Captive breeding of two insular populations of Pachyrhynchus sarcitis (Coleoptera: Curculionidae) from Lanyu and Babuyan Islands

Endemic species of oceanic islands are vulnerable due to their geographical isolation and small population sizes. For endangered island species, captive breeding program is an important strategy for conservation and sustainable management. Pachyrhynchus sarcitis is a flightless weevil decorated with colourful markings and distributed exclusively on several islets of Southeast Asia including Lanyu, Ludao, and Babuyan Islands. The life history of threatened Pachyrhynchus species of these islands was poorly known. This study reared P. sarcitis from Lanyu and Babuyan Islands for the first time in the laboratory using their host plant (Leea guineensis). The two island populations showed significant differences in instar numbers, in which the weevils from Lanyu Island had a higher instar number regardless the length of developmental duration. The adult body size of both sexes of the Babuyan population became smaller under laboratory condition; whereas Lanyu population in the laboratory did not show this trend. The differences in larval development might suggest local adaptation to the host plants or other life history associated characteristics which requires further research.     

Biogeography of the fauna of French Polynesia: diversification within and between a series of hot spot archipelagos

The islands of French Polynesia cover an area the size of Europe, though total land area is smaller than Rhode Island. Each hot spot archipelago (Societies, Marquesas, Australs) is chronologically arranged. With the advent of molecular techniques, relatively precise estimations of timing and source of colonization have become feasible. We compile data for the region, first examining colonization (some lineages dispersed from the west, others from the east). Within archipelagos, blackflies (Simulium) provide the best example of adaptive radiation in the Societies, though a similar radiation occurs in weevils (Rhyncogonus). Both lineages indicate that Tahiti hosts the highest diversity. The more remote Marquesas show clear examples of adaptive radiation in birds, arthropods and snails. The Austral Islands, though generally depauperate, host astonishing diversity on the single island of Rapa, while lineages on other islands are generally widespread but with large genetic distances between islands. More recent human colonization has changed the face of Polynesian biogeography. Molecular markers highlight the rapidity of Polynesian human (plus commensal) migrations and the importance of admixture from other populations during the period of prehistoric human voyages. However, recent increase in traffic has brought many new, invasive species to the region, with the future of the indigenous biota uncertain.     

The land fauna of Ascension Island: new data from caves and lava flows,and a reconstruction of the prehistoric ecosystem

Abstract. Terrestrial arthropods were investigated in 1990 and 1995 on Ascension, a young and extremely isolated volcanic island in the equatorial Atlantic. Three new genera (of Araneae, Oribatida and Psocoptera) were discovered and the number of apparently endemic species was increased from fourteen to about twenty-nine. Some 311 species of land animals (a few now extinct) are known to have established themselves on the island; in a few groups there may be significant numbers of unrecorded species. About ninety-five endemic and non-endemic species are considered to be native (including two marine turtles, twelve seabirds and two extinct landbirds); seventy-eight are of doubtful status; and at least 138 were probably introduced by humans. Natural colonists arrived mainly by air (drifting with the wind during migratory movements) but some evidently travelled on floating objects or attached to birds or other animals. Natural colonization was almost entirely from Africa. Before the arrival of humans, Ascension had an early successional ecosystem. The fauna in the lava and cinder deserts of the lowlands—both on the surface and in subterranean cracks and caves—was dominated by taxonomically varied scavengers and mainly arachnid predators. The scattered angiosperms here and in the foothills supported some host-specific herbivores with associated predators; they were also exploited (especially after exceptional rains) by a number of Orthoptera, Hemiptera and Lepidoptera derived from migratory African populations and perhaps reinforced at intervals by additional groups of colonists. The more extensive and largely cryptogamic vegetation on the central peak had a poor fauna probably composed mainly of micro-arthropods. Along coasts, on islets and in the extensive seabird colonies there were additional arthropod species and also a flightless rail and a night heron (both now extinct). Invertebrate stocks that colonized Ascension underwent a variety of evolutionary changes including phyletic evolution leading to endemic status, adaptation to subterranean life (Araneae, Pseudoscorpiones, Collembola and Psocoptera), character release (phorid Diptera), and probably splitting of lineages (speciation) within the island (Isopoda, Collembola and gryllid Orthoptera). The relatively high diversity of Pseudoscorpiones (five species in five genera) and their 100% apparent endemicity is notable. The indigenous fauna of Ascension provides a view of an early stage in the processes of colonization, adaptive evolution and radiation which—over much longer periods—give rise to the richer and more distinctive faunas of older oceanic islands such as Ascension's nearest neighbour, St Helena, where a few invertebrate clades have undergone repetitive speciation and some adaptive radiation.     

