Sex allocation theory predicts that the optimal sexual resource allocation of simultaneous hermaphrodites is affected by mating group size (MGS). Although the original concept assumes that the MGS does not differ between male and female functions, the MGS in the male function (MGSm; i.e., the number of sperm recipients the focal individual can deliver its sperm to plus one) and that in the female function (MGSf; the number of sperm donors plus one) do not...

Stream grazers have a major impact on food web structure and the productivity of stream ecosystems; however, studies on the longitudinal (upstream versus downstream) and temporal changes in their drift dynamics and resulting distributions remain limited. Here, we investigated the longitudinal and temporal distributions and drift propensity of a trichopteran grazer, the caddisfly, Micrasema quadriloba, during its life cycle in a Japanese stream. The distribution of larvae significantly shifted downstream during the fifth instar larval...

Despite our understanding of chemical defenses and their consequences for plant performance and herbivores, we know little about whether defensive chemicals in plant tissues, such as alkaloids, and their spatial variation within a population play unappreciated and critical roles in plant-herbivore interactions. Neighboring plants can decrease or increase attractiveness of a plant to herbivores, an example of a neighborhood effect. Chemical defensive traits may contribute to neighborhood effects in plant-herbivore interactions. We examined the effects...

There is increasing evidence that herbivore-plant interactions on a focal plant species are influenced by interspecific neighborhood effects via neighboring plants (i.e., an associational effect). However, intraspecific neighborhood effects imposed by plant traits have been less appreciated. Specifically, the significance of intraspecific neighborhood effects in population-level consequences of plants has been totally overlooked. Using two varieties of Nicotiana tabacum (high- and low-nicotine), we evaluated the neighborhood effects based on patch-level interactions in a split-plot 3...

The biomass ratio of herbivores to primary producers reflects the structure of a community. Four primary factors have been proposed to affect this ratio, including production rate, defense traits and nutrient contents of producers, and predation by carnivores. However, identifying the joint effects of these factors across natural communities has been elusive, in part because of the lack of a framework for examining their effects simultaneously. Here, we develop a framework based on Lotka-Volterra equations...

Research in eco-evolutionary dynamics and community genetics has demonstrated that variation within a species can have strong impacts on associated communities and ecosystem processes. Yet, these studies have centred around individual focal species and at single trophic levels, ignoring the role of phenotypic variation in multiple taxa within an ecosystem. Given the ubiquitous nature of local adaptation, and thus intraspecific variation, we sought to understand how combinations of intraspecific variation in multiple species within an...

Terrestrial organic matter (t-OM) has been recognized as an important cross-boundary subsidy to aquatic ecosystems. However, recent evidence has shown that t-OM contributes little to promote secondary production in lakes because it is low quality food for aquatic consumers. To resolve this conflict, we performed a field experiment using leaf litter as t-OM. In the experiment, we monitored zooplankton biomass in enclosures with and without addition of leaf litter under shaded and unshaded conditions and...

Light is a fundamental driver of ecosystem dynamics, affecting the rate of photosynthesis and primary production. In spite of its importance, less is known about its community-scale effects on aquatic ecosystems compared with those of nutrient loading. Understanding light limitation is also important for ecosystem management, as human activities have been rapidly altering light availability to aquatic ecosystems. Here we show that decreasing light can paradoxically increase phytoplankton abundance in shallow lakes. Our results, based...

Aim: Natural disaster risk reduction (DRR) is becoming a more important function of protected area (PAs) for current and future global warming. However, biodiversity conservation and DRR have been handled separately and their interrelationship has not been explicitly addressed. This is mainly because, due of prevailing strategies and criteria for PA placement, a large proportion of PAs are currently located far from human-occupied areas, and habitats in human-occupied areas have been largely ignored as potential...