Abstract
The "Ernesto Tornquist" Provincial Park (ETPP) is located inside the Ventania system (Argentina) and was created to protect one of the last relicts of pampean grasslands. Even though many studies have looked at the vertebrate faunal diversity, biology, and conservation in this Park, few studies have been dedicated to arthropods. Among these, spiders have been used as ecological indicators to evaluate nature conservation status, nevertheless, basic information on their distribution and ecology is necessary for their use as indicator taxa in this region. Thus the goal of this study was to present the phenology and demography of the spider Odo bruchi, a cursorial spider present in the ETPP. For this, spiders were sampled bimonthly using pitfall traps between September 2009-2010 (first year), and March 2011-2012 (second year). A total of 10 traps were placed every 10m along a transect of 100m parallel to the longest axis ofa grassland slope with native vegetation. Traps were filled with 1 500mL of ethylene glycol, that were examined and refilled every 60 day period. We collected a total of 799 specimens in two years. Juveniles were the most abundant reaching 47.8% of the total, while males corresponded to 27.8% and females 24.4%. We found significant differences in the mean abundance of O. bruchi: the abundance during spring-summer (Nov-Dec-Jan-Feb) was significantly higher than the other periods of the two years period. Moreover, we found an even abundance distribution throughout the year in the entire study. This work represents one of the first contributions to the ecology of this spider family in the area. Also, our results comprise relevant information to encourage future studies on this spider species as a bio-indicator of the conservation status of pampean grasslands.
Highlights
Natural grasslands are among the most disturbed ecosystems by human activities (Hannah, Carr & Lankerani, 1995), and have received little conservation consideration respect to other ecosystems such as the temperate and tropical forests (Zalba & Villamil, 2002)
Study area: The study area is located in the “Ernesto Tornquist” Provincial Park, inside the Ventania system in the South-west area of Buenos Aires Province, Argentina (38°00’38°07’ S and 61°52’-62°03’ W)
Phenology and demography structure: We found significant differences in the mean abundance of O. bruchi between the different dates (H=14.95, p=0.0104)
Summary
Natural grasslands are among the most disturbed ecosystems by human activities (Hannah, Carr & Lankerani, 1995), and have received little conservation consideration respect to other ecosystems such as the temperate and tropical forests (Zalba & Villamil, 2002). The genus Xenoctenus has four species and all are endemic to Argentina whereas, from the 27 species in the genus Odo only three, O. bruchi Mello-Leitão 1938, O. roseus Mello-Leitão 1941 and O. sericeus MelloLeitão 1944 are present in the country. These species are endemic to Argentina and were described over 60 years ago, and to date, there is no information about their natural history or ecological aspects in Argentina. The main goal of this paper is to present, for the first time, some ecological aspects (phenology and demography) of the spider Odo bruchi Mello-Leitão 1938 (Zoridae) in the “Ernesto Tornquist” Provincial Park (ETPP)
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