Molecular genetic assessment of bipolarity in the anchovy genus Engraulis
Abstract:To test three hypotheses accounting for bipolar distributions in Engraulis, seven of eight taxa (except E. eurystole) were surveyed with allozymes (34 loci) and 521 bp of the mitochondrial DNA cytochrome b gene. Both allozymes and mtDNA sequences revealed deep separations between New World and Old World anchovies with a mean allozyme genetic distance D = 1·26 and net mtDNA sequence divergence d = 15%. These values reflected separations of 5 to 10 million years. Contrary to previous phylogenetic hypotheses, which place north‐east Pacific E. mordax and south‐east Pacific E. ringens as sister taxa, the south‐west Atlantic E. anchoita and E. ringens are most closely related to each other. The north‐east Pacific E. mordax is the closest lineage to the Old World Engraulis, a group of taxa showing low divergences typical of population‐level separations (mean D = 0·06; mean d = 0·87%). Bipolarities of sister taxa in the east Atlantic and west Pacific reflect recent dispersals. Bipolarities in the east Pacific and west Atlantic represent paraphyletic taxa in lineages isolated since the Miocene. None of the bipolarities can be attributed to tectonic separations or competitive displacements from the tropics, but the latter situation should be re‐evaluated with comparisons to tropical anchovies of the New World.
Document Type: Regular Paper
Affiliations: 1: Coastal and Marine Management, Private Bag X2, Rogge Bay 8012, Republic of South Africa and 2: Hawaii Institute of Marine Biology, University of Hawaii, P. O. Box 1346, Kaneohe Bay, Hawaii, 96744, U.S.A.
Publication date: October 1, 2005