Parasitism of the lucerne pest Sitona discoideus Gyllenhal (Coleoptera: Curculionidae) and non-target weevils by Microctonus aethiopoides Loan (Hymenoptera: Braconidae) in south-eastern Australia, with an assessment of the taxonomic affinities of non-target hosts of M. aethiopoides recorded from Australia and New Zealand

Abstract  The braconid parasitoid Microctonus aethiopoides Loan has been released in Australia and New Zealand for biological control of the lucerne pest Sitona discoideus Gyllenhal. In New Zealand, the parasitoid attacks a number of endemic weevil species. A survey of Curculionoidea found in and near lucerne in south-eastern Australia was carried out to investigate whether similar non-target parasitism was occurring, and to relate this to levels of parasitism found in the target host, S. discoideus . Some of the original M. aethiopoides release sites were particularly targeted in the survey of 25 sites in Victoria, New South Wales and South Australia. Almost 2500 weevils were collected, of which over 90% were S. discoideus , with the remaining 197 other weevils comprising 29 species found at 15 of the 25 sites. Parasitism of S. discoideus by M. aethiopoides occurred at 12 lucerne sites, with levels ranging from 0 to 25%. A single incidence of parasitism of a species of an Australian native weevil Prosayleus sp. by M. aethiopoides was recorded. No parasitism of any other weevil species was observed. The taxonomic affinities between Sitona and native Australian and New Zealand weevils are discussed, concluding that non-target host range in M. aethiopoides may be determined more by ecological factors than by taxonomic affinities among its hosts.     

A comparative analysis of the mechanisms underlying speciation on Lord Howe Island

On Lord Howe Island, speciation is thought to have taken place in situ in a diverse array of distantly related plant taxa (Metrosideros, Howea and Coprosma; Proc. Natl Acad. Sci. USA 108 , 2011, 13188). We now investigate whether the speciation processes were driven by divergent natural selection in each genus by examining the extent of ecological and genetic divergence. We present new and extensive, ecological and genetic data for all three genera. Consistent with ecologically driven speciation, outlier loci were detected using genome scan methods. This mechanism is supported by individual‐based analyses of genotype–environment correlations within species, demonstrating that local adaptation is currently widespread on the island. Genetic analyses show that prezygotic isolating barriers within species are currently insufficiently strong to allow further population differentiation. Interspecific hybridization was found in both Howea and Coprosma, and species distribution modelling indicates that competitive exclusion may result in selection against admixed individuals. Colonization of new niches, partly fuelled by the rapid generation of new adaptive genotypes via hybridization, appears to have resulted in the adaptive radiation in Coprosma – supporting the ‘Syngameon hypothesis’.     

Contrasting patterns of molecular diversity and Wolbachia infection in bisexual and parthenogenetic Strophosoma weevils (Coleoptera: Curculionidae)

It has been postulated that parthenogenesis in weevil species is of hybrid origin, but some have speculated that Wolbachia infection plays a role through the modification of host breeding systems. Here we focus on Strophosoma weevils, which are known to be pests in young forest stands. Using molecular data, we investigated the diversity of the two most common Strophosoma species in Europe: S. capitatum, which reproduces bisexually, and S. melanogrammum, which is parthenogenetic. Also researched were their associations with the endosymbiotic bacterium Wolbachia. These species of weevil were found to be clearly distinguishable based on their mitochondrial DNA, with the bisexual taxa being more diverse. However, the nuclear DNA divergence of the two species was very low, and the parthenogenetic taxon was found to be heterozygous. Wolbachia infection was detected in all individuals of the S. melanogrammum populations and less than half of the S. capitatum populations. Moreover, multiple Wolbachia strains were found in both taxa (two in the former and three in the latter). The results of this research suggest that parthenogenesis in this genus is of hybrid origin and that Wolbachia could have played a role in speciation of these weevils.     

