[Taxacom] Overdoing vicariance again? (tree shrews)

[Michael Heads]

Hi Ken,

The biogeography of gibbons is a fascinating subject. You wrote:
'Chatterjee, 2006, has a very nice map (Figure 3) for gibbon evolution and
dispersal, and it shows gibbons also having a proposed center of origin in
Yunnan Province (and then dispersal both to the south and to the west)'.

This map (the paper is available free at researchgate) is not a good
place for a student to start with, as it doesn't show the actual
distributions, only the *theorised* centre of origin and dispersal routes.
The very precise allopatry among three of the four gibbon genera (Hoolock,
Hylobates and Nomascus) is not mentioned, let alone mapped. This is a good
example of 'plug-and-play' biogeography - you don't need to look at
the distributions, just run a program.  (For an actual distribution map of
the gibbons, see Fig. 5.22 in my Tropics book).

The three allopatric gibbon genera meet at a point in western Yunnan near
the China-Burma border, and the same point is also important in the
distribution of many other groups, as a break zone and a boundary. Other
primate examples include langurs and odd-nosed colobines (Figs. 5.19,
5.21). A very simple model that explains the allopatry among the three
gibons and also among the other groups (all at the same point) is a single
vicariance event. The fourth and final gibbon genus, Symphalangus of
Sumatra and the Malay Pen., overlaps part of the range of Hylobates, and so
a singe dispersal event is indicated there. In contrast, Chatterjee's model
proposes 23 dispersal events, for the gibbons alone. She didn't consider
the countless other groups with the same biogeography, and
these will require 1000s of further events.

Van Ngoc Thinh et al (2010 BMC Evol Biol 10, e74) included a nice map of
the gibbons. Like Chatterjee, they proposed a centre of origin: 'gibbons
most likely originated on the Asian mainland, because all four gibbon
genera occur there'. But again, the striking allopatry of the genera there
is not mentioned or examined. Their model requires  'a complicated
biogeographic pattern leading to the current distribution of gibbon taxa'.

Rather than arguing about vicariance vs dispersal, running the usual
programs such as DIVA, DEC etc., I think it's more interesting and
productive to have a close look at the actual data, especially
distributions in and around areas such as the Hengduan Mts of western
Yunnan.  I'd encourage keen young naturalists not to bother with the
academic debates, and instead to read the primary taxonomic accounts that
have already been published, and then head straight for the field. Areas
such as the Hengduan Mts, the 'tarsier belt' on the islands between
Sulawesi and the Philippines, and the islands off western Sumatra are
already known to be important for primates, and so are guaranteed to be
rich veins for new discoveries in less-studied groups.

On Fri, Jun 29, 2018 at 6:23 AM, Kenneth Kinman <kinman at hotmail.com> wrote:

