Nuclear DNA based species delineations ofCoccusscale insects in symbiosis with plants and ants, and the role of plant epicuticular wax in structuring associations

Abstract

We undertook phylogenetic analysis of nuclear DNA to elucidate species boundaries in the symbiotic Coccus scale insects associated with mutualistic Crematogaster ants and Macaranga plants occurring in the ever-wet forests of Southeast Asia. The coccid specimens clustered into ten lineages, each corresponding to a morphospecies assignment. The lineage identified as C. secretus was separated from the Main Clade by an outgroup. We also examined all pairwise associations among the three symbiont guilds to understand how patterns of association were structured. The analyses revealed that each ant, plant or coccid operational (taxonomic) unit often associated with multiple O(T)Us of each of the other two guilds. However, where testing was feasible, a ‘preference’ for one or sometimes two partner O(T)Us of each guild was often detected. Mutual ‘preferences’ or ‘avoidances’ were relatively common among the symbionts, and no conflicts of interest were apparent. The network of preferred partners among all three guilds showed compartmentalization structured by the presence/absence of plant epicuticular wax, suggesting that this feature plays a fundamental role in how the symbionts select partners that best serve their needs. To a lesser degree, the network was also structured by whether the host plant stems were ant-excavated or hollowed naturally.