Talk:Insular dwarfism

comment

Hmmm...I agree about the merger. They seem to be different versions of the same thing, and except for the list of examples, Insular dwarfism has a more developed explanation and is an actual name for the process. --Kaz 21:50, 12 June 2006 (UTC)

"Human beings along the islands off the coast of India, especially Homo floresiensis" is misleading? Homo floresiensis was found in Flores, Indonesia

Presentation of the article

In the beginning of the article "when their gene pool is limited to a very small environment" does not seem to make much sense. Could somebody fix this so that one actually gets some sensible idea of what insular dwarfism is about. —Preceding unsigned comment added by 203.143.165.107 (talk) 04:42, 15 August 2008 (UTC)

Balance

I was talking to a paleontologist today, and he told me that actually there is an optimal size for woods mammals (about a small dog) and another for plains mammals (like a four-legged human). However species diverge from these sizes when there are other factors besides energy balance. The example he put was elephants who are big to defend themselves from predators. If an elephant species is left alone in an island it evolves towards the optimal size, hence the dwarfism. If it is a small species who becomes isolated, we'll have insular gigantism.

Did I understand it right? Should this theory appear in the article? --Error 23:32, 11 November 2006 (UTC)

We should hold off on inserting this into the article until we see more examples of it in scientific literature. Or at least until we come across a layperson-friendly translation--Mr Fink 02:08, 12 November 2006 (UTC)

There are a couple of theories like this floating around - for instance, I was just reading a paper (Brown, J., Marquet, P.A. and M.L. Taper. 1993. Evolution of body size: consequences of an energetic definition of fitness. American Naturalist 142(4):573-584) where the authors hypothesize that the optimum body size for mammals is about 100 grams, based on a trade-off between metabolism (larger animals have relatively lower metabolic rates) and the "cost" of an offspring (where smaller animals can make offspring more cheaply). In other words, if you're too big, it's easier to accumulate energy, but your offspring are more expensive to make; if you're too small, offspring are cheap but you have to forage constantly just to keep yourself alive. If there are other ecological factors involved - predators driving you to defend yourself, or similar-sized competitors that eat the same things you do - there may be some degree of selection away from this optimum size, but in the absence of those other factors organisms will evolve back to this size.

That's that theory, anyway. Obviously Brown et al.'s calculations come up with a different result than the ones described above, but it's probably the same sort of energetic trade-off theory - the article cites a couple other sources that came up with different results, so the above-mentioned paleontologist may be explicitly referring to one of them (which I haven't read) or amalgamating some of them together. I'm not sure how widely accepted this explanation is, but hopefully I've at least contributed towards your layperson-friendly translation. DaveOTN 19:14, 29 November 2006 (UTC)

Japanese people

Are the Japanese really any shorter than other Asians? I was of the opinion that they were actually a little taller than average. Haplolology 22:17, 29 December 2006 (UTC)

I am not really sure humans are subject to this effect at all. I think the smallness of those other island peoples is due to the fact that they were derived from short mainland populations which had been that way for many thousands of years. Haplolology 00:58, 6 January 2007 (UTC)

Explanation needs major help

The article currently says, "One explanation is an evolved gene-encoded response to environmental stress. Another is a selective process where only smaller animals trapped on the island survive, as food declines to a borderline level. The smaller animals need fewer resources, and so are more likely to get past the break-point where population decline allows food sources to replenish enough for the survivors to flourish."

This does not sound like orthodox evolutionary theory at all to me.

If there is a gene-encoded response to environmental stress, then we should be able to create tiny elephants by witholding food, or recreating whatever that stress is. To my knowledge, there is no record of dwarf elephants appearing in any zoo, circus, or any other environment.

The other explanation—which appears to be advocating group selection—is almost as bad as the first explanation. These sound more like laymans' guesses about how evolution works rather than an explanation from current evolutionary theory. 170.94.105.46 (talk) 23:17, 22 November 2010 (UTC)

"The environmental stress response": see http://gasch.genetics.wisc.edu/pdfs/Gasch_ESRreview_Hohmann-Mager.pdf

"gene-encoded response to environmental stress": Similarly, when the stress is removed the animals should revert to normal. The animals do not change size, so this is wrong. The species is permanently smaller. QuentinUK (talk) 19:45, 8 November 2011 (UTC)

