Abstract Background: For the genus Thylamys , the rivers have been reported as barriers to dispersal, limiting current and historical distribution of its lineages. We hypothesized that the Maipo river has affected the genetic structure of northern and southern lineages of Thylamys elegans , recovering a phylogenetic relationships with reciprocally monophyletic sister groups on opposite river banks. We evaluated the role of other rivers in the Mediterranean zone of Chile as historical and recent modulators of the biogeographic processes of this species. Methods: We applied a phylogeographic approach, using the cytochrome- b mitochondrial gene for 93 individuals of T. elegans , from 37 localities in a latitudinal gradient between 21°25’ and 35˚56’S, encompassing a geographic area between the Atacama Desert and most of the Mediterranean Chilean zone. Results: The phylogenetics results recovered six lineages within T. elegans: Thylamys elegans elegans , Thylamys elegans coquimbensis , the Loa lineage and three other lineages not described previously (Aconcagua, South 1 and South 2). We suggest that following rivers play a role like primary barrier: the Maipo river in the genetic differentiation of northern and southern ancestral lineages, and the Mataquito river and its tributary Teno river for the South 1 and South 2 lineages. On the other hand, the Quilimarí river preserve the genetic divergence in T. e. coquimbensis and Aconcagua lineage and the Aconcagua river in Aconcagua lineage and T. e. elegans acting like secondary barriers. Conclusions: We concluded that the genetic diversity and biogeographic history of T. elegans was shaped by mountain glaciers, changes in river water levels during the Pleistocene glaciations and hyperaridity, promoting the differentiation and persistance of the T. elegans lineages.

Abstract Background: Analysis of morphological variation in archipelagos has been essential to understand the evolution of terrestrial vertebrates. In particular, these natural scenarios allow to assess morphological changes experienced by insular fauna compared to their mainland counterparts. In mammals, morphological changes of insular forms have been observed in size and shape of body and cranial traits. The southern Patagonia of Chile represents a unique scenario to analyze morphological variation in two of the most widely distributed small rodents along western southern South America: Abrothrix olivacea and Oligoryzomys longicaudatus. Methods: We applied linear and three-dimensional geometric morphometric tools to analyze the variation in cranial morphology of A. olivacea ( N = 80) and O. longicaudatus ( N = 49). Sampled localities were distributed in the mainland and islands of the Fuegian archipelago in Chilean Patagonia. Standard multivariate methods, as Principal Components Analysis, and Logistic Regression models were carried out to evaluate differences in size and shape of crania. Results: We detected higher levels of morphological variation in the crania of A. olivacea if compared to O. longicaudatus. The variation was associated to cranial size instead of shape. We observed significant differences between insular and mainland individuals in A. olivacea, being the cranium size of this species significantly bigger on islands. Indeed, specimens of A. olivacea from “Isla Wellington”, exhibited the higher increment in cranium size compared to any other mainland and insular site sampled for this species. In contrast, insular and mainland forms of O. longicaudatus did not show significant differences in cranial morphology. Conclusions: We suggest that the patterns of morphological variation observed in these two small rodents along Patagonia, could be explained in terms of the historical biogeography of the region, and the different ecological features of the studied species.

