For birds in urban environments, the configuration of local habitat within the landscape may be as critical as the composition of the local habitat itself. We examined the relative importance of environmental attributes (e.g., tree cover, composition, and number of tree species) measured at different spatial scales in relation to urban bird species richness and abundance. We expected that some bird species and nesting guilds would have a closer association with landscape-level features (within 1000 m), such as proximity to large forested areas, than with local-scale habitat measures (within 50 m). To investigate this, avian community data were collected at 285 point-count stations in 1997 and 1998 along four roadside transects located in Vancouver and Burnaby, British Columbia, Canada. Transects (5-25 km in length) bisected three large parks (>324 ha) and proceeded along residential streets in urban and suburban areas. In total, 48 bird species were observed, including 25 common species. Species richness declined in relation to a gradient of increasing urbanization, as measured by local- and landscape-level habitat features. We further examined the significance and importance of local- vs. landscape- level habitat attributes using logistic regression and found that both scales explained the presence/absence distributions of residential birds. Local-scale habitat features such as large coniferous trees, berry-producing shrubs, and freshwater streams were of particular importance in estimating the likelihood of finding bird species. Landscape measures, particularly forest cover (within 500 m) and park area (measured at different scales as a function of distance from point-count stations) significantly improved likelihood estimations based solely on local-scale habitat features. Our results suggest that both local- and landscape-scale resources were important in determining the distribution of birds in urban areas. Parks, reserves, and the surrounding residential areas should be integrated into urban planning and development designs to maintain resident avifauna and overall species diversity in urban environments.

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Urban Bird Diversity and Landscape Complexity: Species- environment Associations Along a Multiscale Habitat Gradient

Muller (1942) and Mayr (1963) hypothesized that natural selection indirectly causes the evolution of reproductive barriers between allopatric populations by causing adaptive genetic divergence that pleiotropically pro- motes prezygotic or postzygotic incompatibility. Under this mechanism, herbivorous insect populations should be more prone to speciate if they are adapting to different host plants, because the evolution of reproductive isolation will be accelerated above the rate promoted by genetic drift and host-independent sources of selection alone. Although the Muller-Mayr hypothesis is widely accepted, little direct evidence has been collected in support of selection's role in allopatric speciation. This paper offers a method for isolating and evaluating the contribution of host plant-related natural selection pressures to the reproductive isolation between allopatric herbivore populations. The host-related selection hypothesis (HRSH) predicts that herbivore populations using different host plants should be more reproductively isolated than those using the same host, other things being equal. Here, I test this hypothesis using Neochlamisus bebbianae, an oligophagous leaf beetle with a geographically variable host range. In each of two sets of experiments (contrast I, contrast II), I compared two beetle populations (Georgia and New York) that use the same host (Acer) in nature and a third population that natively uses a different host (Betula in Oklahoma (CI), Salix in Ontario (CII)). Experiments showed that "different-host" populations were more strongly differentiated in host- use traits (oviposition, host fidelity, feeding response, larval performance) than were "same-host" populations and that each population most readily uses foliage from its native host. As predicted by the HRSH, sexual isolation was also greater between the adaptively divergent different-host populations (from Betula vs. Acer, from Salix vs. Acer) than between the same-host populations (from Acer), which were undifferentiated in host-use traits. Interpreting these results in a historical context provided by mtDNA sequences from test populations indicated: (1) that Acer- and Betula-associated N. bebbianae represent separate sibling species whose causal origins have been lost to history, and whose incomplete sexual isolation is fortified by host-associated ecological and "physiological" isolation; and (2) that incipiently speciating Acer- and Salix-associated populations are more closely related to each other than are the two Acer-associated populations, which is consistent with the HRSH. This study thus illustrates the consequences of host-related selection for both the origin and maintenance of reproductive isolation. More important, it provides evidence that the pleiotropic effects of natural selection promote allopatric speciation.

Isolating a role for natural selection in speciation: host adaptation and sexual isolation in neochlamisus bebbianae leaf beetles

Geographic locality and host identity shape fungal endophyte communities in cupressaceous trees.

Many accounts of categorization equate goodness-of-example with central tendency for common taxonomic categories; the best examples of a category are average members#x2014;those that are most similar to most other category members. In the present study, we asked 24 tree experts and 20 novices to rate goodness-of-example for a sample of 48 trees and found (1) that the internal structure of the categorytree differed between novices and experts and (2) that central tendency did not determine goodnessof-example ratings for either group. For novices, familiarity determined goodness-of-example ratings. For experts, the “ideal” dimensions of height and weediness, rather than average similarity to other trees, were the primary predictors of goodness-of-example ratings for experts. The best examples oftree were not species of average height, but of extreme height. The worst examples were the weediest trees. We also found systematic differences in predictors of goodness-of-example as a function of type of expertise. We argue that the internal structure of taxonomic categories can be shaped by goal-related experience and is not necessarily a reflection of the attributional structure of the environment. Implications for models of category structure and category learning are discussed.

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Tall is typical: central tendency, ideal dimensions, and graded category structure among tree experts and novices.

The gall-forming psylloid fauna associated with the temperate Neotropical plant genus Schinus (Anacardiaceae) is revised, and keys are provided for adults, larvae and galls. Fourteen species are recognized in the genus Calophya (Calophyidae), 10 of which are described as new; C. gallifex and C. schini are reinstated from former synonymy with C. rubra. An additional closely related new species, C. clavuligera sp. n., is described from Lithrea spp. In the genus Tainarys (Psyllidae, Rhinocolinae), six species are recognized and, for five of these, Schinus species are confirmed hosts. Two of them are described as new and one is recombined from Leurolophus. A new Leurolophus species is described from Lithrea molleoides. Based on a cladistic analysis Pelmatobrachia, Microceropsylla and Neocalophya are synonymized with Calophya, producing five new and one revised species combinations as well as one nomen nov. A list of the 59 currently recognized species is provided with information on synonymy, distribution and...

Angelo Lomeo

Papers

National Audubon Society field guide to North American trees

The Audubon Society field guide to North American trees