Neotropical Entomology 35(5): 616-624 (2006) Diversidade de Artrópodos Galhadores e Plantas Hospedeiras em uma Floresta Subtropical em Porto Alegre, Sul do Brasil RESUMO -Muitas hipóteses têm sido propostas para explicar os padrões de diversidade de insetos galhadores, porém existem evidências contraditórias quanto aos principais processos ecológicos e evolutivos responsáveis por esses padrões. Adicionalmente, questões como sazonalidade dos artrópodos, suficiência amostral e aprendizado dos amostradores têm sido praticamente ignoradas. Este estudo registra artrópodos galhadores e avalia essas questões. Amostragens sazonais de artrópodos galhadores e suas plantas hospedeiras foram realizadas numa floresta subtropical úmida. Quatro transectos foram amostrados duas vezes por estação, por duas pessoas, procurando galhas na vegetação durante 1h30min. Após 96h.pessoa de amostragem, 130 morfotipos de galhas foram encontrados em 84 espécies de plantas hospedeiras. A análise do número de galhas e morfotipos encontrados por transecto demonstrou que a experiência dos amostradores influencia os resultados sobre riqueza de galhadores e os dados relativos a sazonalidade. Diferentes espécies apresentaram distintos padrões sazonais. A riqueza de artrópodos galhadores demonstrou estar ligada à riqueza de plantas. Os resultados sugerem que a experiência dos amostradores é um fator essencial, bem como os padrões de sazonalidade das diferentes espécies, pelo menos em áreas tropicais/subtropicais. Apesar de a suficiência amostral não ter sido atingida, a heterogeneidade da fauna em escalas espaciais pequenas mostrou-se considerável: mesmo com a proximidade entre os locais amostrados (trilhas não distavam mais que 500 m entre si), estes mostraram possuir faunas específicas. Este trabalho adiciona à literatura registros sugerindo que tanto a riqueza florística quanto a composição específica da vegetação têm forte influência sobre a riqueza de galhadores, pelo menos em escalas locais. PALAVRAS-CHAVE: Morfotipo, amostrador, heterogeneidade ambiental, sazonalidadeABSTRACT -Many hypotheses have been proposed to explain diversity patterns of galling insects. However, there are contradictory evidences on the evolutionary and ecological factors responsible for the trends. Furthermore, questions such as arthropod seasonality, sampling sufficiency and sampling team experience have been almost ignored. This study records galling arthropod diversity while paying attention to these questions. Seasonal sampling of galling arthropods and host plants were conducted in a humid subtropical forest of southern Brazil. Four transects were sampled twice per season, with two persons searching the vegetation for galls during 1h30min. After 96h.persons of sampling, 130 gall morphotypes on 84 species of host plants were recorded. An analysis of the numbers of galls and gall morphotypes found per transect along time showed that sampling team experience influences galler richness results and the interpretation of galler seasonality patterns. Different specie...
-Galling arthropods create plant structures inside which they fi nd shelter. Factors acting on galler diversity are still being discussed, with this fauna considered more diverse in xeric than mesic environments (higrothermic stress hypothesis, HSH), and also in more plant diverse sites. Here we compare galler abundance (N), equitability (E), species richness (S) and composition between adjacent restinga (xeric) and swamp forests (mesic) in Parque Estadual de Itapeva (29°21' S, 49°45' W), Rio Grande do Sul, southern Brazil. Five trails, two in swamp forest and three in restingas, were sampled four times each (January/December 2005). After an effort of 60h/person, 621 galled plant individuals belonging to 104 gall morphotypes were recorded. This suggests a high galler diversity for the Park, comparable to the richest places known. No differences were found for N, E or S between restingas and swamp forests. However, faunal composition differs signifi cantly between the vegetation types. The dominant (most abundant) species are different in either vegetation type, and are rare or absent on the other vegetation type. Such species composition analysis is still largely ignored for gallers, and stresses the fact that the HSH cannot explain this pattern, since the latter is based on preferences by the ovipositing galler for xeric sites instead of mesic ones. The two habitats differ in microclimate, but species richness, as would be predicted by the HSH, does not differ. This small scale pattern can perhaps be attributed to biogeographic processes on larger scales, as suggested by the resource synchronisation hypothesis.
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