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Aim To analyse the diversity and distribution of oceanic pelagic cephalopods along the eastern Pacific Ocean assessing the existence of biogeographic structuring, and the role of physical variables in generating geographical patterns. We hypothesized that the control by environmental factors, and the effect of geometric constraints, determine the range size and limits of distribution of oceanic cephalopods along the eastern Pacific Ocean, generating a latitudinal gradient in species richness. Location Eastern Pacific Ocean (60°N – 60°S), from the Gulf of Alaska to the Southern Ocean. Methods Based on a literature review and >5,000 records obtained from collections, we constructed a presence–absence matrix including 61 latitudinal bands (2° each) along the Eastern Pacific, and estimated species richness and range endpoints at each band. Biogeographic units were determined by means of multivariate analyses. Species richness was compared with null model predictions in order to test for the existence of geometric constraints using the Mid‐Domain Null model. The effects on species richness of environmental variables (temperature, salinity and oxygen) were evaluated separately for surface and depth (0–1,000 m) data, by means of ordinary least squares regression and simultaneous autoregressive models. Rapoport's pattern was assessed by applying the Stevens’ method and the range midpoint method. Results Species richness was high across the tropics and decreased towards the both poles. We identified five biogeographic units, highlighting two major distribution breaks at 40°N and 42°S. Species richness was strongly related with environmental variables, although the combined variables accounted for a large fraction of the variance between 0 and 1,000 m (R2 = 0.99), while temperature was the best single predictor at the surface (R2 = 0.98). Species richness curves showed a mid‐domain effect (MDE), and the mean latitudinal range was higher in the tropics and at warm latitudes, generating an inverse Rapoport's pattern. Main conclusions Along the eastern Pacific Ocean oceanic cephalopods exhibit both a clear biogeographic patterning and an interhemispheric (poleward decreasing) diversity gradient, which appear strongly related with physical factors and external forcing, as well as with a MDE as a seemingly consequence of the naturally bounded domain of the Eastern Pacific.

One of the major mechanisms responsible for the animals’ fitness dynamics is fecundity. Fecundity as a trait does not evolve independently, and rather interacts with other traits such as body and egg size. Here, our aim was to correctly infer the macroevolutionary trade-offs between body length, egg length, and potential fecundity, using cephalopods as study model. The correlated evolution among those traits was inferred by comparative phylogenetic methods. Literature data on biological and reproductive traits (body length, egg length, and potential fecundity) was obtained for 90 cephalopod species, and comparative phylogenetic methods based on a previous molecular phylogeny were used to test the correlated evolution hypothesis. Additionally, we estimated the phylogenetic signal and fitted five different evolutionary models to each trait. All traits showed high phylogenetic signal, and the selected model suggested an evolutionary trend toward increasing body length, egg length, and fecundity in relation to the ancestral state. Evidence of correlated evolution between body length and fecundity was observed, although this relationship was not detected between body length and egg length. The robust inverse relationship between fecundity and egg length indicates that cephalopods evolved a directional selection that favored an increase of fecundity and a reduction of egg length in larger species, or an increase in egg length with the concomitant reduction of fecundity and body length in order to benefit offspring survival. The use of phylogenetic comparative methods allowed us to properly detect macroevolutionary trade-offs.

Artículo Condición reproductiva de la jibia Dosidicus gigas en la zona costera del centro-sur de ChileReproductive condition of the jumbo squid Dosidicus gigas in the coastal area of the south-central ChileAbstract.-The reproductive condition of the jumbo squid Dosidicus gigas is poorly understood in Chile, through an oceanic-coastal migratory pattern during maturity and spawning has been suggested. The aim of this study was to describe the jumbo squid reproductive condition at the coastal zone off south-central Chile. For this, 1,335 specimens were analyzed from January-December 2014 to estimate their macroscopic sexual maturity and gonadosomatic index (IGS). The sexual proportion showed deviations of 1:1 in all months with a high dominance of females in January. Significant differences were found in the IGS between sexes and months, while maturity stages were relatively constant along time. Most recorded squids were immature, and only two mature females were found, suggesting that spawning occurs in oceanic waters off Chile.Resumen.-La condición reproductiva de la jibia Dosidicus gigas no se conoce bien en Chile, aunque se ha sugerido un patrón migratorio oceánico-costero durante la maduración y desove. El objetivo de este estudio fue describir la condición reproductiva de la jibia en la zona costera del centro-sur de Chile. Para esto, se analizaron 1.335 especímenes de enero a diciembre de 2014 para estimar su madurez sexual macroscópica e índice gonadosomático (IGS). La proporción sexual mostró desviaciones de 1:1 en todos los meses con una alta dominancia de hembras en enero. Se encontraron diferencias significativas en el IGS entre sexos y meses, mientras que las etapas de madurez fueron relativamente constantes a lo largo del tiempo. La mayoría de los calamares registrados eran inmaduros, y solo se encontraron dos hembras maduras, lo que sugiere que el desove se produce en aguas oceánicas en Chile.