Under concatenation, both datasets suggest identical species relationships with mostly high statistical support. However, multispecies coalescent and multispecies network approaches suggest markedly different hypotheses and detected significant gene flow.
In the E. rubivora complex, ddRAD data resolved all four species, contrary to morphological and COI data, which supports a potential scenario of host plant-driven speciation where the host plant specialization provides an ecological barrier to hybridization.
To further our understanding of the relationships between populations, both the Alpine and the extra Alpine ones, we sequenced 1,496 bp of the COI gene in 16 Alpine and Jurassian populations and analysed them in combination with published Pyrenean and Carpathian sequences.
Dating analyses indicate a mid-Cretaceous (105.3 Ma) origin of the family, followed by a rapid diversification into the nine subfamilies predating the Cretaceous–Palaeogene extinction. We hypothesize that advanced larval behaviours, such as making keeled or tentiform blotch mines, rolling leaves and galling, allowed gracillariids to better avoid larval parasitoids allowing them to further diversify.
All three species show pronounced evidence of isolation and, in two cases, secondary reconnection. An unexpected monophyletic mtDNA lineage was found in the Central Coast region, in a region thought to represent an intergrade between C. mendocino and C. walterorum.. Our results add to a currently under-appreciated pattern suggesting that coastal Central California is not a transition zone between Northern and Southern California Floristic Province faunas but rather its own unique, periodically isolated, biogeographic region.