An appraisal of simple tree-mounted shelters for non-lethal monitoring of weta (Orthoptera: Anostostomatidae and Rhaphidophoridae) in New Zealand nature reserves

When monitoring rare insect species, or when surveying faunas within nature reserves, it is desirable not to use indiscriminate lethal sampling techniques. In this investigation we assessed the usefulness of simple tree-mounted wooden shelters to monitor endemic weta (Orthoptera) in nature reserves in Canterbury, New Zealand. Fifty shelters were placed out at six sites and examined at three-monthly intervals for a year. A wide variety of invertebrates were found utilizing the shelters, with Arachnida, Blattodea and Collembola being the most common occupants. After three months over 80% of the shelters exhibited signs of use by invertebrates, increasing to 96% after 12 months. Only seven tree weta (Anostostomatidae) and one (dead) ground weta (Hemiandrus sp.) were observed in the shelters over the full 12 month period. There were 52 observations of cave weta (Rhaphidophoridae) in the shelters, 36 of which occurred at one site, Orton Bradley Park. Occupation of the shelters by cave weta was not affected by soil conditions, light intensity or aspect of the shelter. However, cave weta exhibited a preference for shelters less than 50 cm above the ground and for shelters attached to kanuka and vines. Although weta were found in only a small proportion (9%) of the shelters, this method proved useful in confirming the presence of weta without risk of harming vulnerable populations. These shelters are inexpensive and easy to manufacture and have potential for long-term non-lethal monitoring of weta and as a collection/carriage device for live specimens used in conservation translocations.     

Pairing and insemination patterns in a giant weta (Deinacrida rugosa: Orthoptera; Anostostomatidae)

Positive size assortative mating can arise if either one or both sexes prefer bigger mates or if the success of larger males in contests for larger females leaves smaller males to mate with smaller females. Moreover, body size could not only influence pairing patterns before copulation but also the covariance between female size and size of ejaculate (number of spermatophores) transferred to a mate. In this field study, we examine the pre-copulatory mate choice, as well as insemination, patterns in the Cook Strait giant weta (Deinacrida rugosa). D. rugosa is a large orthopteran insect that exhibits strong female-biased sexual dimorphism, with females being nearly twice as heavy as males. Contrary to the general expectation of male preference for large females in insects with female-biased size dimorphism, we found only weak support for positive size assortative mating based on size (tibia length). Interestingly, although there was no correlation between male body size and the number of spermatophores transferred, we did find that males pass more spermatophores to lighter females. This pattern of sperm transfer does not appear to be a consequence of those males that mate heavier females being sperm depleted. Instead, males may provide lighter females with more spermatophores perhaps because these females pose less of a sperm competition risk to mates.     

Diversification of New Zealand weta (Orthoptera: Ensifera: Anostostomatidae) and their relationships in Australasia

New Zealand taxa from the Orthopteran family Anostostomatidae have been shown to consist of three broad groups, Hemiandrus (ground weta), Anisoura/Motuweta (tusked weta) and Hemideina-Deinacrida (tree-giant weta). The family is also present in Australia and New Caledonia, the nearest large land masses to New Zealand. All genera are endemic to their respective countries except Hemiandrus that occurs in New Zealand and Australia. We used nuclear and mitochondrial DNA sequence data to study within genera and among species-level genetic diversity within New Zealand and to examine phylogenetic relationships of taxa in Australasia. We found the Anostostomatidae to be monophyletic within Ensifera, and justifiably distinguished from the Stenopelmatidae among which they were formerly placed. However, the New Zealand Anostostomatidae are not monophyletic with respect to Australian and New Caledonian species in our analyses. Two of the New Zealand groups have closer allies in Australia and one in New Caledonia. We carried out maximum-likelihood and Bayesian analyses to reveal several well supported subgroupings. Our analysis included the most extensive sampling to date of Hemiandrus species and indicate that Australian and New Zealand Hemiandrus are not monophyletic. We used molecular dating approaches to test the plausibility of alternative biogeographic hypotheses for the origin of the New Zealand anostostomatid fauna and found support for divergence of the main clades at, or shortly after, Gondwanan break-up, and dispersal across the Tasman much more recently.     

Robertsonian translocations and B chromosomes in the Wellington tree weta, Hemideina crassidens (Orthoptera: Anostostomatidae)

Two karyotypes within the species Hemideina crassidens are described, 2n = 15 (XO) and 2n = 19 (XO). These two karyotypes have a NF of 28. The 19-karyotype was found exclusively in the southern part of the species range and the 15-karyotype was found in the north. The differences between the two karyotypes are interpreted as arising from two Robertsonian translocations (fission/fusion). Laboratory matings between weta with the two karyotypes produced viable offspring. During meiosis in F1 intraspecific hybrids metacentric and acrocentric autosomes aligned to form two trivalents, confirming homologies predicted by Robertsonian translocations. The subspecies H. c. crassicruris, (confined to Stephens Island) was found to be polymorphic for a metacentric B chromosome. An unusual association of sex and presence of B chromosome was observed in this island population with Bs found only in male weta.     

