Revista Chilena de Historia Natural 78 (4): 635-650, 2005
RESEARCH ARTICLE
Abundance and composition of epigean arthropods from Llanos de Challe
National Park: impacts of ENSO-1997 and effects of the pedological habitat
By using pitfall traps, the effects of rainfall and habitat type on the denso-
activity of epigean arthropods - Tenebrionidae in particular- inhabiting at Llanos de Challe National Park were investigated. This park is
located in the Chile’s transitional coastal desert, Atacama’s III Region. Sampling was conducted during three days per month
(september, october and december) in the period of maximal biological activity of the system, and in 1989 (dry no-ENSO year), 1997
(intense ENSO-year), and 2000 (damp no-ENSO year). Two pedological contrasting sites were used to compare the effects of the
factors being examined: a coastal dune habitat and an interior stony habitat. The presence of 15 orders of Arthropoda was recorded.
Hexapods made the > 95 % of total specimens captured (9,065 individuals), with Collembola (36.1 %) and Coleoptera (29.8 %)
being the orders with the highest numerical representativeness. The numbers of orders with active members varied slightly among
years: 13 orders were recorded in 1989 (44 % rainfall below the average), 15 in 1997 (443 % rainfall above the average), and 11 in
2000 (52 % above average). The effect of the ENSO event was clearly reflected in the numerical contribution both for the years studied
and for most of the recorded taxa. Although more subtlety, this effect was also reflected in the assemblage composition of dominant
taxa and between pedological habitats, particularly in regard to Tenebrionidae and Formicidae. Specially in the coastal dunes,
Tenebrionidae clearly dominated the assemblage of epigean arthropods, being Gyriosomus Guérin-Méneville the most
abundant and diverse genus. The dominance of Gyriosomus sets a number of questions regarding the levels of
endemism, species diversity and distribution, and their functional role in the ecosystem studied.
Key words:
arid zones,
coastal deserts, epigean arthropods, Tenebrionidae, ENSO
