hermaphroditism-dioecy and the molecular clock

Mark Dorris Mark.Dorris at ed.ac.uk
Wed Jan 8 12:00:37 EST 1997

On Fri, 03 Jan 1997 Mircea Podar wrote
> When using molecular data (rRNA or other) in determining the evolutionary
> distance between say two closely related species (related as defined by
> "clasical" analysis), one has to be quite confident that the rate of
> molecular evolution is similar between the two. This is usually (or should
> be) the case.

	Why? Distance is surely determined regardless of rate. Large distances
suggest either rapid rates, ancient divergence or both. Dating
divergence may by done by association with some dateable reference e.g.
mapping parasite evolution to paleontological record of host.

 However, what would happen if one would compare two species
> of invertebrates that are morphologically related but have different
> reproductive strategies : one of them is hermaphroditic and reproduces
> mostly by self-fertilization and the other has separate sexes. The
> population size I think is an important factor, but for sake of simplicity
> suppose both species have large populations and there is no physical
> barrier to limit the dispersal if individuals. 

rRNA genes have been used to infer phylogeny for nematodes which show
all the characteristics above as well as some very different life
cycles. Check out Fitch et al (95) Mol. Biol. Evol. 12 346-58 And also
Winnepenninckx et al (95) Mol. Biol. Evol. 12 1132-37 In which even more
diverse taxa are examined. 
Hope this helps
Mark Dorris   email Mark.Dorris at ed.ac.uk
Institute of Cell, Animal and Population Biology
Ashworth Laboratories, King's Buildings
University of Edinburgh,  West Mains Road
EDINBURGH  EH9 3JT,  United Kingdom
phone: (+44) 131 650 6760  Fax :...650 5450

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