Chrysomelid Beetle Research Articles

Ecological relationship between floral thermogenesis and pollination in Nelumbo lutea (Nelumbonaceae)

Floral thermogenesis is an unusual floral trait with a well-documented physiological process, and yet, there is limited understanding of how this trait influences plant reproduction. The current study was undertaken to gain a better understanding of how floral thermogenesis in Nelumbo lutea impacts pollinator attraction and consequent plant reproduction. We conducted field studies on floral thermogenesis and thermoregulation, flower sexual development, floral visitation patterns, breeding system, pollen transfer dynamics, and floral scent production. The most abundant visitors to the thermoregulatory flowers included the Phoridae (Diptera), Chrysomelidae (Coleoptera), and Hymenoptera. Chrysomelid beetles, particularly Diabrotica, were frequent visitors to both first-day female- and second-day bisexual-phase flowers, while phorid flies were most common in bisexual-phase flowers. Pollen transfer experiments indicated that Diabrotica was equally effective in depositing pollen on stigmas, as were the less frequent, but pollen-loaded halictid bees. Flowers received a taxonomically wide assemblage of floral visitors and appear adapted to attract beetles, primarily Chrysomelidae and medium-sized bees. This study is the first to provide strong support that beetles can comprise the dominant portion of floral visitors and are as effective in pollen transfer as bees. Thermogenesis aids in dispersing the main floral scent component-1,4-dimethoxybenzene-attracting both chrysomelids and bees, while thermoregulation causes chrysomelid beetles to actively seek out new flowers for evening residence. This search behavior likely results in chrysomelids affecting cross-pollination.

Wide Host Ranges of Herbivorous Beetles? Insights from DNA Bar Coding

There are very few studies that have investigated host-specificity among tropical herbivorous insects. Indeed, most of the trophic interactions of herbivorous insects in Southeast Asian tropical rainforests remain unknown, and whether polyphagous feeding is common in the herbivores of this ecosystem has not been determined. The present study employed DNA bar coding to reveal the trophic associations of adult leaf-chewing chrysomelid beetles in a Bornean rainforest. Plant material ingested by the adults was retrieved from the bodies of the insects, and a portion of the chloroplast rbcL sequence was then amplified from this material. The plants were identified at the family level using an existing reference database of chloroplast DNA. Our DNA-based diet analysis of eleven chrysomelid species successfully identified their host plant families and indicated that five beetle species fed on more than two families within the angiosperms, and four species fed on several families of gymnosperms and/or ferns together with multiple angiosperm families. These findings suggest that generalist chrysomelid beetles associated with ecologically and taxonomically distant plants constitute a part of the plant-insect network of the Bornean rainforest.

Tempo and mode of evolutionary radiation in Diabroticina beetles (genera Acalymma, Cerotoma, and Diabrotica)

Adaptive radiation is an aspect of evolutionary biology encompassing microevolution and macroevolution, for explaining the principles of lineage divergence. There are intrinsic as well as extrinsic factors that can be postulated to explain that adaptive radiation has taken place in specific lineages. The Diabroticina beetles are a prominent example of differential diversity that could be examined in detail to explain the diverse paradigms of adaptive radiation. Macroevolutionary analyses must present the differential diversity patterns in a chronological framework. The current study reviews the processes that shaped the differential diversity of some Diabroticina lineages (i.e. genera Acalymma, Cerotoma, and Diabrotica). These diversity patterns and the putative processes that produced them are discussed within a statistically reliable estimate of time. This was achieved by performing phylogenetic and coalescent analyses for 44 species of chrysomelid beetles. The data set encompassed a total of 2,718 nucleotide positions from three mitochondrial and two nuclear loci. Pharmacophagy, host plant coevolution, competitive exclusion, and geomorphological complexity are discussed as putative factors that might have influenced the observed diversity patterns. The coalescent analysis concluded that the main radiation within Diabroticina beetles occurred between middle Oligocene and middle Miocene. Therefore, the radiation observed in these beetles is not recent (i.e. post-Panamanian uplift, 4 Mya). Only a few speciation events in the genus Diabrotica might be the result of the Pleistocene climatic oscillations.

