The conservation of threatened vascular plants and Europe     

S.M. Walters 《Biological conservation》1976,10(1):31-41

With the five-volume work Flora Europaea nearing completion, it has become possible to prepare a reasonably accurate list of threatened vascular plants for the whole European continent. This paper gives an account of this international conservation project, and considers the use of such data in formulating policies of nature conservation on a national, continental and world scale. Recommendations are made for future action.  相似文献   

Computer simulations of the effects of the Sitka eddy on the migration of sockeye salmon returning to British Columbia   总被引：1，自引：0，他引：1  

Healey  Thomson  Leblond  Leonardo Huato  Hinch  & Walters 《Fisheries Oceanography》2000,9(3):271-281

The Sitka eddy is a mesoscale eddy, 300 km in diameter, that develops off SE Alaska in about one year in two. The eddy has surface currents exceeding 50 km day⁻¹ and it has been suggested that the eddy could deflect migrating salmon to the south, thereby reducing the proportion of British Columbia (BC) sockeye salmon accessible to Alaskan fishers. We modelled its effects on the migration of sockeye salmon ( Oncorhynchus nerka ) returning to northern BC, using an individual-based model to simulate migration paths, migration timing and metabolic costs of salmon with different migration behaviours. Except when their migration behaviour included positive rheotaxis, salmon that encountered the eddy had faster migration times and lower metabolic costs than those that did not. The least complex migration behaviour, compass orientation with no rheotaxis, was only slightly less efficient in metabolic terms than the optimal migration paths determined by dynamic programming. Our simulations show that the Sitka eddy itself does not deflect migrating salmon to the south or south-east regardless of migration behaviour, but that by interrupting the normal northward flow of the Alaskan Current, the eddy could influence latitude of landfall of migrating salmon.  相似文献   

Temporal segregation in spawning between native Yellowstone cutthroat trout and introduced rainbow trout     

John M. Fennell  William C. Rosenthal  Catherine E. Wagner  Jason C. Burckhardt  Annika W. Walters 《Ecology of Freshwater Fish》2023,32(1):94-106

Hybridisation with introduced taxa poses a threat to native fish populations. Mechanisms of reproductive isolation can limit or prevent hybridisation between closely related species. Understanding how these mechanisms interact between the same species across geographically distinct occurrences of secondary contact, and how regional factors influence them, can inform our understanding of hybridisation as a threat and management actions to mitigate this threat. We used data collected on adult fish migration timing and approximate emergence timing of subsequent juvenile fish paired with genomic data to assess whether temporal isolation in the timing of spawning exists between Yellowstone cutthroat trout, rainbow trout and hybrids in the North Fork Shoshone River drainage in northwest Wyoming. We found evidence that Yellowstone cutthroat trout spawn, on average, two to four weeks later than rainbow trout and hybrids and two environmental covariates related to water temperature and discharge were associated with differences in spawning migration timing. Despite statistical support for Yellowstone cutthroat trout spawning later, disproportionately high numbers of rainbow trout and hybrids, paired with extended spawning seasons, lead to substantial overlap between all genotypes. Our results provide further evidence of temporal segregation in the timing of spawning as a mechanism of reproductive isolation between closely related species, but substantial spawning overlap suggests temporal segregation alone will not be enough to curtail hybridisation in conservation populations.  相似文献