Introduction to workshop:  studying gene flow on an ecological time scale Victoria L. Sork Sabbatical Research Fellow, NCEAS (until Aug 1998) University of California-Santa Barbara 735 State St. Suite 300 Santa Barbara, CA 93101 and Department of Biology University of Missouri-St. Louis St. Louis, Missouri 63121-4499 email:  sork@nceas.ucsb.edu  http://www.nceas.ucsb.edu/~sork/     Gene flow among populations can be studied using an evolutionary time frame or an on-going time frame. Evolutionary questions concerning the role of gene flow in genetic diversity, population differentiation, species identity, and speciation emphasize the evolutionary time. However, conservation biological questions concerning the role of gene flow in future patterns of genetic diversity, population differentiation, species identity, and speciation must rely on estimates of on-going gene flow under current landscape conditions. My question, and to some extent the main question of the workshop, is to evaluate the extent to which gene flow models developed to answer evolutionary questions in an evolutionary framework can be used to estimate on-going gene flow. In this introductory talk, I will briefly review categories of gene flow models--some of which will be developed in more detail by workshop participants. Then, I will present evidence of ecological and landscape influences on patterns of gene flow.  My talk will end with a list of questions about which models are most appropriate for the estimation of on-going gene flow and whether new models should be developed which utilize metapopulation approaches or the spatially explicit models.