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Kohkichi Kawasaki

Bio: Kohkichi Kawasaki is an academic researcher from Doshisha University. The author has contributed to research in topics: Population & Biological dispersal. The author has an hindex of 19, co-authored 33 publications receiving 2091 citations.

Papers
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Journal ArticleDOI
TL;DR: A stratified diffusion model is constructed, which describes the dynamics of the size distribution of colonies created by long-distance migrants and provides an estimate of range expansion in terms of the rate of expansion due to neighborhood diffusion, the leap distance, and the colonization rate of long- distance migrants.
Abstract: Recent data on biological invasion show that range expansion is driven by various modes of dispersal such as neighborhood diffusion and long-distance dispersal that occur side by side within a species. In such a stratified dispersal process, the initial range expansion mainly occurs by neighborhood diffusion. However, as the range of the founder population expands, new colonies created by long-distance migrants increase in number to cause an accelerating range expansion in the later phase. We classify several well-documented examples of geographi- cal expansions into three major types depending on the nonlinearity of the range-versus-time curve. To examine how long-distance dispersal produces accelerating range expansion, we con- struct a stratified diffusion model, which describes the dynamics of the size distribution of colonies created by long-distance migrants. The model consists of a von Foerster equation combined with a Skellam model. Analyzing the model provides an estimate of range expansion in terms of the rate of expansion due to neighborhood diffusion, the leap distance, and the colonization rate of long-distance migrants. The results explain various types of nonlinear range expansion observed in biological invasions.

409 citations

Journal ArticleDOI
TL;DR: In this paper, a model for a single species population which propagates in a heterogeneous environment in a one dimensional space is presented, where two kinds of patches with different diffusivities and intrinsic growth rates are alternately arranged along the spatial axis.

380 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed a diffusion-reaction model, in which density dependent cell movements are incorporated by the level of nutrient concentration available for the cell, which predicts the growth velocity of a colony as a function of the nutrient concentration.

235 citations

Journal ArticleDOI
TL;DR: A dynamical model for the colony size distribution of multiple metastatic tumors is presented here and predicts a monotonically decreasing or U-shaped pattern according to the values of clinically significant parameters, such as the colonization coefficient and the fractal dimension of blood vessels.

176 citations

01 Jan 1999
TL;DR: A simple mathematical model of coral shape is constructed, in which the number of branches, their angles and lengths are morphological parameters, and the optimal coral shape changes with light intensity, which agrees qualitatively with the observation of P. sillimaniani colony in natural habitats.

120 citations


Cited by
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Journal ArticleDOI
TL;DR: Range edges are characterized by increased genetic isolation, genetic differentiation, and variability in individual and population performance, but evidence for decreased abundance and fitness is lacking, and a better fusion of experimentation and theory will advance understanding of the causes of range limits.
Abstract: Species range limits involve many aspects of evolution and ecology, from species distribution and abundance to the evolution of niches. Theory suggests myriad processes by which range limits arise, including competitive exclusion, Allee effects, and gene swamping; however, most models remain empirically untested. Range limits are correlated with a number of abiotic and biotic factors, but further experimentation is needed to understand underlying mechanisms. Range edges are characterized by increased genetic isolation, genetic differentiation, and variability in individual and population performance, but evidence for decreased abundance and fitness is lacking. Evolution of range limits is understudied in natural systems; in particular, the role of gene flow in shaping range limits is unknown. Biological invasions and rapid distribution shifts caused by climate change represent large-scale experiments on the underlying dynamics of range limits. A better fusion of experimentation and theory will advance our understanding of the causes of range limits.

1,534 citations

Journal ArticleDOI
TL;DR: Elton's "The Ecology of Invasions by Animals and Plants" as mentioned in this paper is one of the most cited books on invasion biology, and it provides an accessible, engaging introduction to the most important environmental crises of our time.
Abstract: Much as Rachel Carson's \"Silent Spring\" was a call to action against the pesticides that were devastating bird populations, Charles S. Elton's classic \"The Ecology of Invasions by Animals and Plants\" sounded an early warning about an environmental catastrophe that has become all too familiar today-the invasion of nonnative species. From kudzu to zebra mussels to Asian long-horned beetles, nonnative species are colonizing new habitats around the world at an alarming rate thanks to accidental and intentional human intervention. One of the leading causes of extinctions of native animals and plants, invasive species also wreak severe economic havoc, causing $79 billion worth of damage in the United States alone. Elton explains the devastating effects that invasive species can have on local ecosystems in clear, concise language and with numerous examples. The first book on invasion biology, and still the most cited, Elton's masterpiece provides an accessible, engaging introduction to one of the most important environmental crises of our time. Charles S. Elton was one of the founders of ecology, who also established and led Oxford University's Bureau of Animal Population. His work has influenced generations of ecologists and zoologists, and his publications remain central to the literature in modern biology. \"History has caught up with Charles Elton's foresight, and \"The Ecology of Invasions\" can now be seen as one of the central scientific books of our century.\"-David Quammen, from the Foreword to \"Killer Algae: The True Tale of a Biological Invasion\

