[Taxacom] Woodpeckers: If any got to Madagascar, they were probably too late

[John Grehan]

From: John 
> Given that the separation of Madagascar from Africa occurred long before the appearance of any of the orders of > terrestrial mammals that now occur there, I think we can assume over-water dispersal as the source for those > faunas.
 
> Huh? How do you come to that conclusion?

> Madagascar separated from African in the Jurassic. The first appearances of Rodentia, Afrosoricida, Primates and 
> Carnivora in the fossil record are much later than this.
 
Here is a nice, crystal clear representation of the earliest fossil as the actual age of origin. Someone else on the list said that biologists were no longer thought this way, but apparently not.
 
>  Until there is evidence that these mammalian orders were around at the time of separation, and thus potentially present > in what would become two separate areas, dispersal seems to be the only option.
 
This seems nonsensical since fossils do not preclude earlier origin, and as for evidence there is biogeographic evidence.
 
>   Exclusive of Palawan, which was connected to Borneo during the Pleistocene, and whose mammal fauna is very 
> similar to that of Borneo, the ancestors of the mammals on all the other islands had to get there by over-water 
> dispersal. 
 
How do you know that this had to be the case?

> Excluding Palawan, all the other Philippine islands are volcanic and have never been connected to any "mainland". 
 
Well they said the same kind of thing about the Galapagos. Just because an island is volcanic this does not have any automatic meaning for the origin of its biota as Heads has extensively documented.
 
During
 > the low sea level periods in the Pleistocene, many of the islands were connected to each other (e.g. "greater Luzon,
 > greater Mindanao"), but the straits between these larger islands and the "mainland" of the Sunda shelf are deep water 
> channels that would have remained even at the lowest sea level.
 
Or the organsims are much older than the Pleistocene.
 
> In that case, the parasite faunas are very similar to those of the presumed mainland source region (Borneo, 
> Sundaland, possibly Sulewesi); no lineages missing & only a few obvious host shifts. The difference between this
 > fauna and that of Madagascar possibly relates to age and the distance over which the original dispersers had to 
> travel; i.e. It was apparently much harder to get to Madagascar from Africa and survive.
 
> Or it JUST relates to survival.
 
> I suppose one can always posit that a taxon got to an area and went extinct without leaving any record. I don't know how 
> that might be tested. - Barry
 
Well, biogeography might provide one test. 

> -So many mites, so little time!
But so much (biogeographic) space!
 
John Grehan


Barry M. OConnor                    phone: 734-763-4354
Curator & Professor                 fax: 734-763-4080
Museum of Zoology                 e-mail: bmoc at umich.edu
University of Michigan
1109 Geddes Ave
Ann Arbor, MI 48109-1079