ABSTRACT Phylogenetic study of the genera of South American Austral Trichopterygini (Lepidoptera: Geometridae, Larentiinae): a new classification. In this work, we evaluate the taxonomy of the Trichopterygini in Chile based on a phylogenetic analysis of the morphological attributes. In our analysis, we used Tatosoma and Sauris as outgroups. Two approaches were used to evaluate phylogenetic relationships: 1) parsimony criterion, and 2) Bayesian inference. Parsimony analysis was conducted in PAUP software, and Bayesian analysis with Markov chain Monte Carlo using the BayesPhylogenies software. Our results based on the phylogenetic hypothesis suggest a new taxonomic order for Trichopterygini of the Andean Region of Southern South America. The valid genera are: Arrayanaria Parra, Butleriana Parra, Danielaparra Kemal & Kocak, Fueguina Parra, Hoplosauris Butler, Lagynopteryx Berg, Llampidken Parra & Santos-Salas, Pachrophylla Blanchard, Parapachrophylla Parra, Rindgenaria Parra, Tomopteryx Philippi, Triptila Warren, Triptiloides Parra & Santos-Salas, Warrenaria Parra. The main changes with respect to the previous taxonomic order are: 1) the genus Lagynopteryx Berg is subordinated under the Trichopterygini; 2) Toxopaltes Warren is a junior synonym of Lagynopteryx; 3) Hoplosauris moesta is transferred to the genus Llampidken; 4) Llampidken valdiviana is a junior synonym of L. moesta; 5) Oparabia arenosa is newly combined with the genus Arrayanaria; 6) Danielaparra viridis is a junior synonym of D. fragmentata; 7) Lobophora imbricaria is newly combined with the genus Danielaparra; 8) Triptiloides fasciata is a junior synonym of T. randallae; and 9) Parapachrophylla michelleae Parra n. sp. is described. Andean Region species are more closely related to the genus Tatosoma from New Zealand, the synapomorphies that demonstrate this are: swollen metaepimeron and hypertrophy of the second abdominal segment. A checklist of the genera and species of the tribe in the region, and the figures of adults and genitalia of some species are included.

RESUMEN En este trabajo se evalúa la taxonomía de los Trichopterygini de Chile a partir de un análisis filogenético de los atributos morfológicos. En nuestro análisis, hemos utilizado Tatosoma y Sauris como grupos externos. Se utilizaron dos enfoques para evaluar las relaciones filogenéticas: 1) criterio de parsimonia, y 2) inferencia bayesiana. El análisis de parsimonia se realizó a través del programa PAUP y el análisis bayesiano con cadenas de Markov y Monte Carlo a través del programa BayesPhylogenies. Nuestros resultados basados en la hipótesis filogenética sugieren un nuevo orden taxonómico para Trichopterygini de la Región Andina del Sur de Sudamérica. Los géneros válidos son: Arrayanaria Parra, Butleriana Parra, Danielaparra Kemal & Kocak, Fueguina Parra, Hoplosauris Butler, Lagynopteryx Berg, Llampidken Parra & Santos-Salas, Pachrophylla Blanchard, Parapachrophylla Parra, Rindgenaria Parra & Santos-Salas, Tomopteryx Philippi, Triptila Warren y Warrenaria Parra. Los principales cambios con respecto al orden taxonómico anterior son: 1) el género Lagynopteryx Berg se incorpora a Trichopterygini; 2) Toxopaltes Warren es el sinónimo junior de Lagynopteryx; 3) Hoplosauris moesta se incorpora al género Llampidken; 4) Llampidken valdiviana es el sinónimo junior de L. Moesta; 5) Oparabia arenosa es incorporada al género Arrayanaria; 6) Danielaparra viridis es el sinónimo junior de D. fragmentata; 7) Lobophora imbricaria es incorporada al género Danielaparra; Triptiloides fasciata es el sinónimo junior de T. randallae; y 9) Parapachrophylla michelleae Parra n. sp. es descrita. Las especies de la Región Andina están más cerca del Tatosoma de Nueva Zelanda, las sinapomorfias que demuestran esto son: el metaepimeron hinchado y la hipertrofia del segundo segmento abdominal. Se incluye un catálogo de los géneros y especies de la tribu en la región, y fotografías de adultos y armaduras genitales de algunas especies.

