Taxonomy, phylogeny and host plants of some Abia sawflies (Hymenoptera, Cimbicidae).

We briefly review the taxonomy of Abia, and attempt to clarify their systematics by phylogenetic tree reconstructions inferred from three (nuclear and mitochondrial) genes of some West Palaearctic and Nearctic species. The main question which we asked is whether the distinction, made by several authors, of two genera within this group is justified. Based on the species here sampled, our results strongly support a clade recognised widely in earlier literature as Abia or Abia (Abia), but do not always support another clade, Zaraea or Abia (Zaraea), as monophyletic. In the interests of nomenclatural stability and for other practical reasons, the two nominal genera should be treated as synonyms. Host plant associations may be useful in the systematics of Abia species, but this topic requires further investigation and inclusion of more species in phylogenetic analyses.

Sawfly taxa (Hymenoptera, Symphyta) described by Edward Newman and Charles Healy.

Type specimens of seven nominal species of sawfly described by Edward Newman and one by Charles Healy were studied. This material is housed in the Oxford University Museum of Natural History, United Kingdom. The following new synonymies are proposed (valid names in parentheses): Hartigia Schiødte, 1839 (Phylloecus Newman, 1838), Cephus helleri Taschenberg, 1871 (Phylloecus faunus Newman, 1838) and Euura gallae Newman, 1837 (Euura mucronata (Hartig, 1837)). The type species of Euura Newman, 1837 and Euura subgenus Gemmura E. L. Smith, 1968 belong to the same taxonomic species, Euura mucronata (Hartig, 1837), so that these genus group names become new synonyms. Lectotypes are designated for Phyllotoma tormentillae Healy, 1868, Fenusa ianthe Newman, 1837, Fenusa parviceps Newman, 1837, Selandria pallida Newman, 1837 and Phylloecus faunus Newman, 1838. 26 new combinations are proposed for species formerly placed in Hartigia and here transferred to Phylloecus, and 4 original combinations are re-instated as valid.

Ecological versus phylogenetic determinants of trophic associations in a plant-leafminer-parasitoid food web.

Specialized trophic interactions in plant-herbivore-parasitoid food webs can spur "bottom-up" diversification if speciation in plants leads to host-shift driven divergence in insect herbivores, and if the effect then cascades up to the third trophic level. Conversely, parasitoids that search for victims on certain plant taxa may trigger "top-down" diversification by pushing herbivores into "enemy-free space" on novel hosts. We used phylogenetic regression methods to compare the relative importance of ecology versus phylogeny on associations between Heterarthrinae leafmining sawflies and their parasitoids. We found that: (1) the origin of leafmining led to escape from most parasitoids attacking external-feeding sawflies; (2) the current enemies mainly consist of generalists that are shared with other leafmining taxa, and of more specialized lineages that may have diversified by shifting among heterarthrines; and (3) parasitoid-leafminer associations are influenced more by the phylogeny of the miners' host plants than by relationships among miner species. Our results suggest that vertical diversifying forces have a significant-but not ubiquitous-role in speciation: many of the parasitoids have remained polyphagous despite niche diversification in the miners, and heterarthrine host shifts also seem to be strongly affected by host availability.

Phylogenetics and evolution of host-plant use in leaf-mining sawflies (Hymenoptera: Tenthredinidae: Heterarthrinae).

The habit of mining within leaves has evolved convergently in numerous plant-feeding insect taxa. Many leaf-mining groups contain a large number of species with distinct feeding preferences, which makes them highly suitable for studies on the evolutionary history of host-plant use and on the role of niche shifts in speciation. We aimed to clarify the origin, classification, and ecological evolution of the tenthredinid sawfly subfamily Heterarthrinae, which contains c. 150 leaf-mining species that collectively feed on over 20 plant genera around the world. For this, we reconstructed the phylogeny of representative heterarthrine species and diverse outgroups from the superfamily Tenthredinoidea on the basis of DNA sequence data collected from two mitochondrial (CoI and Cytb) and two nuclear (EF-1α and NaK) genes. Thereafter, we inferred the history of niche diversification within Heterarthrinae by plotting larval host-plant associations on the trees, and by contrasting a time-calibrated leaf-miner phylogeny with the phylogeny of their host plants. The results show that: (1) heterarthrine leaf-miners constitute a monophyletic group that arose from external-feeding blennocampine lineages within the Tenthredinidae c. 110-80 million years ago; (2) heterarthrines generally radiated well after their host taxa, and extant host-plant associations therefore result from a combination of host conservatism and occasional shifts among available plant taxa; and (3) diversification in Heterarthrinae apparently occurs by multiple mechanisms, including sympatric or allopatric ecological speciation, non-ecological allopatric speciation, and possibly allochronic speciation. Overall, both present and historical host-use patterns within the Heterarthrinae exhibit striking similarities to patterns found in co-occurring herbivore taxa.