[Taxacom] Madagascar (was: Timetree of Life)

[Kenneth Kinman]

Hi Michael,
       Well, the lack of Hystricomorpha, Sciuromorpha, and various other
taxa in Madagascar would be most parsimoniously explained by the
difficulty and rarity of dispersal from mainland Africa to Madagascar.  
        It is probably largely by chance that lemur ancestors floated
over on trees.  However, such dispersal is not so unlikely that I would
turn to a vicariance explanation for lemur origins.  It seems extremely
unlikely to me that lorises and lemurs split before the K-T extinction.  
            ----------Ken               
P.S.  The lack of certain rodent taxa in Australasia may be due to a
more complex combination of factors, but competitive exclusion is one
likely factor in such taxa attempting to island-hop into that area
(perhaps more so than the isolation afforded by the Wallace Line).                                           
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Michael Heads wrote:            
     The trans-Atlantic pattern can be approached in the broader context
of the main rodent clades. It has to be explained together with
the fact that Hystricomorpha are not in Madagascar and are east
only to Borneo (cf. strepsirhines), while Sciuromorpha (squirrels) are
not in Madagascar and east only to Sulawesi (cf. haplorhines). Many
authors have commented on the absence of these groups from both
Madagascar and Australasia (cf. woodpeckers etc.). An
overall dispersal account for the rodents doesn't really explain
these interesting eastern limits in two of the three main rodent
groups, or their repetition in the primates and others.