Insect herbivores, chemical innovation, and the evolution of habitat specialization in Amazonian trees

Herbivores are often implicated in the generation of the extraordinarily diverse tropical flora. One hypothesis linking enemies to plant diversification posits that the evolution of novel defenses allows plants to escape their enemies and expand their ranges. When range expansion involves entering a new habitat type, this could accelerate defense evolution if habitats contain different assemblages of herbivores and/or divergent resource availabilities that affect plant defense allocation. We evaluated this hypothesis by investigating two sister habitat specialist ecotypes of Protium subserratum (Burseraceae), a common Amazonian tree that occurs in white-sand and terra firme forests. We collected insect herbivores feeding on the plants, assessed whether growth differences between habitats were genetically based using a reciprocal transplant experiment, and sampled multiple populations of both lineages for defense chemistry. Protium subserratum plants were attacked mainly by chrysomelid beetles and cicadellid hemipterans. Assemblages of insect herbivores were dissimilar between populations of ecotypes from different habitats, as well as from the same habitat 100 km distant. Populations from terra firme habitats grew significantly faster than white-sand populations; they were taller, produced more leaf area, and had more chlorophyll. White-sand populations expressed more dry mass of secondary compounds and accumulated more flavone glycosides and oxidized terpenes, whereas terra firme populations produced a coumaroylquinic acid that was absent from white-sand populations. We interpret these results as strong evidence that herbivores and resource availability select for divergent types and amounts of defense investment in white-sand and terra firme lineages of Protium subserratum, which may contribute to habitat-mediated speciation in these trees.

Dissecting the Mode of Maize Chlorotic Mottle Virus Transmission (Tombusviridae: Machlomovirus) by <I>Frankliniella williamsi</I> (Thysanoptera: Thripidae)

Maize chlorotic mottle virus (MCMV) (Tombusviridae: Machlomovirus) has been recorded in Hawaii (Kauai Island) since the early 1990s and has since become one of the most widespread corn viruses in the Hawaiian Islands. In the United States Mainland, MCMV has been reported to be transmitted by six different species of chrysomelid beetles, including the western corn rootworm, Diabrotica virgifera virgifera LeConte. However, none of these beetle species have been reported in Hawaii where the corn thrips, Frankliniella williamsi Hood (Thysanoptera: Thripidae) has been identified to be the main vector. In this study, we developed leaf disk transmission assays and real time reverse transcription-polymerase chain reaction to examine the mode of MCMV transmission by the corn thrips. We showed that thrips transmitted the virus with no evidence for latent periods. Both larvae and adults transmitted the virus for up to 6 d after acquisition, with decreasing rates of transmission as time progressed. There was no evidence that adult thrips that acquired the virus as larvae were competent vectors. Real time reverse-transcription polomerase chain reaction assays showed that viral load was depleted from the vector's body after thrips had access to healthy plant tissue. Depletion of viral load was also observed when thrips matured from larvae to adults. Thrips were able to transmit MCMV after acquisition and inoculation access periods of 3 h. However, transmission efficiency increased with longer acquisition and inoculation access periods. Taken altogether our data suggests that corn thrips transmit MCMV in a semipersistent manner. To our knowledge, this is the first work reporting evidence of a plant virus transmitted semipersistently by thrips.

Tradescantia fluminensis, an exotic weed affecting native forest regeneration in New Zealand: Ecological surveys, safety tests and releases of four biocontrol agents from Brazil

