EXTREME HOST PLANT CONSERVATISM DURING AT LEAST 20 MILLION YEARS OF HOST PLANT PURSUIT BY OAK GALLWASPS

Diversification of insect herbivores is often associated with coevolution between plant toxins and insect countermeasures, resulting in a specificity that restricts host plant shifts. Gall inducers, however, bypass plant toxins and the factors influencing host plant associations in these specialized herbivores remain unclear. We reconstructed the evolution of host plant associations in Western Palaearctic oak gallwasps (Cynipidae: Cynipini), a species-rich lineage of specialist herbivores on oak ( Quercus ). (1) Bayesian analyses of sequence data for three genes revealed extreme host plant conservatism, with inferred shifts between major oak lineages (sections Cerris and Quercus ) closely matching the minimum required to explain observed diversity. It thus appears that the coevolutionary demands of gall induction constrain host plant shifts, both in cases of mutualism (e.g., fig wasps, yucca moths) and parasitism (oak gallwasps). (2) Shifts between oak sections occurred independently in sexual and asexual generations of the gallwasp lifecycle, implying that these can evolve independently. (3) Western Palaearctic gallwasps associated with sections Cerris and Quercus diverged at least 20 million years ago (mya), prior to the arrival of oaks in the Western Palaearctic from Asia 5–7 mya. This implies an Asian origin for Western Palaearctic gallwasps, with independent westwards range expansion by multiple lineages.     

Evolutionary shifts between host oak sections and host-plant organs in Andricus gallwasps

Abstract.— Gall-inducing insects have especially intimate interactions with their host plants and generally show great specificity with regard to both the host-plant species and the organ (e.g. flower, leaf) galled. However, the relative roles of shifts between host species and between host-plant organs in the diversification of gall-inducers are uncertain. We employ a novel and general maximum-likelihood approach to show that shifts between host-plant organs occur at a significantly greater rate than shifts between host oak sections in European Andricus gallwasps. This suggests that speciation has more often been associated with gall location shifts than with colonization of new host-plant species, and implies that it may be easier for gall-inducers to colonize new plant organs than new plant species.
Andricus gallwasps have complex life cycles, with obligate alternation of sexual and parthenogenetic generations. Our phylogenetic analyses show that a life cycle with both generations galling white oaks (section Quercus ) is ancestral, with a single shift of the sexual generation onto black oaks (section Cerris ) to generate a clade with a novel host-alternating life cycle. This new life cycle provided the opportunity for further speciation, but may have also increased the risk of extinction of one or both generations by the demographic requirement for co-existence of both host-plant groups. In summary, it appears that Andricus gallwasp radiation may be a two-level process. Speciation events often involve shifts in gall location on the same host species. However, there are only so many ways to gall an oak, and rare shifts to new oak sections may contribute greatly to long-term diversification by opening up whole new adaptive zones.     

Polymorphic microsatellite loci in Eurytoma brunniventris,a generalist parasitoid in oak cynipid galls

Eurytoma brunniventris is a parasitic wasp with a wide range of host species. We have developed primers for nine polymorphic microsatellite loci to allow examination of intraspecific population subdivision associated with two aspects of the biology of their hosts: host species (oak gallwasps) and the tree on which the gallwasp develops (different oak species). All nine loci amplified well across individuals collected from a range of gallwasp species and across two oak taxa. These microsatellite loci are potentially of value in the study of closely related economic pests such as seed predators of almonds (E. amygdali) and pistachios (E. plotnikovi).     

Systematic re‐appraisal of the gall‐usurping wasp genus Synophrus Hartig, 1843 (Hymenoptera: Cynipidae: Synergini)

Several unanswered questions remain regarding the taxonomy and phylogeny of inquiline gallwasps (Cynipidae: Synergini), obligate inhabitants of plant galls induced primarily by other gallwasps (Cynipidae: Cynipini and Diplolepidini). Here we use morphological and molecular data to revise the inquiline genus Synophrus, members of which are notable for extensively modifying the structure of galls induced by oak gallwasp hosts on oaks in the section Cerris of Quercus subgenus Quercus in the Western Palaearctic. Previous taxonomic treatments have recognized three Western Palaearctic species of Synophrus: S. pilulae, S. politus and S. olivieri. Our results support the establishment of four additional Western Palaearctic species: Synophrus hungaricus sp.n. , S. libani sp.n. , S. syriacus sp.n. and S. hispanicus sp.n. We describe and diagnose these new taxa, analyse their phylogenetic relationships, and show that Synophrus inquilines are able to impose their own gall phenotypes on those of their hosts. We provide an updated key to Synophrus.     

Parasitoid complexes of lepidopteran leaf miners on oaks (Quercus dentata andQuercus mongolica) in Hokkaido,Japan

Parasitoid complexes of four microlepidopteran leaf-mining genera,Phyllonorycter, Caloptilia (Gracillariidae),Tischeria (Tischeriidae) andStigmella (Nepticulidae), which make mines on two oaks,Quercus dentata andQuercus mongolica, were studied at the Ishikari Coast, Hokkaido, northern Japan. In total, twenty-five parasitoid species were recognized.Phyllonorycter showed the highest parasitoid-species richness among the four leaf-mining genera. The number of parasitoid species associated with leaf miners onQ. dentata was nearly equal to that associated with miners onQ. mongolica, but a considerable difference was observed in the faunal make-up of parasitoids between leaf miners on the two oaks. The dominant parasitoid species differed betweenPhyllonorycter leucocorona andPhyllonorycter similis even on the same oak,Q. dentata. Factors influencing the host ranges of parasitoids and the parasitoid richness of host species or genera are discussed on the basis of the koinoparasitism/idioparasitism categorization.     

