Pollen DNA metabarcoding reveals cryptic diversity and high spatial turnover in alpine plant-pollinator networks.

Alpine plant-pollinator communities play an important role in the functioning of alpine ecosystems, which are highly threatened by climate change. However, we still have a poor understanding of how environmental factors and spatiotemporal variability shape these communities. Here, we investigate what drives structure and beta diversity in a plant-pollinator metacommunity from the Australian alpine region using two approaches: pollen DNA metabarcoding (MB) and observations. Individual pollinators often carry pollen from multiple plant species, and therefore we expected MB to reveal a more diverse and complex network structure. We used two gene regions (ITS2 and trnL) to identify plant species present in the pollen loads of 154 insect pollinator specimens from three alpine habitats and construct MB networks, and compared them to networks based on observations alone. We compared species and interaction turnover across space for both types of networks, and evaluated their differences for plant phylogenetic diversity and beta diversity. We found significant structural differences between the two types of networks; notably, MB networks were much less specialized but more diverse than observation networks, with MB detecting many cryptic plant species. Both approaches revealed that alpine pollination networks are very generalized, but we estimated a high spatial turnover of plant species (0.79) and interaction rewiring (0.6) as well as high plant phylogenetic diversity (0.68) driven by habitat differences based on the larger diversity of plant species and species interactions detected with MB. Overall, our findings show that habitat and microclimatic heterogeneity drives diversity and fine-scale spatial turnover of alpine plant-pollinator networks.

A conspectus of Australian Apotropina (Diptera, Chloropidae) with the description of two new species.

The genus Apotropina (Diptera, Chloropidae) has a global distribution with more than 80 valid described species, of which 22 are known to occur in Australia. The Australian Apotropina fauna is poorly studied, with many species known from single type specimens, more with the morphology of the other sex unknown, and there have been no new species descriptions since 1959. Here, we describe two new species from Australia, A.maculigena Riccardi, sp. nov. and A.popeye Ang, sp. nov., and provide an updated illustrated key. We also provide a conspectus of the known Australian Apotropina with images of types and collate all original descriptions and subsequent taxonomic notes of relevance as supplementary information. Finally, we discuss the validity of two known syntype specimens of A.bispinosa due to incongruencies with the species description.