Edge effects often exacerbate the negative effects of habitat loss on biodiversity. In forested ecosystems, however, many pollinators actually prefer open sunny conditions created by edge disturbances. We tested the hypothesis that forest edges have a positive buffering effect on plant-pollinator interaction networks in the face of declining forest area. In a fragmented land-bridge island system, we recorded ~20,000 plant-pollinator interactions on 41 islands over 3 yr. We show that plant richness and floral resources decline with decreasing forest area at both interior and edge sites, but edges maintain 10-fold higher pollinator abundance and richness regardless of area loss. Edge networks contain highly specialized species, with higher nestedness and lower modularity than interior networks, maintaining high robustness to extinction following area loss while forest interior networks collapse. Anthropogenic forest edges benefit community diversity and network robustness to extinction in the absence of natural gap-phase dynamics in small degraded forest remnants.
Four species of velvet ants (Mutillidae) were reared from nests of solitary bees and wasps collected using trap nests in southwest Australia and identified using morphological and DNA barcoding approaches. All four species, Aglaotilla micra sp. nov., A. lathronymphos sp. nov., A. chalcea sp. nov. and A. schadophaga sp. nov., are described as new, the last three from both sexes. A. micra, A. lathronymphos and A. chalcea are parasitoids of wasps in the genera Pison and Aulacophilinus (Crabronidae), with A. chalcea also recorded from Paralastor (Vespidae). Aglaotilla schadophaga is a parasitoid of bees in the genus Megachile (Megachilidae). The biologies and known hosts of Australian Mutillidae are reviewed. Photographs are also provided of type material for Ephutomorpha aeneidorsis Turner, 1914 (=Aglaotilla discolor Brothers, 2018), Mutilla metallica Smith, 1855 and Ephutomorpha subelegans Rayment, 1933. The lectotype of E. subelegans is formally designated.
The second known specimen of the bee Hesperocolletes douglasi Michener, 1965 is here reported as a serendipitous find among a collection of insect pollinators from an isolated woodland remnant in the Southwest Floristic Region of Western Australia. The unique male holotype of this monotypic genus of bees was collected 80 years ago and officially gazetted as presumed extinct in 1994. With our collection of a female specimen in 2015, however, it now appears that H. douglasi may persist as an extant localised population. Follow-up efforts to find more specimens at the collection locality so far proved unsuccessful, indicating that the species is likely either very rare or inhabits an ecological niche that is yet to be discovered. Analysis of the pollen load carried by the female indicates that the species may be polylectic. We discuss the context of the rediscovery of the bee, provide a detailed description and illustrations of the female, and make observations about the unusual morphological characteristics of the species. The rediscovery of H. douglasi emphasizes the importance of conservation efforts for remnant woodlands in the region, both as potential habitat for the bee and as remaining habitat essential for other rare and threatened species in this global biodiversity hotspot.
Research into pollinators in managed landscapes has recently combined approaches of pollination ecology and landscape ecology, because key stressors are likely to interact across wide areas. While laboratory and field experiments are valuable for furthering understanding, studies are required to investigate the interacting drivers of pollinator health and diversity across a broader range of landscapes and a wider array of taxa. Here, we use a network of 96 study landscapes in six topographically diverse regions of Britain, to test the combined importance of honeybee density, insecticide loadings, floral resource availability and habitat diversity to pollinator communities. We also explore the interactions between these drivers and the cover and proximity of semi-natural habitat. We found that among our four drivers, only honeybee density was positively related to wild pollinator abundance and diversity, and the positive association between abundance and floral resources depended on insecticide loadings and habitat diversity. By contrast, our exploratory models including habitat composition metrics revealed a complex suite of interactive effects. These results demonstrate that improving pollinator community composition and health is unlikely to be achieved with general resource enhancements only. Rather, local land-use context should be considered in fine-tuning pollinator management and conservation.
This article is part of the theme issue ‘Natural processes influencing pollinator health: from chemistry to landscapes’.
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