In the native range of Tradescantia fluminensis in SE Brazil surveys revealed a natural enemy biota attacking the plant that was rich in potential biocontrol agents for New Zealand (NZ), including nine fungi and 10 herbivorous insect species. Similar surveys in NZ, where T. fluminensis is an invasive exotic weed, revealed no specialist insect herbivores or pathogens. The Brazilian insect herbivores included leafmining, stemboring and gall-forming feeding guilds that were absent in NZ. Mean foliar damage levels per site on T. fluminensis were 7.8× higher for folivores in Brazil cf. NZ, and 21.2× higher for pathogens. The presence of rust pustules, or ‘brown lesions’, on leaves in Brazil was negatively associated with damage by folivores, perhaps indicating an antagonistic interaction. In contrast, damage by the white smut fungus, Kordyana sp., was not negatively associated with folivore damage. Mean dry biomass of T. fluminensis was significantly lower in Brazil (164gm−2) cf. NZ (455gm−2). In NZ, 85% of sites had biomass measures >200gm−2 (the previously determined threshold above which native forest regeneration fails). In Brazil, only 27% of sites had biomass measures >200gm−2. Among the insect herbivores, three chrysomelid beetles, Neolema ogloblini, Neolema abbreviata and Lema basicostata were prioritised as potential biocontrol agents. Their larvae cause potentially complementary damage to leaves, shoot-tips and mature stems, respectively. Several pathogens, including a rust, were rejected before we selected the Kordyana species. Host range testing of all four agents showed sufficient host-specificity for consideration for release in NZ. Neolema ogloblini and L. basicostata were field-released in NZ in 2011 and 2012, with the field-release of N. abbreviata due late 2012. An application to release Kordyana sp. in NZ has been made.

Correction: Phenology of Scramble Polygyny in a Wild Population of Chrysolemid Beetles: The Opportunity for and the Strength of Sexual Selection

There was a typographical error in the title and citation. The correct title is: Phenology of Scramble Polygyny in a Wild Population of Chrysomelid Beetles: The Opportunity for and the Strength of Sexual Selection. The correct citation is: Baena ML, Macias-Ordonez R (2012) Phenology of Scramble Polygyny in a Wild Population of Chrysomelid Beetles: The Opportunity for and the Strength of Sexual Selection. PLoS ONE 7(6): e38315. doi:10.1371/journal.pone.0038315

Phenology of scramble polygyny in a wild population of chrysomelid beetles: the opportunity for and the strength of sexual selection [corrected

Recent debate has highlighted the importance of estimating both the strength of sexual selection on phenotypic traits, and the opportunity for sexual selection. We describe seasonal fluctuations in mating dynamics of Leptinotarsa undecimlineata (Coleoptera: Chrysomelidae). We compared several estimates of the opportunity for, and the strength of, sexual selection and male precopulatory competition over the reproductive season. First, using a null model, we suggest that the ratio between observed values of the opportunity for sexual selections and their expected value under random mating results in unbiased estimates of the actual nonrandom mating behavior of the population. Second, we found that estimates for the whole reproductive season often misrepresent the actual value at any given time period. Third, mating differentials on male size and mobility, frequency of male fighting and three estimates of the opportunity for sexual selection provide contrasting but complementary information. More intense sexual selection associated to male mobility, but not to male size, was observed in periods with high opportunity for sexual selection and high frequency of male fights. Fourth, based on parameters of spatial and temporal aggregation of female receptivity, we describe the mating system of L. undecimlineata as a scramble mating polygyny in which the opportunity for sexual selection varies widely throughout the season, but the strength of sexual selection on male size remains fairly weak, while male mobility inversely covaries with mating success. We suggest that different estimates for the opportunity for, and intensity of, sexual selection should be applied in order to discriminate how different behavioral and demographic factors shape the reproductive dynamic of populations.

Potential feeding deterrents found in hemlock woolly adelgid, Adelges tsugae

The nonnative hemlock woolly adelgid (Adelges tsugae Annand, Hemiptera: Sternorrhyncha: Adelgidae) has been a significant mortality agent of eastern hemlock (Tsuga canadensis Carriere) throughout a large portion of its geographic range. During a study investigating adelgid vigor in relation to host health, it was noted that adelgid extracts ranged from a yellow to a deep red color. Analysis by GC-MS identified the presence of the anthraquinone, chrysophanol and its anthrone precursor, chrysarobin in the extract. These compounds are predator deterrents in several other insects, including chrysomelid beetles. It is hypothesized that these compounds serve a similar purpose in the hemlock woolly adelgid.

The natural home for agricultural entomologists?