According to the vicariant hypothesis proposed by Brakoniecki (1986) the closure of the Sea of Tethys and the opening of the Atlantic Ocean would play an important role in the history of squids of the family Loliginidae, which is reflected in its current neritic distribution. Our study evaluated this hypothesis and alternative ideas to understand the historical biogeography of loliginid squids. This work is based on a phylogenetic hypothesis rebuilt with mitochondrial and nuclear sequences that incorporates the estimation of divergence times and ancestral distribution. Our results sustain that the squids of the family Loliginidae would have originated in the Western Pacific during the Late Paleocene about 59 My, following, during their diversification, at least 20 dispersion and 6 vicariant events. The first vicariant event fragments the ancestral distribution, remaining the ancestor of Sepioteuthis in the south and the subfamily Loligininae in the north. Successive events of dispersion, and some of vicariance (unrelated with the movement of tectonic plates and opening of the Atlantic Ocean), modeled it distribution. Our inference suggest a different origin compared to proposed by Brakoniecki (Tethys Sea), consistent with a center of origin that supports the most diversity of the family, with a predominance of dispersion processes over vicariant events, which explain the present distribution pattern.

La clausura del Mar de Tetis y la apertura del Océano Atlántico jugarían un papel relevante en la historia de los calamares de la familia Loliginidae, lo que se reflejaría en su actual distribución nerítico-costera, según la hipótesis vicariante propuesta por Brakoniecki (1986). Este estudio evalúa esta hipótesis y otras ideas alternativas para entender la historia del grupo, sobre la base de una hipótesis filogenética, reconstruida con secuencias mitocondriales y nuclear, que incorpora la incertidumbre, permitiendo estimar tiempos de divergencia para sugerir un nuevo escenario histórico sustentado en la señal filogenética y reconstrucción de la distribución ancestral. Los resultados permiten inferir que Loliginidae se habría originado en el Pacífico Oeste durante el Paleoceno Tardío hace unos 59 Ma, y que durante su diversificación habrían ocurrido al menos 20 eventos de dispersión históricos y 6 de vicarianza. El primer evento de vicarianza fragmenta la distribución ancestral permaneciendo el ancestro de Sepioteuthis en el rango sur y la subfamilia Loligininae en el rango norte. Luego, sucesivos eventos de dispersión, y algunos de vicarianza desvinculados del movimiento de placas tectónicas y apertura del Océano Atlántico, modelaron su distribución. La presente inferencia apunta a un origen distinto al propuesto por Brakoniecki (Mar de Tetis), coherente con un centro de origen que sustenta la mayor diversidad de la familia, con predominancia de los procesos de dispersión (como se evidencia en todos los géneros considerados, salvo Heterololigo), restringidos a desplazamientos nerítico-costeros, que explicarían el patrón de distribución actual.

Free-living nematodes are an important component of the marine benthos. In Chile there have been few studies on this group, and the majority has focused on the morphological aspect only. In this study, ribosomal 18S RNA and mitochondrial COI genes were used as genetic markers to complement morphological analyses to study the continental and Antarctic Chilean marine nematofauna. Different protocols for fixing, extracting and amplifying DNA were also tested. Not all the possible combinations produced good results. In fact, only the 18S gene showed consistently results. Phylogenetic analyses showed some discordance between classical taxonomy (i.e., based on morphology) and molecular data. These results suggest that taxonomic classification using integrative approaches including morphological characteristics and molecular information is needed to study the diversity and evolution of this complex group.

We evaluate the genetic divergence between the two morphs of the genus Macrocystis found in the Chilean coast (pyrifera and integrifolia), and the historical relationships with the other morphs of the genus using the ITS-2 DNA region sequences. The analyses sustain that the morphotypes, and its distribution, have a strong phylogenetic signal, indicating that historical process associated to the diversification has determined the current distribution and morphological variability. Finally, the pyrifera morph is the most probable ancestor of the actual morphological variability of the genus, which originated in the Northeastern Pacific and later colonized the Southern Pacific.

