[Taxacom] Fwd: Woodpeckers, primates, as well as the Wallace Line gauntlet

[Michael Heads]

Hi Jason,
 
You say 'I am not sure why you bring albatrosses to the table'. Why not? They're a well-studied group with much local endemism as well as precise, intercontinental  connections. In other words they show a high order of geographic structure despite their staggering powers of dispersal.  They show the same patterns as land snails, onychophora and lots of other groups. 
 
JM: ''dispersal is a mathematical certainty, even if philosophically unpleasant'. MH: Using the chance aspect of dispersal to explain a pattern is not just philosophically unpleasant, it makes for very boring reading.   
 
JM: 'Not only is it too difficult to gather the data but the most vital piece of information, how many colonists left in the first place, is unobtainable. Is that why you´d rather ignore it?' MH:  I ignore data that aren't available.
 
JM: 'But you are deliberately ignoring contingency. Are you saying that biogeography should be teleological? What about history?'. I'm not ignoring contingency, I just don't use it to explain a pattern. There are many contingent aspects of distribution (a meter this way or that), and these tend to be less interesting than other aspects. I definitely do not support the use of teleology in biology, and I don't believe that eyes evolved 'in order that we could see' , as accepted by the group: neoplatonists + creationists + neodarwinians. (For a biogeographic critique of teleology, see my paper in J. Biogeogr. 36: 1018. 2009). I'm not sure what you mean by 'What about history?'. All my biogeographical explanations are 'historical'.    
 
I asked why biologists had overlooked the Musicians and preferred making up ad hoc stories for individual clades rather than studying the geology. You replied 'Ad hoc doesn´t mean making it up, it means weaving a story based on something for a purpose. The mounts are there but it is still a story'. Perhaps the main point is, does the story go anywhere? Is it interesting? Ad hoc stories don't go anywhere almost by definition. Why would dispersalists trawl the literature looking for guyots? That's the last thing they want. The guyots in the Musicians are an interesting find and I predict the discovery of many more, e.g. between Hawaii and California, as the topographies of the individual seamounts there are mapped.    
   'Ad hoc' has nothing to do with purpose, it refers to the fact that the explanation only deals with this (hoc) particular example, not broader patterns. An ad hoc explanation for the sunrise would be different for every day.  
 
JM: 'for why ignore the atolls, I would say because they didn´t fulfill the necessary ecological requirements of the species in question. Just because you have sand in the middle of the ocean it doesn´t mean that it is suitable'. 
 
MH: Of course, but that is now and we are talking about then. The point is that the atolls were once high (i.e. wet) islands. For example, the Line Islands are now all atolls but they once formed an archipelago of high islands that stretched 4000 km from SE Polynesia towards Hawaii. The great entomologist Zimmerman understood the fundamental significance of this for the Hawaiian biota in the 1950s but since the 1960s people like EO Wilson seem to have forgotten it. They think it's a fact that all Hawaii's biota arrived from America or Asia. Why would you assume this?  
 
 
JM: 'the logic here is that D. montrouzieiri montrouzieiri colonized NC too recently to develop racial or ssp differences'. 
 
MH: This assumes an evolutionary clock. There is very little evidence for this and plenty of evidence against it. At many time scales, degree of divergence is probably not related to time.  
 
JM: 'I look at Parastasia and I see a lucky vagrant'. 
 
MH: That may be because you haven't really looked closely at the geology or other, unrelated groups in the region. It's interesting! Villagers in New Guinea used to think their stone axes were fantastic for chopping down trees (it takes about a day) until they tried out machetes/bushknives/cutlasses. Everyone starts out as a dispersalist.
   You asked if I had comments on the others you mentioned. I'm happy to discuss aspects of morphology or distribution but I don't have time to look up the details - could you summarise the relevant data? For the Malagasy Aphodius, you just said: 'so similar morphologically to mainland groups that there is little doubt how they got there'. Again, degree of divergence has no necessary relationship to clade age.They established this in the 19th century. (The evolutionary clock idea was only resurrected after WWI as part of the so-called neo-darwinian synthesis - Matthew, Mayr etc.). This is not good enough evidence to base an entire case on.

   The Hawaiian Hydrophilidae sound interesting but you just mentioned there were two endemic species of Limnoxenus. Any more information? Likewise for the Australian Onthophagus and Podotenus (Aphodiinae) and Sphaenognathus queenslandicus (Lucanidae). 
 
 JM: 'Then there are the recorded captures of insects (all good fliers) far from the mainland (Cicindela trifasciata in oil rigs in the Gulf and Cicindela campestris in the North Sea (I believe)) both well over 100Km from the nearest island or coastline. Or Danaus plexippus and Vanessa virginiensis that arrive to Europe every other year (OK, they are good fliers, but it is obvious that dispersal is important for some groups)'. 

MH: I am not denying that plants and animals move. Organisms move. I've seen them. It happens all the time. Everyone knows this. What is your point exactly - that organisms move?!
 
Michael
Wellington, New Zealand.