With the plethora of entomological journals, applied and otherwise, now available, why should an entomologist attempt to publish in Annals of Applied Biology? At first sight it may seem a less than obvious choice, but the Annals of Applied Biology has a long and distinguished tradition of entomological publishing and in the first ever editorial the point is made very strongly that applied entomologists were very much seen as important readers and contributors to the journal (Maxwell-Lefory, 1914). During the 1920s and 1930s almost half the papers published were entomological in nature and many focused on cereal crops (Petheridge, 1921). The current emphasis on statistical excellence was also evident in those early days with statisticians from Rothamsted Experimental Station (Mathetes, 1924) leading the way. Then as now, however, the crops covered were not all cereals, as a study by Newton (1934) investigating an attack of chrysomelid beetles on henbane (Hyoscyamus niger) reveals. During the war years, although papers on plant pathogens were in the ascendant, studies of insect pests on cereals were still prevalent (Barnes & Weil, 1944). During the 1950s the Annals led the way in publicising new monitoring technology such as the early development of the Rothamsted suction traps (Johnson & Taylor, 1955) and the understanding of the modes of action of insecticides (Stringer et al., 1955). During the 1960s plant pathology dominated the journal but entomologists still saw the Annals as a useful outlet for work on orchard pests (Avery & Briggs, 1968). The advent of large scale cereal aphid outbreaks in the 1970s saw important pioneering work appearing in the journal throughout the 1970s and early 1980s (Dean, 1973, 1974; Watt, 1979; Leather & Dixon, 1981). The Annals continued to be a home for papers investigating pests of cereals during the 1990s (Howard & Dixon, 1995) and despite the presence of rivals such as Journal of Economic Entomology and Bulletin of Entomological Research and the launch of Agricultural & Forest Entomology in 1999, continued to attract good quality agricultural and forest entomology papers from around the world as the 21st century began (Kaspi & Parrella, 2003; Oberg & Ekbom, 2006; Timms & Leather, 2008). Now as we progress through the second decade of the century, the Annals has become ever more international and topical, publishing papers on the effective rearing of biological control agents (Colinet & Hance, 2010), pests of coconuts (Gitau et al., 2011), hemipteran virus vectors (Kirchner et al., 2011), the effects of Bt maize on pests and natural enemies (Petzold-Maxwell et al., 2012), modern insecticide efficacy (Tome et al., 2012) and the ever present pests of cereals (Aqueel & Leather, 2012). The Annals of Applied Biology also publishes influential reviews such as that examining insect pest movement in agricultural landscapes (Mazzi & Dorn, 2012). Many of us these days are encouraged by our employers to submit to journals with the highest impact factors. This is not necessarily good for our science or our intended audience. It is much better to target a journal where we will get the widest readership, and a high impact factor does not necessarily go hand in hand with readership. Applied journals tend to be read much more than they are cited, as their readership includes a high number of practitioners, for example in the case of a journal such as the Annals of Applied Biology, advisory and extension entomologists, agronomists, people from the agro-chemical industry, biological control practitioners etc. In 2010 for example there were 73 170 full-text downloads from the Annals and in 2011 this had risen to almost 82 000. Thus, as an agricultural entomologist it makes a great deal of sense to publish in a journal such as the Annals of Applied Biology that speaks directly to the agricultural and associated sectors as well as to the research community. We are particularly interested in receiving submissions dealing with global food security issues, in particular innovative crop protection methods, for example, modern approaches to biological control and integrated pest management. We also welcome papers dealing with the

Estimating direct resistance in willows against a major insect pest, Phratora vulgatissima, by comparing life history traits

AbstractMany Salix species (Salicaceae) have a high energy quotum and efficient nitrogen use, resulting in a high and stable biomass production, making these plants suitable as bioenergy crops. However, Salix coppices are sensitive to herbivory by chrysomelid beetles, such as Phratora vulgatissima L. (Coleoptera: Chrysomelidae), and to maintain high biomass yields over several years, durable plant resistance is necessary. We have developed a reliable and efficient bioassay that can be used as a tool for detection of resistance against P. vulgatissima in Salix. Screening of six clones of one susceptible (Salix viminalis L.) and one resistant (Salix dasyclados Wimm.) willow species, by the response of several life history traits of larval and adult P. vulgatissima, identified egg production as the most reliable trait for resistance. We show that a 2‐week bioassay of oviposition rate is sufficient for a trustworthy estimation of both total egg production and survival of adult leaf beetles. In addition, to elucidate the variation in resistance among the studied clones, leaf concentrations of various phenolic compounds were compared with the key life history traits of the beetles. Phenolic compounds, especially salicylates, have previously been reported as the main factor controlling Salix resistance against P. vulgatissima. Indeed we found higher levels of salicylates in the resistant clones and larval performance was negatively correlated to the concentration of salicylates in the leaves. In addition, we found indications of negative effects of a luteolin derivative and quercetin‐3‐glucoside on leaf beetle performance, but further studies are needed to elucidate the specific roles that the different phenolic compounds play in plant resistance.

