sistemas

Material and methods
An expedition was undertaken aboard the M/V Carlos Porter for the period of February 17- March 12, 1997. Collections were made at San Ambrosio Island from February 20-23, at San Félix from February 24-28, at Robinson Crusoe Island from February 28 to March 9, and at Alexander Selkirk Island on March 5-6. All material collected was subdivided between participatinginstitutions: Field Museum of Natural History, Chicago (FMNH: http://emuweb.fieldmuseum.org/fish/Query.php), Universidad del Mar (UMAR: www.ern.udelmar.cl/investigacion/ictiologia/coleccionpeces.htm), Museo Nacional de Historia Natural, Santiago (MNHNC; Meléndez & Cornejo 2001) and Universidad Austral de Chile, Valdivia (IZUA-P, destroyed by fire in 2008). Some specimens were studied from the Anton Bruuncruises 12 and 13 deposited at Cornell University (CU), University of Harvard’s Museum of Comparative Zoology (MCZ), and Scripps Institute of Oceanography (SIO). Additional material was collected from Robinson Crusoe and Alejandro Selkirk Islands in 1999 and 2000, respectively, all specimens of which are deposited at MNHNC. Material examined by us is listed in Table 1.

The primary method forcollection of fishes was scuba diving at depths of 5 to 35 m and the release of small (1 kg) bags of powdered derris root. Some collections were taken also at intertidal pools. Other methods for collecting fishes included small mesh gill nets deployed on rocky reefs and monitored by scuba divers, small hand spears and hand nets, and collecting from the deck of the ship by hook and line, dip nettingand pulling a small 10 ft trawl down to depths of 100 m. In addition, color photographs were taken underwater (by Marcel Duhart, Marcelo Rossi and Álvaro Sepúlveda) and in aquaria (by authors). Muscle tissue samples from most of the fishes collected, enabling interested researchers to analyze evolutionary relationships using DNA.

Taxonomy follows Eschmeyer (2010), except recent changes that havemade it into the periodic updates of the online database1 and is presented in Table 2. Biogeographic accounts consider coastal fishes only as presented in Table 3.

Discussion
The Juan Fernández and Desventuradas Islands have a total of 52 species of coastal fishes, with 41 and 43 species in each, respectively. The number of endemic species for Juan Fernández is down from 13 (25.5%; Pequeño &Sáez 2000) to 5 (12.2%; Sicyases brevirostris, Odontesthes gracilis, Chironemus delfini, Parapercis dockinsi, and Paratrimma nigrimenta), however three species are presented as new records for these islands (Gymnothorax cf. obesus, Gnathophis sp. and Suezichthys sp). The Desventuradas Islands has only 2 endemic species (4.6%; Chromis meridiana and Paratrimma urospila) but 4 species are new records(Scorpaenodes englerti, Maxillicosta reticulata, Suezichthys sp., and Aseraggodes bahamondei).

The eastern extension of the Indo West Pacific Region to include the Nazca Ridge, Desventuradas and Juan Fernández Islands (Parin 1991, Pequeño & Lamilla 1996a, 2000, Pequeño & Sáez 2000) is supported in this paper. The zoogeographical affinities between Desventuradas and western Pacific islands(Easter Island to Australia), includes 16 species, adding 4 new species to previous lists (Gymnothorax cf. obesus, Gonorynchus greyi, Scorpaenodes englerti, Aseraggodes bahamondei). Three phylogenetic studies (Pseudolabrus, Nemadactylus, and Chironemus) indicate a Western Pacific origin with one or more dispersal events to the Desventuradas and Juan Fernández Islands, and only one (Odontesthes)indicates a continental origin with a westward dispersal. The pattern of historical relationships of the Desventuradas and Juan Fernández Islands with the Western Pacific is supported with another 7 genera with relatively few species and restricted to the southern Pacific region. Furthermore, the Juan Fernández and Desventuradas Islands share 22 coastal fish species that are endemic to those island...