Masanori J. Toda

A revision of the Asian and European species in the subgenus Amiota Loew (Diptera, Drosophilidae) and the establishment of species-groups based on phylogenetic analysis

A total of 53 Amiota (s. str.) species (75% of the world total) from Asia and Europe, including 10 new species, kamui, kimurai and planata from Japan, and aristata, cuii, macai, magniflava, nuerhachii, spinata and watabei from China, are reviewed with designation of two new synonymies and phylogenetic analysis. Based upon the result of cladistic analysis with 31 adult male morphological characters, the following conclusions are deduced: (1) The subgenus Amiota is monophyletic, so far as the Asian and European forms are concerned. (2) Seven monophyletic groups are recognized within this subgenus. Two of them correspond to known species-groups, the apodemata and sinuata groups, and the remaining five are established as new species-groups, the nagatai, basdeni, taurusata, alboguttata and rufescens groups. A key to all the studied species from Asia and Europe is provided.

Spatio-temporal variation in lepidopteran larval assemblages associated with oak, Quercus crispula : the importance of leaf quality

Abstract.  1. Lepidoptera larval abundance and diversity in the canopies of oak (Quercus crispula) trees and saplings were surveyed in a cool‐temperate, deciduous broadleaf forest in northern Japan.

Polyphyly of Lordiphosa and its relationships in Drosophilinae (Diptera: Drosophilidae)

The phylogenetic relationships of Lordiphosa and some taxa in Drosophilinae were analysed on the basis of a total of forty‐one selected drosophilid species. These included eighteen species of five Lordiphosa species‐groups as the main target, twenty‐three species representative of the major drosophiline ingroup taxa and four species of Steganinae as outgroup. Sixty‐eight morphological characters of adults were subjected to cladistic analysis. From the results it is concluded that Lordiphosa is polyphyletic; the Lo. tenuicauda species‐group and genus Nesiodrosophila form a single monophyletic group; Lordiphosa proper (i.e. Lordiphosa spp. minus the tenuicauda group) comprises another monophyletic group; within Lordiphosa proper the fenestrarum, nigricolor and denticeps groups are all monophyletic, but monophyly of the miki group is not strongly supported; genera Hirtodrosophila and Scaptomyza and subgenus Sophophora are all monophyletic; and within Drosophilinae, genus Scaptodrosophila is the first to have split from the main lineage, but the branching order of other clades, Chymomyza, Lordiphosa proper, Sophophora, Hirtodrosophila, Nesiodrosophila+ Lo. tenuicauda group, Scaptomyza, Dorsilopha and subgenus Drosophila, remains unresolved. The topology of maximum parsimony cladograms suggests that Lordiphosa proper lies close to Sophophora as proposed previously, although its phylogenetic position could not be determined conclusively. By contrast, bootstrap values tended to contradict another hypothesis that Lordiphosa and Scaptomyza are sister groups.

Tree shape, forest structure and diversity of drosophilid community: Comparison between boreal and temperate birch forests

Some models, based on the latitudinal variation in sun angle distribution, predict that trees at high latitudes have narrowly conical crowns and constitute simple-layered forests, whereas trees at low latitudes have shallowly dome-shaped and form more structurally complex multilayered forests. There is a hypothesis that structurally complex habitats can harbor potentially more species than simple ones. In this study, we examined latitudinal correlations between tree shape, forest structure and diversity in drosophilid communities, comparing boreal and cool-temperate forests. We selected secondary birch forests with a common canopy tree species, white birch (Betula platyphylla Sukatchev), as study sites. The crown shape of white birch tended to be spherical in the cool-temperate forest, but narrowly conical in the boreal forest. The foliage structure differed between the two forests. The cool-temperate forest was characterized by a clearly two-layered structure, whereas foliage in the boreal forest was less clearly stratified, being distributed somewhat continuously from the ground to the canopy at lower densities. The structural complexity expressed by foliage height diversity was greater in the cool-temperate forest than in the boreal forest. Various measures of drosophilid diversity were higher in the cool-temperate forest than in the boreal forest, probably resulting from the impoverishment of the canopy subcommunity in the boreal forest. Thus, a physical environmental factor (i.e. the angle of solar inclination) could be a potentially important factor in structuring latitudinal patterns of sylvan animal communities through changes in plant structure at the individual and community levels.

