Network structure variation across scales offers clues to the macroevolutionary persistence of specialised mutualisms

This is a study of the diversity and species-specificity of a plant-insect
mutualism that uses multilocus molecular phylogenetic and species
interaction network analyses. Field sampling collected larvae of
leafflower moths (Lepidoptera: Gracillariidae: Epicephala spp.) from
different host species of leafflower trees (Phyllanthaceae: Glochidion) at
eight sites in southern China (Guangzhou and Hainan provinces and Guangxi
Zhuang Autonomous Region). Larvae were preserved in ethanol or reared to
adulthood (and the resulting adults preserved in ethanol) for DNA
extractions; collection site and host plant species were recorded for each
individual moth collected. DNA was Sanger-sequenced for three loci
(mitochondrial cytochrome oxidase I, COI; nuclear arginine kinase, ArgK;
nuclear elongation-factor 1-alpha, EF1-α). Phylogenetic inference was
conducted on these samples. Minimally monophyletic clades with posterior
probabilities >0.90 identified in the phylogenetic analyses were
treated as candidate “species” of leafflower moths in the subsequent
network analyses. Local quantitative species interaction networks for each
site were manually drawn based on the phylogenetic tree, in which each OTU
(tip on phylogeny) represented a single interaction event between that
Epicephala moth “species” and its host Glochidion tree species. Network
structural analyses were then performed with the resulting local networks
and the combined regional networks for the five sites on the island of
Hainan, the three sites in continental China, and all eight sites
together. Turnover analyses on the dataset were also performed.