[Taxacom] Juan Fernandez

Wed Jun 1 17:40:16 CDT 2011

Hi Richard,

There is no difference between stepping-stone dispersal and long-distance jump dispersal. These both refer to a model of speciation and distance is irrelevant. The key factor is 'chance' (in the pre-Fermat-Pascal sense), not distance. The model is used to explain differentiation on both sides of a river or on both sides of an ocean basin or continent. Normal ecological movement is a different concept and is discussed in different journals by autecologists rather than systematists. They calculate probabilities of diaspore movement using actual data (i.e. 'chance' in the post-Fermat-Pascal sense). 

What are your views on the (Australasia + Juan Fernandez) (South America) pattern, as seen in bryophytes, shorefishes etc.?

Michael 

Wellington, New Zealand.

My papers on biogeography are at: http://tiny.cc/RiUE0

--- On Thu, 2/6/11, Richard Zander <Richard.Zander at mobot.org> wrote:

From: Richard Zander <Richard.Zander at mobot.org>
Subject: RE: [Taxacom] Juan Fernandez
To: "Michael Heads" <michael.heads at yahoo.com>, taxacom at mailman.nhm.ku.edu
Received: Thursday, 2 June, 2011, 9:43 AM

What are you guys talking about? What is the exact difference between jumping between stepping stone islands and jumping across a larger distance? How far is too far? 50 km? 500 km? And please please don't duck it by saying it is different for each species. 

_______________________

Richard H. Zander
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166 U.S.A.
richard.zander at mobot.org

From: taxacom-bounces at mailman.nhm.ku.edu on behalf of Michael Heads
Sent: Wed 6/1/2011 4:38 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Juan Fernandez

Hi John and Tod,

The most interesting aspect of the Juan Fernandez + Desventuradas area is not so much the endemic families Lactoridaceae and Thyrsopteridaceae, as these were formerly widespread. The real problem is the great similarity of the islands' biota with Australasia and Polynesia, and the great biotic break between the islands and adjacent mainland Chile. You cited angiosperms (you could add Mida, Santalum etc.), but many species of mosses and shorefishes are in Australasia and Juan Fernandez, but are not on South America. As far as I know, there has been no modern study of the break or the reason for it. A survey of invertebrates would be especially valuable.

In his discussion of Juan Fernandez, Moreira-Munoz (2011. Plant geography of Chile. Springer, Dordrecht) stressed the closer affinity with Australasia and the break with South America. Here's a quote from the conclusions (p. 169):  
'islands might instead ‘inherit’ flora and fauna from prior volcanic islands in the
same region” (Heads 2009, p 236). Heads (2009) exemplifies his proposal with
Fitchia (Asteraceae) a small tree endemic to montane forests in SE Polynesia.
The genus has “presumably survived as a metapopulation on the volcanic islands
and atolls which have come and gone around the Cook Islands/Tokelau and other
localities in SE Polynesia. Its ancestors may date back to the origin of the Pacific
plate and the Cretaceous plateaus” (Heads 2009, p 236). A similar history can be
hypothesized for the small trees Robinsonia, Dendroseris, Yunquea, endemic to Juan
Fernández, and Thamnoseris and Lycapsus endemic to the Desventuradas Islands.
These Asteraceous genera could be the remnants of a more “ancient Asteraceous
world” related to the origins of the Pacific plate'.

Michael

Wellington, New Zealand.

My papers on biogeography are at: http://tiny.cc/RiUE0

--- On Thu, 2/6/11, John Grehan <jgrehan at sciencebuff.org> wrote:

From: John Grehan <jgrehan at sciencebuff.org>
Subject: Re: [Taxacom] We're on a road to nowhere
To: "Taxacom" <taxacom at mailman.nhm.ku.edu>
Received: Thursday, 2 June, 2011, 2:22 AM

Dear John,

  As we have worked in the Juan Fernandez Islands for 30 years, I would be

interested to learn what the "biotic features" are that suggest the biota is

not completely "oceanic."  Any thoughts on this?

Regards,

Tod

T. Stuessy

Vienna, Austria

Tod,

My observation did not stem from Head's comments on the Lactoridaceae. I have not studied Juan Fernandez in any particular detail and so my comment only reflected my impression that the islands were part of a broad geographic structuring of distributions across the Pacific - i.e. sets of distinctive distributional relationships rather than everything being everywhere or just related to the nearest South American mainland. In this respect the islands are biogeographically continental even though the individual location is 'oceanic' and that the biogeographic position of these islands indicates that they may be stratigraphically oceanic, but biogeographically their biota is not.

My characterization of biotic features that are non-oceanic refer to the geographic structure of biotas. If one treats taxa in isolation any one case can be explained away by dispersal - which one may chose if one wants to, but only by ignoring the patterns in general as being meaningless coincidence (which is what most biogeographers do in practice).

Examples for consideration would be Abrotanella. The population of A linearifolia on Juan Fernandez (Más Afuera Island). Presumably you are aware of this example discussed by Heads who pointed out that this might be taken as evidence of long-distance dispersal from mainland South America as the exposed rocks on Más Afuera are only 1-2.4 million years old and were never joined to the mainland. He points out that the stratigraphy is less important for biogeographic analysis than the general tectonic history of the while east Pacific. But that aside, he also notes that the Chile-Juan Fernandez disjunction has its parallel in the California-Chile disjunction of Blennosperma. And then one has to take into account the distribution of Abrotanella overall, with its trans-Pacific range and tectonic correlations in the Old World along with its vicariant relationships with the trans-Pacific Blennosperma-Ischnea clade. You are presumably aware of all of this. The
 point is that Juan Fernandez here falls into a broad non-oceanic pattern of biogeography.