Food preferences and nematode parasitism in mycophagousDrosophila

AbstractFood preferences and nematode parasitism were studied in natural populations of mycophagousDrosophila in and near Sapporo, northern Japan. Species which preferred fresh mushrooms showed species-specific responses toPleurotus mushrooms:D. pirka bred only onPleurotus cornucopiae, D. trivitata onP. cornucopiae andP. ostreatus, D. trilineata on these twoPleurotus mushrooms and some other mushrooms, whileD. sexvittata bred on a wide variety of mushrooms but seldom onPleurotus mushrooms. Species which preferred decayed mushrooms (D. quadrivittata, D. histrioides, D. testacea and species of thequinaria species-group) showed host preferences different from those of the above species. The rate of parasitism by nematodes was generally higher in species which prefer decayed mushrooms than in species which prefer fresh mushrooms. Among species which prefer fresh mushrooms, onlyD. trilineata was parasitized frequently by nematodes. It was not clear what factors determine the rate of parasitism in these mycophagousDrosophila. D. pirka, D. trivittata andD. trilineata passed through three or four generations per year and entered reproductive diapause in early September in and near Sapporo.

Assessment of higher insect taxa as bioindicators for different logging-disturbance regimes in lowland tropical rain forest in Sabah, Malaysia

One of the serious environmental problems since the 1980s has been the conflict between the high rate of deforestation and maintenance of healthy ecosystem services and biological values in tropical forests. There is an urgent demand for setting up an appropriate environmental assessment to keep healthy ecosystem functions and biodiversity along with sustainable forest use based on ecology. In this study, we tried to assess logging-disturbance effects on the abundances of several flying insect groups (higher-taxon approach) in lowland tropical rain forest (Deramakot Forest Reserve, Sabah, Malaysia), while considering seasonal changes and vertical forest stratification. The season was the most important factor affecting the abundances of all the insect groups. Effects of logging disturbance were prominent in the understorey but obscure in the canopy. Changes in physical conditions caused by logging—possibly an increased evaporation due to solar radiation—may have decreased the abundance of desiccation-sensitive insects, especially in the understorey. There are also two probable reasons for the difference between events in the understorey and those in the canopy: (1) noise effects of various physical, environmental factors may have obscured insect responses to logging disturbance in the canopy; (2) higher spatio-temporal variation in quality and quantity of living food resources—such as leaves, flowers and fruits—provided in the canopy may have affected the abundance of their consumer insects independently of logging disturbance. Thus, this study suggests that the abundance of some insect groups at higher-taxon level, especially in the understorey, can be used as bioindicators for assessing effects of logging disturbance on the forest ecosystem.

Polyphyly of the Zaprionus genus group (Diptera: Drosophilidae)

The Zaprionus genus group comprises three drosophilid genera (Zaprionus, Phorticella and Samoaia) that are thought to be related to the Drosophila immigrans species group. We revised the phylogenetic relationships among the three genera and their placement within the subfamily Drosophilinae using one mitochondrial (COII) and one nuclear (Amyrel) gene. The Bayesian tree inferred from concatenated amino acid sequences of the two genes strongly suggests the polyphyly of the Zaprionus genus group and of each of the genera Zaprionus and Phorticella. Paraphyly of the D.immigrans species group was also shown here; the quadrilineata subgroup formed the sister clade to the genus Samoaia. These results suggest the necessity of taxonomic revisions for some relevant genera and species groups included within the genus Drosophila.

Phylogeny and classification of Colocasiomyia (Diptera, Drosophilidae), and its evolution of pollination mutualism with aroid plants