Revision of the Eastern Asian genera Ambrostoma Motschulsky and Parambrostoma Chen (Coleoptera: Chrysomelidae: Chrysomelinae)

The leaf beetle genera AmbrostomaMotschulsky, 1860 and ParambrostomaChen, 1934 have been revised and now include 14 species. Two new species from Nepal are described, Parambrostoma kippenbergisp.n. and P. medvedevisp.n. Three new synonymies are established: Ambrostoma rugosopunctatum Chen = Ambrostoma (Parambrostoma) laosensis Kimoto & Gressitt, syn.n., Ambrostoma rugosopunctatum Chen = Ambrostoma daccordii Medvedev, syn.n.,Ambrostoma fortunei (Baly) = Ambrostoma quadriimpressum chusanica Gruev, syn.n. One species was transferred from Chrysomela Linnaeus to Ambrostoma Motschulsky: A. superbum (Thunberg), comb.n. All the species now included are described and illustrated. Microcomputer tomography was applied for the first time in a study on chrysomelid beetles. A cladistic analysis based on morphological characters of adults was conducted to reconstruct the intergeneric and interspecific phylogeny of Ambrostoma and Parambrostoma. The results show that the monophyly of both genera is well supported. Ambrostoma is widespread in East Asia, whereas Parambrostoma is restricted to the southern slope of the Himalayas, where a relatively recent and modest speciation took place.

Improved synthesis of the chrysomelid pheromone (6R,7S)-(+)-himachala-9,11-diene via spontaneous bromination and didehydrobromination of 2,6,6,9-tetramethyl-bicyclo[5.4.0]undec-8-ene

A convenient synthesis of (6 R,7 S)-(+)-himachala-9,11-diene, the pheromone of the chrysomelid beetle Phyllotreta striolata is described. The diene is obtained in a single op eration by a spon- taneous bromination/dehydrobromination of 2,6,6,9-tetramethylbicyclo(5.4.0)undec-8-ene. The halogenation/dehalogenation sequence proceeds spontaneously in CCl 4, and is less uniform in CH 2Cl 2 and CHCl 3. 1 H NMR experiments carried out in presence of the radical scavenger di- tert -butyl-4-methylphenol suggest an ionic mechanism for this reaction. Theoretical calculations demonstrate that the spontaneous reaction profits f rom the strongly exergonic addition of Br 2 to the double bond and an almost neutral energy differ ence between the starting olefin and the diene pheromone.

The adipokinetic hormone family in Chrysomeloidea: structural and functional considerations

The presented work is a hybrid of an overview and an original research paper on peptides belonging to the adipokinetic hormone (AKH) family that are present in the corpora cardiaca of Chrysomeloidea. First, we introduce the AKH/red pigment-concentrating hormone (RPCH) peptide family. Second, we collate the available primary sequence data on AKH peptides in Cerambycidae and Chrysomelidae, and we present new sequencing data (from previously unstudied species) obtained by liquid-chromatography coupled with ion trap electrospray ionisation mass spectrometry. Our expanded data set encompasses the primary structure of AKHs from seven species of Cerambycidae and three species of Chrysomelidae. All of these species synthesise the octapeptide code-named Peram-CAH-I (pGlu-Val-Asn-Phe-Ser-Pro-Asn-Trp amide). Whereas this is the sole AKH peptide in Cerambycidae, Chrysomelidae demonstrate a probable event of AKH gene duplication, thereby giving rise to an additional AKH. This second AKH peptide may be either Emppe-AKH (pGlu-Val-Asn-Phe-Thr-Pro-Asn-Trp amide) or Peram-CAH-II (pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp amide). The peptide distribution and structural data suggest that both families are closely related and that Peram-CAH-I is the ancestral peptide. We hypothesise on the molecular evolution of Emppe-AKH and Peram-CAH-II from the ancestral peptide due to nonsynonymous missense single nucleotide polymorphism in the nucleotide coding sequence of prepro-AKH. Finally, we review the biological significance of the AKH peptides as hyperprolinaemic hormones in Chrysomeloidea, i.e. they cause an increase in the circulating concentration of proline. The mobilisation of proline has been demonstrated during flight in both cerambycid and chrysomelid beetles.