Heads also referred to Darwiniothamnus of Galapagos and an endemic Erigon from Juan Fernandez (JF). The paper by Andrus et al (2009) argued that Erigeron fernandezianus was the sister group to E. rosulatus of Peru and Bolivia and this clade had an unresolved relationship with the Galapagos-northern Chile and Galapagos-Greater Antilles clade, and with Conyza bonariensis (which is so widespread as a weed that its native range in Central and South America may be lost?). So again there is a geographic structure to the Juan Fernandez location with respect to the broader biological affinities. If one just proposes chance dispersal to JF then one would have to appeal to the same origin for all the rest - despite their not occurring all over the place.

And as another example is the affinitiy between Euphrasia sect Paradoxae of JF and E. sect Novaezeelandiae rather than the adjacent South American E. sect Trifidae which is closer to E. sect Anagospermae of New Zealand.

There is also the postion of JF at the eastern limit of trans-Pacific Santalum and Coporsma, its position as part of the trans-Pacific Nerterea and Orobolus. I recall that there is a penguin nesting pattern a bit like that of the range of A linearifolia - but that's just from memory.

There are no doubt plenty of other examples of showing that JF is just one station on a broad set of localities that together point to their derivation from historical geographies in the Pacific (for which there is also considerable support argued in the geological literature). In this case it may be that the biogeography provides more evidence for the origins of JF biota than the visible stratigraphy. Whatever one may believe about the origin of JF biota, its biogeographic structure is real.

This might have made a good biogeography graduate exam question!

John Grehan

-----Original Message-----
From: Tod Stuessy [mailto:tod.stuessy at univie.ac.at]
Sent: Monday, May 30, 2011 12:19 PM
To: John Grehan
Subject: Re: [Taxacom] We're on a road to nowhere

Dear John,

  Sure.  I wonder if this stems from Heads' comments about Lactoridaceae in

his Syst. Biol. article.  If so, I think that this is not a good example of

the point he was trying to make.  I have already chatted with him about it

in an e-mail.

Cheers,

Tod

----- Original Message -----

From: "John Grehan" <jgrehan at sciencebuff.org>

To: "Tod Stuessy" <tod.stuessy at univie.ac.at>

Cc: "Daniel J. Crawford" <dcrawfor at ku.edu>

Sent: Monday, May 30, 2011 2:32 PM

Subject: RE: [Taxacom] We're on a road to nowhere

Tod,

Since this stems from a public conversation on TAXACOM I will respond to

this question on the list if I may.

John

-----Original Message-----

From: Tod Stuessy [mailto:tod.stuessy at univie.ac.at]

Sent: Monday, May 30, 2011 2:59 AM

To: John Grehan

Cc: Daniel J. Crawford

Subject: Re: [Taxacom] We're on a road to nowhere

Dear John,

  As we have worked in the Juan Fernandez Islands for 30 years, I would be

interested to learn what the "biotic features" are that suggest the biota is

not completely "oceanic."  Any thoughts on this?

Regards,

Tod

T. Stuessy

Vienna, Austria

----- Original Message -----

From: "John Grehan" <jgrehan at sciencebuff.org>

To: "Taxacom" <taxacom at mailman.nhm.ku.edu>

Sent: Sunday, May 29, 2011 9:18 PM

Subject: Re: [Taxacom] We're on a road to nowhere

Of course it assumes that what we think we know about the geological history

of an 'oceanic island' is true. And 'never connected to the mainland' is

tricky anyway. Galapagos may never have had a connection to the American

mainland at any one time, but it did sequentially through the island arc

that was at one time at the Galapagos, and at another time at the American

'mainland'

The biogeography of Juan Fernandez includes biotic features that belie the

simplistic notion that its biota is all 'oceanic'.

John Grehan

-----Original Message-----

From: taxacom-bounces at mailman.nhm.ku.edu

[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Richard Zander

Sent: Sunday, May 29, 2011 3:10 PM

To: Rob Smissen; taxacom at mailman.nhm.ku.edu

Subject: Re: [Taxacom] We're on a road to nowhere

What passes for the null hypothesis of dispersalists is "if a species occurs

on an oceanic island never connected to the mainland, you can't use it as

informative in vicariance biogeography." Juan Fernandez is the usual

example.

I forget who formulated this, but it seems cogent.

ï»¿

* * * * * * * * * * * *

Richard H. Zander

Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USAï¿½ Web

sites: http://www.mobot.org/plantscience/resbot/ï¿½and

http://www.mobot.org/plantscience/bfna/bfnamenu.htm

Modern Evolutionary Systematics Web site:

http://www.mobot.org/plantscience/resbot/21EvSy.htm

-----Original Message-----

From: taxacom-bounces at mailman.nhm.ku.edu

[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Rob Smissen

Sent: Sunday, May 29, 2011 5:20 AM

To: taxacom at mailman.nhm.ku.edu

Subject: [Taxacom] We're on a road to nowhere

Despite my sympathies with Jason, I'm with Michael and John on this one.

Dispersalism is biogeographic Nihilism.

"Everything is everywhere" is the dispersalists null hypothesis. Not good

for biogeography.

But very hard to disprove!

John Grehan has dispersed to Buffalo.

Oh well.

Glad I'm not a biogeographer.

Back to taxonomy.

cheers

Rob

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