The Great American Schism: Divergence of Marine Organisms After the Rise of the Central American Isthmus

Abstract

After a 12-million-year (My) process, the Central American Isthmus was completed 2.8 My ago. Its emergence affected current flow, salinity, temperature, and primary productivity of the Pacific and the Atlantic and launched marine organisms of the two oceans into independent evolutionary trajectories. Those that did not go extinct have diverged. As no vicariant event is better dated than the isthmus, molecular divergence between species pairs on its two coasts is of interest. A total of 3 8 regions of DNA have been sequenced in 9 clades of echinoids, 38 of crustaceans, 42 of fishes, and 26 of molluscs with amphi-isthmian subclades. Of these, 34 are likely to have been separated at the final stages of Isthmus completion, 73 split earlier and 8 maintained post-closure genetic contact. Reproductive isolation has developed between several isolates, but is complete in only the sea urchin Diadema. Adaptive divergence can be seen in life history parameters. Lower primary productivity in the Caribbean has led to the evolution of higher levels of maternal provisioning in marine invertebrates. 63

Molecular phylogenetics and evolution of Holacanthus angelfishes (Pomacanthidae)

“…This value again falls within the range of other geminate fish pairs (using the same gene region) that are most likely to have been separated at the closure of the Isthmus of Panama (3.3-4.8%, Lessios, 2008). …”

“…In the case of the mitochondrial control region, average pairwise sequence divergence between the Western Atlantic and TEP clades was 18.7%. A thorough review performed by Lessios (2008) on multiple species of geminate pairs of marine fish found that the species that most likely separated due to the rise of the Isthmus of Panama exhibited a divergence range of 9.7-22%. These values are consistent with the idea that the rise of the Isthmus may have coincided with the divergence of the two Trans-Isthmian Holacanthus clades.…”

A dated molecular phylogeny of manta and devil rays (Mobulidae) based on mitogenome and nuclear sequences

“…4) is consistent with the closing of the Isthmus of Panama, which most likely took place between 3.1 and 2.8 Mya (Coates et al, 2003;Coates and Obando, 1996). This event created a permanent separation between East Pacific and Atlantic mobulids as is the case for many marine species (Lessios, 2008) including various elasmobranchs (Daly-Engel et al, 2012;Keeney and Heist, 2006;Schultz et al, 2008;Stelbrink et al, 2010).…”

Surgeons and suture zones: Hybridization among four surgeonfish species in the Indo-Pacific with variable evolutionary outcomes

“…Each site (and species) was also fitted with the population parameter  in order to estimate the time since the most recent population expansion ( = 2μt; Rogers and Harpending, 1992), where t is the age of the population in generations and μ is the mutation rate per generation for the sequence (μ = number of bp · divergence rate within a lineage · generation time in years). We used a range of approximate cyt b mutation rates available from previous fish studies (1% per million years [MY] to 1.55% per MY within lineages; Bowen et al, 2001;Lessios, 2008;Reece et al, 2010) and a generation (replacement) time of 12 years for all species based on existing life-history information (i.e. age-at-maturity ~ two years, longevity ~ 27 to 36 years; J.H.…”

“…japonicus, A. leucosternon and A. nigricans based on mitochondrial DNA (cytochrome b) sequence data. Time since the most recent population expansion was calculated using a range of mutation rates (1% to 1.55% per million years within lineages; Bowen et al, 2001, Lessios, 2008, Reece et al, 2010 and a generation time of 12 years for all species (see Materials and Methods). 2 2 n/a c n/a n/a n/a Johnston Atoll (JON) 3 2 n/a n/a n/a n/a Hawaiian Islands (HAW) 2 2 n/a n/a n/a n/a Acanthurus leucosternon Socotra, Yemen (SOC) 5 n/a n/a n/a n/a n/ Table 1).…”