Fuminori Ito

Bio: Fuminori Ito is an academic researcher from Kagawa University. The author has contributed to research in topics: Spermatheca & Exocrine gland. The author has an hindex of 24, co-authored 110 publications receiving 1999 citations. Previous affiliations of Fuminori Ito include Hokkaido University.

Colony dispersal and the evolution of queen morphology in social Hymenoptera.

Abstract: ▪ Abstract Social Hymenoptera show two contrasting strategies of colony reproduction. A reproductive female can raise the first generation of brood alone (independent foundation), or a colony can divide into autonomous parts in which the reproductive female is helped by sterile relatives (fission, budding, swarming). In independent-founding ants, queens can histolize their flight muscles after dispersal; in many species, large flight muscles and metabolic reserves reduce or eliminate the need for risky foraging trips during the vulnerable solitary stage. Colony division is a derived strategy, and we review the selective pressures leading to its occurrence in the different social taxa. In various ants, fission coexists with independent foundation, and alate queens are retained. However, in ants exhibiting obligate fission (e.g. all army ants and many Ponerinae), queens are permanently wingless (ergatoid), or the queen caste is missing altogether. When reproductive females are flightless, dispersal distance...

Widespread occurrence of the micro-organism Wolbachia in ants

Abstract: For more than 20 years, sex allocation in hymenopteran societies has been a major topic in insect sociobiology. A recurring idea was that relatedness asymmetrics arising from their haplodiploid sex determination system would lead to various parent-offspring conflicts over optimal reproduction. A possible weakness of existing theory is that only interests of nuclear genes are properly accounted for. Yet, a diversity of maternally transmitted elements manipulate the reproduction of their host in many solitary arthropod groups. The bacterium Wolbachia is a striking example of such a selfish cytoplasmic element, with effects ranging from reproductive incompatibility between host strains, induction of parthenogenesis and feminization of males. This paper reports on a first PCR-based Wolbachia screening in ants. Out of 50 Indo-Australian species, 50% screened positive for an A-group strain. One of these species also harboured a B-group strain in a double infection. Various factors that might explain the unusually high incidence of Wolbachia in ants are discussed. In general, Wolbachia may represent a widespread and previously unrecognized party active in the conflicts of interest within social insect colonies.

A linear dominance hierarchy regulating reproduction and polyethism of the queenless ant Pachycondyla sublaevis

Abstract: In the vast major i ty of ants, females are divided into two morphological ly distinct castes: queens which principally perform reproduct ion and workers which are engaged in other tasks. However, some species o f the primitive subfamily Ponerinae have no morphologically distinct queens. In the queenless colonies of such species as Rhytidoponera metallica [1], Rhytidoponera sp. 12 [2], and Ophthalmopone berthoudi [3], reproduct ion is performed by several workers that have fortuitously succeeded in mating. In the queenless species Diacamma australe [4] and D. rugosum [5], however, colonies have only one mated egg-layer, called a gamergate. Their reproductive dominance is controlled by a unique mechanism, in which retention of a pair of thoracic appendages determines mating and reproduction. A single gamergate with vestigial wings controls reproduct ion by inhibiting the mating and oviposit ion of other nestmates whose vestigial wings have been removed by the gamergate soon after their emergence. The colonies of Pachycondyla krugeri also have only one gamergate [6]; however, the mechanism controlling the reproductive dominance is as yet unknown. In the queenless ant Pachycondyla (= Bothroponera) sublaevis we discovered an almost linear dominance hierarchy in which (1) the dominance display was well ritualized with no occurrence of fighting, (2) only a top-ranked worker was inseminated and laid eggs, (3) all colony members other than bo t t omranked workers could develop their ovaries when higher-ranked workers were removed, and (4) higher-ranked workers conducted the care of eggs and larvae and lower-ranked workers were engaged in foraging. In ants, this is the first discovery of dominance hierarchy in which most members of a colony are potential successors of the reproductive female. P. sublaevis belongs to the rufipes group, and occurs in the dry Eucalyptus woodland of nothern Australia. Its colonies are possibly among the smallest of all ants, comprising an average of 9 ( + 2.5 s.d.) workers. In most colonies, only one of these is inseminated and bears a reproductive ovary [7]. The behavior of workers was observed in the labora tory in colonies collected at Mr. Garnet , Nor th Queensland, Austral ia, in October to December of 1987 and 1989. In colony A, comprising 11 workers, antagonistic interactions between individuals were observed 85 times during a total of 42 h of observation (Table 1). In the typical sequence, the dominant worker rapidly lunged her vibrating antennae and aggressively pummeled the head of a subordinate (Fig. 1). She repeated this behavior o n e to eight times in each display. The subordinate crouched with her antennae drawn backward until the dominant ceased her coercive behavior. This dominance display was well ritualized with no occurrence of fighting. Between a given pair of workers, the dominance was unilateral except between No. 10 and No. 30 in which the former was dominant three times and subordinate two times. Al though it was difficult to determine the order among low-ranked workers, who were usually ignored by other nestmates, the dominance hierarchy appeared almost linear with few tripart i te deadlocks. The posit ion in the hierarchy was apt to determine the function of the worker concerned. Only the top worker possessed a sperm-filled spermatheca and a well-developed ovary and actually laid eggs. This gamergate and other highranked workers preferred care of eggs and larvae to foraging, which was mostly performed by low-ranked workers (Fig. 2). Cocoons were most frequently tended by middle-ranked workers.