> Dear all,
>
>       Chatterjee, 2006, has a very nice map (Figure 3) for gibbon
> evolution and dispersal, and it shows gibbons also having a proposed center
> of origin in Yunnan Province (and then dispersal both to the south and to
> the west).  The only major difference for tree shrews is that Anathana went
> further west.
>
>        Anyway, John's constant use of the phrase "chance dispersal" ad
> nauseum is like listening to a broken record.  The same with "imaginary
> centers of origin".  Everything he doesn't like is imagined or just
> chance.   Perhaps he should criticize Heads for an imagined "widespread
> proto-Scandentia".   Therefore, I won't be wasting any more time responding
> to his posts.
>
>               ------------Ken
>
> P.S.   For anyone interested, Chatterjee's Figure 3 can be found in his
> 2006 article on gibbons here:  https://link.springer.com/
> article/10.1007/s10764-006-9044-1
>
>
> ________________________________
> From: John Grehan <calabar.john at gmail.com>
> Sent: Thursday, June 28, 2018 9:49 AM
> To: Kenneth Kinman
> Cc: taxacom
> Subject: Re: [Taxacom] Overdoing vicariance again? (tree shrews)
>
>
> Thanks Ken for outlining your perspective on tree shew biogeography as it
> illustrates quite well the traditional dispersalist paradigm as first
> proposed by Darwin and dominating biogeography ever since (and especially
> in its molecular clock version). As noted below, Ken asserts belief in a
> limited center of origin for widespread allopatry, the center of origin
> being determined by one or other criteria that are imagined to represent
> the imagined center of origin. So this is a nice illustration of the
> different perspectives in biogeography.
>
> “I believe dispersal was the dominant factor …….And I especially see no
> compelling evidence of a "widespread proto-Scandentia" splitting up as a
> "simple vicariance".
>
> This observation is fine as a personal opinion. Heads has presented the
> spatial evidence for a vicariance understanding of the distribution (which
> is also consistent with patterns of allopatry of other groups in the
> region) and it is for every reader to determine for themselves.
>
> “A more limited center of origin followed by dispersals seems more
> probable (and also more interesting).”
>
> When it comes to asserting probability then it would be desirable to know
> the basis for that. Whether vicariance or chance dispersal is considered
> more ‘interesting’ has no bearing on what actually happened.
>
> “ It looks like tree shrews most likely had their center of origin in or
> near the area of Myanmar or Yunnan Province (China).  The oldest known
> fossil tree shrew (Ptilocercus kylin of the Early Oligocene) was recently
> discovered in Yunnan (note: whether or not the older Eodendrogale fossil is
> a tree shrew is controversial).”
>
> What Ken is introducting here is one of the several contradictory criteria
> that have been invented to identify the imaginary center of origin. The
> location of the oldest fossil has historically been invoked as being or
> approximating the center of origin. Trouble here is that the location of
> the oldest fossil only denotes the location of the oldest fossil. The rest
> is invention
>
> “The dispersal of Ptilocercus southward towards Borneo could very well
> have begun early in the Cenozoic since it split off so early.”
>
> The dispersal is invented based on location of the oldest fossil imagined
> to represent the imagined center of origin.
>  “Dendrogale and Tupaia would have expanded southward much later.
> Anathana instead dispersed westward into India.”
>
> All imagined stories based on a misunderstanding of what the location of
> the oldest fossil actually informs.
>
> “So I don't see any need to invoke "simple vicariance" (much less a
> widespread proto-Scandentia) in a case where there was a combination of
> both vicariance and dispersal (perhaps a lot more of the latter than the
> former).”
>
> Heads illustrated the fact that the patterns of allopatry and sympatry
> were consistent with original allopatry followed by some subsequent range
> overlap. Naturally if one wishes to invoke a center of origin followed by
> chance dispersals to get the current distributions that is certainly an
> alternative, but not one based on any empirical evidence as Ken’s argument
> has showed – in my opinion.
>
> John Grehan
>
>
> On Thu, Jun 28, 2018 at 7:48 AM, Kenneth Kinman <kinman at hotmail.com
> <mailto:kinman at hotmail.com>> wrote:
> Dear All,
>
>        Heads (2012) says "Tupaia has expanded its range to overlap that of
> the two basal genera, and the two basal genera
> themselves show minor overlap, but apart from this, the biogeography of
> the Scandentia genera reflects their original evolution by simple
