Phylogeny and biogeography of Muusoctopus (Cephalopoda: Enteroctopodidae)

Abstract

Deep‐sea octopuses of the genus Muusoctopus are thought to have originated in the Pacific Northern Hemisphere and then diversified throughout the Pacific and into the rest of the World Ocean. However, this hypothesis was inferred only from molecular divergence times. Here, the ancestral distribution and dispersal routes are estimated by Bayesian analysis based on a new phylogeny including 38 specimens from the south‐eastern Pacific Ocean. Morphological data and molecular sequences of three mitochondrial genes (16S rRNA, COI and COIII) are presented. The morphological data confirm that specimens newly acquired from off the coast of Chile comprise two species: Muusoctopus longibrachus and the poorly described species, Muusoctopus eicomar. The latter is here redescribed and is clearly distinguished from M. longibrachus and other closely related species in the region. A gene tree was built using Bayesian analysis to infer the phylogenetic position of these species within the species group, revealing that a large genetic distance separates the two sympatric Chilean species. M. longibrachus is confirmed as the sister species of Muusooctopus eureka from the Falkland Islands; while M. eicomar is a sister species of Muusoctopus yaquinae from the North Pacific, most closely related to the amphi‐Atlantic species Muusoctopus januarii. Molecular divergence times and ancestral distribution analyses suggest that genus Muusoctopus may have originated in the North Atlantic: one lineage dispersed directly southward to the Magellan region and another dispersed southward along the Eastern Pacific to the Southern Ocean and Antarctica. The Muusoctopus species in the Southern Hemisphere have different phylogenetic origins and represent independent invasions of this region.

Global Patterns of Species Richness in Coastal Cephalopods

“…Closure of the Isthmus of Panama (about 3.1 My; Emiliani, 1966;Coates and Obando, 1996) led to the isolation of octopus and squid populations by vicariance and thence to allopatric speciation (Voight, 1988;Gleadall, 2013;Ibáñez et al, 2016;Ulloa et al, 2017). This geological event and accompanying historical sea-level changes and formation of refugia (cf.…”

“…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).…”

Systematics and Phylogenetic Relationships of New Zealand Benthic Octopuses (Cephalopoda: Octopodoidea)

“…For the deep-sea species of the genera Graneledone and Thaumeledone, an Antarctic origin is probable based on the findings by Strugnell et al (2008). In the case of Muusoctopus, dispersal events from the North Pacific to the Southern Ocean and Atlantic (Gleadall, 2013) and from the Atlantic to the Southern Ocean (Ibáñez et al, 2016) have been previously proposed. The molecular phylogenetic approach presented here has added important information to the current systematics of the New Zealand octopod fauna; nonetheless, further studies are still required considering larger sampling sizes and a mixture of both mitochondrial and nuclear molecular markers to properly clarify their biogeographic origin and diversification.…”

“…Therefore, there is no reason in retaining both Benthoctopus and Muusoctopus (e.g., Norman et al, 2014). In this context, Ibáñez et al (2016) also suggested (based on morphology and genetics) that all New Zealand species of Benthoctopus should be included within the genus Muusoctopus. Future research should therefore target to compare morphometrics and genetic data to specifically determine the number of Muusoctopus species present in New Zealand waters.…”

“…The relationships among benthic octopuses from New Zealand, Australia, and South America has been hypothesized from evidence based on morphology and distribution (O'Shea, 1999). Previous biogeographic studies based on ancestral distribution inferred from phylogenies did not include the New Zealand octopod fauna (i.e., Strugnell et al, 2008Strugnell et al, , 2011Ibáñez et al, 2016), suggesting that the inclusion of those species could dramatically change not only the phylogenetic hypothesis but also our knowledge of the biogeographic events that would explain the origin of the octopus in this region.…”