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On Thu, 28 Sep 2000 darren.naish@port.ac.uk wrote:

> On tigers and lions and defining species etc.
> First of all, George's comment about hybridism between lions and 
> tigers does not count for much. Apparently disparate genera within 
> clades can sometimes hybridise. This depends on which group of 
> animals you are looking at: some seem to be particular good at it. 
> Example: _Tursiops_ (bottlenosed dolphin) has hybridised with 
> _Pseudorca_, _Lagenorhynchus_ and _Grampus_. _Pseudorca_ and 
> _Grampus_ are often put in a different 'subfamily' (the 
> Globicephalinae or one of its many synonyms) from _Tursiops_.

Amongst Australian lizardz there is evidence for lineages that have been
distinct since the Oligocene still being able to hybridise. Cunningham's
(Egernia cunninghami) can hybridise with the common bluetongue (Tiliqua
scincoides). Tiliqua is a robust clade with fossils members in the
Oligo-Miocene limestones of Riversleigh. Therefore the two lineages must
be at least as old as these fossils.
As someone (Can't remember who) once said to me, during my undergraduate
years, "The ability to interbreed is a plesiomorphic character,
therefore species by definition aren't clades".


Adam Yates