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Since the publication of the theory of island biogeography, ecologists have postulated that fragmentation of continuous habitat presents a prominent threat to species diversity. However, negative fragmentation effects may be artifacts; the result of species diversity declining with habitat loss, and habitat loss correlating positively with degree of fragmentation. In this study, we used butterfly assemblages on islands of Lake of the Woods, Ontario, Canada to decouple habitat fragmentation from habitat loss and test two competing hypotheses: (1) the island effect hypothesis, which predicts that decreasing fragment size and increasing fragment isolation reduces species diversity beyond the effects of habitat loss, and (2) the habitat amount hypothesis, which negates fragmentation effects and predicts that only total habitat area determines the diversity of species persisting on fragmented landscapes. Using eight independent size classes of islands (ranging from 0.1 to 8.0 ha) that varied in number of islands while holding total area constant, species diversity comparisons, species accumulation curves, and species-area relationship extrapolations demonstrated that smaller insular habitats contained at least as many butterfly species as continuous habitat. However, when highly mobile species occurring on islands without their larval food plants were excluded from analyses, island effects on potentially reproducing species became apparent. Similarily, generalized linear models suggested that effects of island isolation and vascular plant richness on insular butterfly richness were confounded by species of high mobility. We conclude that inter-fragment movements of highly mobile species may obscure important fragmentation effects on potentially reproducing populations, questioning support for the habitat amount hypothesis.

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Mayr, 1963; Nosil, 2012). When genetic divergence has a strong spatial component, causes are generally attributed to spatial variation in evolutionary processes, such as gene flow, genetic drift,

The structure of carabid and other adephagan mandibles can provide information about the mechanics of feeding in these beetles and about the major features of carabid and adephagan evolution. Homologies among mandibular features are proposed, based on a transformation series for adult mandibles from plesiotypic cupedid-like structure to derived conditions characteristic of herbivorous carabids in the subtribe Harpalina. Terms for mandibular parts are revised so that all ridges and teeth are referred to as such. The following terms are introduced: superior and inferior terebral ridges, superior and inferior retinacular ridges, supraterebral ridges, anterior and posterior occlusal grooves, and basal face. Masticatory function is elucidated for the mandibles of adult Euryderus grossus (Say) in which the mandibles shear food matter in both a horizontal and a vertical plane, as well as compacting food into a bolus that is forced posteriorly into the buccal cavity. Many of the features of E. grossus mandibles are characteristic of other herbivorous carabids, but not all such taxa show such derived mandibular structure.