Zoogeographic patterns of pelagic oceanic cephalopods along the eastern Pacific Ocean

Abstract

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.

Global Patterns of Species Richness in Coastal Cephalopods

“…Although cephalopod diversity and distribution have been studied extensively in the past, most such research and knowledge has been compiled as species accounts (see examples in Roper, 2005, 2010;Jereb et al, 2014). Large-scale biogeographic studies on cephalopod diversity are scarce and mostly concentrated in the Atlantic Ocean (Rosa et al, 2008a,b;Judkins et al, 2010), polar zones (e.g., Xavier et al, 1999;Allcock et al, 2011;Golikov et al, 2013;Xavier et al, 2016bXavier et al, , 2018 and the Pacific Ocean (Ibáñez et al, 2009(Ibáñez et al, , 2019 or specific taxonomic groups (e.g., Ibáñez et al, 2016;Ulloa et al, 2017). Moreover, some of those studies were designed to investigate broad-scale latitudinal gradients (e.g., richness and body-size data across latitudinal bins) and describe the respective environmental determinants (e.g., Rosa et al, 2008aRosa et al, , 2012Ibáñez et al, 2019).…”

Assessing the need for temporary fishing closures to support sustainability for a small-scale octopus fishery

“…They also provide rich nutrition and bioactive compounds to the oceanic microbial community (Fitahia et al 2018). Further, their abundance varies drastically with a wide range of ocean conditions including sea surface and bottom temperature, salinity, currents, and sediment type (Catalán et al 2006;Ibáñez et al 2019;Van Nieuwenhove, Ratsimbazafy, and Kochzius 2019). Compared to other exploited marine organisms, cephalopods have a short lifespan coupled with a fast reproduction rate and high fecundity.…”

“…However, this requires a deeper understanding of the characteristics of Octopus cyanea in this fishery in order to be properly instituted. Instituting effective temporary closures in octopus fisheries can be difficult due to their short lifespan, high mortality, and sensitivity to environmental conditions (Catalán et al 2006;Emery, Hartmann, and Gardner 2016;Ibáñez et al 2019;Van Nieuwenhove, Ratsimbazafy, and Kochzius 2019). Lack of field data and difficulty of enforcement has also been a challenge in octopus fisheries, especially in Madagascar (Emery, Hartmann, and Gardner 2016;Benbow et al 2014).…”

“…Cephalopods act as both predators and prey in an ecosystem (Rodhouse & Nigmatullin, 1996; Santos et al, 2001; Vase et al, 2021), situating them in a key role in food webs. Further, their abundance varies drastically with a wide range of ocean conditions including sea surface and bottom temperature, salinity, currents, and sediment type (Catalán et al, 2006; Ibáñez et al, 2019; Van Nieuwenhove et al, 2019). Compared to other exploited marine organisms, octopus have a short lifespan coupled with a fast reproduction rate and high fecundity which makes their populations more responsive to fishing pressures (Langley, 2005; Humber et al, 2006).…”

Body size variation in polyplacophoran molluscs: Geographical clines and community structure along the south‐eastern Pacific

“…In coastal marine systems, the geographical distribution of species is highly influenced by changes in seawater temperature, oxygen, pH, and primary productivity levels, which determine the transport and connectivity of larvae (e.g. Fenberg et al., 2015; Ibáñez, Braid, et al., 2019). In temperate systems in particular, heterogeneity in habitat continuity, productivity and temperature greatly influence species distribution and directly generate large changes in abundance, diversity and endemism (e.g.…”