Variation in hostplant preference and performance by the milfoil weevil, Euhrychiopsis lecontei Dietz, exposed to native and exotic watermilfoils

Exotic plants often displace native plants and thus alter the availability of native hostplants for specialist herbivorous insects. The submersed aquatic weevil Euhrychiopsis lecontei Dietz is endemic to North America, but there are now source populations on the exotic Eurasian watermilfoil (Myriophyllum spicatum L.) as well as on the weevil's ancestral host, northern watermilfoil (Myriophyllum sibiricum Komarov). This provides an opportunity to examine a host range expansion in progress. To further define the host range of the weevil and to determine how population source and rearing plant influence host plant preference and performance, we conducted a series of preference and rearing experiments with weevils from two source populations reared on northern milfoil, on Eurasian milfoil, switched late in larval development from northern to Eurasian milfoil, and vice versa. We also included two rearing treatments with milfoils on which the weevil has not been documented: the native M. verticillatum L. and the exotic M. aquaticum Verd. Preference by weevils in the switched rearing treatments was similar to preferences exhibited by weevils reared solely on the second (later) milfoil species and an increase in preference for Eurasian milfoil was induced by adult exposure to Eurasian milfoil for 2 weeks. In contrast, sizes and development times of weevils in the switched rearing treatments were similar to sizes and development times exhibited by weevils reared solely on the first (early) milfoil species. These results indicate that preference by the milfoil weevil is determined late in larval development or later and Hopkins' host selection principle is not supported. However, size and development time were most affected by hostplant quality during larval development when larvae must acquire the resources needed for pupation. Oviposition preference in the milfoil weevil was a population attribute, not a fixed individual attribute and there was no significant variation in preference among individuals reared on northern milfoil, but significant variation in preference was detected among weevils reared on Eurasian milfoil. Weevils oviposited on all four milfoil species and completed development on three of them, but did not develop beyond the larval stage on M. aquaticum. Weevils reared on Eurasian milfoil developed faster and reached larger adult sizes than weevils in any other rearing treatment. The smallest sizes and longest development times were for weevils reared on the natives, northern milfoil and M. verticillatum. The milfoil weevil oviposits on an array of milfoil species and is unable to distinguish an unsuitable host (M. aquaticum) within this genus. The influence of rearing plant and adult exposure to Eurasian milfoil on hostplant preference suggests that host range expansion to novel congeners may occur more rapidly than predicted by models which assume that genetic variation is required. Significant variation among individuals in hostplant preference suggests the potential for a host shift to a plant for which E. lecontei appears pre-adapted.     

Genetic variation can promote system persistence in an experimental host-parasitoid system

We tested experimentally the effects of genetic variation in host population on the host-parasitoid system persistence. The experimental systems consisted of one parasitoid wasp species (Heterospilus prosopidis), one bean weevil species (Callosobruchus chinensis), and one bean species, of which only the host species (bean weevil) was genetically manipulated. As control treatments with low genetic heterogeneity in the host population, we used two bean weevil strains (Kyoto and Niigata strains) which have several contrasting ecological traits. For the high genetic heterogeneity treatment, hybrid bean weevils which were generated by crossbreeding the strains Kyoto and Niigata were used. In the multiple-generation experiments, all three treatments had different patterns of extinction. The control treatment with the Niigata strain was very prone to system extinction, whereas the treatment with hybrids showed coexistence of constituent species in almost all replicates and also showed stabilized population dynamics. The other control treatment, using the Kyoto strain, showed intermediate proneness. To interpret the results of multiple-generation experiments, we conducted several short-term experiments. The different persistence patterns between the two control treatments were explained by the shapes of the host-finding abilities of wasps and the growth rate of the bean weevils. The mean values of many ecological traits of hybrid lines were not different from those of the Kyoto strain, but their variability increased. These outcomes corresponded well to the prediction of models by Doebeli [J Theor Biol (1997) 188:109–120]. We discuss the mechanisms in which the variability in host species population was effective for the prolonged system persistence.     