Lifecycle closure, lineage sorting, and hybridization revealed in a phylogenetic analysis of European oak gallwasps (Hymenoptera: Cynipidae: Cynipini) using mitochondrial sequence data

Oak gallwasps are cyclically parthenogenetic insects that induce a wide diversity of highly complex species- and generation-specific galls on oaks and other Fagaceae. Phylogenetic relationships within oak gallwasps remain to be established, while sexual and parthenogenetic generations of many species remain unpaired. Previous work on oak gallwasps has revealed substantial intra-specific variation, particularly between regions known to represent discrete Pleistocene glacial refuges. Here we use statistical phylogenetic inference methods on sequence data for a fragment of the mitochondrial cytochrome b gene to reconstruct the relationships among 62 oak gallwasp species. For 16 of these we also include 23 additional cytochrome b haplotype sequences from different Pleistocene refuge areas to test the effect of intra-specific variation on inter-specific phylogeny reconstruction. The reconstructed phylogenies show good intra-generic resolution and identify several conserved clades, but fail to reconstruct either very recent or very ancient divergences. Nine of the 16 species represented by multiple haplotypes are not monophyletic. The apparent discordance between the recovered gene tree and the current taxonomic classification can be explained through: (a) collapsing of some species currently known only from either a sexual or a parthenogenetic generation into a single cyclically parthenogenetic entity; (b) sorting of ancestral polymorphism in diverging lineages, and (c) horizontal transfer of haplotypes, perhaps due to hybridization within glacial refuges. Our conclusions emphasise the need for careful intra-specific sampling when reconstructing phylogenies for radiations of closely related species and imply that for certain taxonomic groups full phylogenetic resolution (using molecular markers) may not be attainable.     

Synopsis of the tribe Bocageeae (Annonaceae), with revisions of Cardiopetalum,Froesiodendron, Trigynaea,Bocagea, and Hornschuchia

The tribal name Bocageeae Endlicher is reestablished and the tribe is circumscribed on the basis of solitary internodal ebracteate pedicels that are articulated at the base, and pollen shed in polyads of eight or more grains. Septate anther locules, large pollen size, and seed appendages are prevalent in the tribe. Intectate pollen with free-standing columellae, rare in Annonaceae, occurs not only in the genusTrigynaea but also in some species ofBocagea andHornschuchia. As defined here, the Bocageeae include seven neotropical genera:Cymbopetalum, Porcelia, Bocagea, Cardiopetalum, Froesiodendron, Hornschuchia, andTrigynaea. The latter five genera are revised and the treatments include ten new species:Cardiopetalum plicatum, Froesiodendron urceocalyx, Hornschuchia lianarum, H. santosii, H. leptandra, Trigynaea cinnamomea, T. lanceipetala, T. triplinervis, T. lagaropoda, andT. axilliflora, all from tropical South America. A new combination,Froesiodendron longicuspe, changes the rank of that taxon from subspecies to species.Cardiopetalum surinamense is removed fromFroesiodendron and reassigned toCardiopetalum on the basis of its connate petals, dehiscent monocarps, and seeds with bilobed arils. A cladogram provides an explicit hypothesis of intergeneric relationships in the tribe. The new combinationOnychopetalum periquino, based onTrigynaea periquino, is made.     

Two new species ofMycena from eastern Honshu, Japan

Two new species ofMycena are described and illustrated from eastern Honshu, Japan:Mycena brevicapillata sp. nov. (sectionHiemales), forming tall and slender basidiomata covered overall with long, fusiform or sublageniform dermatocysts, was found on a dead branch ofHydrangea involucrata; Mycena chrysanthemiformis sp. nov. (sectionFragilipedes), forming small, white basidiomata with a campanulate, shallowly sulcate-striate, occasionally subumbonate pileus and adnate-decurrent lamellae, was found on living bark or a dead fallen twig ofAphananthe aspera, Cryptomeria japonica, andZelkova serrata.     

The taxonomy ofVaccinium sectionHemimyrtillus

In view of their awnless stamens and pseudo-10-loculed berries borne on short racemes several NE Asian species ofVaccinium (includingV. hirtum, V. smallii, V. versicolor, andV. yakushimense) were transferred toVaccinium sectionCyanococcus by Sleumer (1941). Subsequently, however, Stevens (1969) and Vander Kloet (1972, 1981) argued on the basis of further study that these taxa should be transferred instead to sectionHemimyrtillus. Phenetic analyses of data from representatives of sectionsCyanococcus andHemimyrtillus, including NE Asian taxa transferred by Sleumer, demonstrate the distinctness of the two sections and support the assignment of the NE Asian taxa to sectionHemimyrtillus. A revised taxonomic treatment and key to the species ofVaccinium sectionHemimyrtillus is provided.