Adaptive advantages of ant-dispersed seeds in the myrmecochorous plant Trillium tschonoskii (Liliaceae)

Abstract: Trillium tschonoskii Maxim. is a myrmecochorous perennial herb which grows in single-species stands in the cool temperate broad-leaved deciduous woodland of Hokkaido, northern Japan. Its many-seeded fruit initially falls close to the parent, over 50% within 20 cm. Ants, principally Myrmica ruginodis and Aphaenogaster japonica, transport seeds to their nests, a mean distance of 64 cm. The nests are overdispersed and short-lived, and are no richer in nitrogen or phosphorus than surrounding soils. There are proportionally more older (3-leaved) than younger (1-leaved) juvenile Trillium plants at distances > 60 cm from the nearest parent plant than at 0-30 or 30-60 cm. This indicates that the relatively short-distance dispersal of T. tschonoskii seeds by ants is sufficient to reduce seedling mortality, by reducing competition between seedlings; and that this is the primary advantage of myrmecochory in this species. This contrasts with previous studies, involving ant species with longer-lived nests, where the main advantage to the plant is nutrient-enhanced seedling microsites.

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Modern Applied Statistics With S

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The Insect Societies

Abstract: In his introduction to this detailed survey of knowledge of insect societies, the author points out that research on insect sociology has proceeded in three phases, the natural history phase, the physiological phase and the population-biology phase. Advances in the first two phases have permitted embarkation in the third phase on a more rigorous theory of social evolution based on population genetics and writing this book, the author wished to relate the three phases of research on insects and to express insect sociology as population biology. A glossary of terms, a considerable bibliography and a general index are included. Other CABI sites 

Wolbachia pipientis: microbial manipulator of arthropod reproduction.

Abstract: ■ Abstract The fi-proteobacterium Wolbachia pipientis is a very common cyto- plasmic symbiont of insects, crustaceans, mites, and filarial nematodes. To enhance its transmission, W. pipientis has evolved a large scale of host manipulations: partheno- genesis induction, feminization, and male killing. W. pipientis's most common effect is a crossing incompatibility between infected males and uninfected females. Little is known about the genetics and biochemistry of these symbionts because of their fas- tidious requirements. The affinity of W. pipientis for the microtubules associated with the early divisions in eggs may explain some of their effects. Such inherited microor- ganisms are thought to have been major factors in the evolution of sex determination, eusociality, and speciation. W. pipientis isolates are also of interest as vectors for the modification of wild insect populations, in the improvement of parasitoid wasps in biological pest control, and as a new method for interfering with diseases caused by filarial nematodes.

The Ecological Consequences of Shared Natural Enemies

Abstract: When multiple victim species (e.g. prey, host) are attacked by one or more shared enemy species (e.g. predator, pathogen), the potential exists for apparent competition between victim populations. We review ideas on apparent com­ petition (also called "competition for enemy-free space") and sketch illustrative examples. One puzzling aspect of this indirect interaction is the repeated rediscovery of the essential ideas. Apparent competition arises between focal and alternative prey populations because, in the long term, enemy abundance depends on total prey availability; by increasing enemy numbers, alternative prey intensify predation on focal prey. A frequent empirical finding, consistent with theory, is exclusion of victim species from local communities by resident enemies. Theory suggests victim-species coexistence depends on particular conditions. To understand fully the consequences of shared enemies requires a body of contingent theory, specifying the time-scale of the interactions (short­ and long-term consequences of sharing enemies generally differ), the structure of the food-web encompassing the interactions, its spatial context, etc. The "core criterion" for a focal victim species to invade a community supporting a resident, polyphagous enemy is r> aP (the invader's intrinsic rate of increase