A biogeographic framework of octopod species diversification: the role of the Isthmus of Panama

Abstract

The uplift of the Isthmus of Panama (IP) created a land bridge between Central and South America and caused the separation of the Western Atlantic and Eastern Pacific oceans, resulting in profound changes in the environmental and oceanographic conditions. To evaluate how these changes have influenced speciation processes in octopods, fragments of two mitochondrial (Cytochrome oxidase subunit I, COI and 16S rDNA) and two nuclear (Rhodopsin and Elongation Factor-1α, EF-1α) genes were amplified from samples from the Atlantic and Pacific oceans. One biogeographical and four fossil calibration priors were used within a relaxed Bayesian phylogenetic analysis framework to estimate divergence times among cladogenic events. Reconstruction of the ancestral states in phylogenies was used to infer historical biogeography of the lineages and species dispersal routes. The results revealed three well-supported clades of transisthmian octopus sister species pair/complex (TSSP/TSSC) and two additional clades showing a low probability of species diversification, having been influenced by the IP. Divergence times estimated in the present study revealed that octopod TSSP/TSSC from the Atlantic and Pacific diverged between the Middle Miocene and Early Pliocene (mean range = 5–18 Ma). Given that oceanographic changes caused by the uplift of the IP were so strong as to affect the global climate, we suggest that octopod TSSP/TSSC diverged because of these physical and environmental barriers, even before the complete uplift of the IP 3 Ma, proposed by the Late Pliocene model. The results obtained in this phylogenetic reconstruction also indicate that the octopus species pairs in each ocean share a recent common ancestor from the Pacific Ocean.

Traditional Knowledge Aids Description When Resolving the Taxonomic Status of Unsettled Species Using Classical and Molecular Taxonomy: The Case of the Shallow-Water Octopus Callistoctopus furvus (Gould, 1852) From the Western Atlantic Ocean

“…This is in part due the remoteness of many of these regions, and a generalized lack of locally trained taxonomists. As expected, knowledge on tropical shallow-water octopus fauna remains rudimentary (Voight, 1998;Leite et al, 2008;Lima et al, 2020), particularly in the southwestern Atlantic Ocean, including the South American mainland and oceanic islands (Voss and Toll, 1998). Among these poorly known octopuses, the genus Callistoctopus comprises a speciose monophyletic group supported by both morphological and genetic analyses (Norman and Hochberg, 2005;Kaneko et al, 2011).…”

“…The taxonomic status of the western Atlantic Callistoctopus has long been problematic and, along with C. furvus, at least two other described species [i.e., Callistoctopus bermudensis (Hoyle, 1885) and Callistoctopus chromatus (Heilprin, 1888)] were initially recognized in the region but later synonymized within C. macropus (Voss and Toll, 1998). However, earlier authors did not have access to modern multivariate statistics and molecular tools that allowed us to recognize C. furvus as a valid species distinct from C. macropus, a conclusion also supported by genetic studies of tropical western Atlantic shallowwater octopus fauna recently conducted by Ritschard et al (2019) and Lima et al (2020).…”

“…Our results suggest a close phylogenetic affinity among C. furvus, C. macropus, and C. ornatus, where each of those constitutes well-supported phylogenetic lineages. In addition, the three species share behavioral and morphological similarities (Lima et al, 2020). The recently estimated time divergence between C. macropus and C. furvus (identified as 'Callistoctopus sp.'…”

“…Two newer lots (one from the same region and another from Fernando de Noronha Island) were deposited at the University of Rio Grande Oceanographic Museum (Leite and Haimovici, 2006). Leite et al (2008) urged a critical revision on the taxonomic status of "Brazilian" C. macropus, and recent genetic analysis suggest that the western Atlantic Callistoctopus is distinct form C. macropus stricto sensu (Ritschard et al, 2019;Lima et al, 2020).…”

Can citizen science help delimit the geographical distribution of a species? The case of the Callistoctopus sp. (“eastern octopus”) on the Brazilian coast

“…This work may be the first to use citizen science as a complementary approach for the identification and distribution of a species of octopus on the Brazilian coast, namely the eastern octopus, Callistoctopus sp. (Lima et al, 2020).…”