species is critical for biodiversity conservation in human‐modified landscapes. Here, we propose a conceptual framework to identify such factors and apply it to the case of Pteridium aquilinum (bracken fern), a light‐demanding species, tolerant of low soil fertility and fire. We hypothesize that bracken proliferation is promoted by land‐use changes that increase light availability, especially in sites with low soil fertility and land uses involving fire. We assessed this idea using agricultural fields in southeastern Mexico with different land‐use change histories and quantifying prevalence and cover of bracken. Five different land‐use change histories resulted from transitions among forest, crop, pasture, and fallow field stages. Of the 133 fields sampled, 71 percent had P. aquilinum; regression tree analysis indicated that 65 percent of inter‐field variation in prevalence and 90 percent in cover was explained by land‐use change history and soil type. Maximum prevalence, cover, and rates of increase in bracken were found on fields with low fertility sandy/clay soils, which had been used for crops and pasture, were frequently burned, and had high levels of light. Fields on fertile alluvial soil never used for pasture were bracken‐free. Agriculture promoting high light environments on less fertile soils is a major cause of bracken proliferation and likely that of other MDP species.     

FgFim,a key protein regulating resistance to the fungicide JS399‐19, asexual and sexual development,stress responses and virulence in Fusarium graminearum

Fimbrin is an actin‐bundling protein found in intestinal microvilli, hair cell stereocilia and fibroblast filopodia. Its homologue Sac6p has been shown to play a critical role in endocytosis and diverse cellular processes in Saccharomyces cerevisiae. FgFim from the wheat scab pathogenic fungus Fusarium graminearum strain Y2021A, which is highly resistant to the fungicide JS399‐19, was identified by screening a mutant library generated by HPH‐HSV‐tk cassette‐mediated integration. The functions of FgFim were evaluated by constructing a deletion mutant of FgFim, designated ΔFgFim‐15. The deletion mutant exhibited a reduced rate of mycelial growth, reduced conidiation, delayed conidium germination, irregularly shaped hyphae, a lack of sexual reproduction on autoclaved wheat kernels and a dramatic decrease in resistance to JS399‐19. ΔFgFim‐15 also exhibited increased sensitivity to diverse metal cations, to agents that induce osmotic stress and oxidative stress, and to agents that damage the cell membrane and cell wall. Pathogenicity assays showed that the virulence of the FgFim deletion mutant on flowering wheat heads was impaired, which was consistent with its reduced production of the toxin deoxynivalenol in host tissue. All of these defects were restored by genetic complementation of the mutant with the parental FgFim gene. Quantitative real‐time polymerase chain reaction (PCR) assays showed that the basal expression of three Cyp51 genes, which encode sterol 14α‐demethylase, was significantly lower in the mutant than in the parental strain. The results of this study indicate that FgFim plays a critical role in the regulation of resistance to JS399‐19 and in various cellular processes in F. graminearum.     

Using unmanned aerial vehicle (UAV) surveys and image analysis in the study of large surface‐associated marine species: a case study on reef sharks Carcharhinus melanopterus shoaling behaviour

A novel image analysis‐based technique applied to unmanned aerial vehicle (UAV) survey data is described to detect and locate individual free‐ranging sharks within aggregations. The method allows rapid collection of data and quantification of fine‐scale swimming and collective patterns of sharks. We demonstrate the usefulness of this technique in a small‐scale case study exploring the shoaling tendencies of blacktip reef sharks Carcharhinus melanopterus in a large lagoon within Moorea, French Polynesia. Using our approach, we found that C. melanopterus displayed increased alignment with shoal companions when distributed over a sandflat where they are regularly fed for ecotourism purposes as compared with when they shoaled in a deeper adjacent channel. Our case study highlights the potential of a relatively low‐cost method that combines UAV survey data and image analysis to detect differences in shoaling patterns of free‐ranging sharks in shallow habitats. This approach offers an alternative to current techniques commonly used in controlled settings that require time‐consuming post‐processing effort.     

