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

Abstract

1. 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.2. 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.3. 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.4. 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. 5. 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.

Protecting trees at an individual level provides insufficient safeguard for urban forests

“…Kuschel's (1990) landmark study showed that native trees and bush patches in urban Auckland support far more diverse endemic beetle communities than exotic vegetation. While research has shown that urban gardens and some types of exotic vegetation in New Zealand can support diverse invertebrate assemblages (Barratt et al, 2015;Harris, Toft, Dugdale, Williams, & Rees, 2004) and some native bird species (Waite et al, 2013), the fauna that exotic vegetation supports tend to be exotic species, or native generalist species with flexible foraging strategies (Gardner-Gee, Stanley, & Beggs, 2015;Kuschel, 1990;Müller, Ignatieva, Nilon, Werner, & Zipperer, 2013;van Heezik, Smyth, & Mathieu, 2008;Waite et al, 2013). A study of bird use of urban vegetation in Hamilton (New Zealand) found that many native birds, including the insectivorous grey warbler (Gerygone igata) and fantail (Rhipidura fuliginosa), were most abundant in gardens with higher native plant biomass (Day, 1995), while Dunedin greenbelt fragments with higher proportions of native plants contain more native birds, and fewer exotic birds, than fragments dominated by exotic vegetation (van Heezik et al, 2008).…”

Engaging with risk (or not): shared responsibility for biosecurity surveillance and the role of community gardens

“…Kuschel (1990) found during a 15-year survey of urban gardens in Auckland the presence of 81 novel foreign species of beetles and weevils (Coleoptera spp.). These findings suggest that monitoring domestic gardens can be valuable in biosecurity surveillance, not only near ports of possible entry of new species but also because they are repositories for new plants distributed by nurseries (Barratt et al, 2015). Barratt et al (2015) also found that their study stimulated considerable interest from participants, which suggests that with appropriate engagement householders can effectively participate in biosecurity surveillance.…”

“…Research in New Zealand also has demonstrated the value of monitoring domestic gardens to detect incursions of new insect species (Barratt et al, 2015;Kotze et al, 2011). Barratt et al (2015) also found that their study stimulated considerable interest from participants, which suggests that with appropriate engagement householders can effectively participate in biosecurity surveillance. These findings suggest that monitoring domestic gardens can be valuable in biosecurity surveillance, not only near ports of possible entry of new species but also because they are repositories for new plants distributed by nurseries (Barratt et al, 2015).…”

“…Research in New Zealand also has demonstrated the value of monitoring domestic gardens to detect incursions of new insect species (Barratt et al, 2015;Kotze et al, 2011). In particular, there were high levels of compliance with movement restrictions of non-commercial and home-grown fruit material and accommodation of repeated property visits from government inspectors (Western Australia Department of Agriculture and Food, 2016).…”

“…In particular, there were high levels of compliance with movement restrictions of non-commercial and home-grown fruit material and accommodation of repeated property visits from government inspectors (Western Australia Department of Agriculture and Food, 2016). These findings suggest that monitoring domestic gardens can be valuable in biosecurity surveillance, not only near ports of possible entry of new species but also because they are repositories for new plants distributed by nurseries (Barratt et al, 2015). Kuschel (1990) found during a 15-year survey of urban gardens in Auckland the presence of 81 novel foreign species of beetles and weevils (Coleoptera spp.).…”