Minoru Ishii

Genetic diversity and structure of urban populations of Pieris butterflies assessed using amplified fragment length polymorphism.

Conservation programs in urban ecosystems need to determine the genetic background in populations of urban dwellers. We examined the genetic diversity and structure of Pieris rapae and P. melete using AFLP markers, and compared them between species and between urban and rural environments. As a result: (i) in both species, there was no reduction in genetic diversity within urban populations by direct comparison of diversity measurements, although the analysis of molecular variance suggested significant reductions in the variance within seasonal subpopulations in urban populations; (ii) P. rapae retained greater genetic diversity within species and populations; (iii) populations of both species showed significant genetic differentiation, and P. melete was more strongly subdivided; (iv) in both species, geographically close populations did not cluster with one another in the upgma analysis; (v) there was no genetic isolation due to geographical distance in either species; (vi) the genetic composition of seasonal subpopulations differed in urban populations of both species, and the genetic distances among subpopulations were correlated with seasonal differences in P. rapae and with temporal differences in P. melete. These results indicate that the genetic diversity in urban populations of both species was reduced at times, but was maintained by dispersal from genetically differentiated populations. Differences in the ability and mode of dispersal in the two species may be reflected in the degree of population subdivision and patterns of seasonal change in the genetic composition.

The water system of traditional rice paddies as an important habitatof the giant water bug, Lethocerus deyrollei (Heteroptera: Belostomatidae)

The population dynamics of Lethocerus deyrollei, including the seasonal change in the habitat utilization, were studied in five types of waters, permanent and temporary pools, ditch, rice paddy and marsh in a Satoyama, the traditional landscape in Japan consisting of mixtures of coppice woodlands, farmlands, and settlements, in northern Osaka, from June, 1999 to December, 2001. A mark and recapture census was carried out with adults, and the stage and the number were recorded in nymphs. A total of 95 adults were numbered, and 48 (51%) were recaptured in all the five water types during the study period. Adults of the new generation appeared from late July, and disappeared before the winter in all types of waters. A total of three overwintered adults were recaptured in permanent and temporary pools, ditch, and paddy from between early April and early June. Densities of both L. deyrollei adults and their prey, tadpoles and frogs, were high in permanent and temporary pools, and ditch, in which water temperatures were high in the summer season. Third to fifth (final) instar nymphs were also observed in all water types with different densities in summer, while first and second instars were found only in permanent pool, ditch and paddy habitats in which water temperatures were high and oviposition substrata such as the rice plant, other hygrophytes and wooden stakes existed. These results show that the traditional water system of paddy in the Satoyama landscape as a whole provides an important habitat for L. deyrollei which is now under threat by changing agricultural practices like other native biota inhabiting the system.

Host acceptance behavior of the Japanese aquatic wasp,Agriotypus gracilis (Hymenoptera: Ichneumonidae) toward the caddisfly host,Goera japonica (Trichoptera: Limnephilidae)

The host acceptance behavior of the Japanese aquatic wasp,Agriotypus gracilis Waterston, an ectoparasitoid of the sand case building caddisfly,Goera japonica Banks was investigated in the laboratory. Female wasps were observed to enter the water by walking down a stone protruding from the water surface. Antennae were held backward and not utilized in searching for hosts under the water. Female wasps examined hosts from the outside of their cases by 2 consecutive steps, “turning” and “probing”. Turning behavior, in which female wasps move between the anterior and posterior ends of host cases, may be related to the measurement of case size. Host stages are considered to be discriminated by probing, in which females probe host cases with their sheathing ovipositors. Female wasps most frequently accepted and oviposited on pupal and prepupal hosts.

Development and Future of Insect Conservation in Japan

Japan is located at the eastern edge of the Eurasian Continent, and is an island nation composed of four large islands—Hokkaido, Honshu, Shikoku, and Kyushu—and a large number of small islands. Although the Japanese Archipelago is relatively small (with the total area of land approximately 380,000 km2 ), the climate ranges from subtropical to the Frigid Zone, with a temperate zone that has four distinct seasons at the centre; the Japanese Archipelago is approximately 3,000 km from north to south, extending from latitude about 45° N to about 20° N. Moreover, Japan is a volcanic country, and mountain ranges run in all directions on each island. There are numerous mountains with various heights including the highest mountain, Mt. Fuji (3,776 m).

Genital segments of sexual mosaic offspring from Wolbachia-infected female Zizina emelina (Lepidoptera: Lycaenidae).

ABSTRACT: Eight sexual mosaic offspring of Zizina emelina (Lepidoptera: Lycaenidae) were obtained from females infected with male-killing Wolbachia (wEmeTn2), though they were mostly dead at the stage of pharate adult. Uninfected females or females infected with another strain of Wolbachia (wEmeTn1) produced no mosaics. Therefore, the occurrence of these sexual mosaics was associated with wEmeTn2 infection. In sexual mosaics, the ventral and dorsal parts of genitalia differentiated independently into male-specific and female-specific formations, respectively, i.e., the ventral part of abdominal segment IX may have tendencies to retain male structures, while the dorsal parts of abdominal segments IX and X possess female structures. More than two pairs of ill-developed valvae were observed in several individuals in a deep pouch. The presence of additional valvae would mean that the segment IX or the ventral phallic lobe is at least partly duplicated.

