Indigenous plants promote insect biodiversity in urban greenspaces.

The contribution of urban greenspaces to support biodiversity and provide benefits for people is increasingly recognized. However, ongoing management practices favor vegetation oversimplification, often limiting greenspaces to lawns and tree canopy rather than multi-layered vegetation that includes under- and midstorey, and the use of nonnative species. These practices hinder the potential of greenspaces to sustain indigenous biodiversity, particularly for taxa like insects that rely on plants for food and habitat. Yet, little is known about which plant species may maximize positive outcomes for taxonomically and functionally diverse insect communities in greenspaces. Additionally, while cities are expected to experience high rates of introductions, quantitative assessments of the relative occupancy of indigenous vs. introduced insect species in greenspace are rare, hindering understanding of how management may promote indigenous biodiversity while limiting the establishment of introduced insects. Using a hierarchically replicated study design across 15 public parks, we recorded occurrence data from 552 insect species on 133 plant species, differing in planting design element (lawn, midstorey, and tree canopy), midstorey growth form (forbs, lilioids, graminoids, and shrubs) and origin (nonnative, native, and indigenous), to assess (1) the relative contributions of indigenous and introduced insect species and (2) which plant species sustained the highest number of indigenous insects. We found that the insect community was overwhelmingly composed of indigenous rather than introduced species. Our findings further highlight the core role of multi-layered vegetation in sustaining high insect biodiversity in urban areas, with indigenous midstorey and canopy representing key elements to maintain rich and functionally diverse indigenous insect communities. Intriguingly, graminoids supported the highest indigenous insect richness across all studied growth forms by plant origin groups. Our work highlights the opportunity presented by indigenous understory and midstorey plants, particularly indigenous graminoids, in our study area to promote indigenous insect biodiversity in urban greenspaces. Our study provides a blueprint and stimulus for architects, engineers, developers, designers, and planners to incorporate into their practice plant species palettes that foster a larger presence of indigenous over regionally native or nonnative plant species, while incorporating a broader mixture of midstorey growth forms.

Five new Pycnomerus Erichson (Coleoptera: Zopheridae: Pycnomerini) from Raivavae, French Polynesia.

We describe five new species of Pycnomerus (P. mahanatoa, P. rairua, P. raivavae, P. taralewisae, and P. vavitu spp. nov.) from subfossil material collected on the island of Raivavae in the Austral Archipelago of French Polynesia. Like the two species of Pycnomerus recently described from Rimatara (Porch Smith 2017), we consider it is probable that some or even most of the endemic Raivavae species are globally extinct. This is because the species have, so far, only been found in as subfossil specimens in sediments that date to the period immediately before or just after human arrival on the island (c.1300 AD), they have not been collected historically, and very little indigenous forest of Raivavae remains. These species add to the growing body of knowledge regarding the zopherid fauna of eastern Polynesia, which is, and unfortunately will always likely be, based primarily on the subfossil record from the region.

New Pycnomerus Erichson (Coleoptera: Zopheridae: Pycnomerini) from Rimatara, French Polynesia.

We describe two species of Pycnomerus, P. rimatara and P. prebblei, using subfossil material, from the island of Rimatara in the Austral Archipelago of French Polynesia. We consider it likely that these species are globally extinct, a result of the combination of a range of factors including: their probable single island endemic status, the lack of intact indigenous forest on Rimatara, their occurrence in the subfossil record only in samples older than 200-300 years before the present, and lack of historical collections. The potential extinction of these species reflects the long history of human transformation of Polynesian lowland forest habitats, especially the use of fire to transform landscapes, and parallels extensive and well-known extinctions in birds and land snails.