> vicariance."  And he makes reference to a "widespread proto-Scandentia".
>
>       Although I would agree with Heads that there was some vicariance
> involved in the evolution of tree shrews, I believe dispersal was the
> dominant factor (dispersal over land or temporary land bridges, but no
> evidence of any transoceanic dispersal in this case).  And I especially see
> no compelling evidence of a "widespread proto-Scandentia" splitting up as a
> "simple vicariance".  A more limited center of origin followed by
> dispersals seems more probable (and also more interesting).
>
>        It looks like tree shrews most likely had their center of origin in
> or near the area of Myanmar or Yunnan Province (China).  The oldest known
> fossil tree shrew (Ptilocercus kylin of the Early Oligocene) was recently
> discovered in Yunnan (note: whether or not the older Eodendrogale fossil is
> a tree shrew is controversial).  The dispersal of Ptilocercus southward
> towards Borneo could very well have begun early in the Cenozoic since it
> split off so early.  It was presumably well-established across a large area
> before those other genera began to split away from one another.
>  Dendrogale and Tupaia would have expanded southward much later.  Anathana
> instead dispersed westward into India.
>
>       Therefore, the present distribution of the basal genus Ptilocercus
> is probably just a relict of a much broader distribution before genus
> Tupaia later won the competition for much of that broad territory.
> Dendrogale no doubt lost territory to Tupaia as well.   Anathana met no
> such competition once it expanded into southern India (although it was
> perhaps competition that eliminated it from the territory where it
> originated).  Lucky break for Anathana that India had crashed into Asia
> earlier.    Tupaia vs. Ptilocercus (and Dendrogale) have probably managed
> to coexist where they do because Ptilocercus and Dendrogale are more
> arboreal than Tupaia, and Ptilocercus is the only tree shrew that is
> nocturnal.
>
>       So I don't see any need to invoke "simple vicariance" (much less a
> widespread proto-Scandentia) in a case where there was a combination of
> both vicariance and dispersal (perhaps a lot more of the latter than the
> former).  As with primates, I think that male aggression could have played
> a role in Tupaia's expansion at the expense of Ptilocercus and Dendrogale.
> But in the case of tree shrews, it was the younger genus Tupaia that
> largely prevailed, probably because it dispersed over land (not a chance
> dispersal over water).  And also the fact that Tupaia species are mostly
> larger and heavier (and have longer, sharper claws) would tend to make them
> physically dominant.  I would predict that carefully designed studies would
> provide evidence of this,  But unfortunately, the research that has been
> done regarding Tupaia aggression has been on conspecific males.  Research
> on Tupaia males vs. Ptilocercus or Dendrogale males would be more helpful
> and interesting.
>
>                         ---------------Ken
>
> P.S.   Anyway, I found Roberts et al. (2011) to be much more informative,
> so here is a weblink to that paper  ( http://linkolson.org/research/
> publications/My%20pubs/Roberts%20et%20al.%202011.pdf ).
>
> And here is a weblink to the paper describing the earliest known fossil
> tree shrew:  https://www.nature.com/articles/srep18627
>
> ________________________________
> From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu<mailto:taxacom-bounces@
> mailman.nhm.ku.edu>> on behalf of John Grehan <calabar.john at gmail.com<
> mailto:calabar.john at gmail.com>>
> Sent: Tuesday, June 26, 2018 3:24 PM
> To: taxacom
> Subject: [Taxacom] tree shrew vicariance and tectonics
>
> Below and excerpt (allowing for typos) from Heads (2012) for those curious
> about the relationship between vicariance and tectonics. A nice
> illustrative example for the Scandentia (tree shrews) showing patterns of
> vicariance and dispersal (sympatry) in tree shew distribution and phylogeny
> show tectonic concordance and evidence of primary allopatry as the result
> of vicariance. Sorry not to be able to reproduce the map here.
>
> "The Southeast Asian order Scandentia (Fig. 5-17) is closely related to
> primates (Fig. 5-1). In the main clade of Scandentia (Olsonet al., 20005),
> Anathana (Indian Plate) is allopatric with its sister group Tupaia
> (Eurasian plates) + Urogale (Philippine mobile belt). These breaks
> correlated with the India/Eurasia plate boundary and the Eurasia
> plate/Philippine mobile belt boundary. Olsen et al. (2005: 666) wrote that
> the circumstances leading to the disjunction between Anathana and the other
> genera across the Bay of Bengal “remain a mystery fo which our results
> offer no clear explanation.” The same break occurs in lorisid primates
