JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. We used mark-recapture methods to estimate the number of Parnassius smintheus (Papilionidae) butterflies moving among 20 alpine meadows separated by varying amounts of forest along the east slope of the Rocky Mountains in Alberta, Canada. We combined generalized additive models and generalized linear models to estimate the effects of intervening habitat type and of population size on butterfly movement. By incorporating habitat-specific distances between patches, we were better able to estimate movement compared to a strictly isolation-by-distance model. Our analysis estimated that butterflies move readily through open meadow but that forests are twice as resistant to butterfly movement. Butterflies also tended to stay at sites with high numbers of butterflies, but readily emigrate from sites with small populations. We showed that P. smintheus are highly restricted in their movement at even a fine spatial scale, a pattern reflected in concurrent studies of population genetic structure. As an example of the utility of our approach, we used these statistical models, in combination with aerial photographs of the same area taken in 1952, to estimate the degree to which landscape change over a 43-year interval has reduced movement of butterflies among subpopulations. At these sites, alpine meadow habitat has declined in area by 78%, whereas the estimated effect of fragmentation has been to reduce butterfly movement by 41%.

In 1999, the leaf roller Caloptilia fraxinella (Ely) (Lepidoptera: Gracillariidae) was noticed for the first time in the city of Edmonton, Alberta, Canada, on ornamental green ash (Fraxinus pennsylvanica Marsh. var. subintegerrima (Vahl) Fern.) and black ash (F. nigra Marsh.) (Oleaceae). It has since been found there on Manchurian ash (F. mandshurica Rupr.) and white ash (F. americana L.). Specimens were collected and reared, and vouchers have been deposited in the Canadian Forest Service Arthropod Collection in Edmonton and the Canadian National Collection of Insects (CNC) in Ottawa, Ontario.

Herbivores usually consume a mere fraction of available plant biomass. Spatial patterns in feeding damage may be attributable to induced defences by the host plant; a damaged plant reacts by lowering its nutritional value, thereby forcing herbivores to move on before food gets worse. In this study, we test this general hypothesis on a specific model system: caterpillars of the alpine butterfly Parnassius smintheus feeding on lance-leaved stonecrop Sedum lanceolatum. We first describe spatial patterns in host distribution and feeding damage within alpine meadows. We then use laboratory experiments to test a key assumption behind the proposed mechanisms: that the host plant exhibits an induced response with a negative impact on larval performance, and that this response is activated with a delay. Finally, we relate the patterns observed to the actual behaviour of Parnassius larvae. Overall, we found the level of feeding damage to be low (on damaged plants, only 5% of all leaves were fed upon). Within meadows, both host plants and feeding damage were clumped at a small spatial scale. This pattern seemed directly explicable by the timing of the host's induced defence. Laboratory experiments revealed a delay of 1Á2 d before the defence reached a level affecting larval performance, and wild larvae switch plants more quickly than this. A simulation model demonstrated that the spatial distribution of host plant damage can be generated by a simple random walk, based on the empirically observed step frequency, length and turning angles. Hence, as the most parsimonious explanation for the observed level and pattern of host plant damage, we offer a scenario where induced changes in host-plant quality limits the time spent per plant, but the herbivore moves throughout the landscape without any particular directionality.

Abstract. 1. Many butterfly populations persist in networks of naturally fragmented habitat patches. Movement and reproductive decisions made by adult females are critical to the persistence of these populations because colonisation of extinct habitat patches in the network requires emigration of fecund adult females from their natal meadow and their subsequent establishment in the extinct patch.2. Movement and oviposition behaviours of mated Parnassius smintheus females released in suitable meadows (a good-and a poor-quality meadow) and an unsuitable meadow were compared, to determine whether adult females consider meadow suitability for their offspring despite frequent oviposition events off the larval host plant.3. Bootstrap and correlated random walk analyses of female step lengths and turn angles demonstrated that females flew more randomly in the unsuitable meadow than in the suitable meadows. Although females tended to turn the sharpest angle between landing sites in the good-quality meadow, and fly the smallest distance between landing sites and displace the smallest distance from the release site in the suitable meadows, no significant differences were detected in turn angle, step length, and dispersal rates between suitable and unsuitable meadows.4. Results from female flight observations and a caged oviposition study suggest that females lay significantly more eggs in suitable habitat than in unsuitable habitat despite not ovipositing on the host plant, and support the above findings.5. Movement and oviposition behaviours of adult female P. smintheus promote their retention within meadows that can support their offspring.

Herbivores usually consume a mere fraction of available plant biomass. Spatial patterns in feeding damage may be attributable to induced defences by the host plant; a damaged plant reacts by lowering its nutritional value, thereby forcing herbivores to move on before food gets worse. In this study, we test this general hypothesis on a specific model system: caterpillars of the alpine butterfly Parnassius smintheus feeding on lance-leaved stonecrop Sedum lanceolatum. We first describe spatial patterns in host distribution and feeding damage within alpine meadows. We then use laboratory experiments to test a key assumption behind the proposed mechanisms: that the host plant exhibits an induced response with a negative impact on larval performance, and that this response is activated with a delay. Finally, we relate the patterns observed to the actual behaviour of Parnassius larvae.Overall, we found the level of feeding damage to be low (on damaged plants, only 5% of all leaves were fed upon). Within meadows, both host plants and feeding damage were clumped at a small spatial scale. This pattern seemed directly explicable by the timing of the host's induced defence. Laboratory experiments revealed a delay of 1Á2 d before the defence reached a level affecting larval performance, and wild larvae switch plants more quickly than this. A simulation model demonstrated that the spatial distribution of host plant damage can be generated by a simple random walk, based on the empirically observed step frequency, length and turning angles. Hence, as the most parsimonious explanation for the observed level and pattern of host plant damage, we offer a scenario where induced changes in host-plant quality limits the time spent per plant, but the herbivore moves throughout the landscape without any particular directionality.