Barbara I. P. Barratt

Biodiversity of Coleoptera and other invertebrates in urban gardens: a case study in a New Zealand city

Invertebrate biodiversity was investigated in 55 domestic gardens in the city of Dunedin in southern New Zealand. The influence of habitat types within the gardens (lawns, open beds, and closed canopy beds) on invertebrate community structure was investigated by pitfall trapping. Species richness of Coleoptera, the proportion of native species, and effects of pesticide use by householders was examined. The most abundantly trapped taxa were Collembola, Amphipoda, and Diptera. Most taxa were represented in all three habitat types, but Collembola, Diptera, and Araneae were most frequently collected in lawns and Isopoda in open beds. The use of pesticides had no effect on total trap catch, but detritivore numbers were higher in gardens where no insecticide had been used. Opiliones and Acarina were captured in greater numbers in gardens where herbicides had not been used. Over 1400 Coleoptera were identified to 164 species/morphospecies. Species richness averaged 12 species per garden. Staphylinidae, Curculionidae, and Carabidae were the most abundantly collected Coleoptera, both for species and individuals. Species richness was not affected by vegetation type. The coleopteran fauna was predominantly native (80–90%) for species and individuals. The capture of a new to New Zealand weevil species (Exomias pellicidus (Boheman)) suggests that urban studies could play a role in alerting authorities to biosecurity incursions. The study stimulated considerable interest in invertebrates from householders, which might help fill the gap between acquiring environmental awareness and encouraging changes in behaviour towards support for native biodiversity.

The New Zealand experience of varroa invasion highlights research opportunities for Australia

The Varroa mite (Varroa destructor) is implicated as a major disease factor in honey bee (Apis mellifera) populations worldwide. Honey bees are extensively relied upon for pollination services, and in countries such as New Zealand and Australia where honey bees have been introduced specifically for commercial pollinator services, the economic effects of any decline in honey bee numbers are predicted to be profound. V. destructor established in New Zealand in 2000 but as yet, Australia remains Varroa-free. Here we analyze the history of V. destructor invasion and spread in New Zealand and discuss the likely long-term impacts. When the mite was discovered in New Zealand, it was considered too well established for eradication to be feasible. Despite control efforts, V. destructor has since spread throughout the country. Today, assessing the impacts of the arrival of V. destructor in this country is compromised by a paucity of data on pollinator communities as they existed prior to invasion. Australia’s Varroa-free status provides a rare and likely brief window of opportunity for the global bee research community to gain understanding of honey bee-native pollinator community dynamics prior to Varroa invasion.

Invasive redback spiders (Latrodectus hasseltii) threaten an endangered, endemic New Zealand beetle (Prodontria lewisii)

AbstractAustralian redback spiders (Latrodectus hasseltii Thorell, 1870) are invasive, opportunistic predators that threaten New Zealand fauna. Initially recorded in Central Otago in 1981, they were observed in 2012 preying on the endemic, nationally endangered Cromwell chafer beetle (Prodontria lewisii Broun, 1904) in the species’ last occupied habitat, the 81xa0ha Cromwell Chafer Beetle Nature Reserve (CCBNR). We surveyed the redback spider population over the entire reserve in October (spring) and December (summer) 2013, recording web occupants, web condition, and prey caught. During the 5xa0weeks between surveys, prey caught in half of the recorded spider webs were monitored each week. We estimated a redback population of between 208 and 371 spiders, an average of between 2.57 and 4.58 spiders per hectare within the CCBNR, with maximum web densities ranging between 8.7 and 10.7 webs per hectare. In the final survey in December, 278 P. lewisii cadavers were found in redback spider webs. Redback spiders occupied a large portion of the habitat to which the Cromwell chafer beetles are restricted. Ten of the 26 prey species recorded in webs were native, including McCann’s skink (Oligosoma maccanni); the first record of skink predation by redback spiders in New Zealand.n

Two species of adventive weevil (Coleoptera: Curculionidae) from Europe, hitherto unrecorded from New Zealand

Two curculionid weevils, Orthochaetes setiger (Beck, 1817) and Exomias pellucidus (Boheman, 1834) are recorded in New Zealand for the first time. The former has a wide distribution through the eastern South Island, while the latter has so far only been located in a single suburban garden in Dunedin. Both species are polyphagous and flightless. Although neither is expected to cause notable economic damage, their potential to invade native ecosystems makes them worthy of further investigation.