> (Fig. 5-18) and could be the result of vicariance. As Olson et al. (2005:
> 668) noted, the absence of Scandentia from such proximatee islands as the
> Andamans “suggests severe limitations to overwater dispersal [and]
> vicariance can almost certainly be assumed to have played a prominent role
> in the past diversification and resulting distribution of tree shrews.” The
> same conclusion is reached here for primates.
>
> The two basal clades in the Scandentia, Ptilocercus and Dendrogale, have
> different overall distributions but meet and overlap in Borneo. The main
> clades in the widespread Tupaia also have their main breaks in Borneo:
>
> Tupaia group 1: Borneo species basal to others which range to Nepal.
> Tupaia group 2: Borneo species basal to others which range to Thailand>
> Tupaia group 3: (T. gracilis): Borneo.
>
> Although these phylogenetic breaks all involve Borneo, this does not
> necessarily imply a center of origin there. (Likewise, the oldest fossils
> of Scandentia are found in Thailand, but this does not necessarily mean the
> area was a center of origin). Borneo is a geological composite, and several
> clades may have been juxtaposed there with terrane accretion of
> differentiated during accretion. Thus Borneo – or rather the terranes that
> became Borneo – could represent sites of differentiation in an already
> widespread proto-Scandentia. The distribution of Ptilocercus is centered on
> the Riau (Riouw) Islands region (off Singapore), while that of Dendrogale
> is based further north around the central South China Sea, and the two are
> almost completely allopatric. (The South China Sea basins opened with the
> Late Cretaceous and Cenozoic rifting of continental crust). The allopatry
> of the two genera suggests early zones of differentiation around the two
> regions before the opening of the South China Sea and before the plate
> boundary breaks in Anathana/Tupaia/Urogale. Within Borneo, Ptilocerus and
> Dendrogale are restricted to the north and northwest of the island (north
> of the Lupar line, cf. Heads, 2003, and west of the Mangkalihat terrane).
> Within this region they remain largely allopatric. Tupaia has complex
> diversity in different parts of Borneo, including the south and east, and
> so perhaps this was its original sector in “Borneo”. When the terranes of
> Borneo were juxtaposed, so were the genera. Tupaia has expanded its range
> to overlap that of the two basal genera, and the two basal genera
> themselves show minor overlap, but apart from this, the biogeography of the
> Scandentia genera reflects their original evolution by simple vicariance.
> _______________________________________________
> Taxacom Mailing List
> Send Taxacom mailing list submissions to: Taxacom at mailman.nhm.ku.edu<
> mailto:Taxacom at mailman.nhm.ku.edu>
>
> _______________________________________________
> Taxacom Mailing List
> Send Taxacom mailing list submissions to: Taxacom at mailman.nhm.ku.edu<
> mailto:Taxacom at mailman.nhm.ku.edu>
>
> http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
> The Taxacom Archive back to 1992 may be searched at:
> http://taxacom.markmail.org
> To subscribe or unsubscribe via the Web, visit:
> http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
> You can reach the person managing the list at:
> taxacom-owner at mailman.nhm.ku.edu<mailto:taxacom-owner at mailman.nhm.ku.edu>
>
> Nurturing Nuance while Assaulting Ambiguity for 31 Some Years, 1987-2018.
>
> _______________________________________________
> Taxacom Mailing List
> Send Taxacom mailing list submissions to: Taxacom at mailman.nhm.ku.edu
>
> http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
> The Taxacom Archive back to 1992 may be searched at:
> http://taxacom.markmail.org
> To subscribe or unsubscribe via the Web, visit:
> http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
> You can reach the person managing the list at:
> taxacom-owner at mailman.nhm.ku.edu
>
> Nurturing Nuance while Assaulting Ambiguity for 31 Some Years, 1987-2018.
>



-- 
Dunedin, New Zealand.

My books:

*Biogeography and evolution in New Zealand. *Taylor and Francis/CRC, Boca
Raton FL. 2017.
https://www.routledge.com/Biogeography-and-Evolution-in-New-Zealand/Heads/p/book/9781498751872


*Biogeography of Australasia:  A molecular analysis*. Cambridge University
Press, Cambridge. 2014. www.cambridge.org/9781107041028


*Molecular panbiogeography of the tropics. *University of California Press,
Berkeley. 2012. www.ucpress.edu/book.php?isbn=9780520271968


*Panbiogeography: Tracking the history of life*. Oxford University Press,
New York. 1999. (With R. Craw and J. Grehan).
http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC
<http://books.google.co.nz/books?id=Bm0_QQ3Z6GUC&dq=panbiogeography&source=gbs_navlinks_s>