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301.
We examined morphology of 4 sucker species (Catostomidae) from Klamath and Rogue River basins, Oregon and California. Different pairs of these species have been suspected of hybridizing, and field biologists have experienced difficulty identifying individuals in some areas. The suite of morphological characters used for initial identification was poorly supported by other morphometric characters but well supported by meristic characters, especially when analyses were restricted geographically. In some species sexual dimorphism was evident, with males having longer pectoral fins and females having longer pre-anal counts and measurements. Each species showed geographic differentiation, either between the Lost River subbasin and other Klamath subbasins or between Klamath and Rogue basins. Classification was most difficult for Catostomus snyderi , which was frequently misclassified as all other species, but especially as Chasmistes brevirostris . Despite this, the 2 species are ecologically segregated in the upper subbasins with lake-spawning Ch. brevirostris spatially segregated and river-spawning Ch. brevirostris temporally segregated from river-spawning C. snyderi . We discuss the possibility that a large-headed, thin-lipped species has become extinct in Upper Klamath Lake and alternatively suggest that the form could represent an ecophenotype of Ch. brevirostris that is no longer produced in hypereutrophic Upper Klamath Lake. 相似文献
302.
Land managers and scientists need context in which to interpolate between or extrapolate beyond discrete field points in space and time. Ecological classification of land (ECL) is one way by which these relationships can be made. Until regional issues emerged and calls were made for ecosystem management (EM), each land management institution chose its own ECLs. The need for economic efficiency and the increasing availability of geographic information systems (GIS) compel the creation of a national ECL so that communication across ownership boundaries can occur. ECOMAP, an 8-level, top-down, nested, hierarchical, multivariable approach designed to solve this problem has been endorsed by the Federal Geographic Data Committee. While the coarsest, upper 4 levels of ECOMAP have been produced for the entire U.S., the task of completing the 4 finer-grained levels has been left to local practitioners. We tried to apply the suggestions of ECOMAP for completing an ECL for a 4.5-million-hectare area centered in western Utah. Due to the lack of complete and consistent sets of spatial databases suggested as necessary by ECOMAP for completing the ECL for this area, we developed alternatives to complete the ECL using extant information. We stressed 1 dominant landscape feature per hierarchical level, using repeatable protocols to identify landscape units. We added 2 additional levels below the 8 suggested by ECOMAP. Ecological sites (ESs), the 9th level, are designed to overcome the nestedness of ECOMAP that we found prevented us from using important data on ESs already available from the Natural Resources Conservation Service. Vegetation stands (VSs), the 10th and finest-grain level, are subdivisions of individual polygons of ESs based on differences in disturbance histories that have led to differing current vegetation structure and composition. The ECL we created should help federal, state, and private land managers in western Utah more easily communicate about issues that cross ownership boundaries. 相似文献
303.
This report is a comparative study of the hyobranchial skeleton of the three species in the family Cyptobranchidae and four species of the family Hynobiidae, all of which are figured. Anatomical differences between the cryptobranchids and their relationship to hynobiids are noted and discussed. Reference is made to a relationship that may exist between these families and other salamander families, particularly the possible relationship of the Hynobiidae to the super families Ambystomatoidea or possibly Plethodontoidea. 相似文献
304.
We determined home-range overlap among northern flying squirrels ( Glaucomys sabrinus ) to assess their spatial organization. We found extensive home-range overlap among females, and though this overlap could reflect social behavior, we found no evidence of attraction among females, with only one instance of den-sharing. Instead, our results suggest that females share foraging areas but may be territorial in portions of the home range, especially around den trees and during young-rearing. Home-range overlap could also result from the extrinsic effect of forest fragmentation due to timber harvest, which might impede dispersal and force squirrels to cluster on remaining fragments of suitable habitat. Determinamos el sobrelapamiento del rango hogareño entre las ardillas voladoras del norte ( Glaucomys sabrinus ) para evaluar su organización espacial. Encontramos un extenso sobrelapamientos en los rangos hogareños entre las hembras; aunque esto podría reflejar su comportamiento social, no encontramos evidencia de atracción entre hembras, y en sólo un caso compartieron su guarida. Vienen su lugar, nuestros resultados sugieren que las hembras comparten áreas de forrajeo pero pueden ser territoriales en ciertas partes de su rango hogareño, particularmente cerca de los árboles donde tienen guaridas y cuando tienen cría. El sobrelapamiento del rango hogareño también podría ser el resultado del efecto extrínseco de la fragmentación forestal debido a la tala de madera, el cual podría impedir la dispersión y forzar a las ardillas a agruparse en fragmentos de hábitat adecuado que queden. 相似文献
305.
R. Douglas Holt Matthew J. Butler Warren B. Ballard Curtis A. Kukal Heather Whitlaw 《西北部美国博物学家》2011,70(2)
Lesser Prairie-Chicken ( Tympanuchus pallidicinctus ) populations have experienced dramatic rangewide declines (up to 92%) since settlement of the Great Plains. This decline has been attributed to changes in land-use practices, such as conversion of native rangelands to intensive agriculture and increased grazing pressure. These changes may increase the impact of interspecific competition on populations. We documented disturbance of lekking Lesser Prairie-Chickens by Ring-necked Pheasants ( Phasianus colchicus ). Future management and research should take into account possible impacts to Lesser Prairie-Chickens during the breeding season. 相似文献