Ryo Yamaguchi 교수

Allopatric speciation is a mechanism to evolve reproductive isolation; it is caused by the accumulation of genetic differences between populations while they are geographically isolated. Here, we studied a simple stochastic model for the time until speciation caused by geographical isolation in fragmented populations that experience recurrent but infrequent migration between subpopulations. We assumed that mating incompatibility is controlled by a number of loci that behave as neutral characters

The formation of new species via the accumulation of incompatible genetic changes is thought to result either from ecologically based divergent natural selection or the order by which mutations happen to arise, leading to different evolutionary trajectories even under similar selection pressures. There is growing evidence in support of both ecological speciation and mutation-order speciation, but how different environmental scenarios affect the rate of species formation remains underexplored. We

AbstractPopulation genomic analysis of hybrid zones is instrumental to our understanding of the evolution of reproductive isolation. Many temperate hybrid zones are formed by the secondary contact between two parental populations that have undergone postglacial range expansion. Here, we show that explicitly accounting for historical parental isolation followed by range expansion prior to secondary contact is fundamental to explaining genetic and fitness patterns in these hybrid zones. Specifical

Abstract The origin and patterns of species diversity are fundamental themes in ecology and evolutionary biology. Insular systems play an important role in biogeography, and the species richness within an insular system has classically been considered as determined by the balance between the rate of speciation plus net migration and the rate of species extinction. A recent wave of studies integrating comprehensive phenotypic, phylogenetic, and environmental data is accumulating additional macroe

The present study observationally examines relationship between Pi2 pulsations and the bursty bulk flow (BBF) in the plasma sheet. At a Pi2 onset of August 14, 1996, the GEOTAIL satellite and the GOES8 geosynchronous satellite were aligned in the X direction observing transient signatures. Those signatures were examined by referring to a ground low‐latitude Pi2 wave detected at the same meridian as GOES8. In the present event, a BBF started prior to the ground Pi2 onset, but it was preceded by a

The present study investigates the energy storage and release processes of substorms as a function of both position and substorm intensity in a model‐independent manner. As an index of the substorm intensity, we use the amplitude of the positive bay observed at middle and low latitudes. As an index of the energy storage and release in the magnetotail, we use the total pressure measured by Geotail. We have performed a superposed epoch analysis of the total pressure for each substorm group binned

In an archipelagic system, species diversity is maintained and determined by the balance among speciation, extinction and migration. As the number of species increases, the average population size of each species decreases, and the extinction likelihood of any given species grows. By contrast, the role of reduced population size in geographic speciation has received comparatively less research attention. Here, to study the rate of recurrent speciation, we adopted a simple multi-species two-islan

We studied the time to speciation by geographical isolation for a species living on three islands connected by rare migration. We assumed that incompatibility was controlled by a number of quantitative loci and that individuals differing in loci by more than a threshold did not mix genetically with each other. For each locus, we defined the geographical configuration (GC), which specifies islands with common alleles, and traced the stochastic transitions between different GCs. From these results

Genetic divergence among allopatric populations builds reproductive isolation over time. This process is accelerated when populations face a changing environment that allows large-effect mutational differences to accumulate, but abrupt change also places populations at risk of extinction. Here we use simulations of Fisher's geometric model with explicit population dynamics to explore the genetic changes that occur in the face of environmental changes. Because evolutionary rescue leads to the fix

Abstract Many consequences of reproductive interference have important implications in biodiversity conservation policy. After briefly summarizing our comments on the articles in this special feature, we focus on the role of reproductive interference in speciation due to geographic isolation with only infrequent migration between islands (or island‐like habitats). As two isolated populations accumulate incompatible genes, they became genetically distinct. When a rare migration occurs from one is

Abstract The formation of new species via the accumulation of incompatible genetic changes is thought to result either from ecologically-based divergent natural selection or the order by which mutations happen to arise, leading to different evolutionary trajectories even under similar selection pressures. There is growing evidence in support of both ecological speciation and mutation-order speciation, but how different environmental scenarios affect the rate of species formation remains underexp