In natural forest ecosystems and plantations, most trees live in mutualistic association with mycorrhizal fungi. Studies of this association in South America are still scarce, especially when referring to the causes of temporal dynamics of this symbiotic community, despite its importance in countries with a thriving forestry industry like Chile. This study evaluates the dynamics of the ectomycorrhizal community of Pinus radiata stands of 3, 10 and 20 years of age, identifying and quantifying the most common fungal colonizers of fine roots in each age class. The results confirm that the mycobiont community changes with host tree age but that age classes differ in dominance patterns rather than in species richness, with the three- and ten-year-old tree cohorts forming a group separate from the 20-year-old trees. A total of eleven ectomycorrhizal root morphotypes could be distinguished. Four of them which were identified as Hebeloma crustuliniforme, Inocybe sp., Russula sardonia and Pinirhiza spinulosa, were the most abundant (77, 29, 78 and 8 % respectively) and were found in more than one root sample whereas the remaining morphotypes accounted for less than 100 (< 7 %) root tips and showed a patchy distribution. Inocybe sp. was only found on root tips of three-year-old trees, characterizing as an early-stage mycobiont. H! crustuliniforme appeared as a multi-stage colonizer in all three age classes but was clearly dominant on roots of three- and ten-year-old trees, whereas R! sardonia was mainly found on roots of 20-year-old trees, classifying as a late-stage species together with the unidentified morphotype Pinirhiza spinulosa which is reported for the first time from Chile. Our results suggest that the observed changes in the ectomycorrhizal community are not induced by the site per se, but are rather an effect of the interaction between the trees and their environment.

En ecosistemas naturales y plantaciones, las coníferas establecen asociaciones mutualistas con una comunidad diversa de hongos micorrícicos. El estudio de este tema en Sudamérica es aún incipiente, y no existen antecedentes sobre la dinámica temporal de esta comunidad, y menos de sus potenciales causas, a pesar de su importancia para un país forestal como Chile. En el presente trabajo se evaluó la dinámica de la comunidad ectomicorrícica, identificando y cuantificando los hongos formadores de esta asociación en raíces finas de Pinus radiata en plantaciones de 3, 10 y 20 años. Los resultados confirman que la comunidad ectomicorrícica de P. radiata cambia con la edad de los árboles, la cual difiere más bien en el patrón de dominancia que en la riqueza de especies, separándose un primer grupo de árboles de 3 y 10 años de un segundo grupo de 20 años. Un total de once morfotipos de micorrizas fueron diferenciados. Cuatro de ellos, identificados como Hebeloma crustuliniforme, Inocybe sp., Russula sardonia y Pinirhiza spinulosa, fueron los más abundantes (77, 29, 78 y 8 % respectivamente), mientras las otras se encontraron colonizando menos de 100 puntas de raíz (< 7 %), mostrando además una distribución en parches. La especie Inocybe sp. fue encontrada exclusivamente en ápices radicales de árboles de tres años, caracterizándose como micobionte de estado temprano. Hebeloma crustuliniforme, como colonizador de estado múltiple, estuvo presente en raicillas de todas las clases de edad, sin embargo fue dominante en árboles de 3 y 10 años, mientras R! sardonia, como especie de estado tardío, dominó en los árboles de 20 años junto con el morfotipo no identificado Pinirhiza spinulosa que fue registrado por primera vez en Chile. Nuestros resultados sugieren que no es el sitio per se el que genera el cambio de la comunidad ectomicorrícica, sino la interacción del bosque con el entorno.

The Oryzomyini rodent tribe is the most diverse taxon within the Sigmodontinae subfamily. This tribe includes 120 species and 31 genera, of which 83 are endemic to the South American continent. This tribe presents a wide distribution, covering the entire Neotropical biogeographic province, and is characterized by the presence of greater richness in the Amazonian area, with a monotonic decrease towards the south and north of South America. This pattern is well-known in many taxa, for which various causal mechanisms have been proposed. However, the mechanisms that explain this pattern of species richness along the latitudinal gradient in the Oryzomyini tribe are unknown. Given that these species are native to Amazonia, and that throughout their history they colonized new and more variable environments (towards the south and north), we evaluated the source-sink hypothesis, mediated by processes of colonization and extinction, as a potential explanation for the observed pattern of richness. To test this hypothesis we built a database of species' distribution and richness every one degree of latitude for the entire South American continent. Subsequently we assessed the degree of nestedness using the T (temperature), BR (discrepancy) and NODF indices. Our results show a significant degree of nesting in the Oryzomyini distribution, and a significant degree of nesting of the rows and columns of the data matrix, separately. Therefore, we conclude that source-sink dynamics affect the pattern of richness distribution of Oryzomine rodents, through a process of colonization during its expansion in South America, which was conditioned by the range of tolerance of the species. This resulted in the extinction of the less tolerant species, which finally resulted in a lower number of species towards the south and north of Amazonia.