Associational resistance and associational susceptibility: specialist herbivores show contrasting responses to tree stand diversification

Heterospecific neighbors may reduce damage to a focal plant by lowering specialist herbivore loads (associational resistance hypothesis), or enhance damage by increasing generalist herbivore loads (associational susceptibility hypothesis). We tested the associational effects of tree diversity on herbivory patterns of the tropical focal tree Tabebuia rosea in an experimental plantation setup, which contained tree monocultures and mixed stands. We found higher herbivore damage to T. rosea at higher tree diversity, indicating that T. rosea did not benefit from associational resistance but rather experienced associational susceptibility. The specific consideration of the two dominant insect herbivore species of T. rosea, the specialist chrysomelid Walterianella inscripta and the specialist pyralid Eulepte gastralis, facilitated understanding of the detected damage patterns. Tree diversity exerted opposite effects on tree infestation by the two herbivores. These findings point to resource concentration effects for the chrysomelid beetle (favored by tree monoculture) and to resource dilution effects for the pyralid caterpillar (favored by tree mixture) as underlying mechanisms of herbivore distribution. A strong contribution of the pyralid to overall damage patterns in diversified stands suggests that associational susceptibility may not necessarily be related to higher abundances of generalist herbivores but may also result from specialized herbivores affected by resource dilution effects. Thus, the identity and biology of herbivore species has to be taken into account when attempting to predict damage patterns in forest ecosystems.

Validation of RNA interference in western corn rootworm Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) adults

RNA interference (RNAi) is commonly used in insect functional genomics studies and usually involves direct injection of double-stranded RNA (dsRNA). Only a few studies have involved exposure to dsRNAs through feeding. For western corn rootworm (Diabrotica virgifera virgifera) larvae, ingestion of dsRNA designed from the housekeeping gene, vacuolar ATPase (vATPase) triggers RNAi causing growth inhibition and mortality; however, the effect of dsRNA feeding on adults has not been examined. In this research, WCR adults were fed with vATPase-dsRNA-treated artificial diet containing a cucurbitacin bait, which is a proven feeding stimulant for chrysomelid beetles of the subtribe Diabroticina to which rootworms belong. Real-time PCR confirmed suppression of vATPase expression and western blot analysis indicated reduced signal of a protein that cross-reacted with a vATPase polyclonal antiserum in WCR adults exposed to artificial diet treated with dsRNA and cucurbitacin bait. Continuous feeding on cucurbitacin and dsRNA-treated artificial diet resulted in more than 95% adult mortality within 2 weeks while mortality in control treatments never exceeded 20%. This research clearly demonstrates the effect of RNAi on WCR adults that have been exposed to dsRNA by feeding and establishes a tool to screen dsRNAs of potential target genes in adults. This technique may serve as an alternative to target screening of larvae which are difficult to maintain on artificial diets.

Sequestration of Camptothecin, an Anticancer Alkaloid, by Chrysomelid Beetles

Camptothecin (CPT), a monoterpene indole alkaloid, is a potent inhibitor of eukaryotic toposiomerase-I. Several derivatives of CPT are in clinical use against ovarian and lung cancers. CPT has been reported from several plant species belonging to the order Asterids, with the highest concentration in Nothapodytes nimmoniana (family Icacinaceae). In this paper, we report an intriguing observation of chrysomelid beetles (Kanarella unicolor Jacobby) feeding on the leaves of N. nimmoniana without any apparent adverse effect. LC-MS/MS analysis of the beetles indicated that 54.9% of the ingested CPT's was recovered from the wings, followed by lesser amounts in the head and abdomen. LC-HRMS analysis revealed that most of the CPT in the insect body was in the parental form available in the plants without any major metabolizable products, including sulfated and glucuronilated forms. The mechanism by which the beetles are able to tolerate substantially high levels of CPT in their body tissue is under investigation.

