The observable traits of wild populations are continually shaped and reshaped by the environment and numerous agents of natural selection, including predators. In stark contrast with most predators, humans now typically exploit high proportions of prey populations and target large, reproductive-aged adults. Consequently, organisms subject to consistent and strong 'harvest selection' by fishers, hunters, and plant harvesters may be expected to show particularly rapid and dramatic changes in phenotype. However, a comparison of the rate at which phenotypic changes in exploited taxa occurs relative to other systems has never been undertaken. Here, we show that average phenotypic changes in 40 humanharvested systems are much more rapid than changes reported in studies examining not only natural (n ‫؍‬ 20 systems) but also other human-driven (n ‫؍‬ 25 systems) perturbations in the wild, outpacing them by >300% and 50%, respectively. Accordingly, harvested organisms show some of the most abrupt trait changes ever observed in wild populations, providing a new appreciation for how fast phenotypes are capable of changing. These changes, which include average declines of almost 20% in size-related traits and shifts in life history traits of nearly 25%, are most rapid in commercially exploited systems and, thus, have profound conservation and economic implications. Specifically, the widespread potential for transitively rapid and large effects on size-or life history-mediated ecological dynamics might imperil populations, industries, and ecosystems.contemporary evolution ͉ evolutionary rates ͉ fisheries ͉ harvest ͉ phenotypic change P henotypic traits of wild populations are constantly molded by changes in the environment and by numerous agents of natural selection (1, 2). Among these myriad influences, however, modern humans have emerged as a dominant evolutionary force (3). For example, among wild vertebrates and invertebrates, and via various perturbations such as introductions into novel environments and pollution of their habitat, humans can cause more rapid phenotypic changes than can many natural agents (4).Human predators, by exploiting at high levels and targeting fundamentally different age-and size-classes than natural predators (5-7), can generate seemingly rapid phenotypic changes in both morphological and life history traits in exploited prey (8, 9). But how might the rate of phenotypic change in exploited systems compare with other systems subject to strong directional selection? Here, we report a summary of the magnitudes of phenotypic change in 40 systems of exploited prey (fish, ungulates, invertebrates, and plants) and test whether observed changes can outpace those reported in other wild populations subject to either 'natural' or 'other anthropogenic' perturbations.We also ask what harvesting and prey characteristics elicit the most rapid of phenotypic changes in exploited systems. ResultsData combined from 40 'human predator' systems, comprised of 475 estimates from 29 species, revealed extensive change...

Experimental evidence of trophic cascades initiated by large vertebrate predators is rare in terrestrial ecosystems. A serendipitous natural experiment provided an opportunity to test the trophic cascade hypothesis for wolves (Canis lupus) in Banff National Park, Canada. The first wolf pack recolonized the Bow Valley of Banff National Park in 1986. High human activity partially excluded wolves from one area of the Bow Valley (low‐wolf area), whereas wolves made full use of an adjacent area (high‐wolf area). We investigated the effects of differential wolf predation between these two areas on elk (Cervus elaphus) population density, adult female survival, and calf recruitment; aspen (Populus tremuloides) recruitment and browse intensity; willow (Salix spp.) production, browsing intensity, and net growth; beaver (Castor canadensis) density; and riparian songbird diversity, evenness, and abundance. We compared effects of recolonizing wolves on these response variables using the log response ratio between the low‐wolf and high‐wolf treatments. Elk population density diverged over time in the two treatments, such that elk were an order of magnitude more numerous in the low‐wolf area compared to the high‐wolf area at the end of the study. Annual survival of adult female elk was 62% in the high‐wolf area vs. 89% in the low‐wolf area. Annual recruitment of calves was 15% in the high‐wolf area vs. 27% without wolves. Wolf exclusion decreased aspen recruitment, willow production, and increased willow and aspen browsing intensity. Beaver lodge density was negatively correlated to elk density, and elk herbivory had an indirect negative effect on riparian songbird diversity and abundance. These alternating patterns across trophic levels support the wolf‐caused trophic cascade hypothesis. Human activity strongly mediated these cascade effects, through a depressing effect on habitat use by wolves. Thus, conservation strategies based on the trophic importance of large carnivores have increased support in terrestrial ecosystems.

Large carnivores need large areas of relatively wild habitat, which makes their conservation challenging. These species play important ecological roles and in some cases may qualify as keystone species. Although the ability of carnivores to control prey numbers varies according to many factors and often is effective only in the short term, the indirect effects of carnivores on community structure and diversity can be great. Perhaps just as important is the role of carnivores as umbrella species (i.e., species whose habitat area requirements encompass the habitats of many other species). Conservation areas large enough to support populations of large carnivores are likely to include many other species and natural communities, especially in regions such as the Rocky Mountains of Canada and the United States that have relatively low endemism. For example, a plan for recovery of grizzly bears (Ursus arctos) proposed by Shaffer (1992) covers, in part, 34% of the state of Idaho (compared to 8% covered by a U.S. Fish and Wildlife Service proposal) and would capture 10% or more of the statewide ranges of 71% of the mammal species, 67% of the birds, 61% of the amphibians but only 27% of the reptiles native to Idaho. Two‐thirds (67%) of the vegetation types in Idaho would have 10% or more of their statewide area included in the Shaffer plan. The U.S. Fish and Wildlife Service recovery zones provide a much poorer umbrella. The umbrella functions of large carnivores are expected to be poorer in regions with high endemism. The application of metapopulation concepts to large carnivore conservation has led to proposals for regional reserve networks composed of wilderness core areas, multiple‐use buffer zones, and some form of connectivity. The exceptional vagility of most large carnivores makes such networks feasible in a region with low human population density, such as the Rocky Mountains, but mortality risks still need to be addressed. Roads are a major threat to carnivore recovery because of barrier effects, vehicle collisions, and increased accessibility of wild areas to poachers. Development, especially for tourism, is also becoming a threat in many parts ofthe region.

