Feeding of mussel-associated leeches Hemiclepsis kasmiana on bitterling embryos: Novel interaction between parasites in a shared host.

We investigated an interaction between bitterlings and a parasitic leech Hemiclepsis kasmiana in freshwater mussel hosts. We found that leeches fed on bitterling eggs and embryos; this may exert a considerable negative effect on bitterling fitness. Host choices by females of three bitterling species may be differently affected by the presence of leeches within mussels; Tanakia limbata apparently avoided laying eggs in infested mussels while T.

Habitat partitioning in native Geranium species through reproductive interference.

Background And Aims: Heterospecific pollen transfer may reduce the fitness of recipient species, a phenomenon known as reproductive interference. A theoretical study has predicted that distributions of species pairs affected by reproductive interference may be syntopic under negligible reproductive interference, sympatric but with partitioning at small spatial scale (i.e.

Skewed male reproductive success and pollen transfer in a small fragmented population of the heterodichogamous tree Machilus thunbergii.

Heterodichogamy is defined as the presence of two flower morphs that exhibit the male and female functions at different times among individuals within a population. Heterodichogamy is regarded as an adaptation to promote outcrossing through enhanced inter-morph mating, together with a 1:1 morph ratio. However, in highly fragmented populations, the morph ratio may be more likely to be biased by stochastic events.

Variation in the strength of reproductive interference from an alien congener to a native species in Taraxacum.

Reproductive interference (RI) may be a contributing factor to the displacement of native species by an alien congener, and RI strength has been shown theoretically to affect distributional relationships between species. Thus, variations in RI strength from alien to native species result in different consequences of invasions and efforts to conserve native species, but the variations have seldom been examined empirically. We therefore investigated RI strength variations from the alien species Taraxacum officinale and its hybrids to eight populations of native dandelions, four T.

Sexual shape dimorphism accelerated by male-male competition, but not prevented by sex-indiscriminate parental care in dung beetles (Scarabaeidae).

Dimorphic sexual differences in shape and body size are called sexual dimorphism and sexual size dimorphism, respectively. The degrees of both dimorphisms are considered to increase with sexual selection, represented by male-male competition. However, the degrees of the two dimorphisms often differ within a species.

Different suitability of improved irrigation channels as reproductive sites for Cyprininae and Silurus asotus.

Irrigation channels around paddy fields have been drastically improved over the past several decades in Japan. This has been accomplished exclusively by covering all the sides of channels with concrete. Although it is conventionally accepted that channel improvement has deteriorated quality of spawning and nursery sites for fish, to date, there is little evidence to support this claim.

Asymmetric reproductive interference between specialist and generalist predatory ladybirds.

1. Closely related species often differ greatly in the quality and breadth of resources exploited, but the actual mechanisms causing these differences are poorly understood. Because in the laboratory specialized species often survive and perform as well or better on host species that are never utilized in nature, negative ecological interactions restricting host range must exist.

Effective range of reproductive interference exerted by an alien dandelion, Taraxacum officinale, on a native congener.

Reproductive interference (RI), defined as the fitness cost of interspecific sexual interactions, such as interspecific pollen transfer (IPT) in plants, is ecologically important. Theoretically, RI could result in competitive exclusion, as it operates in a frequency-dependent manner. Additionally, IPT may have a greater range than resource competition, although information about the range of IPT is lacking.

Camouflage effects of various colour-marking morphs against different microhabitat backgrounds in a polymorphic pygmy grasshopper Tetrix japonica.

Background: Colour-marking polymorphism is widely distributed among cryptic species. To account for the adaptive significance of such polymorphisms, several hypotheses have been proposed to date. Although these hypotheses argue over the degree of camouflage effects of marking morphs (and the interactions between morphs and their microhabitat backgrounds), as far as we know, most empirical evidence has been provided under unnatural conditions (i.

Reproductive interference determines persistence and exclusion in species interactions.

1. Reproductive interference is a negative interspecific sexual interaction that adversely affects the fitness of males and females during reproductive process. Theoretical studies suggest that because reproductive interference is characterized by positive frequency dependence it is far more likely to cause species exclusion than the density dependence of resource competition.

Optimal-foraging predator favors commensalistic Batesian mimicry.

Background: Mimicry, in which one prey species (the Mimic) imitates the aposematic signals of another prey (the Model) to deceive their predators, has attracted the general interest of evolutionary biologists. Predator psychology, especially how the predator learns and forgets, has recently been recognized as an important factor in a predator-prey system. This idea is supported by both theoretical and experimental evidence, but is also the source of a good deal of controversy because of its novel prediction that in a Model/Mimic relationship even a moderately unpalatable Mimic increases the risk of the Model (quasi-Batesian mimicry).

Sequential rapid adaptation of indigenous parasitoid wasps to the invasive butterfly Pieris brassicae.

The introduction of a new species can change the characteristics of other species within a community. These changes may affect discontiguous trophic levels via adjacent trophic levels. The invasion of an exotic host species may provide the opportunity to observe the dynamics of changing interspecific interactions among parasitoids belonging to different trophic levels.

Adaptive significance of death feigning posture as a specialized inducible defence against gape-limited predators.

Death feigning is fairly common in a number of taxa, but the adaptive significance of this behaviour is still unclear and has seldom been tested. To date, all proposed hypotheses have assumed that prey manage to escape predation by sending a death-mimicking signal, although death-feigning postures are markedly different from those of dead animals. Moreover, the efficacy of this technique may largely depend on the foraging mode of the predator; death feigning seldom works with sit-and-wait predators that make the decision to attack and consume prey within a very brief time.

Homosexual tandem running as selfish herd in Reticulitermes speratus: novel antipredatory behavior in termites.

We investigated the predator avoidance mechanism of post-swarming alates of the lower subterranean termite, Reticulitermes speratus Kolbe. In some lower termites, homosexual tandem running is observed in addition to ordinary heterosexual tandem running. An experiment designed to compare the risk of predation by a termite-hunting ant, Brachyponera chinensis Emery, showed that homosexual tandem running reduced the predation risk until termites encounter the opposite sex.