Synergy between two invasive species, redback spiders and rabbits, threaten the endangered Cromwell chafer beetle

Interactions between invasive species can be difficult to predict and can result in unanticipated impacts of significance for native fauna. Here we show that introduced European rabbits (Oryctolagus cuniculus) create habitat that enables invasive redback spiders (Latrodectus hasselti Thorell, 1870) to establish and prey upon the nationally endangered, endemic Cromwell chafer beetle (Prodontria lewisii Broun, 1904). We examined the spatial relationship between rabbit holes and redback spider occurrence, recorded all prey caught in redback spider webs over a 4-month period, and tested the role rabbit holes play in providing habitat for redback spiders experimentally, by filling in rabbit holes in areas used by spiders and monitoring subsequent occupation of the areas over four months. Redback spiders predominately resided in old rabbit holes, with the highest densities of spiders coinciding with high densities of rabbit holes. Cromwell chafer beetles were commonly caught in webs. Filling in rabbit holes eliminated the presence of redback spiders at all treated sites and reduced prey capture in those areas. Conservation management to protect Cromwell chafer beetles should focus on eliminating rabbits and their holes from beetle habitat.

Investigation of two new putative pheromone components of the invasive Australian redback spider, Latrodectus hasseltii, with potential applications for control

ABSTRACT The Australian redback spider, Latrodectus hasseltii preys on at least 10 endemic species in New Zealand, highlighting a need for control. Male redbacks are attracted to virgin females by an airborne pheromone. The aim of this study was to analyse the response of male redback spiders to two volatile chemicals found on the silk of virgin but not mated females, to determine whether these compounds constitute components of the airborne pheromone. Mature male redback spiders were placed in an olfactometer where they had a choice of two stimuli. We compared their response to paired combinations of a control, virgin silk, butyric acid and isovaleric acid. Male redbacks responded equally strongly to butyric acid and virgin silk, in terms of time spent near the stimulus. The identification of butyric acid as a component of the airborne sex pheromone of L. hasseltii provides the groundwork for developing a pheromone-based control.

Are introduced plants a threat to native pollinator services in montane–alpine environments?

While introduced plants often have restricted distributions at high elevations, their impacts may be more extensive if they compete for native pollinators, potentially reducing pollinator services to native biotically pollinated plants. Conversely, introduced biotically pollinated plants might facilitate improved pollinator services to native plants by supporting higher pollinator densities and extending the flowering season. We examined weekly pollinator visitation to native and introduced plants, at five elevations over two flowering seasons on The Remarkables range, south-central South Island, New Zealand. In this area, introduced plants dominate the vegetation at lower elevations but are restricted to disturbed areas above treeline. We tested whether pollinator visitation rates and quantities of introduced pollen on insects or transferred to native flowers differed with elevation and community context, or with the local abundance of introduced flowers regardless of elevation. Introduced biotically pollinated plants produced more flowers and flowered later than most native species and were extensively utilised by native solitary bees. Weekly visitation rates to native flowers were higher in the first half of the flowering season than the second half, and were positively correlated with visitation rates to co-occurring introduced flowers. Introduced flower abundance did not affect visitation to native flowers but did significantly predict the occurrence of introduced pollen on native insects and stigmas of native flowers. Pollen contamination was also higher in the latter part of the flowering season. While an increase in introduced flowers at high elevations may benefit native pollinators by increasing the quantity and duration of floral resources available, the heavy use of introduced flowers by native bees will lead to at least localised stigma contamination, particularly for late flowering species. However, more information is required on foraging ranges of native pollinators and pollen limitation in native species to understand the consequences of introduced species expansion into alpine areas.

Correction to: Are introduced plants a threat to native pollinator services in montane–alpine environments?

The Editor-in-Chief has retracted this article [1] because the three studies included in the meta-analysis [2,3 and 4] (cited as references 16, 17 and 18) have been retracted due to concerns regarding the data, which has rendered the results of this meta-analysis invalid.

Diet of tuatara (Sphenodon punctatus) translocated to Ōrokonui Ecosanctuary in southern New Zealand

ABSTRACT Scats from tuatara (Sphenodon punctatus) were investigated in autumn at Ōrokonui Ecosanctuary on South Island, New Zealand. Eighty-seven tuatara had been translocated there 5–7 months previously, either directly from Stephens Island/Takapourewa or via captivity. Tuatara at Ōrokonui fed on diverse invertebrates, including beetles, millipedes, spiders, dipteran flies and cave wētā. Prey occurrence in large scats (presumed to come from adults) was similar in frequency to that in small scats (presumed to be from medium–large juveniles), apart from a higher incidence of spiders in those from adults. Tuatara scats contained scarabaeid and large carabid beetles more frequently, and tenebrionid beetles less frequently, than reported on Stephens Island. Unlike tuatara on Stephens Island, those at Ōrokonui do not have access to seabirds or tree wētā, and showed no certain predation on passerines or reptiles. Some differences in diet composition may reflect differences in prey availability resulting from the past presence of rodents at Ōrokonui.