Viability analysis of well-selected focal species can complement ecosystemlevel conservation planning by revealing thresholds in habitat area and landscape connectivity. Mammalian carnivores are good candidates for focal species because their distributional patterns often strongly reflect regional-scale population processes. We incorporated focal species analysis of four carnivore species, fisher (Martes pennanti), lynx (Lynx canadensis), wolverine (Gulo gulo), and grizzly bear (Ursus arctos), into a regional conservation plan for the Rocky Mountains of the United States and Canada. We developed empirical habitat models for fisher, lynx, and wolverine based on a geographically extensive data set of trapping and sighting records. Predictor variables derived directly from satellite imagery were significantly correlated with carnivore distribution and allowed us to predict distribution in areas lacking detailed vegetation data. Although we lacked similar distributional data for grizzly bear, we predicted bear habitat by adapting and extrapolating previously published, regional-scale habitat models. Predicted habitat for grizzly bear has high overlap with that for wolverine, intermediate overlap with fisher, and low overlap with lynx. High-quality habitats for fisher and lynx, unlike those for wolverine and grizzly bear, are not strongly associated with low levels of human population and roads. Nevertheless, they are naturally fragmented by topography and vegetation gradients and are poorly represented in existing protected areas. Areas with high biological productivity and low human impact are valuable habitat for all four species but are limited in extent. Predicted habitat values for lynx and wolverine are significantly correlated with trapping data from an area outside the extent of the original data set. This supports the use of empirical distribution models as the initial stage in a regional-scale monitoring program. Our results suggest that a comprehensive conservation strategy for carnivores in the region must consider the needs of several species, rather than a single, presumed umbrella species. Coordinated planning across multiple ownerships is necessary to prevent further fragmentation of carnivore habitat, especially in the U.S.-Canada border region.

The origin and taxonomy of the red wolf (Canis rufus) have been the subject of considerable debate and it has been suggested that this taxon was recently formed as a result of hybridization between the coyote and gray wolf. Like the red wolf, the eastern Canadian wolf has been characterized as a small "deer-eating" wolf that hybridizes with coyotes (Canis latrans). While studying the population of eastern Canadian wolves in Algonquin Provincial Park we recognized similarities to the red wolf, based on DNA profiles at 8 microsatellite loci. We examined whether this relationship was due to similar levels of introgressed coyote genetic material by comparing the microsatellite alleles with those of other North American populations of wolves and coyotes. These analyses indicated that it was not coyote genetic material which led to the close genetic affinity between red wolves and eastern Canadian wolves. We then examined the control region of the mitochondrial DNA (mtDNA) and confirmed the presence of coyote sequences in both. However, we also found sequences in both that diverged by 150 000-300 000 years from sequences found in coyotes. None of the red wolves or eastern Canadian wolf samples from the 1960s contained gray wolf (Canis lupus) mtDNA sequences. The data are not consistent with the hypothesis that the eastern Canadian wolf is a subspecies of gray wolf as it is presently designated. We suggest that both the red wolf and the eastern Canadian wolf evolved in North America sharing a common lineage with the coyote until 150 000-300 000 years ago. We propose that it retain its original species designation, Canis lycaon. 2166 Résumé : Les origines et la taxonomie du Loup roux (Canis rufus) font l'objet d'une controverse importante et une hypothèse a été émise, à savoir qu'il s'agit d'un taxon récent issu de l'hybridation entre le Coyote et le Loup gris. Comme le Loup roux, le Loup de l'est du Canada est décrit comme un petit loup « mangeur de cerfs » qui s'hybride avec le Coyote (Canis latrans). L'étude de la population de Loups de l'est du Canada dans le parc provincial Algonquin nous a permis de reconnaître des similarités avec le Loup roux d'après les profils d'ADN à 8 locus microsatellites. Nous avons tenté de déterminer si cette relation était due à des degrés semblables d'introgression de matériel génétique en comparant les allèles microsatellites avec ceux d'autres populations nord-américaines de loups et de coyotes. Les analyses ont révélé que ce n'est pas du matériel génétique de coyote qui a mené à la grande affinité génétique entre le Loup roux et le Loup de l'est du Canada. Nous avons ensuite examiné la région de contrôle de l'ADN mitochondrial (ADNmt) et confirmé la présence de séquences du Coyote chez les deux loups. Cependant, nous avons également