La tribu de roedores Oryzomyini es la más diversa dentro de la subfamilia Sigmodontinae. Está constituida por 120 especies y 31 géneros, de las cuales 83 son endémicas del continente sudamericano. Este grupo exhibe una extensa distribución que abarca toda la región Neotropical, caracterizada por la presencia de una mayor riqueza en la Amazonia con una disminución monotónica hacia el sur y norte de Sudamérica. Este es un patrón bastante conocido en la mayoría de los taxones, por lo que se han propuesto varios mecanismos causales. Sin embargo, se desconocen los mecanismos que dan cuenta de este gradiente latitudinal en la riqueza de especies de Oryzomyini. Debido a que estas especies son originarias de la Amazonia, y que a través de su historia colonizaron ambientes nuevos y más variables (sur y norte), se evaluó la hipótesis fuente-sumidero, mediada por procesos de colonización y extinción, como potencial explicación al patrón de riqueza observado. Para evaluar esta hipótesis se reunió una base de datos de distribución y riqueza de especies por grado de latitud para todo el continente sudamericano. Posteriormente se evaluó el grado de anidamiento mediante los índices de T (temperatura), BR (discrepancia) y NODF. Nuestros resultados evidenciaron un grado de anidamiento significativo en la distribución de Oryzomyini, y un anidamiento significativo separadamente en filas y columnas de la matriz. Por lo tanto, se concluye que la dinámica fuente-sumidero afecta el patrón de distribución de la riqueza de roedores Oryzominos, a través de un proceso de colonización durante su expansión en Sudamérica que fue mediado por los rangos de tolerancia de las especies. Finalmente, las especies menos tolerantes se habrían extinguido, lo que determinaría un menor número de especies hacia el sur y norte de la Amazonia.

The aim of this study was to evaluate the utility of COI, of the mitochondrial DNA, for the taxonomic determination of soft-bottom benthic polychaetes in the Chiloé Inner Sea as a particularly important zone for polychaete fauna of the southeast Pacific. The results show high genetic differentiation between morphological species of polychaetes (posterior probabilities upper 0.9), and Onuphis pseudoiridescens showed the greatest divergence (3.08 ± 0.08 S.D.). The results support the role of the COI gene as a useful molecular marker for fast and accurate taxonomic determination of benthic polychaetes. This study leads the way for research on the biodiversity and systematics of polychaetes off the Chilean coast using molecular phylogenetic criteria.

In this work we evaluate the taxonomy of the Lithinini of Austral South America based on a phylogenetic analysis. In our analysis we used outgroup Catophoenissa. Two approaches were used to evaluate phylogenetic relationships: 1) parsimony criterion, and 2) Bayesian inference. Parsimony analysis was conducted in PAUP software, and Bayesian analysis with Markov chains Monte Carlo using the BayesPhylogenies software. Our results based on the phylogenetic hypothesis suggest a new taxonomic order for Austral American Lithinini. The valid genera are: Asestra Warren, Acauro Rindge, Calta Rindge, Euclidiodes Warren, Franciscoia Orfila and Schajovskoy, Incalvertia Bartlett-Calvert, Lacaria Orfila and Schajovskoy, Laneco Rindge, Maeandrogonaria Butler, Martindoelloia Orfila and Schajovskoy, Nucara Rindge, Odontothera Butler, Proteopharmacis Warren, Psilaspilates Butler, Rhinoligia Warren and Tanagridia Butler. The main changes with respect to the previous taxonomic order are: 1) Yalpa Rindge is the synonymous junior of Odontothera; 2) the genus Rhinoligia Warren is incorporated into the Lithinini; 3) while our analysis reaffirms that Siopla Rindge is junior synonym of Asestra, Yapoma Rindge and Duraglia Rindge are synonymous of Euclidiodes Warren, while Callemo Rindge and Guara Rindge are synonymous of Tanagridia; 4) the genus Calta Rindge, Incalvertia Rindge, Odontothera Butler and Proteopharmacis Warren, synonymized by Pitkin, are redefined, revalidated and incorporated into the Lithinini tribe. A new species for the genus Franciscoia, F. ediliae Parra is described. A catalogue of the genera and species of the tribe in the region, and the figures of adults and genitalia of some species are included.

