[Taxacom] competition on Peleng (actually versus two species of cuscus)

[Kenneth Kinman]

Dear all,

       I am still catching up on the changing taxonomy of the cuscuses.  Back when I was working on our 1st Edition of the reference book "Mammal Species of the World" (1st Edition, by Honacki, Kinman, and Koeppl, 1982), Strigocuscus was included within genus Phalanger, but genetic data since then has apparently shown them to be in separate subfamilies.

      In any case, although the species of Strigocuscus on Sulawesi and Peleng Island is a "pygmy" species, the other species on Peleng is a more normal size.  I had overlooked is that the bear cuscus is also on Peleng Island.  So any monkey trying to become established on Peleng Island would have faced two species of well-established species of cuscuses.

      So it is even less surprising that monkeys did not expand east of Sulawesi.  The battle ground between monkeys and marsupial cuscuses seems most intense between Sulawesi and nearby Peleng Island.  This battleground in Wallacea seems to have favored cuscus over monkeys, even though they managed to coexist on the westernmost Wallacean island of Sulawesi.  Just a matter of Sulawesi being a larger island with more competition allowing a stalemate of sorts.  Both monkeys and cuscuses survived there, but not further east, and cuscuses did not survive further west.  Something that neither Wallace's Line nor Weber's Line seems to have anticipated.

                            -----Ken Kinman

P.S. When cuscuses were first discovered they were thought to be a species monkey.  So similar to monkeys in their form, habitat, and food sources, but only the discovery that cuscuses were pouched marsupials did their true relationship become known.  I'm not sure if you could say that they are more like monkeys or lemurs.  In any case, monkeys would have met their match in both Madagascar (versus lemurs) and east of Sulawesi (versus the two species of cuscuses).


________________________________
From: Taxacom <taxacom-bounces at mailman.nhm.ku.edu> on behalf of Kenneth Kinman <kinman at hotmail.com>
Sent: Monday, June 18, 2018 8:54 AM
To: Michael Heads; taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] competition on Peleng (was: Jurassic primates???)

Hi Michael,

       Well, I was talking about monkeys in general, but even with macaques, I would think a male cuscus could take on a female macaque.  When I talk about transoceanic dispersal of primates, I am usually thinking about of a group of pregnant females.  No adult males required, as long as one or more of the females are pregnant with male offspring.

     Such a group of pregnant female monkeys landing on a small island like Peleng that has a well-established cuscus population could have a very rough time trying to get established.  If not killed by male cuscuses, the cuscuses could drive the pregnant monkeys away from the best food sources (and they just die from malnutrition).  Likewise, cuscuses haven't spread further east because monkeys were already well established there.

      Monkeys introduced by humans in New Guinea is a different story.  They get established around human habitations and then spread out from there.  And there is a lot more territory than on a small island like Peleng.

                     --------------Ken


________________________________
From: Michael Heads <m.j.heads at gmail.com>
Sent: Monday, June 18, 2018 2:09 AM
To: Kenneth Kinman
Subject: Re: [Taxacom] competition on Peleng (was: Jurassic primates???)

Hi Ken,

You say: 'Cuscuses are a very monkey-like marsupial', and suggest that they prevented monkeys from establishing east of Sulawesi.

I know cuscuses and monkeys quite well (I lived for a long time in Africa and in New Guinea) and I wouldn'y describe them as very similar at all really - for a start, the monkeys concerned (macaques) are at least twice the size of a cuscus, much smarter and much more aggressive.  But in any case, New Guinea is very rich in cuscuses and, as I mentioned, introduced monkeys have established there with no problems.

   I'm sure you can think up an ad hoc reason for that particular phenomenon, but I prefer to look at the group, and all its biogeographic boundaries, overall. As Edgar Allan Poe said, 'the ingenious are always fanciful, and the truly imaginative never otherwise than analytic'.


On Mon, Jun 18, 2018 at 2:49 PM, Kenneth Kinman <kinman at hotmail.com<mailto:kinman at hotmail.com>> wrote:

Hi Michael,

      Sulawesi and Peleng (being in the western part of "Wallacea") are an interesting battleground between the Asian and Australian faunas.  In answer to your question, I suspect that monkeys could have encountered competitive exclusion on Peleng by a combination of not only the tarsiers there, but even more so by the marsupial species Strigocuscus pelengensis.  This marsupial is also in the Sula Islands, which might also explain why monkeys didn't get into the Molucca Islands either (although a greater distance gap might also explain that).

      The other species of Strigocuscus does live on Sulawesi, but being called a dwarf cuscus, I assume it is smaller (and therefore less competitive and aggressive) than the species on Peleng.  So I would say that studying the possible battle between the cuscus marsupials and monkeys in western Wallacea (especially on Peleng) could be far more fruitful than just tarsiers vs. monkeys.  It could be a combination of both battles in this transition zone.

      The males of cuscuses in particular can be quite aggressive.  And the cuscus on Peleng (presumably being larger than those on Sulawesi and being on a much smaller island) might be the main reason any attempted monkey dispersals would fail.  Probably more so than tarsiers.  Cuscuses are a very monkey-like marsupial.

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


________________________________
From: Michael Heads <m.j.heads at gmail.com<mailto:m.j.heads at gmail.com>>
Sent: Sunday, June 17, 2018 6:31 PM
To: Kenneth Kinman
Cc: Taxacom
Subject: Re: [Taxacom] Jurassic primates???

Hi Ken,

Mesozoic mammal fossils are very different from modern groups, and their affinities are often very controversial or simply admitted as unknown. If modern morphological work identified the phylogenetic position of groups such as cetaceans incorrectly - when the vast wealth of morphological information was available from complete specimens - isn't it very likely that they have misidentified many, fragmentary Mesozoic fossil groups in which the key features are not preserved?

Did you see the lizard paper I mentioned (pushing back dates by 75 m.y.)? Do you agree with my earlier statement that Goswami & Upchurch's reasoning is illogical (they wrote that fossils provide minimum ages, but then treated the fossil age of eutherians as a maximum age for primates)? Also, you haven't said which examples of vicariance you accept.

Some other 'extraordinary' evidence for primates:
Monkeys are diverse on Philippines/Sulawesi, but they reach their limit there and are entirely absent from islands to the east, such as Peleng, 20 km off eastern Sulawesi, the Moluccas etc. If monkeys dispersed across the Atlantic long after it opened, why would a 20 km strait block their dispersal?

Peleng is a small island, so you might think that large monkeys could not exist there. But macaques are famously 'weedy' and Peleng is the same size as Zanzibar (30 km off the African mainland), which has endemic monkeys.

You might hypothesize that the tarsiers on Peleng prevented the monkeys from establishing there by competition, but monkeys and tarsiers overlap through most of the tarsiers' range.

You might suggest that islands east of Philippines/Sulawesi are ecologically unsuitable for some other reason, but monkeys introduced to Palau and to western New Guinea have thrived and are now pests.

Of course, the 'extraordinary' break between Sulawesi and Peleng could just be due to the vagaries of chance dispersal, but wouldn't it be useful to investigate other possibilities?



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