Res. Popul. Ecol. 40(2), 1998, pp. 173-174. 9 1998 by the Society of PopulationEcology !i~:!~:!:!:!i! Special feature i!~:!:i~!!~*!:!:i~:!:!~:!~!:!:!~!:~:!~:!~:!~!~:~:i:!:!~!~:!:~i:~:~:!~:!:!~:~:~:i:!i~:!:~:i:~:~:!:~:~:~:~:~:~i~:~:~:~:~:~:~:~ Speciation, its ecological and biogeographical consequences 18th Symposium of the Society of Population Ecology Specialfeature Speciation, its Ecological and Biogeographical Consequences from the 18th symposium of the Society of Population Ecology in Okinawa, 1997 Although the concept of "species" is one of the most difficult issues in biology and we know little about how species arise in nature, every ecologist uses the notion of species. From one respect, it is sometimes troublesome to think about the species involved in the ecological systems that we study. We may often abandon identification to species, lumping seemingly related organisms together in community ecology. This may be inevitable because we cannot start any analysis at the community level if we are stuck in a muddle of species identification. It is not cer- tain, however, that such a taxonomic treatment does not have significant effects on the results of our analyses. From other aspects, thinking about species can be fas- cinating and exciting for ecologists. For example, popu- lation ecologists who work with the comparative life history and dynamics of geographical populations, such as Epilachna lady bird beetles, may feel the species problem to be very important. This is because adaptation to local conditions, such as hosts and climate, may often be associated with genetic divergence of local populations, which can result in speciation. Since biological diversity originates from speciation, it is quite natural that ecologists who work with species diversity have a deep concern with species and speciation. Further, recent popularization of molecular phylogenetics provides a greater chance for ecologists to deal with a phylogenetic context in their analysis of adaptation, community struc- ture and diversity. After all, concern about "species" is of interest to a great many ecologists. The Society of Population Ecology held its 18th sympo- sium at Chinen, Okinawa, on October 24-26, 1997. The organizing committee selected "Ecology of speciation" as one of the symposium sessions, with the above mentioned general interest of society members in mind. They invited four speakers, introduced below. Despite the title, "Ecology of speciation', the talks were not necessarily concerned with ecological aspects of speciation. Rather, this session reflected the diversity of issues around species and speciation, and was appreciated by many participants at the meeting. The symposium committee invited Guy Bush of Michigan State University as an overseas guest speaker. One reason for inviting him was that he is a prominent researcher in the study of sympatric speciation, the reality of which has long been controversial among evolutionary biologists. The other reason was, more importantly, that his favorite insects are fruit flies of the family Tephritidae. Okinawa, the location of the symposium, has been the center for a long-term eradication program against melon flies, an introduced pest on Okinawa and other islands of the Ryukyu Archipelago. This program used mass-reared sterilized male flies and resulted in eradication of the alien species by 1993. Many entomologists, including members of our society, joined in this program, and in addition to the great success of the eradication program, they were able to achieve valuable scientific results in the population dynamics, behavioral and evolutionary ecology of melon flies. So Dr. Bush was a very sought after speaker by the people of Okinawa. Dr. Bush provided a comprehensive review of sympatric speciation and his long-term study on the North American fruit flies of the genus Rhagoletis. His collaborator, James Smith at Michigan State Univer- sity is a coauthor in this special feature. The island situation of Okinawa led us to have two guest speakers from taxonomy-based fields of biology, Hidetoshi Ota and Motomi Ito, who study biogeography and evolution on islands. The Ryukyu Archipelago, where Okinawa is located, is a row of island chains be- tween the East China Sea and the Pacific Ocean. Consist- ing of some 140 subtropical islands with various environ- mental conditions and geohistorical backgrounds, the Ryukyu Archipelago has been an interesting subject for the study of island biogeography. Ota, a herpetologist at the University of the Ryukyus, has analyzed in detail the biogeographical patterns of amphibians and reptiles of the Ryukyu Archipelago, and has tested recently-submitted hypotheses of the paleogeography of the Ryukyus. Ito, a botanist at Chiba University, has been working on evolu- tionary aspects of higher plants on the Bonin Islands, a Pacific archipelago consisting of some 20 small islands. He showed that some remarkable morphological and reproductive adaptations, coupled with rises of distinct endemic species, have occurred within short periods after long-distance migration of ancestors from East and Southeast Asia. Hybridization between previously diverged populations may have significant effects on the speciation process of organisms having sexual reproduction. The effect of