Estudio filogenético de los géneros de Lithinini de Sudamérica Austral (Lepidoptera, Geometridae): una nueva clasificación. Se evalúa la taxonomía de la tribu Lithinini de Sudamérica Austral sobre la base de un análisis filogenético. Para el análisis se utilizó a Catophoenissa como grupo externo. Se usaron dos aproximaciones filogenéticas para evaluar las relaciones de parentesco: 1) criterio de parsimonia; e 2) inferencia bayesiana. El análisis de parsimonia se realizó a través del programa PAUP y el análisis bayesiano con cadenas de Markov y Monte Carlo a través del programa BayesPhylogenies. Los resultados generados a partir de la hipótesis filogenética permiten proponer una nueva taxonomía para los Lithinini de Sudamérica Austral. Los géneros validos son: Asestra Warren, Acauro Rindge, Calta Rindge, Euclidiodes Warren, Franciscoia Orfila y Schajovskoy, Incalvertia Bartlett-Calvert, Lacaria Orfila y Schajovskoy, Laneco Rindge, Maeandrogonaria Butler, Martindoelloia Orfila y Schajovskoy, Nucara Rindge, Odontothera Butler, Proteopharmacis Warren, Psilaspilates Butler, Rhinoligia Warren, Tanagridia Butler. Los principales cambios respecto de ordenamientos taxonómicos previos son: 1) Yalpa Rindge, es tratado como sinónimo junior de Odontothera. 2) El género Rhinoligia Warren es incorporado a los Lithinini; 3) Se reafirma que Siopla Rindge es sinónimo junior de Asestra, Yapoma Rindge y Duraglia Rindge son sinónimos de Euclidiodes Warren, mientras que Callemo Rindge y Guara Rindge son sinónimos de Tanagridia; 4) Los géneros Calta Rindge, Incalvertia Rindge, Odontothera Butler y Proteopharmacis Warren, sinonimizados por Pitkin, son redefinidos, revalidados e incorporados a la tribu Lithinini. Se describe una nueva especie para el género Franciscoia, F. ediliae Parra. Se incluye un catálogo con los géneros y especies de la tribu de la región, más las figuras de los adultos y genitalias de las principales especies.

In addition to the close relationship between community composition and available resources, the physical structure of the forest has often been cited as an important factor affecting patterns of arthropod diversity. The objective of this study was to evaluate the effect of two native tree species, differing in physical structure, on the diversity of araneofauna in the Pedro del Río Zañartu (Hualpén) Botanical Park. We estimated the abundance, diversity, similarity and structure of the arboreal spider community associated with the two native trees, Peumus boldus Mol. (boldo) and Luma apiculata (D.C.) Burret (arrayán). We sampled spiders from eight randomly selected trees of each species using entomological umbrellas with vegetation beating. Sampling was conducted monthly from March 2001 to June 2002. We collected a total of 1602 specimens belonging to 7 families. The most abundant families present on the two tree species were Anyphaenidae, Theridiidae and Araneidae. We obtained similar values for the diversity indices of both tree species (1.576 for boldo and 1.288 for arrayán). Cluster analysis based on Jaccard similarity did not indicate differences between spider guilds inhabiting either tree species. In this sense, spiders are not restricted by the arboreal structure of these native tree species, but may be affected by other environmental variables such as food availability.