Reproductive and physiological costs of repeated immune challenges in female Wellington tree weta (Orthoptera: Anostostomatidae)

Fitness‐related traits, such as immunity and reproduction, are typically condition dependent, and are predicted to trade off against each other because they share a pool of energy and resources. It is generally assumed that the resources and energy required for immune processes and reproduction is contained in the body fat; however, few studies quantify the effect of an immune insult on fat load. I tested the hypothesis that if mounting an immune response is physiologically costly in terms of consuming limited resources from body fat, and reproduction also relies on these resources, then an immune challenge should cause a reduction in fat load and an associated decline in reproduction. I tested this hypothesis by assaying the fat content of female Wellington tree weta (Hemideina crassidens) after repeated challenges with lipopolysaccharide (LPS), and counting the number of oviposited eggs in addition to assaying the egg protein content, a possible measure of egg quality. In line with my prediction, immune‐challenged females had significantly smaller fat loads and laid significantly fewer eggs than saline‐injected controls. Moreover, the protein content of the eggs laid by immune‐challenged females was significantly lower than that of controls. My experimental results show that an immune challenge with a non‐pathogenic stimulant increases fat consumption, which in turn limits the resources available for reproduction. These findings support the hypothesis that reproduction and immunity are condition dependent, and are traded off against each other. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 38–46.     

Sexual selection and infection by ectoparasites in Wellington tree weta,Hemideina crassidens (Orthoptera: Anostostomatidae)

Abstract Sexual selection can affect the prevalence and intensity of infection of individuals by ectoparasitic mites. According to this theory, males should exhibit greater infection by parasites than females and juveniles should be less infected than adults. In the wild, I investigated whether prevalence and intensity of the chyzeriid mite, Nothotrombicula deinacridae (Dumbleton) differed between the sexes and between developmental stages in Wellington tree weta, Hemideina crassidens. Despite being under strong sexual selection, male tree weta did not exhibit greater parasitism and there was some evidence that adults and juveniles differed in prevalence. The sexual selection hypothesis was not supported in this study.     

Tracking tunnels: a novel method for detecting a threatened New Zealand giant weta (Orthoptera: Anostostomatidae)

Several species of giant weta, including wetapunga (Deinacrida heteracantha, Orthoptera: Anostostomatidae), New Zealand?s largest terrestrial invertebrate, have high conservation value, yet no methods for detecting and monitoring them have been developed. Here we show that rodent tracking tunnels set over three consecutive nights can be used to detect wetapunga on Little Barrier Island. Adult wetapunga footprints had significantly longer tarsal pad lengths than subadult wetapunga and Auckland tree weta, but tarsal pad length does not distinguish between subadult wetapunga and adult Auckland tree weta. Results suggest that setting tunnels on the ground is more effective than setting them on tree branches and that peanut butter as an attractant bait increases the detection rate of adult wetapunga. Future research is required to determine if the footprints of ground weta, tree weta and giant weta of different ages can be distinguished and to determine how tracking rates of giant weta relate to the population density.     

History of weta (Orthoptera: Anostostomatidae) translocation in New Zealand: lessons learned, islands as sanctuaries and the future

Establishing new populations by transferring founder individuals from source populations has been effective for managing the recovery of many threatened species including some weta (Orthoptera: Anostostomatidae) in New Zealand. These large-bodied flightless insects are ‘flagship species’ for insect conservation in New Zealand and many are rare or threatened. The declining abundance of most weta species, particularly giant weta, can be attributed to the introduction of mammalian predators, habitat destruction, and habitat modification by introduced mammalian browsers. New populations of some weta have been established in locations, particularly on islands, where these threats have been eliminated or severely reduced in order to reduce the risk of extinction. Some populations were established to provide food for endemic vertebrates, ecosystem restoration and ready access for the general public. We illustrate how methods for both transferring weta and monitoring them have become more sophisticated by using a series of case studies. Other transfers of weta not included in the case studies are also summarised. We conclude by re-iterating the importance of documenting the transfer and post-release monitoring for all insect transfers, both for biogeographical reasons and to provide information to improve future transfers.     

