The generality of ecological patterns depends inextricably on the scale at which they are examined. We investigated patterns of crab distribution and the relationship between crabs and vegetation in salt marshes at multiple scales. By using consistent monitoring protocols across 15 U.S. National Estuarine Research Reserves, we were able to synthesize patterns from the scale of quadrats to the entire marsh landscape to regional and national scales. Some generalities emerged across marshes from our overall models, and these are useful for informing broad coastal management policy. We found that crab burrow distribution within a marsh could be predicted by marsh elevation, distance to creek and soil compressibility. While these physical factors also affected marsh vegetation cover, we did not find a strong or consistent overall effect of crabs at a broad scale in our multivariate model, though regressions conducted separately for each site revealed that crab burrows were negatively correlated with vegetation cover at 4 out of 15 sites. This contrasts with recent smaller-scale studies and meta-analyses synthesizing such studies that detected strong negative effects of crabs on marshes, likely because we sampled across the entire marsh landscape, while targeted studies are typically limited to low-lying areas near creeks, where crab burrow densities are highest. Our results suggest that sea-level rise generally poses a bigger threat to marshes than crabs, but there will likely be interactions between these physical and biological factors. Beyond these generalities across marshes, we detected some regional differences in crab community composition, richness, and abundance. However, we found striking differences among sites within regions, and within sites, in terms of crab abundance and relationships to marsh integrity. Although generalities are broadly useful, our findings indicate that local managers cannot rely on data from other nearby systems, but rather need local information for developing salt marsh management strategies.

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RESUMOCorythucha ciliata (Hemiptera: Tingidae) é um inseto nativo da América do Norte que foi introduzido na Europa, pela Itália, em 1964. Desde então tem se expandido por toda a Europa, desconhecendo-se a data de chegada e a sua área de distribuição em Portugal. Esta importante praga invasora alimenta-se na face inferior das folhas de plátano, uma das mais importantes árvores ornamentais nos espaços verdes urbanos em Portugal, causando senescência prematura e eventualmente morte, em casos de infestações severas consecutivas. A modelação de nicho está se tornando uma ferramenta cada vez mais importante na gestão de invasões biológicas, tanto antes como depois da introdução do organismo invasor. Neste estudo, o software MaxEnt (máxima entropia) foi usado na modelação da distribuição invasiva potencial de Corythucha ciliata em Portugal, a partir de um conjunto de variáveis ambientais e de dados de presença do inseto, obtidos a partir da observação de folhas de plátanos amostrados por todo o país. De acordo com o melhor modelo gerado pelo MaxEnt, as áreas de maior adequabilidade potencial à invasão de Corythucha ciliata encontram-se no norte de Portugal apresentando o sul e as regiões de maior altitude do norte e centro adequabilidade reduzida ou nula. Observações laboratoriais da biologia de Corythucha ciliata aliadas aos registos de ausência em várias localidades do sul de Portugal e ocorrência predominante na metade norte de Espanha suportam o modelo desenvolvido. Porém, a validação do modelo requer futuras prospecções nas áreas de reduzida adequabilidade e onde a praga se encontrava virtualmente ausente no momento em que foi realizada a amostragem. Os modelos de adequabilidade podem ser usados como ferramenta auxiliar na tomada de decisão no que concerne à gestão dos espaços verdes. Palavras-chave: MaxEnt; gestão de espaços verdes; espécie invasora; Platanus spp. ABSTRACTCorythucha ciliata (Hemiptera: Tingidae) is an insect native to North America which has been introduced into Europe, through Italy, in 1964. Since then it has expanded across Europe being its date of arrival and distributional range in Portugal unknown. This important invasive pest feeds on the underside of the leaves of sycamore trees, one of the most widespread ornamental tree in urban areas of Portugal, causing their premature senescence and eventually death, in case of consecutive severe infestations. Habitat modeling is becoming an increasingly important tool for managing biological invasions, either prior or

Droserone (2) as such has been known for a long time (4), it has even been isolated already from another Andstrocladus species (5). The occurrence of droserone in A. robe rtsoniorum, moreover in a crystalline form, however, is completely unprecedented. As the crystals are found only in those parts that have been damaged either by insects or mechanically and regarding the pesticidal activity of related naphthoquinones (6), it can be assumed that droserone is produced as a "chemical weapon".

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The National Estuarine Research Reserve System provides an ideal platform for evaluating the relative importance of different threats to US salt marshes, because vegetation is sampled across all marsh elevations and across many regions. Our recent investigation at 15 reserves revealed that at a local scale, near tidal creeks in 4/15 of the reserves, crabs appear to have a strong negative effect on plants. However, at a broader scale, elevation has a stronger effect on marshes, suggesting that sea level rise poses a greater threat than crab herbivory or burrowing, although the two threats interact: Crab effects are likely to increase as waters rise.

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