Metapopulation structure depends on spatial scale in the host-specific moth Wheeleria spilodactylus (Lepidoptera: Pterophoridae).

Menéndez, Rosa and Thomas, Chris D. (2000) Metapopulation structure depends on spatial scale in the host-specific moth Wheeleria spilodactylus (Lepidoptera: Pterophoridae). Journal of Animal Ecology, 69 (6). pp. 935-951. ISSN 0021-8790

Abstract

Summary 1. The distribution and dynamics of a host-specific moth Wheeleria spilodactylus were studied between 1998 and 1999 at a hierarchy of spatial scales: geographic (c. 8000 km2), regional (c. 35 km2), subregional (mean c. 12 km2) and local (c. 0·03 km2). We tested the hypothesis that resource quantity and isolation would assume different levels of importance at different scales of analysis, with respect to habitat occupancy and population turnover. 2. Experimental releases in occupied and empty habitats showed that W. spilodactylus dispersal was very rare over distances in excess of 100 m, and that relatively large plants were more likely to be colonized. 3. The host-plant distribution was very fragmented and the moth did not occupy the entire distribution of its host-plant at any of the spatial scales studied. At most spatial scales, occupancy decreased with isolation and increased with habitat quantity. 4. Colonization was most likely to occur in non-isolated habitat patches at the regional scale, in patches with large numbers of plants at the subregional scale, and in patches with large plants at the local scale. Relatively isolated populations were more likely to go extinct at the subregional scale of analysis. 5. At a geographic scale, the distribution apparently depends on metapopulation persistence, which itself depends principally on the amount of habitat in each region. At regional and subregional scales, distributions and dynamics reflect colonization–extinction dynamics within metapopulations; these are affected by the interaction of habitat quantity (number and size of host-plants) and isolation. At the local scale, distributions and dynamics are affected by relatively frequent movements of individuals between resource patches (influenced by behavioural choices). 6. Long-term metapopulation dynamics of the moth also reflect population dynamics of its disturbance-dependent host-plant Marrubium vulgare. The metapopulation dynamics of the moth are superimposed on the dynamics of its host.