After the deluge: mitochondrial DNA indicates Miocene radiation and Pliocene adaptation of tree and giant weta (Orthoptera: Anostostomatidae)

Aim New Zealand broke away from the margins of Gondwana c. 75 Ma. Since then, New Zealand taxa derived from the Gondwanan biota are thought to have been exposed first to a subtropical climate on a low lying terrain, then severe land reduction during the Oligocene marine transgression, followed by much cooler climates of the Pliocene and Pleistocene, at which time mountain ranges emerged. The biological consequence of New Zealand's geological and climatic history is not well understood, in particular the extent to which the Oligocene acted as a biological bottleneck remains unresolved. Methods We used mitochondrial cytochrome oxidase I and 12S DNA sequences to examine the extent of diversity and inferred timing of speciation of New Zealand weta (Anostostomatidae), a group of Orthoptera with a Gondwanan distribution generally thought to be ancient inhabitants of New Zealand. Main conclusions We hypothesize that at least three distinct groups of weta survived the Oligocene marine transgression and radiated subsequently. Speciation followed during the Miocene and radiation into new habitats occurred during the Pliocene when mountain building created novel environments. Patterns of genetic diversity within species reflect, in some instances, geographical subdivision in the Pliocene, and in other cases, Pleistocene range changes resulting from climate change.     

The secondary copulatory organ in female ground weta (Hemiandrus pallitarsis,Orthoptera: Anostostomatidae): a sexually selected device in females?

Secondary sexual devices in female insects, primarily abdominal modifications, appear to function as a means of thwarting coercive mating attempts by males or are, in rare cases, sexually selected adaptations. Female ground weta, Hemiandrus pallitarsis (Orthoptera: Anostostomatidae), have an elaborate elbowed device on the underside of the mid-abdomen. Experimental removal of this accessory organ shows that it does not increase the probability of mating as predicted by the thwart-copulation hypothesis. Instead, removal prevents copulation, thus demonstrating that it is a secondary copulatory device. The male attaches to the organ both at the beginning of copulation and at the end, when he positions himself to adhere a spermatophylax food gift onto the mid-ventral region of his mate. The female accessory organ does not function to manipulate eggs or larvae (females provide care to their single clutch of offspring) and is unlikely to be a copulatory structure that prevents hybridization. The great extent of the modification of the ventral abdominal segments of H. pallitarsis females compared to other Hemiandrus species is consistent with a history of sexual selection on the accessory organ. Taken together, these results and the finding that the length of the accessory organ of H. pallitarsis correlates with female fecundity, suggest that this structure evolved under sexual selection to acquire nuptial gifts from males.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 463–469.     

A new species of tusked weta from the Raukumara Range,North Island,New Zealand (Orthoptera: Anostostomatidae: Motuweta)

Abstract

A new species of weta from mainland New Zealand is described and assigned to the previously monotypic genus Motuweta Johns and the genus redefined. Mandibles of adult males bear prominent horns. Motuweta riparia n. sp. is a moderate‐sized species (36 mm) found on the margins of first or second order streams in the eastern mid North Island ranges. Its escape reaction is to leap into the stream and remain underwater until danger has passed, a strategy which has probably enabled it to survive in predator‐infested areas.     

A comparison of five hybrid zones of the weta Hemideina thoracica (Orthoptera: Anostostomatidae): degree of cytogenetic differentiation fails to predict zone width

Abstract Tension zones are maintained by the interaction between selection against hybrids and dispersal of individuals. Investigating multiple hybrid zones within a single species provides the opportunity to examine differences in zone structure on a background of differences in extrinsic factors (e.g., age of the zone, ecology) or intrinsic factors (e.g., chromosomes). The New Zealand tree weta Hemideina thoracica comprises at least eight distinct chromosomal races with diploid numbers ranging from 2n = 11 (XO) to 2n = 23 (XO). Five independent hybrid zones were located that involve races differing from one another by a variety of chromosomal rearrangements. The predicted negative correlation between extent of karyotypic differentiation (measured in terms of both percent of genome and number of rearrangements) and zone width was not found. Conversely, the widest zones were those characterized by two chromosome rearrangements involving up to 35% of the genome. The narrowest zone occurred where the two races differ by a single chromosome rearrangement involving approximately 2% of the genome. The five estimates of chromosomal cline width ranged from 0.5 km to 47 km. A comparative investigation of cline width for both chromosomal and mitochondrial markers revealed a complex pattern of zone characteristics. Three of the five zones in this study showed cline concordance for the nuclear and cytoplasmic markers, and at two of the zones the clines were also coincident. Zones with the widest chromosomal clines had the widest mitochondrial DNA clines. It appears that, even within a single species, the extent of karyotypic differentiation between pairs of races is not a good predictor of the level of disadvantage suffered by hybrids.     

