[Taxacom] Long distance dispersal of Amborella's ancestors

Tue Dec 11 12:16:43 CST 2018

        Well, the pollen of Amborella is pretty distinctive (even from the somewhat similar pollen of Austrobaileya).  If your ancestral angiosperm was "global", surely some very similar fossil pollen (with the convoluted tectal elements) would have been found somewhere.
           The lack of such pollen evidence is much less of a problem to explain for me.  It would probably only exist in a more restricted area, probably some part of eastern Australia during the Mesozoic or earliest Cenozoic.  Once such pollen is found, a more intensive search for body fossils in that area would be warranted.
                     ----------------Ken
________________________________
From: John Grehan <calabar.john at gmail.com>
Sent: Tuesday, December 11, 2018 11:44 AM
To: Ken Kinman
Subject: Re: [Taxacom] Long distance dispersal of Amborella's ancestors

It gets a bit problematic when one demands that there has to be a particular kind of pattern for a particular process ('surely'). What would constitute evidence of any global distribution for an extinct taxon - fossils in every locality across the world? If so, then one is not likely to find that, more a problem with fossils than actuality.

Ken's model is that Amborella lived somewhere else before it 'arrived' in New Caledonia. This is a common explanation for the occurrence of basal endemics being absent from other regions. In this case it would require that the common ancestor of angiosperms diverged into Amborella somewhere else, and then Amborella dispersed to New Caledonia before becoming extinct somewhere else (and without a fossil record). Presumably other angiosperms came later, without their relatives becoming extinct. This is all well and good as a theory, but it is one that is necessary unless one want's to ignore the fact that distributions in general are tectonically correlated and the appeal to chance dispersal has no driving empirical imperative.

There are lots (maybe tons) of other distribution patterns involving a localized sister taxon. In New Zealand there is the micro moth family Mnesarchaeidae which is the sister group to all other ghost moths which collectively has a near global range (with some geologically pertinent exceptions), including New Zealand. The same vicariance model applies with the common ancestor (now represented by the clade Exoporia) diverging into the ancestor of Mnesarchaeidae in an area that is now New Zealand, and the ancestor of Hepialoidea more widely ranging. It is possible that eruption of the Large Silicic Province about 135 Ma provided the vicariance mechanism and Hepialoidea subsequently expanded its range to overlap Mnesarchaeidae prior to separation of Zelandia. Interestingly one researcher who denounced panbiogeography as non-science has accepted this model for the Mnsarchaeidae (as a personal communication, so it will be interesting to see what is published in due course).

John Grehan

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On Tue, Dec 11, 2018 at 12:26 PM Kenneth Kinman <kinman at hotmail.com<mailto:kinman at hotmail.com>> wrote:
Dear All,
       Are such simple panbiogeographic explanations actually just simplistic?  If there was a "global ancestor" of angiosperms that then split, where is the evidence?  Surely some trace of this ancestor would have been discovered if it was global.
       Seems to me that the real (and more important) question is where the Amborella ancestor lived before it arrived in New Caledonia in the mid-Cenozoic.  Most likely somewhere in Australia where it later became extinct when its habitat dried up.
                       ----------------------Ken
________________________________
 In John's response (apparently from the Heads article):
"Yet the origin of Amborella can be explained simply if a global ancestor split into
a New Caledonia clade and its sister found in the
rest of the world. This was followed by invasion of
New Caledonia by the sister group. The persistence of
Amborella in New Caledonia through the Paleogene flooding
can be explained most simply by the same process of
metapopulation dynamics that has allowed survival in other
groups."

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On Tue, Dec 11, 2018 at 9:37 AM Kenneth Kinman <kinman at hotmail.com<mailto:kinman at hotmail.com>> wrote:
Dear All,
        I was reading an interesting 2015 article on fruiting in Amborella of New Caledonia.  It offers hypotheses about how fruits (or seeds) of this ancient angiosperm's ancestors probably arrived in New Caledonia by avian dispersal, but have now lost such dispersibility during evolution on the island.  Here are two quotes from the paper followed by a weblink to the paper:

 "Another hypothesis to explain the particular fruiting cycle of A. trichopoda might refer to one of the “insular syndromes” described by Sir Sherwin Carlquist: the loss of dispersibility in island plants (Chapter 11 in Carlquist 1974<https://link.springer.com/article/10.1007/s10265-015-0744-5#CR001>). The flora of oceanic islands must have arrived by long-distance dispersal, yet, during evolution on the island, some groups may have naturally lost dispersibility."

"The original dispersing bird species might no longer be present in New Caledonia as many extinctions/extirpations of bird species have been shown to have occurred in the last 4,000 years subsequently to the arrival of Melanesian settlers (Balouet and Olson 1989<https://link.springer.com/article/10.1007/s10265-015-0744-5#CR5>; Pascal et al. 2006<https://link.springer.com/article/10.1007/s10265-015-0744-5#CR35>). The hypothesis of a pre-human extinction of the avian disperser(s) of A. trichopoda, while not proven, also remains open."

Here's a weblink to the article:

https://link.springer.com/article/10.1007/s10265-015-0744-5

------------------------------Ken Kinman

________________________________
From: Michael Heads <m.j.heads at gmail.com<mailto:m.j.heads at gmail.com>>
Sent: Monday, December 10, 2018 6:33 PM
To: Ken Kinman
Cc: Taxacom
Subject: Re: [Taxacom] New Caledonia as a classic lesson in dispersal

Hi Ken,

The problem with the Nattier paper is that the approach they used, long distance dispersal theory, didn't work; it did not
explain critical groups such as the New Caledonian endemic Amborella, sister to all other angiosperms. Dispersal theorists
concluded that the group remains ‘puzzlingly enigmatic’ (Grandcolas et al., 2008, p. 3312) and ‘paradoxically difficult to
interpret’ (Nattier et al., 2017, p. 6).

Michael

On Tue, Dec 11, 2018 at 3:09 AM Kenneth Kinman <kinman at hotmail.com<mailto:kinman at hotmail.com><mailto:kinman at hotmail.com<mailto:kinman at hotmail.com>>> wrote:
Dear All,
         The paper by Nattier et al. (2017) is definitely worth reading.  Here is a weblink to that article:
                         https://www.nature.com/articles/s41598-017-02964-x

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