1,321 citations

Journal ArticleDOI
01 Oct 1999-Oikos
TL;DR: It is found that much of the historical work that has contributed to the perception that diverse communities are less invasible, including Elton's observations and MacArthur's species-packing and diversity-stability models is based on controversial premises.
Abstract: It is commonly believed that diverse communities better resist invasion by exotic species than do simple communities. We examined the history of this notion, and evaluated theoretical and empirical work linking diversity and invasions. We found that much of the historical work that has contributed to the perception that diverse communities are less invasible, including Elton's observations and MacArthur's species-packing and diversity-stability models, is based on controversial premises. Nevertheless, more recent theoretical studies consistently supported the predicted negative relationship between diversity and invasibility. The results of empirical studies, however, were decidedly mixed. Constructed community studies directly manipulating diversity found both positive and negative effects of diversity on invasibility in both field and microcosm settings. Other empirical studies tracking the assembly of ecological communities generally suggested that communities decline in invasibility as species accumulate over time, though the role of diversity itself was often ambiguous. Studies of the spatial correlation between diversity and invasion and studies experimentally adding invaders to natural systems indicated that diverse communities tend to be more invasible. We argue that these results most likely reflect environmental factors spatially covarying with diversity in natural communities (e.g. resources, disturbance). and not the effects of diversity itself as uncovered by constructed community studies. Nevertheless, the consistent positive relationship between exotic species abundance and resident species diversity found in spatial pattern studies suggests that invaders and resident species are more similar than often believed, and the implications of this for theories of invasion are discussed.

1,284 citations

Journal ArticleDOI
TL;DR: Interestingly, most of these patterns had been previously attributed to distinct selective processes, showing that taking into account the dynamic nature of a species range can lead to a paradigm shift in the authors' perception of evolutionary processes.
Abstract: Although range expansions have occurred recurrently in the history of most species, their genetic consequences have been little investigated. Theoretical studies show that range expansions are quite different from pure demographic expansions and that the extent of recent gene flow conditions expected patterns of molecular diversity within and between populations. Spatially explicit simulation studies have led to unexpected and fascinating results about genetic patterns emerging after a range expansion. For instance, spatial expansions can generate allele frequency gradients, promote the surfing of rare variants into newly occupied territories, induce the structuring of newly colonized areas into distinct sectors of low genetic diversity, or lead to massive introgression of local genes into the genome of an invading species. Interestingly, most of these patterns had been previously attributed to distinct selective processes, showing that taking into account the dynamic nature of a species range can lead to a paradigm shift in our perception of evolutionary processes.

1,154 citations

Journal ArticleDOI
TL;DR: It is argued that genetic methods provide a broadly applicable way to monitor long-distance seed dispersal and, hence, that better data is needed from the tails of seeds that travel long distances.
Abstract: Long-distance seed dispersal influences many key aspects of the biology of plants, including spread of invasive species, metapopulation dynamics, and diversity and dynamics in plant communities. However, because long-distance seed dispersal is inherently hard to measure, there are few data sets that characterize the tails of seed dispersal curves. This paper is structured around two lines of argument. First, we argue that long-distance seed dispersal is of critical importance and, hence, that we must collect better data from the tails of seed dispersal curves. To make the case for the importance of long-distance seed dispersal, we review existing data and models of long-distance seed dispersal, focusing on situations in which seeds that travel long distances have a critical impact (colonization of islands, Holocene migrations, response to global change, metapopulation biology). Second, we argue that genetic methods provide a broadly applicable way to monitor long-distance seed dispersal; to place this argument in context, we review genetic estimates of plant migration rates. At present, several promising genetic approaches for estimating long-distance seed dispersal are under active development, including assignment methods, likelihood methods, genealogical methods, and genealogical/demographic methods. We close the paper by discussing important but as yet largely unexplored areas for future research.

1,121 citations