>Host: 横浜国立大学グローバルCOEプログラム「アジア視点の国際生態リスクマネジメント」
>Date: 2007年10月25日（木） 17:00-19:00
>Place: 横浜国立大学環境情報1号棟315室
>Speakers
カトリォナ・シェイ博士（ペンシルバニア州立大学）
オッター・ビヨルンスタッド博士（ペンシルバニア州立大学）
>Program
17:00-17:05 Opening Speach by Hiroyuki Matsuda
17:05-17:55 "Demography, dispersal and spread of invasive thistles."
by Dr. Katriona Shea (Penn State University, U.S.A.)
17:55-18:05 Coffe Break
18:05-18:55 "Spatial contact networks and timing of outbreaks in epidemic metapopulations: theory, data and statistics." by Dr. Ottar N. Bjornstad (Penn State University, U.S.A.)
18:55-19:00 Closing Remarks
● 来聴歓迎（お申し込みの必要はありません）
● 言語：英語
● 問い合わせ先：秋田鉄也d07tf001＠ynu.ac.jp (@を半角にして送信してください）
●横浜駅バス停案内 http://www.ynu.ac.jp/access/acc_12.html
バス時刻表 http://risk.kan.ynu.ac.jp/matsuda/bus.html
「横浜新道(ガストのそばです)」下車
地図を参考に南通用門から構内へ入り、環境情報学府1号棟までお越しください。
地図 http://www.ynu.ac.jp/access/acc_19.html
"Spatial contact networks and timing of outbreaks in epidemic metapopulations: theory, data and statistics." by Dr. Ottar N. Bjornstad (Penn State University, U.S.A.)
ABSTRACT: Infectious diseases provide a particularly clear illustration of the spatio-temporal underpinnings of consumer-resource dynamics. The paradigm is the locally unstable, oscillatory dynamics of extremely contagious, directly transmitted, immunizing infections caused by morbilliviruses for which more or less irregular epidemics are interspersed by prolonged periods of local extinction of the parasite. Spatial transmission and 'recolonization' in such systems are ultimately tied to movement by the hosts. The network of spatial spread may therefore be related to the transportation network within the host metapopulation. I discuss two critical issues in the spatiotemporal dynamics of host-pathogen interactions. First, how do rates of movement of hosts between patches affect the timing and predictability of outbreaks? Second, how can we reconstruct topology of transportation networks from outbreak data? I address the first using stochastic epidemic models, and the second the models' associated hazard likelihoods. The theory and methods are discussed with particular reference to measles. I propose a gravity model for the spatial transmission networks and discuss how recurrent epidemics may either be periodic and relatively predictable or erratic and unpredictable depending on the strength of spatial transmission.
His abstract for the Hokkaido University Seminar on the 22nd.
ABSTRACT: Herbivourous forest insects can become pest when local population
growth is geographically synchronized to result in regionalized outbreaks.
The spatial synchrony is important in at least four different ways. First,
it dilutes the regulating effects of any natural enemy that could otherwise
provide local control. Second, it reduces the ecological landscape's ability
for buffering because most areas within a watershed or greater ecosystem
will experience simultaneous disturbance. Third, it greatly exacerbates
the economic burden on any individual stake-holder because a majority of
his/her tract of land may be damaged during any given outbreak. Finally,
the massive geographical scale of many of these outbreaks -- for example
the 65 million cumulative acres defoliated by the gypsy moth over the last
25 years -- vastly overwhelms the budgetary and logistical capabilities
of federal or state agencies to suppress populations and thereby mitigate
impacts. Despite its ecological significance, studying the process of synchronization
is difficult because most fluctuating populations are, at least locally,
fully or partially synchronized. The gypsy moth offers an interesting opportunity
for studying synchronization because outbreaks along the invasion front
are initially out of phase with well-established populations, yet synchronize
with 'the great attractor' within 15-20 years of invasion. We develop a
spatial-extended theoretical model for the system and show that the initial
asynchrony is caused by a strong Allee effect in nascent populations. We
further use the model to explore plausible causes for the rapid synchronization.