BULLETIN OF MARINE SCIENCE, 67(1): 359–372, 2000 DIVERSITY AND DISTRIBUTION OF CHILEAN BENTHIC MARINE POLYCHAETES: STATE OF THE ART Nicolás Rozbaczylo and Javier A. Simonetti ABSTRACT Current knowledge of Chilean benthic marine polychaetes is reviewed. The history of the studies, researchers involved, the rate and localities of species descriptions are pre- sented, as they relate to the assessment of biogeographic units along the Chilean coast. Taxonomic richness along the Chilean coast is associated with differential sampling ef- forts weakening the assessment of biogeographic units. Juan Ignacio Molina (1740–1829), in his pioneer work on the biological diversity of Chile, Saggio sulla storia naturale del Chili published in 1782, described numerous in- vertebrate species. However, he did not refer to polychaetes. The first descriptions of polychaetes from continental Chile were published in 1849. Based on specimens col- lected by the French naturalist Claudio Gay, all 15 species were described by Blanchard (1849) as new to science (Rozbaczylo, 1985). During the following years, the knowledge of Chilean polychaetes increased due principally to the activity of foreign expeditions and researchers who visited various places of Chile. In the last 30 yrs, the taxonomic knowledge of polychaetes has been increasing largely due to the work of Chilean scien- tists who have done studies on local faunas or reviewed specific groups of polychaetes. With almost 450 species known, this figure is considered an underestimate due to the overall scarcity of research carried out on Chilean polychaetes (Rozbaczylo and Carrasco, 1995). In this work we analyze the knowledge of benthic polychaetes along the Chilean conti- nental coast and oceanic islands, in terms of the taxonomic richness, the main expeditions that have collected specimens in these areas, the researchers who have studied this mate- rial, and location of the main collections containing type specimens of Chilean species, as they relate to the assessment of faunal provinces. The recognition of biogeographic re- gions along the coast of Chile has been based on the distribution patterns of several inver- tebrate taxa including polychaetes. However, faunal studies along these geographical ar- eas have been unequally carried out, being concentrated mainly in the central and south- ern regions while the north has been comparatively less studied which might bias the distinction of biogeographical regions based on invertebrate distributions. TAXONOMIC RICHNESS AND ENDEMICITY OF MARINE BENTHIC POLYCHAETES IN CONTINENTAL CHILE AND OCEANIC ISLANDS CONTINENTAL CHILE.—The coast of mainland Chile is about 4200 km long, extending from Arica (18°20'S) to Cape Horn in subantarctic waters (56°S) (Fig. 1). Some authors, such as Olsson (1961) and Marincovich (1973), based on the distribution of different groups of invertebrates, distinguished two biotic provinces along the temperate coast of Pacific South America, named Peruvian and Magellanic, and considered the Chiloé Is- land (ca 42°S) the boundary between them. Others, e.g., Dahl (1960) and Viviani (1979), have limited the southern extent of the Peruvian Province to ca 30°S, recognizing a tran- 359 360 BULLETIN OF MARINE SCIENCE, VOL. 67, NO. 1, 2000 Figure 1. Map showing the main geographical regions considered for comparison of polychaete fauna along mainland Chile and the location of oceanic islands (drawn not to scale). ROZBACZYLO AND SIMONETTI: CHILEAN BENTHIC POLYCHAETES 361 Table 1. Taxonomic composition of marine benthic polychaetes in continental Chile compared with the World. Teaxononmic level C*hil World O5rders 1 . (560%) 2 F6amilies 4 . (753%) 8 G4enera 21 . (021%) 1.00 S9pecies 44 . (5%) >8.000 *Pettibone (1982) sition zone of cold temperate mixed waters between 30 and 42°S. Knox (1960) character- ized this zone as the Central Chilean Province, but others, Dahl (1960) and Dell (1971), have insisted on its transitional character. The different propositions about biogeographic provinces and provincial boundaries along Chile have been recently reviewed by Santelices (1991). World-wide, the taxonomic richness of polychaetes is estimated at more than 8000 species, grouped in 25 orders, 87 families and around 1000 genera (Fauchald, 1977, Pettibone, 1982). Along the coast of continental Chile, from Arica to Cape Horn, a total of 46 families belonging to 15 orders, with 214 genera and 449 species have been regis- tered so far (Table 1). This region presents high endemicity at the species level estimated to be around 43% (Table 2). Similarly, high values of endemicity are also depicted by other groups of marine invertebrates, for instance, 55.6% of the littoral mollusks (Dall, 1909), 53.3% of the anomuran decapods (Haig, 1965), and 23.3% of the brachyuran crabs (Garth, 1957). The number of benthic polychaete species differs markedly among the three main geo- graphic regions along continental Chile (Fig. 1): northern Chile from Arica (18°28'S) to south of Coquimbo (32°S), central Chile from north of Valparaíso (32°S) to south of Chiloé Island (44°S), and southern Chile from Golfo de Corcovado (44°S) to Cape Horn (56°S). The number of species as well as genera and families are fewer in the northern region and greatest in the central region while the southern region presents intermediate values (Table 3). This tendency parallels the number of authors and publications about polychaetes in each of the regions (Table 4), strongly suggesting that the number of spe- cies both recorded and described in each of these regions are more an artifactual result than a biological phenomenon. Unpublished records of polychaetes from northern Chile collected in Antofagasta (23°29'S) and Carrizal Bajo (28°04'S) in 1996 and 1997 by one of us (NR), have indicated that at least three families and 20 species are new for these localities. Therefore, the comparatively low number of species known for the northern region of Chile could be explained by the low number of samples taken. Table 2. Taxonomic richness and percentage of endemism of marine benthic polychaetes in continental Chile and oceanic islands*. Asrea Faamilie Gsener Smpecie Endemis ()n) ()n ()n (% C6ontinental Chile 44291 434 4 . E5aster Island 205064.** Jáuan Fern n8dez Archipelag o 1633452 . (é*) no data for San F ló.ix and San Ambrosio Islands and Sala y Gmez Island (**) calculated from species identified to specific level 362 BULLETIN OF MARINE SCIENCE, VOL. 67, NO. 1, 2000 Table 3. Taxonomic richness of marine benthic polychaetes occurring in northern, central and southern Chile and shared by the three regions. Rsegion Faamilie Gsener Specie ()n) ()n (n N°'orthern Chile (18 28 −3°2 S ) 259 7611 C°entral Chile (32 −4°4 S ) 454 197 32 S°outhern Chile (44 −5°6 S ) 335 121 16 S1hared taxa 15102 CHILEAN OCEANIC ISLANDS.—Chile’s main oceanic islands, defined as those located in an ocean at a long distance from a continent, or those which emerge from the ocean floor and are isolated from the continent by water depths exceeding 200 m (Castilla and Oliva, 1987), are: (1) Easter Island, (2) the islands of the Juan Fernández Archipelago, (3) San Félix and San Ambrosio islands (formerly “Desventuradas”), and (4) Sala y Gómez Island. They are of volcanic origin and emerged in the Plio-Pleistocene (Gonzalez-Ferrán, 1987). They are of special interest to biologists given their geographical isolation and the possibility that through the study of their fauna and that of the continental shelf could be possible to unravel their zoogeographical relations as well as probable paths of colonization. The only information available about benthic polychaetes of these islands comes from Easter Island and the Juan Fernández Archipelago. There are neither records for San Félix and San Ambrosio islands nor for Sala y Gómez. The scientific knowledge for San Félix and San Ambrosio islands ( 26°17'S) is limited and recently emerging (Bahamonde, 1987, Rozbaczylo and Castilla, 1987). The tiny island of Sala y Gómez, located at 26°27'S, 3400 km west of the Chilean coast and 415 km west of Easter Island, has been rarely visited by expeditions in spite of its proximity to Easter Island (Rehder, 1980; Castilla and Rozbaczylo, 1987). EASTER ISLAND.—Easter Island (27°09'S, 109°3'W), named Rapa Nui (Great Island) or Te Pito o Te Henua (Navel of the world) in the native language, is located 3700 km off the South American continent and 4050 km from Tahiti, in Polynesia. Pitcairn Island, located 2200 km to the west, is the nearest inhabited island. At least 60 species of benthic polychaetes belonging to 25 families have been recorded from Easter Island, but only 47 of these have been identified to species, whereas the remaining 13 taxa are known only to genus or family level (Table 2). These values do not include the pelagic polynoid Podarmus ploa Chamberlin, 1919 described from off Easter Island. The polychaete fauna of Easter Island conforms to the pattern of tropical Indo-west Pacific affinity as in several other groups of marine invertebrates (Castilla and Rozbaczylo, Table 4. Number of species of marine benthic polychaetes described for northern, central and southern Chile compared with the number of authors and publications in each geographical region. Region Sdpecies dfescribe Number o Number of authors publications Northern Chile (18°'28 −3°2 S ) 289 1 0 Central Chile (32°−4°4 S ) 1268 204 Southern Chile (44°−5°6 S ) 648 122 T0otals for Chile 247 346 ROZBACZYLO AND SIMONETTI: CHILEAN BENTHIC POLYCHAETES 363 1987). Considering percentage of identified polychaetes, approximately 4% are endemic. However, according to Rehder (1980), the relatively high values of endemicity shown by other groups of marine animals of Easter Island justify Schilder’s (1965) placement of Easter Island and Sala y Gómez island in the Rapanui Province, rather than the Polynesian Province where they were previously located (Schilder, 1938–1939 fide Rehder, 1980).