Dietary shifts in pollen-feeding lacewings (Nemopteridae) in relation to vegetation, biome and phylogeny
The spoon-winged and threadwinged lacewings are a diverse nemopterid family that have flourished in the winter rainfall region of South Africa. Their diversity is thought to be linked to the radiation of Aizoaceae, a member of the Ruchioideae subfamily that radiated at the same time as the recently diversified nemopterids in the Succulent Karoo. Phylogenetic data supported this assertion, and seperated the family into two distinct lineages, a recently diversified Aizoaceae-dependent Succulent Karoo lineage and a basal Aizoaceae-independent Fynbos lineage. This study aimed to determine if the nemopterid diet is phylogenetically contrained or if diet was mearely a reflection of plant availability. This was investigated by carrying out a dietary analysis of the gut contents of nemopterids from different biomes, vegetation and localities. It was hypothesised that diet would be phylogenetically constrained and dietary grouping would reflect phylogeny. In addition, the derived nemopterid lineage thought to have co-evolved with Aizoaceae, (Palmipenna, Nemopterella, Nemia, and Knersvlaktia) would reflect this in its diet. The older lineage (Nemeura, Sicyoptera, Semirhynchia, and Derhynchia) was hypothesised to have its phylogenetic grouping reflected in its diet by having very little to no Aizoaceae in its diet. The results showed that dietary groupings did not reflect phylogenetic groupings and dietary similarities were shared across most genera, including subfamilies, with Lauhervasia, a member of the Crocinae subfamily sharing 80% of its pollen sources with Semirhynchia, of the Nemopterinae subfamily. Aizoaceae reliance was only consistantly present in Nemia, which belonged to the phylogenetic lineage expected to rely on Aizoacea. All the members of the phylogenetic lineage not expected to rely on Aizoaceae, did not have any Aizoaceae in their diet. The diet of the nemopterids was very diverse across all vegetation types and biomes. The study suggests that spoon-winged and threadwinged lacewings are generalist pollinators and recent diversification was most likely linked to their ability to utilise the large range of available resources and not linked to a single plant family that radiated around the same time.
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