Reproduction, growth rate and dispersal of the dark chub, Candidia sieboldii, as estimated by using the mark–release–recapture method

ABSTRACT We investigated the breeding season, growth rate and dispersal of the dark chub, Candidia sieboldii, an endangered species in Japan. A mark–release–recapture survey was performed in three branches of the Ishizu River system in Osaka Prefecture, Japan, between May 2012 and August 2013. A total of 963 individuals were marked in one river branch and 275 (29%) were recaptured at least once in the same river section. The breeding season was determined to be June–August, and the size at maturity for both males and females was estimated at about 70 mm standard length. Growth rates calculated from standard lengths of recaptured individuals were higher between April and September than between October and March. Among 963 marked individuals, only a single fish was found 500 m downstream from the release point. Moreover, although we released 409 more marked individuals in the three branches to follow inter-branch dispersal between September and December 2013, we observed none. These results indicate that this species has low dispersal and a short lifespan of 1–2 years. This short lifespan could increase the risk of breeding failure, and the low frequency of dispersal, restricted by weirs, could make population re-establishment and recovery difficult.

Genetic population structure of the fluvial eight-barbel loach Lefua sp. 1 in the three river systems in central Honshu, Japan, revealed by microsatellite DNA markers

The fluvial eight-barbel loach Lefua sp. 1 is an undescribed species distributed from the Kinki to Chugoku districts, Honshu, and also on Shikoku Island, Japan. Genetic relationships among local populations are unclear and management units remain undetermined. To aid conservation, we determined genetic population structures from microsatellite loci for 20 populations from three river systems on Honshu. The genetic diversity within populations is relatively low; the majority has experienced genetic bottlenecks. Statistical analysis revealed significant divergence among river systems suggesting that each should be recognized as a management unit. Any conservation program should consider the populations’ genetic uniqueness.

Differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail, Papilio machaon (Lepidoptera: Papilionidae), from the Osaka population

To clarify differences in pupal cold hardiness and larval food consumption between overwintering and non‐overwintering generations of the common yellow swallowtail, Papilio machaon, we reared larvae from the Osaka population under photoperiods of 16 h light : 8 h dark (LD 16:8) (long day) or LD 12:12 (short day) at 20°C. We examined the relationship between food consumption and weight during the final larval stadium and pupae, and measured the pupal supercooling point (SCP). Although the ratio of assimilation to consumption did not differ significantly between photoperiods, the ratio of assimilation to pupal weight differed significantly between individuals reared under long and short days. All diapausing pupae were brown, whereas 56% of non‐diapausing pupae were green with the remainder brown. The mean pupal body length (L), dorsal width (W1) and lateral width (W2) were larger in non‐diapausing than in diapausing pupae, and the W1/L and W1/W2 ratios differed significantly between non‐diapausing and diapausing pupae. SCP was approximately –20°C and did not differ among pupae 5, 15 and 30 days after pupation under long‐day conditions. However, under short‐day conditions, mean SCP gradually decreased, stabilizing at approximately –24 to –25°C by 30 days after pupation. After freezing, some diapausing pupae emerged as adults, whereas all non‐diapausing pupae died. Both egestion and assimilation were greater under long‐day conditions. The results revealed that pupae of this papilionid exhibit seasonal polyphenism in physiological and morphological traits. Energy from food appears to be expended on increasing cold hardiness in the overwintering generation and on reproduction in the non‐overwintering generation.

A danaid butterfly, Ideopsis similis, overcomes parasitization by a tachinid fly, Sturmia bella

The danaid butterfly Ideopsis similis, which occurs in the Ryukyu Islands, Japan, is a sedentary and monophagous species, whose larval food plant, Tylophora tanakae (Asclepiadaceae), is shared with the migratory and polyphagous danaid Parantica sita. The tachinid Sturmia bella is known to be a principal parasitoid of larval P. sita, whereas there have been no records of parasitization of I. similis by this tachinid. We conducted laboratory experiments and field surveys at seven sites in the Ryukyu Islands to determine how I. similis evades parasitization by this tachinid. We found eggs of S. bella at four sites and eggs and/or larvae of I. similis on the leaves of T. tanakae at all seven sites in the field survey. Out of 40 I. similis allowed to ingest S. bella eggs, 28 (70%) emerged as normal host adults and nine (22.5%) emerged as host adults with crippled wings. Only three (7.5%) died of parasitization in the pupal stage, whereas 27 (87%) of 31 P. sita given S. bella eggs yielded parasitoid flies and eventually died. Melanized dead larvae of S. bella were found in the abdomens of the I. similes adults that had been parasitized but did not yield parasitoid flies. When I. similis females parasitized by S. bella were released in a greenhouse with males, one of them laid fertile eggs. Out of 125 field‐collected I. similis adults, nine had melanized dipteran larvae within their abdomens, which were considered to be S. bella. These results demonstrate that I. similis has the ability to overcome parasitization by S. bella and develop into a fertile adult. It is possible that I. similis remains sedentary and monophagous because it has a strong defense mechanism against S. bella, whereas P. sita escapes from parasitization using its migratory and polyphagous capability.