Sexual dimorphism in head structures of the weevil Rhopalapion longirostre (Olivier 1807) (Coleoptera: Curculionoidea): a response to ecological demands of egg deposition

Extreme sexually dimorphic phenotypes are frequently attributed to strong sexual selection but they can also arise as a consequence of different ecological demands. The evolutionary emergence of elongated rostra was a key event in the adaptive radiation of weevils. Exaggerated female rostra evolved in numerous weevil taxa, enabling females to bore long channels for egg deposition into various parts of host plants. The investigated ecological scenario involves three species of brentid weevils, all associated with the same host plant, Alcea rosea. The present study reveals that: (1) Rhopalapion longirostre bores egg channels into the buds, and the female rostrum is twice as long and its surface is smoother than in the male; (2) Alocentron curvirostre and Aspidapion validum live on the same host plant but use the stems for egg deposition; in these species, female rostra are not exaggerated; (3) the females of all three species possess a stronger mandible musculature than males; (4) the elongated female snout of R. longirostre is a response to the requirements of boring egg channels of maximal depth into the buds of the host plant; and (5) female muscle strength is an adaptation to boring into hard plant tissues, irrespective of rostrum length. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 642–660.     

Evidence for a substantial host‐use bottleneck following the invasion of an exotic,polyphagous weevil

1. The successful establishment of novel plant–insect interactions may depend on the availability of suitable hosts, which itself is influenced by the inherent flexibility of the herbivore for the native plants in its new range. The polyphagous beech leaf mining weevil, Orchestes fagi L., is a recent invader to eastern Canada, and while beech is a primary host, it remains unclear the extent to which it might also utilise co‐occurring secondary hosts, as has been observed in its native European range. 2. A combination of field and laboratory feeding trials were used to quantify weevil secondary host use. Based on its expansive native host range in Europe, it was predicted that American beech (Fagus grandifolia Ehrh.), as well as several additional plant species, would be susceptible to weevil damage. 3. Contrary to this prediction, weevil feeding was almost entirely exclusive to beech in both the field and laboratory feeding trials. This result is further supported by field observations that revealed an absence of weevils and eggs on species other than beech. In general, the lack of pre‐diapause feeding on any alternate host species represented an extreme departure from feeding habits observed within the native range. 4. Overall, this host‐use bottleneck suggests that the adoption of a novel primary host by O. fagi, in this case American beech, may remove the normal requirement for secondary hosts and suggests a significant departure from native feeding habits with possible consequences for related life‐history parameters such as overwintering survival and fecundity.     

Factors driving adaptive radiation in plants of oceanic islands: a case study from the Juan Fernández Archipelago

Adaptive radiation is a common evolutionary phenomenon in oceanic islands. From one successful immigrant population, dispersal into different island environments and directional selection can rapidly yield a series of morphologically distinct species, each adapted to its own particular environment. Not all island immigrants, however, follow this evolutionary pathway. Others successfully arrive and establish viable populations, but they remain in the same ecological zone and only slowly diverge over millions of years. This transformational speciation, or anagenesis, is also common in oceanic archipelagos. The critical question is why do some groups radiate adaptively and others not? The Juan Fernández Islands contain 105 endemic taxa of angiosperms, 49% of which have originated by adaptive radiation (cladogenesis) and 51% by anagenesis, hence providing an opportunity to examine characteristics of taxa that have undergone both types of speciation in the same general island environment. Life form, dispersal mode, and total number of species in progenitors (genera) of endemic angiosperms in the archipelago were investigated from literature sources and compared with modes of speciation (cladogenesis vs. anagenesis). It is suggested that immigrants tending to undergo adaptive radiation are herbaceous perennial herbs, with leaky self-incompatible breeding systems, good intra-island dispersal capabilities, and flexible structural and physiological systems. Perhaps more importantly, the progenitors of adaptively radiated groups in islands are those that have already been successful in adaptations to different environments in source areas, and which have also undergone eco-geographic speciation. Evolutionary success via adaptive radiation in oceanic islands, therefore, is less a novel feature of island lineages but rather a continuation of tendency for successful adaptive speciation in lineages of continental source regions.     

Weevils Lixinae (Coleoptera,Curculionidae) as gall formers

Galls induced by six species of Lixinae weevils from Ukrainian steppes are described. The gall formation by Larinus species is doubtful. One gall may in some cases be jointly occupied by different weevil species. The adaptive significance of gall formation in Lixinae is discussed.     

