Genetic relationships among merluccius species.

Genetic data from nine species of Merluccius (Euro-African species merluccius, capensis, paradoxus, polli, senegalensis; American species bilinearis, productus, hubbsi, australis) from 21 informative allozyme loci provided insights into the phylogenetic and biogeographical relationships within the genus. The highest values of polymorphic loci and mean heterozygosity occur in the four American species. These values are consistent with large population sizes during speciation (through vicariant processes), and continuing through to the present. Conversely, the lower values of Euro-African species are consistent with bottlenecks occurring during or subsequent to speciation. Euro-African and American species formed two distinct clades. In the former group, merluccius, capensis and senegalensis clustered together as the most derived species, with distinct relationships between polli and paradoxus from an earlier divergence. Similarly, productus, australis and hubbsi clustered closely as the most derived American species, clearly diverging from the more ancestral bilinearis. Analyses including comparative data previously published for M. gayi indicated a close pairing to hubbsi. The data support a north-west Atlantic origin of the genus with unsampled M. albidus of broad Caribbean distribution proposed as the most primitive extant species.