Question about anglerfish evolution

[Homer Ellison]

The question regards a paper by W.S. Grant and R.W. Leslie, J. Zoology, 
London, 1993, 231:465-485.  In this paper the authors analyze allozyme 
hetreogeneity among 6 species of Lophius using cladistics to arrive at a 
postulated phylogeny for the genus. Lophiomus is used as the outgroup.  

Geological events are used to explain the distribution of the seven 
species of Lophius, and this gets to the heart of my question.  On page 
481 of the paper, Grant and Leslie suggest that the 'first split in the 
ancestral tropical Atlantic population of Lophius followed the separation 
of the South American and African Plates'.  The paper previously stated 
that the ancestral tropical Atlantic population did not exist before 27 
my.  I don't understand how the separation of the population followed an 
event (separation of the S.American and African plates) which occurred 
before the popultaion existed.  My understanding is that by the time the 
ancestral population had evolved (27my), the two plates were almost 
completely separated and in their present positions.  

How could plate separation result in a vicariant event resulting in the 
spliiting of ther ancestral Lophius population?

Please e-mail responses to ellison at csulb.edu


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______                                         ______
 |  |  Homer O. Ellison, ellison at csulb.edu      |  |
 |  |  Department of Biological Sciences        |  |
 |  |  California State University, Long Beach  |  |
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