Migration potential of the banana weevil Cosmopolites sordidus

• 1 The banana weevil Cosmopolites sordidus Germar (Coleoptera: Curculionidae) is a major pest in banana (Musa spp.) growing areas. The weevil is known to be relatively sedentary and closely associated with its host plant but little is known about the species' ability to migrate between banana fields and in nonhost habitats.
• 2 Mark–recapture experiments were conducted to assess the weevils' migration potential, possible differences between the sexes, and the relative attractiveness of pseudostem and pheromone baits.
• 3 One thousand two hundred marked weevils were released in the nonhost habitat at five distances (5, 10, 20, 40 and 70 m) from fresh pseudostem, and from pitfall traps baited with 45 mg of sordidin.
• 4 Two hundred males and 200 females were marked and released at five distances (5, 10, 20, 40 and 70 m) from the pheromone traps.
• 5 Distance and distance/bait interactions had a significant effect on recaptured weevils (binary logistic regression). The two baits were almost equally attractive to weevils in the range 0–10 m, whereas the pheromone was more attractive in the range 10–100 m.
• 6 Distance, bait and distance/bait interactions had a significant effect on the time elapsed from release to recapture (regression with life data) but the pattern observed was not consistent.
• 7 There was no significant difference between males and females with respect to distance or time elapsed from release to recapture.
• 8 The results obtained in the present study show that the migration potential of the banana weevil is greater than previously reported. This should be taken into account when new banana fields are established with clean planting material.

     

Metapopulation structure of a seed-predator weevil and its host plant in arms race coevolution

Although the importance of gene flow in the geographic structuring of host-parasite interactions has been well discussed, little is known about how dispersal drives the spatial dynamics of other types of coevolutionary interactions in nature. We evaluated the roles of gene flow in the geographically structured processes of a predator-prey arms race involving a seed-predatory weevil with a long mouthpart and its host camellia plant with a thick fruit coat. Molecular genetic analyses showed that both weevil and camellia populations were structured at a spatial scale of several kilometers. Importantly, the spatial pattern of the migration of weevils, but not that of camellias, imposed significant effects on the geographic configuration of the levels of coevolutionary escalation. This result suggests that even if migration is limited in one species (camellia), local coevolution with the other species that migrates between neighboring localities (weevil) can reduce the interpopulation difference in the local adaptive optima of the former species. Thus, gene flow of a species potentially homogenizes the local biological environments provided by the species and thereby promotes the evolutionary convergence of its coevolving counterparts. Consequently, by focusing on coevolutionary interactions in natural communities, "indirect" effects of gene flow on the adaptive divergence of organisms could be identified.     

The terrestrial Isopoda (Crustacea,Oniscidea) of Rapa Nui (Easter Island), with descriptions of two new species

Nine species of terrestrial isopods are reported for the Polynesian island of Rapa Nui (Easter Island) based upon museum materials and recent collections from field sampling. Most of these animals are non-native species, but two are new to science: Styloniscus manuvaka sp. n. and Hawaiioscia rapui sp. n. Of these, the former is believed to be a Polynesian endemic as it has been recorded from Rapa Iti, Austral Islands, while the latter is identified as a Rapa Nui island endemic. Both of these new species are considered ‘disturbance relicts’ and appear restricted to the cave environment on Rapa Nui. A short key to all the oniscidean species presently recorded from Rapa Nui is provided. We also offered conservation and management recommendations for the two new isopod species.     

Competitive speciation

A new mode of speciation, competitive speciation, is suggested. It assumes that fitness is depressed by the density of a phenotype's competitors, and that the adaptive landscape of phenotypes is complex. From this it follows that some intermediate forms may be fit if and only if some extreme forms are rare or absent. Subsequent to the evolution and population growth of both extreme forms, the intermediate may disappear and homogamy evolve among each of the extremes because of disruptive selection If so, sympatric speciation has occurred and niche space has been rendered into discrete segments.
The limitations of the forces leading to competitive speciation are explored. Competitive speciation is discussed in relation to stasipatric speciation and host race formation. It may be responsible for both. Finally the rates of geographical speciation and polyploidy are compared to those of competitive speciation. The latter should be almost as fast as polyploidy and may be at the root of adaptive radiation. Unlike either polyploidy or geographical speciation, competitive speciation accelerates when species diversity declines.     