More than meets the eye: a morphological and phylogenetic comparison of long‐spurred,white‐flowered Satyrium species (Orchidaceae) in South Africa

Superficial similarities among unrelated species are often a result of convergent evolution and can cause considerable taxonomic confusion. A case in point is Satyrium eurycalcaratum , described here as a new species, which has been confused with several other Satyrium spp. with similar long‐spurred, white flowers. A phylogenetic analysis, based on molecular data, indicated that S. eurycalcaratum is not closely related to any of the species with which it has been previously confused. A comparative analysis of morphological characters in the seven South African Satyrium spp. with long‐spurred, white flowers showed that each of these, including S. eurycalcaratum , is characterized by a unique combination of traits. Despite the similarity in pollination syndrome characters, such as spur length and flower colour, variation in rostellum structure was particularly pronounced and four distinctive forms were present. There was no phylogenetic signal in patterns of interspecific rostellum variation, as some closely related species had different rostella, whereas some distantly related species shared similar rostellum structures. We therefore conclude that the use of rostellum traits in conjunction with phylogenetic evidence can resolve species delimitations among orchid species that share the same pollination syndrome. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 166 , 417–430.     

Little shrimp left on the shelf: the roles that sea‐level change,ocean currents and continental shelf width play in the genetic connectivity of a seagrass‐associated species

Aim Caridean shrimp are diverse and abundant inhabitants of seagrass beds. Anthropogenic disturbances have already reduced and fragmented seagrass habitat, and the rate of change is likely to increase in the future. It is therefore becoming increasingly important to build a basis of understanding of connectivity among populations of seagrass‐associated fauna. Phycomenes zostericola is closely associated with seagrass and makes an ideal study species with which to explore patterns of connectivity and the influence of biogeographic boundaries and historical sea‐level changes on seagrass‐associated species. We hypothesized that strong currents and the high potential of P. zostericola for dispersal and adult movement would result, for the most part, in panmixia. We also hypothesized that if structure was evident, it would occur close to known biogeographic boundaries in Queensland. Location Phycomenes zostericola is an abundant shrimp species distributed throughout Queensland’s seagrass habitats. Nineteen seagrass sites from the Torres Strait Islands and Queensland coastlines were sampled. Methods Molecular sequence data for a 590 base pair fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI) was analysed for 279 specimens of P. zostericola. Phylogeographic patterns were analysed using nested clade phylogeographic analysis (NCPA); an isolation‐by‐distance effect was tested using a Mantel test; the effect of biogeographic boundaries was tested using an analysis of molecular variance (AMOVA), and also a spatial analysis of molecular variance (SAMOVA); demographic expansions were tested for using Tajima’s D, Fu’s F_S and timing estimated using mismatch analysis; the timing of vicariant events was estimated using coalescent analysis (im program). Results Contrary to our original hypothesis, the strong marine currents are not a connective influence among populations of P. zostericola. Regional genetic structure and an isolation‐by‐distance effect are enhanced by existing coastal biogeographic boundaries. Population genetic structure and demographic history are intricately linked to the effects of a tumultuous Pleistocene sea‐level history on the Queensland continental shelf. Main conclusions Connectivity diminishes among populations of P. zostericola over scales larger than a few hundred kilometres. As seagrass habitats world‐wide become increasingly fragmented, low levels of connectivity will result in an isolated future for P. zostericola and other species reliant on seagrass as habitat.     

Variation in hostplant relations and courtship signals of weed-associated populations of the brown planthopper, Nilaparvata lugens (Stål), from Australia and Asia: a test of the recognition species concept

Populations of the morphological species, Nilaparvata lugens (Stål), were found to breed and feed on the grass, Leersia hexandra Schwartz, at six sites in Queensland, Australia. They differ from sympatric rice-feeding populations in characters of pulse repetition frequencies of male and female acoustic courtship signals. The two host-derived populations hybridize freely in the laboratory, but in mate choice experiments show very significant preferences for homogametic matings. No indication of field hybridization has been found, so that the two morphologically inseparable populations represent sympatric biological species in Australia.
Populations from L. hexandra are also reported from four localities in Sri Lanka and one in Orissa, India. These resemble previously studied populations from the Philippines. They differ significantly in courtship call characters, both from sympatric rice-associated populations and from allopatric Leersia -associated populations from Australia.
The geographical variation reported for acoustic signals is not consistent with Paterson's recognition concept of species, but may be interpreted in terms of theories of allopatric speciation involving sexual selection for mate recognition signals.