Además de la cercana relación entre composición comunitaria y recursos disponibles, la estructura física del bosque a menudo se ha citado como un factor importante que afecta los patrones de diversidad de artrópodos. El objetivo de este estudio fue evaluar el efecto de dos especies nativas de árbol, que difieren en su estructura física, sobre la diversidad de araneofauna en el Parque Botánico Pedro del Río Zañartu (Hualpén). Con este fin se estimó la abundancia, diversidad, semejanza y composición de la comunidad de arañas arborícolas asociadas al follaje de dos especies de árboles nativos, Peumus boldus Mol. (boldo) y Luma apiculata (D.C.) Burret (arrayán). Las arañas fueron muestreadas mensualmente usando paraguas entomológico desde marzo del 2001 hasta junio del 2002, desde 8 árboles elegidos aleatoriamente de cada especie. Un total de 1.602 ejemplares agrupados en siete familias fueron recolectados de las dos especies arbóreas, siendo las más abundantes Anyphaenidae, Theridiidae y Araneidae. Se obtuvo un índice de diversidad muy similar en los dos árboles, 1,576 para boldo y 1,288 para arrayán. El análisis de conglomerado basado en similitud de Jaccard no indica diferencias entre los gremios de araña que habitan las dos especies de árbol analizadas. En este sentido, las arañas no son restringidas por la estructura arbórea de estas especies nativas, pero pueden ser afectadas por otras variables ambientales tales como la disponibilidad de alimento.

We studied the association of polychaetes with the cirriped, Austromegabalanus psittacus on the Peninsula of Gualpén (VIII Region, Chile). Here we report and discuss the importance of this association for assemblages of subtidal polychaetes, we also investigated about the importance of cirriped body size on the abundance and biodiversity of polychaetes. All of the cirripeds examined contained polychaetes. We obtained 793 individuals belonging to 19 species of 12 families. The majority of the polychaetes were found in the calcareous part of the cirripeds. The most abundant and prevalent were: Sylidae (Typosyllis sp., Autolytus sp.), Nereididae (Nereis callaona), Spinonidae (Polydora sp.), Chyrospetalidae (Paleanotus chrysolepis) and Cirratulidae (Dodecaceria opulens). We observed that the biodiversity of polychaetes and the abundances of Typosyllis sp. significantly increased with the size of the cirriped host. The relationship between the size of A. psittacus and the richness of polychaete species is explained by the potential equation (Y=cXz), which empirically describes the known ratio species-area in the equilibrium model of MacArthur & Wilson (1963), where the cirripeds behave like islands for the associated polychaetes. We discuss the importance of the recorded polychaetes in relation to similar associations on other coasts of the world.

Se estudió la asociación de poliquetos con el cirripedio Austromegabalanus psittacus en la Península Gualpén (VIII Región, Chile). Se informa y discute la importancia de esta asociación para los ensambles de poliquetos submareales, y se indaga sobre la importancia que tiene el tamaño corporal del cirripedio en la abundancia y biodiversidad de poliquetos. Todos los cirripedios examinados tenían poliquetos, obteniéndose 793 individuos pertenecientes a 19 especies de 12 familias. La mayoría de los poliquetos se encontraron en la parte calcárea de los cirripedios. Los más abundantes y frecuentes fueron Syllidae (Typosyllis sp., Autolytus sp.), Nereididae (Nereis callaona), Spionidae (Polydora sp.), Chrysopetalidae (Paleanotus chrysolepis) y Cirratulidae (Dodecaceria opulens). Se observó que la biodiversidad de poliquetos y la abundancia de Typosyllis sp. aumentan significativamente con el tamaño del cirripedio. La relación entre el tamaño de A. psittacus y la riqueza de poliquetos está determinada por la ecuación potencial (Y = cXz) que empíricamente describe la conocida relación especies-área en el modelo de equilibrio de MacArthur & Wilson (1963), por lo que los cirripedios se comportarían como islas para los poliquetos asociados. Se discute la importancia de los poliquetos registrados en relación con asociaciones semejantes en otras costas del mundo.