Cytogenetic effect of Alternanthera philoxeroides (alligator weed) on Agasicles hygrophila (Coleoptera: Chrysomelidae) in its native range

Plant genotypic effects can alter insects’ ability of utilizing their host plant. Alligator weed, Alternanthera philoxeroides, is a South American amphibious Amaranthaceae, which invades aquatic and terrestrial habitats. Populations with varying morphotypes and cytotypes were identified and further associated with a polyploid hybrids complex in Argentina, which probably is the centre of origin and diversification of alligator weed. The current model of the hybrid complex formation proposes that diploid ancestors gave rise to allotetraploids and allohexaploids. Agasicles hygrophila is a monophagous chrysomelid beetle which successfully controls A. philoxeroides in regions with mild winters and where the weed grows in aquatic habitats. However, plant genetic characteristics could constrain insect development and reproduction, providing an alternative explanation for the restricted success of biological control of alligator weed with A. hygrophila. We investigated the effect of four A. philoxeroides populations with varying cytogenetical characteristics on plant–insect interaction with A . hygrophila in the native range of the weed. The insect’s life cycle on each host population was studied. In addition, the genetic relationships among the weed populations was explored using dot blot analysis. Plant population affected insect survival and fecundity, but not life cycle length nor third larval instar mortality, pupal mortality or female proportion. Plant internode diameter was not a restriction for insect pupation. All hexaploid populations of A. philoxeroides, as well as the close related A. aquatica, hybridized with the tetraploid population probe with similar intensity, meaning that this population is a component of their polyploid genome.

Oxygen consumption of the aquatic leaf beetles Macroplea mutica and Macroplea appendiculata is low and not influenced by salinity

Leaf beetles of the genus Macroplea live permanently under water. Species‐specific preferences for either freshwater or brackish water are available in the literature. To detect potential physiological differences, the oxygen consumption of Macroplea mutica and Macroplea appendiculata from habitats with differing salinities is measured at two different salinities (0 and 10). The specific oxygen consumption does not depend on oxygen saturation of the water (values in the approximate range of 25–100% occur during the experiments). There is no difference between species or sampling locations. Similarly, the salinity during the measurements does not affect the oxygen consumption of the beetles, either when compared as salinity per se (0 versus 10), or when classified as home salinity or atypical salinity. Comparisons with other chrysomelid beetles and aquatic insects (using available published data) reveal that the two Macroplea species have relatively low metabolic rates. This finding is discussed in the light of activity patterns and morphology, especially the reduction of flight muscles, which comprise a highly metabolically active tissue.

St. John’s wort beetles would not have been introduced to New Zealand now: A retrospective host range test of New Zealand’s most successful weed biocontrol agents

St. John’s wort, Hypericum perforatum, was a serious weed in New Zealand (NZ) pastures in the 1930s. Following successful biological control of the weed in Australia, two agents, the chrysomelid beetles Chrysolina hyperici and C. quadrigemina, were introduced to NZ in 1943 and 1965, respectively. At the time, the Australian host specificity testing, which had not included other Hypericum spp., was deemed sufficient for approval for release in NZ. We reviewed worldwide reports which suggest that St. John’s wort beetles will attack a range of Hypericum species in the field. A series of laboratory tests were conducted to simulate modern host-range-testing protocols. Larval feeding choice, larval development and female oviposition choice all suggested that at least two of NZ’s indigenous Hypericum species were suitable hosts for the two Chrysolina species, and a third indigenous Hypericum, while an unsuitable host, was not altogether avoided. We conclude that the two Chrysolina species would not have been approved for introduction to NZ under current risk assessment protocols. Had this happened, NZ would have missed out on one of its greatest biocontrol success stories, despite there being no evidence for subsequent impacts on the populations of indigenous congeners. This case stresses the need for better procedures to predict the realized host-range of an agent from the potential range in contained host-range testing, and raises issues surrounding risks and benefits to indigenous biodiversity.