Physical and ant-mediated refuges from parasitism: Implications for non-target effects in biological control

A promising natural enemy for release against the Asian soybean aphid, Aphis glycines Matsumura, in North America is the aphidiine braconid wasp Binodoxys communis (Gahan). The aphid Aphis monardae Oestlund, a native of North America’s tall-grass prairies, is a non-target species that may be at risk from releases of B. communis. This paper describes ecological facets of A. monardae populations in their native habitat that could protect them from attack by this exotic biological control agent. In prairie habitats, A. monardae populations aggregate in flower heads of their host plant, Monarda fistulosa L. On this host plant, aphids are also commonly tended by four ant species, and ant-tended colonies are larger than un-attended colonies. Laboratory studies showed that parasitism rates of A. monardae by B. communis are significantly higher on vegetative M. fistulosa than on M. fistulosa flower heads. In addition, attendance of A. monardae by the ant Lasius neoniger Emery significantly decreased parasitism by B. communis. Ants attacked and killed host-seeking adult parasitoids, and preyed upon B. communis mummies. No evidence was found that B. communis reared from A. monardae are less susceptible to attack by ants than parasitoids reared from A. glycines. M. fistulosa flower heads and attendance by L. neoniger may act as refuges for A. monardae against B. communis. Our work describes spatial refuges as ecological filters that separate non-target organisms from exotic natural enemies. Implications for classical biological control of A. glycines are discussed.     

Movements, behaviour and survival of adult Cook Strait giant weta (Deinacrida rugosa; Anostostomatidae: Orthoptera) immediately after translocation as revealed by radiotracking

Giant weta (Orthoptera: Anostostomatidae) are large flightless New Zealand insects vulnerable to predation from introduced mammals. Some species have been transferred to islands or mammal-free mainland sanctuaries to establish additional populations. Radiotelemetry was used to investigate behaviour, movements and survival of adult Cook Strait giant weta (Deinacrida rugosa) immediately after translocation into Karori Sanctuary, New Zealand, to describe their initial movements, and to assess the importance of this establishment phase in relation to the long-term viability of the population. The average distance moved between consecutive daytime refuges for translocated male D. rugosa within Karori Sanctuary was significantly further than for resident weta on Matiu-Somes Island. In contrast, translocated female weta moved significantly smaller distances between consecutive daytime refuges within Karori Sanctuary than those on Matiu-Somes Island. Translocated D. rugosa travelled significantly further between consecutive daytime refuges between 19 and 45?days after release than during the first 19?days and more than 45?days of radiotracking. Deinacrida rugosa survived well following translocation and there was only limited evidence of predation despite an increased abundance of indigenous avian and reptilian predators being present, and the presence of low numbers of mice. The establishment potential of this population was not adversely affected by movements and survival of the weta immediately after translocation. It still remains to be seen if a self-sustaining population of D. rugosa develops in Karori Sanctuary but the indications are that the species is present because progeny of the translocated weta are regularly seen within Karori Sanctuary. Radiotelemetry provided valuable insights into the behaviour of adult D. rugosa and it could be appropriate for monitoring other large bodied invertebrates.     

Sexually dimorphic effect of mating on the melanotic encapsulation response in the harem‐defending Wellington tree weta,Hemideina crassidens (Orthoptera: Tettigonioidea: Anostostomatidae)

Reproductive activities are generally costly to immune responsiveness because limited resources required by reproduction are diverted away from immunity (and vice versa). Reproduction, however, is not expected to affect the immune response in males and females similarly as mating is expected to negatively affect male immunity more so than female immunity. Here, I test the phenotypic plasticity hypothesis in the Wellington tree weta (Hemideina crassidens), a sexually dimorphic orthopteran insect that is endemic to New Zealand. My laboratory experiment showed that although males had higher rates of melanotic encapsulation than females, contrary to prediction, females were the only sex significantly affected by mating and the effect was positive. In addition to immunity differing between the sexes, immune function can differ intrasexually, particularly when males are polymorphic and different investment strategies are used to maximize fitness. Male H. crassidens exhibit alternative mating strategies that are represented by three different morphotypes. I therefore explored whether the morphs differed in their melanotic encapsulation response and whether mating affected the morphs differently. I found no difference among morphs or an effect of mating on male immune response.     