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

--- On Wed, 1/6/11, Jason Mate <jfmate at hotmail.com> wrote:


From: Jason Mate <jfmate at hotmail.com>
Subject: Re: [Taxacom] Fwd: Woodpeckers, primates, as well as the Wallace Line gauntlet
To: "Taxacom" <taxacom at mailman.nhm.ku.edu>
Received: Wednesday, 1 June, 2011, 10:37 AM



Some thoughts on your comments.


> Hi Jason,
>  
> Every individual of every plant and animal (except in colonial organisms) has dispersed to where it is now. The problem lies in integrating that process - normal physical movement - with other processes in phylogeny and geography, especially range expansion and vicariance. The physical movement of individuals may have little or nothing to do with the distribution pattern of their clade. Jim pointed out the paradox in ferns and marine groups with pelagic larvae, and many other authors have discussed the problem. Individual albatrosses fly around the world at the drop of a hat, and yet the clades have very precise, allopatric, locally endemic, breeding ranges. Why? How? 
>  
> You write: 'I am not sure even what you mean by dispersal anymore since you brought up ecological dispersal. Is there a distance threshold that you have in mind?'. Long distance dispersal could be better termed 'chance dispersal' because the distance is irelevant. People use the concept of l.d.d. to explain differentiation across a river. The term 'dispersal' has (at least) two distinct meanings, one is normal movement, one is a mode of speciation. They may or may not be related, but they are not the same thing. 
>  Likewise, 'chance' can mean very different things. Chance in the ancient sense of Fortune, i.e. 'factors we don't understand', has never been regarded as a 'scientific' explanation (outside of biogeography), but chance in the sense of calculated probabilities is a fundamental concept in science. 
>  > You say: 'The fact that the movement of living organisms has been observed should suffice to recognize that the mechanism is probable'. Obviously movement (normal ecological dispersal) occurs - no-one is denying that. What you call 'the mechanism' , i.e. chance dispersal, is something else. 
Specific examples are always cherry-picked (I´m guilty as well), yet I am not sure why you bring albatrosses to the table. Vagrant albatrosses (and many other birds for example) are commonly seen, so obviously every year a few albatrosses get lost. But why aren´t they everywhere you ask. Well, dispersals, like mutations, are costly and lethal most of the time. So whereas a small hop between islands in an archipelago (the equivalent of a neutral mutation) is not very costly (and hence survivable most of the time) a major movement would most likely lead to death (ecological mismatch (most extreme case no island found at all), no other members found, etc). So most areas are sinks and even if a honeypot is found you still have to contend with founder effects, bottlenecks.... Maybe that´s why aptery is so common on oceanic islands? Yet amongst all these possible scenarios, where death is by far the most probable, there is a small number (maybe even only
 one) scenario with a low (how low?) probability of success. We don´t have the hard numbers of course. Not only is it too difficult to gather the data but the most vital piece of information, how many colonists left in the first place, is unobtainable. Is that why you´d rather ignore it?  It could be interesting to look at the distribution of trip length vs frequency for selected (monophyletic maybe?) groups of species in and around archipelagos. This would be one way of objectively assessing what consitutes long dispersal and maybe infer on the probability of successful dispersal. Or more Krakataus for that matter ( by 1933 290 plants, 720 insects, 4 reptiles, 41 bird and 4 mammal species had colonized it. It is obvious that insects, plants and birds are better suited to dispersal).
Finally, IMO missing information or 'factors we don't understand' is very much part of science. We know the probability that a photon will be reflected from a sheet of glass but not why or if a particular photon will reflect. And this is after 100 years of gathering data on the simplest of particles. Hence the ultimate causes of nature can be hidden from us yet a strong, predictive scientific field is possible. On the other hand complexity can generate randomness. Neural networks generating behaviours that cannot be predicted from the individual parts is an apt example, as are ecological networks. So regardless of the minuscule probability of succesful dispersal, considering the millions of species, and the incalculable number of individuals, dispersal is a mathematical certainty, even if philosophically unpleasant.
>  
> You write: 'Dispersal is one probable mechanism to account for the presence of a taxon in a place' - and vicariance is another. Dispersal in the sense of simple movement does not explain why a taxon is different from its relatives. The question: 'Why is this organism here?' has two parts: why is it *here*, and why is it *this organism* and not another. 
>You suggest: 'What happens afterwards [after dispersal] (evolution, radiation, extinction) is besides the point'. But evolution is not besides the point - it is the main focus of investigation. If there was no endemism and everything was everywhere the subject of biogeography would not exist. 
I´ll be  honest, I have no idea what you wrote here. I can understand that the niche of a species is, in a way, an extension of the phenotype or the environmental translation of it. But you are deliberately ignoring contingency. Are you saying that biogeography should be teleological? What about history? You can ask why til you go green and not get an answer with some deep philosophical meaning.  One can see general patterns in history but you can´t pick each individual story and see in it the finality of history. It has been influenced by it of course, in the same way that biotas have been shaped by vicariance, but ignoring the noise (dispersal) is looking at half the story, albeit simpler.
> You say: 'how did the taxa arrive to those recently discovered flat-topped mounts? In the end to support your particular hypothesis you are forced to resort to the same scenario-building excercise that you criticized from Kenneth'. The difference is that Ken's ideas were ad hoc, mine are based on geology. Why has no biologist even mentioned the Musicians guyots? Because they are more concerned with making up ad hoc hypotheses than with  trawling the primary literature in geology. Why did the founder of island biogeography (the most cited book in biogeography!) completely ignore not only the seamounts between Hawaii and the mainland as a possible center of origin, but also all the atolls (former high islands)? 
>  
> To answer your question: the taxa on the Musicians islands (before they sank) arrived there by the same processes that taxa arrived in Hawaii - by normal ecological movement from other nearby islands that no longer exist.   

