Projects

Taxonomic and phylogenetic studies of myrmecophilous insects

Myrmecophily is a phenomenon whereby an animal depends on ant societies or colonies during part or all of its life; in other words, the animal is inquilinous to ants. This dependency is mainly observed in insects, and diverse groups of insects exhibit myrmecophily. These types of insects are called myrmecophilous insects or myrmecophiles. To gain a fuller understanding of the biodiversity and evolution of myrmecophilous insects, I have undertaken several projects in the following areas:

Taxonomy: The species diversity of Japanese ants has been well clarified, and much applied and ecological research has been conducted based on ant taxonomic data. However, little information has been obtained on the biodiversity of Japanese myrmecophilous insects and there remain largely unsurveyed Asian areas, apart from Japan. First, I aim to create a framework of general biological information on Asian myrmecophilous insects, particularly staphylinid beetles, paussine beetles, myrmecophilous hoverflies and myrmecophilous crickets, based mainly on taxonomic studies and arrangements of their bionomic data. Myrmecophilous insects have very interesting life histories and associations with ant communities. Consequently, the taxonomic study of myrmecophilous insects in itself provides many topics that may constitute bases for evolutionary or ecological studies.

Phylogeny: Myrmecophilous insects are associated with many kinds of ants. Most species have restricted host specificity, and myrmecophilous insects are considered to have diversified along with the diversification of ants. For this reason, in many cases, myrmecophilous insects may be suitable for use in studies of the co-evolution of symbiotic systems. However, relatively few studies on myrmecophile co-evolution have been carried out to date. I plan to make analyses of the phylogenies of both ants and myrmecophiles, inferred from molecular information, to examine their evolutionary processes. To this end, I am presently examining a symbiotic system between staphylinid beetles of the genus Homoeusa and ants of the genus Lasius.

Evolution of social parasitic ants focusing on ants of the genus Lasius

Apart from the inquilines of ants such as the myrmecophiles introduced above, I am also interested in the evolution of social parasitic ants. I have undertaken a number of projects focused largely on ants of the genus Lasius. Lasius ants are mainly distributed in the subarctic to temperate zones of the Holoarctic region. They depend on the honey drops of melliferous aphids or coccids as their principal food, and they are the commonest ants in their distributional ranges. Six subgenera (Lasius, Cautolasius, Chthonolasius, Dendrolasius, Austrolasius, Acanthomyops) are known in the genus Lasius, of which four subgenera other than Lasius and Cautolasius are known to be temporary social parasites, parasitizing ants of the other Lasius subgenera.

My main focus is on the evolution of social parasitism in the genus. The host-parasite relationship within the genus Lasius is exceptionally complicated, as compared to host-parasite relationships in other ant genera. I collect material from the tribe Lasini, to which Lasius belongs, on a worldwide basis, and conduct molecular analyses on this material. Almost all representatives of the genus Lasius (members of all subgenera) have been accumulated, and the evolutionary history of social parasitism in Lasius is becoming clear.

I am also investigating the evolution of the chemical makeup of the mandibular and poison gland contents in Lasius, based on gas chromatography analysis and bioassays. Ants have many kinds of secretory glands and secrete diverse chemical substances from those glands for communication between nest mates and defence against enemies. In the genus Lasius, the developmental state of each secretory gland is highly diverse among species, as compared to other ant groups. I expect this study will prove to be crucial in clarifying the complicated host-parasite relationship in Lasius.

Higher phylogeny and classification of the staphylinid subfamily Aleocharinae

The staphylinid subfamily Aleocharinae is one of the most taxonomically problematic groups in the Coleoptera, i.e., except for a few groups, its species diversity has not been comprehensively investigated, and its higher taxonomy is quite chaotic.

The Aleocharinae are a major group of myrmecophilous insects, and it is vital to study the systematics of aleocharine beetles in order to understand myrmecophilous insects. The chaotic situation surrounding the higher classification of Aleocharinae tends to be a barrier to the systematic study of aleocharine taxa (genera or tribes). Therefore, although it is a gargantuan project, I intend to carry out an investigation that will clarify the higher phylogeny and classification of the Aleocharinae.

As one aspect of this project, I will make a generic revision of the tribe Lomechusini, which is comprised mostly of myrmecophilous species, and which is highly confused with regard to subtribal and generic concepts, I will also conduct a comparative morphological study of the members of related tribes (“higher” aleocharines).