Diversification rates have declined in the Malagasy herpetofauna

The evolutionary origins of Madagascar''s biodiversity remain mysterious despite the fact that relative to land area, there is no other place with consistently high levels of species richness and endemism across a range of taxonomic levels. Most efforts to explain diversification on the island have focused on geographical models of speciation, but recent studies have begun to address the island''s accumulation of species through time, although with conflicting results. Prevailing hypotheses for diversification on the island involve either constant diversification rates or scenarios where rates decline through time. Using relative-time-calibrated phylogenies for seven endemic vertebrate clades and a model-fitting framework, I find evidence that diversification rates have declined through time on Madagascar. I show that diversification rates have clearly declined throughout the history of each clade, and models invoking diversity-dependent reductions to diversification rates best explain the diversification histories for each clade. These results are consistent with the ecological theory of adaptive radiation, and, coupled with ancillary observations about ecomorphological and life-history evolution, strongly suggest that adaptive radiation was an important formative process for one of the most species-rich regions on the Earth. These results cast the Malagasy biota in a new light and provide macroevolutionary justification for conservation initiatives.     

补充营养对枹栎象成虫寿命的影响

在饲养笼内分别饲喂枹栎(Quercus serrata Murray)幼果、枹栎嫩枝、清水和10%蔗糖水,以不饲喂任何食物为对照,研究营养补充对枹栎象Curculio haroldi Faust成虫寿命的影响。同时,还研究枹栎象的个体大小和性别对其寿命是否有潜在影响。结果表明:补充不同营养对枹栎象的寿命有显著影响,其中10%蔗糖水组的寿命最长,是其他营养组的3~4倍。另外,虫体大小(即体长)对枹栎象寿命也有显著影响,且雌虫寿命一般比雄性略长,但性别间无显著差异。研究结果说明,营养品质和虫体大小可显著影响枹栎象寿命,进而影响其繁殖以及对寄主植物的危害。     

Could bacterial associations determine the success of weevil species?

The weevil superfamily Curculionoidea is the largest insect group and so the largest animal group on earth. This taxon includes species which represent an important threat to many economically important crops and, therefore, pose a risk to agriculture and food security. Insect–bacteria associations have been recognised to provide the insect host with many benefits, such as ensuring the acquisition of essential nutrients or protecting the host from natural enemies. The role of bacteria associations within the weevil superfamily remains nonetheless understudied in comparison with other insect taxa. This review draws together existing knowledge on the influence of bacteria associated with weevils known to be agricultural pest species. The implications of these weevil–bacterial associations in determining pest status and their relevance to targeted pest management interventions are discussed. Specific consideration is given to the role of bacteria in cuticle formation, flight activity, reproduction manipulation and adaptation to different environments and food sources.     

Movement of adult pecan weevils Curculio caryae within pecan orchards

1 The pecan weevil Curculio caryae (Horn) (Coleoptera: Curculionidae) is an indigenous pest of pecan Carya illinoinensis (Wangenh.) K. Koch, in North America. Understanding the movement of this pest from the orchard floor to host trees could lead to pest management practices that exploit weevil behaviour and thus reduce insecticide application to the entire orchard canopy. Furthermore, no information exists on diel periodicity of pecan weevil movement. 2 Movement of adult pecan weevils crawling and flying to the host trunk, flying to the host canopy, crawling within the host canopy and flying between host trees was studied using four types of passive traps over four seasons. Each type of trap was used to capture weevils at different locations on or near the tree and to discriminate flying versus crawling behaviour. 3 More pecan weevils crawl to the trunk than fly and a proportion of the population flies directly from the orchard floor into the pecan canopy. The majority of this movement occurs at dusk. 4 The vertical distribution of weevils was generally uniform throughout the canopy but more weevils were captured in suspended traps nearest tree tops, rather than traps near the ground, when flying between trees and this was significantly so for two of 4 years. 5 The results of the present study are contrary to previous reports suggesting that most adult pecan weevils fly to the pecan trunk after emergence from the soil; however, our results did indicate that a proportion of the population flies directly from the orchard floor into the pecan canopy and thus would circumvent strategies that attempt to control weevils moving up the trunk.