Diet of the ground weta Zealandosandrus gracilis (Orthoptera: Stenopelmatidae)

Abstract

The diet of the ground weta Zealandosandrus gracilis Salmon was investigated by examining the crop contents of 68 individuals collected throughout the year from the Cass area, Canterbury. Specimens representing all instars of both sexes, as well as adults, were obtained. Z. gracilis is carnivorous, preying on immature and adult invertebrates (mostly insects) of the forest litter. Similar prey was taken by early instars of both sexes; late instars captured a wider range of prey, including larger and more active species. Late-instar and adult females preyed more on adult insects such as mycetophilid flies than did males, which took more insect larvae.     

The genus Troglophilus Krauss, 1879 (Orthoptera: Rhaphidophoridae) in the west Balkans

We present a revision of the genus Troglophilus in the western part of the Balkan Peninsula based on morphological and genetic analysis, and provide distribution data for the species. The results of these analyses reduced the number of the known taxa within the genus Troglophilus in this area to five valid species: Troglophilus cavicola ( Kollar, 1833 ), Troglophilus neglectus Krauss, 1879 , Troglophilus ovuliformis Karny, 1907 , Troglophilus brevicauda Chopard, 1934, and Troglophilus lazaropolensis Karaman, 1958. A new species Troglophilus zorae sp. nov. is described and Troglophilus neglectus serbicus Maran, 1958, Troglophilus neglectus vlasinensis Maran, 1958, Troglophilus bukoviki Karaman, 1968 and Troglophilus pretneri Us, 1970 are synonymized. The distribution pattern of the western Balkan species supports a general east?west migration route. We also determined the centres of origin and spreading directions of particular species according to the distribution of the taxa and the structure of the haplotypes. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1035–1063.     

Effects of an aerial 1080 possum poison operation using carrot baits on invertebrates in artificial refuges at Whirinaki Forest Park, 1999– 2002

The effects of an aerial 1080 possum poison operation using carrot baits on invertebrates in Whirinaki Forest Park are described from an un-replicated study of artificial refuges attached to tree trunks. Auckland tree weta (Hemideina thoracica), cave weta (Pharmacus sp. and Isoplectron sp.), cockroaches, spiders and harvestmen, and leaf-veined slugs (Athoracophorus bitentaculatus) were the most frequent occupants, but snails, millipedes, centipedes, flatworms, lepidopteran larvae, glowworm larvae (Arachnocampa luminosa), peripatus, slaters and beetles were also present occasionally. Invertebrate numbers were monitored every second or third month for a year before the poison operation, and for two years afterwards. Numbers of tree weta, cave weta, cockroaches, spiders and harvestmen, and leaf-veined slugs did not decline substantially in refuges in the treatment area relative to those in the non-treatment area immediately after the poison operation. Our results, and those from two other similar studies, suggest that aerial 1080 poison operations are unlikely to have a detrimental effect on invertebrates that occupy cavities above ground.     

Tempo and mode of species diversification in Dolichopoda cave crickets (Orthoptera, Rhaphidophoridae)

This study focuses on the phylogenetic relationships among ninety percent of known Dolichopoda species (44 out of 49); primarily a Mediterranean genus, distributed from eastern Pyrenees to Caucasus. A total of 2490 base pairs were sequenced corresponding to partial sequences of one nuclear (28SrRNA) and three mitochondrial genes (12S, 16S and COI). A relaxed molecular clock, inferred from Bayesian analysis was applied to estimate the divergence times between the lineages using well dated palaeoevents of the study areas. Molecular substitution rates per lineage per million years were also obtained for each analyzed gene. Based on the nearly complete species phylogeny, temporal patterns of diversification were analyzed using Lineage-Through-Time plots and diversification statistics. Alternative hypotheses about the colonization of present range by Dolichopoda species were tested by means of Approximate Bayesian Computation analysis. Results from this analysis carried out on the 90% of known Dolichopoda species confirmed the previous ones based on subgroups of species, suggesting the ABC analysis as a remarkable tool in biogeographic studies. Based on these results, the distribution of Dolichopoda species appears to have been shaped by the palaeogeographic and climatic events that occurred from Late Miocene up to the Plio-Pleistocene. Both vicariance and dispersal events appear to have influenced Dolichopoda species distributions, with many processes occurring in ancestral epigean populations before the invasion of the subterranean environment.     

Isolation and characterization of five microsatellite loci in Dolichopoda cave crickets (Orthoptera Rhaphidophoridae)

Five microsatellite loci are described for the cave cricket genus Dolichopoda. Preliminary data on allelic variation of these loci are presented for one population of D. schiavazzii and one population of D. laetitiae to test their usefulness in fine‐scale studies of the genetic aspect of cave colonization. Cross‐species amplifications were carried out in four other Dolichopoda species and in two species belonging to another cave cricket genus (Troglophilus) to test the potential use of these microsatellite markers in studies of both congeneric species and species belonging to the same family.