Ad hoc doesn´t mean making it up, it means weaving a story based on something for a purpose. The mounts are there but it is still a story. As for why ignore the atolls, I would say because they didn´t fulfill the necessary ecological requirements of the species in question. Just because you have sand in the middle of the ocean it doesn´t mean that it is suitable. Also I like how movements between islands (even remote ones) can be normal. And the Musician islands are aptly named, like musical chairs. ;)
>  
> I asked for examples of chance dispersal, 'horrendous dispersers that have indeed made it', and you cited Aphodius holderi. I looked this up and apparently it was the most abundant dung beetle in Britain and other parts of Eurasia during the colder parts of the last glaciation, but now restricted to a very small area in the high plateau of Tibet. Where is the chance dispersal? Its range expands and contracts with climate (not chance). 

Chance is where it ends up. Surely the mountain ranges along the way could have been equally suitable? After all its companion in frozen Ol´Blightey found the mountains in Spain suitable (which begs the question, why not the Pyrenees, the Alps or the Caucasus or any of the ranges all the way to the Himalayas?). I just see chance all along. Any comments on the others?
> In another example, you say that in New Caledonia 'there are 3 species which appear to have arrived on their own "recently" (collected by Montreuzier in the 1850´s): Parastasia percheroni (Rutelinae), Dipelicus montrouzieri (Dynastinae) and Cyphopisthes sp (Cerathocanthidae)'.  
> I've just found the information - it's in Paulian's 1991 book on Scarabaeoidea of New Caledonia (Google books). He thought that New Caledonian endemics have usually followed the Solomons-Vanuatu route. So he argued that Dipelicus must be a relatively recent introduction because it was related to things in Australia and New Guinea, while the Solomons/Vanuatu form is distinct. The logic here is very obscure.  Cyphopisthes is 'Indo-Malayan'. Paulian seemed to think that this distribution also means dispersal - why? 

Dipelicus montrouzieiri is found In PNG and Australia , Solomon Islands, NC and New Hebrides, but three ssp occur: the montrouzieiri montrouzieiri in PNG, Australia and NC, Dipelicus m. oryctoides in New Hebrides and Dipelicus m. salomonensis. D .montrouzieiri is part of a group of 5 closely related species (genitalia very similar, males clearly different) which occur in the Bismarck (alveolatus, triangularis, integriceps), Moluccas (alveolatus), PNG (alveolatus, triangularis, integriceps, bowilli), Australia (integriceps, bowilli, optatus, duples). Another 12 species also occur from India to Java. So the logic here is that D. montrouzieiri montrouzieiri colonized NC too recently to develop racial or ssp differences.  
Regarding Cyphopisthes, only one specimen available and I haven´t examined it myself so I am going on Paulian here.
> Parastasia occurs in India, Indonesia, New Guinea, and (with P. perchoneri) New Caledonia/Vanuatu. Why did Paulian think this is dispersal? (or recent?). P. perchoneri ('bien distincte') is related by Paulian to forms of Woodlark Island and this area of endemism (New Caledonia plus the tip of the 'tail' of New Guinea, 1500 km away), is one of the most intriguing patterns anywhere (see my paper in J. Biogeogr. 37: 1179. 2010). The tectonics are incredibly dynamic, complex, and controversial, but at least the geologists are hard at work on it, while the biogeography is hardly ever mentioned, and when it is, it's just 'chance'.  Things may be changing though. Metzger et al. (2010, Mol. Phylogen. Evol.) attributed disjunction between Woodlark and the Louisiades in elapid snakes to the opening of the Woodlark Rift.      

Parastasia´s range covers China, India, Malaya, Indonesia, North America and a couple of species make it into PNG and P. percheroni PNG, NC, Australia (QLD) and Vanuatu. In addition the rest of Parastasina is Oriental, not Oceanian (Australia has its own ruteline groups which it shares with South America but not Parastasina) . I have no doubt that NC´s geology is complex, yet I look at Parastasia and I see a lucky vagrant. 
You make no comment on the Malagasy Aphodius, the Hawaiian Hydrophilidae or the butterfly examples, to which i would also like to add the Australian Onthophagus as a case of dispersal. But to make it up, you may want to look at Podotenus (Aphodiinae) and Sphaenognathus queenslandicus (Lucanidae) as some impressive South American vicariant genera.
Best
Jason


                          
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