Resumo

GIRALDO, Alfredo; PEREZ, Dante  e  ARELLANO, Germán. Response of a epigeic spider assemblage (Araneae) in the nature reserve "Lomas of Lachay" (Lima, Perú) in the face of the 1997-1998 El Niño. Ecol. apl. [online]. 2004, vol.3, n.1-2, pp.45-58. ISSN 1726-2216.

The present study describes the response of epigeic spider assemblages facing environmental changes caused by the 1997-1998 El Niño event in "lomas" formations of the Peruvian central coast. Spiders were sampled during 1998 and 1999 (four times per year), using pitfall traps that were distributed in a mixed area of herbaceous lomas and park type lomas in the Lachay National Reserve. The response of the assemblage was evaluated analyzing temporary variation patterns corresponding to the following: composition and abundance of families, relative abundance of the guilds, community variables (abundance, individual biovolume, richness and diversity) and abundance of the ten most common families. The most abundant family was Linyphiidae, including 68% of the registered abundance during the two years and reaching a dominant position in six evaluations ( 80% of the abundance per evaluation). During most part of the study, web builders were more abundant than the wanderers as is indicated by the values of the web builders:wanderers ratio of abundance. The guild of the web builders was represented mostly by the ground weavers (i.e. Linyphiidae) during both years. Particular guilds of wanderer spiders, showed different variation trends: foliage runners and ambushers were more abundant during 1998, whilst ground runners and stalkers were so during 1999. Community variables were notoriously influenced by the Linyphiidae dominance during 1998. As a consequence, abundance was increased from February to August, diversity decreased in the same period and also, richness and individual biovolume decreased in August. Among the ten most common families there were different kinds of responses: four were favorable, three were unfavorable, one was uncertain and two were of relative indifference.

Palavras-chave : epigeic spider assemblage; El Niño 1997-98; temporary variation patterns; lomas vegetal formations; Lachay National Reserve.

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