Abstract Colocasiomyia, a moderate‐sized genus in the subfamily Drosophilinae, comprises seventy (twenty‐six described and forty‐four undescribed) species. Several Colocasiomyia species have evolved intimate mutualisms with specific host plants, especially of the family Araceae: the flies depend throughout the entire life cycle, oviposition, larval growth, pupation, and adult feeding and mating, on inflorescences of their host plants, and in turn act as species‐specific pollinators for their host plants. To understand the evolution of this mutualism between Colocasiomyia flies and their host plants, the phylogenetic relationships of this genus and some possibly related taxa are inferred from a cladistic analysis based on sixty‐two characters of adult morphology. We conclude that Colocasiomyia is polyphyletic, with the C. arenga species group clearly separate. Colocasiomyia without the arenga group (Colocasiomyia proper) is sister to all other studied drosophilines, whereas the arenga group is relatively derived within the Drosophilinae. Within Colocasiomyia proper, four clades are recognized, three of which correspond to previously proposed species groups: the cristata, toshiokai and baechlii groups. The other clade, C. sp.1 aff. nepalensis+C. sp.2 aff. nepalensis, is defined as a new species group. Relationships amongst the four clades and three independent species (C. micheliae, C. gigantea and C. sp.K1) remain almost unresolved, except for a sister group relationship between the toshiokai and baechlii groups. The classification of species groups in Colocasiomyia is revised by erecting two new species groups (crassipes and zeylanica groups) in addition to the three known (baechlii, cristata and toshiokai) groups. Revision of the arenga group, which should be removed from Colocasiomyia, is left for future studies. The evolution of host plant selection in Colocasiomyia is discussed by mapping host plant taxa (families, subfamilies and tribes) on the phylogenetic tree deduced from the cladistic analysis. Cohabitation in the same host inflorescence by a pair of species with microallopatric niche separation on the spadix is hypothesized to have evolved independently at least more than twice in Colocasiomyia.

Three-dimensional dispersion of drosophilid flies in a cool temperate forest of northern Japan

Three-dimensional dispersion of drosophilid flies was studied within a secondary broad-leaved forest in relation to forest structure. The survey area included the forest margin and old canopy gaps and varied in the foliage height profile from place to place. Using multivariate analyses on the data of drosophilid dispersion, five microhabitats which were different from one another for drosophilids were recognized: (i) canopy layer; (ii) middle layer; (iii) floor layer of forest interior; (iv) upper layer of forest margin; and (v) herbaceous layer of forest margin and gap. The height of living space of canopy species was remarkably lowered at the forest margin. The forest edge was richer in both numbers of individuals and species than the forest interior from the overlap of the grassland and the forest canopy subcommunities and the addition of invaders from other habitats. However, no ‘edge’ species, which were mostly restricted to or spend most of their time in ecotones, were found. It is hypothesized that the above-ground forest structure consists fundamentally of three zones: (i) the canopy; (ii) the floor; and (iii) the edge. A significant positive correlation was found between the foliage height diversity and the degree of vertical habitat segregation among drosophilid species. The patchiness of vegetation structure influential to the three-dimensional dispersion in a forest drosophilid community was estimated to be on the scale of 110–450 m2. This scale of subjective habitat patchiness or ‘ecological neighbourhood’ corresponds well with the most prevalent size of canopy gaps occurring in various forests.

Phylogenetic relationships between Sophophora and Lordiphosa, with proposition of a hypothesis on the vicariant divergences of tropical lineages between the Old and New Worlds in the family Drosophilidae

Despite many studies on the phylogeny of the subgenus Sophophora, its monophyly has not been established, especially in relation to its putative relative, the genus Lordiphosa. We analyzed their phylogenetic relationships using DNA sequence data of two mitochondrial genes (ND2 and COII) and two nuclear genes (Adh and 28SrRNA). In constructing phylogenetic trees, we accounted for the problem of among-taxa nucleotide compositional heterogeneity, and took a sequence-partitioning approach to allow multiple substitution models for nucleotide sequences that have evolved under different evolutionary processes, particularly developing a novel, sequence-partitioning procedure for Neighbor Joining (NJ) tree construction. Trees constructed by different methods showed an almost identical and strongly supported topology in which Sophophora was paraphyletic: Lordiphosa was placed as the sister to the Neotropical Sophophora consisting of the saltans and willistoni groups, and Sophophora was divided into the clade of Lordiphosa+Neotropical Sophophora and the clade of the obscura+melanogaster groups. Based on the estimated time, 45.9 Mya, of divergence between the Old World Lordiphosa and the Neotropical Sophophora and evidence from paleontology, paleo-geography and -climatology, we propose a hypothesis that this vicariant divergence should have occurred when the North Atlantic Land Bridge between Europe and North America broke in the middle Eocene Epoch.