Sardinian Lynx

The Sardinian Lynx article says it was "1 meter long" and the article on the Eurasian Lynx ("biggest lynx" according to it, by the way) says it is "80 to 120 cm long". Surely the Sardinian lynx does not qualify as an example, then, or is the info in the SL article wrong? Also, wasn't the (sub)species a relative recent newcomer, at least compared to other animals like the Sardinian Dhole?--150.244.131.195 (talk) 17:58, 25 February 2011 (UTC)

prime apes

what about some species of lemurs such as mouse lemur wich are really small and one of the smalled primeapes in the world and smaller then its other lemur relatives and they are native to the island of madagascar. so i think some species grew larger like the indri and the Diademed Sifaka whiles other grew smaller such as mouse lemurs and relatives (and theirs a reason why their called moused lemurs) and some lemurs stayed pretty much the same size while they evolved and populated on the island of madagascar.--Jasonz2z (talk) 16:02, 26 February 2011 (UTC)

Mouse lemurs aren't a good example, because lemurs in general are too small to be expected to be affected by island dwarfing. WolfmanSF (talk) 18:28, 26 February 2011 (UTC)

What about penguins

the galapagos penguin is 2nd smallest penguine the in world so may island dwarfism may explain for this?--Jasonz2z (talk) 21:50, 26 February 2011 (UTC)

The problem with that idea is that penguins are mostly marine, and therefore not obviously subject to reduction in food supply related to island size. Usually, when we think about insular dwarfing, we are thinking about terrestrial animals. WolfmanSF (talk) 02:31, 27 February 2011 (UTC)

ok but wouldn't the lack of predators might be another reason for this, and evan though penguins are semi aquitic aniamls they arnt truely aquitic because they only go into the water for one purpose food they come back on shore for many other purposes, sleep,mate ,rais young , etc. but i guass u could say it that way because they are the best adapted to swimming in cold water and to efficienlt their prey then other birds that wouldn't spend that much time in the water or underwater to their prey however like all birds the penguin must come back out of the water to breath and they only hold their breath smaller then truly aquitic aimals such as whales, dolphin, and poirposes. so yah.--Jasonz2z (talk) 04:18, 27 February 2011 (UTC)

what about elephants

The borneo pygmy elephant to be exact. cause they live in the tropical islands of asia such as borneo and this may explain y the elephants their r the smallest living subspecies then the mainland asian elephants subspecies found in places like india, and china. And it is possible since paleontoligical evidence suggests that it is possible since remains of other extinct species of elephants known as dwarf elephants did suffer from this and explains y they became so small and their remains were found not to far from the native habitat of the now present borneo pygmy elephant.--Jasonz2z (talk) 13:52, 27 February 2011 (UTC)

This is not the best example, since their history is uncertain (they may be descended from domesticated Javanese elephants); also, they aren't as small as the extinct dwarf elephants already listed. WolfmanSF (talk) 19:15, 27 February 2011 (UTC)

true, but despite that they are still listed as their own subspecies cause most zoologists believe they are their own sub species that evolved their and is still classified like that, so far the time being it is and evan though they did not become as small as the dwarf elephants they still became small due to island dwarfism so they do count.--Jasonz2z (talk) 19:25, 27 February 2011 (UTC)

what about birds

The Dwarf Cassowary is the smallest subspecies of cassowary native to new guenie and is smaller then its larger mainland cousine the Southern Cassowary.--Jasonz2z (talk) 14:54, 5 March 2011 (UTC)

I'm not convinced this is a good example. The Northern Cassowary also lives on New Guinea, but is similar in size to the Southern Cassowary. So, the reason the Dwarf Cassowary is smaller may be that it is a highland species. WolfmanSF (talk) 17:49, 5 March 2011 (UTC)

ok but still, ill show u it by my point of view like the extinct bali tiger was the smallest subspecies of tiger however the now still living sumatran tiger lived close by to that neiboring subspecies and the sumatran tiger is close in size as its mainland counterparts like the bengal tiger yet the bali tiger shrank while the sumatran stayed pretty much the same size. or another better example is the Hokkaidō Wolf and the smaller honshu wolf, both shared the same habitat and would sometimes come across eachother in their only native home of the isolated island of japan. yet one shrank and the other species stayed the same size, as the mainland wolves, such as gray wolves.so u c my point and the same thing could be with the dwarf cassowary and the northern cassowary.--Jasonz2z (talk) 18:23, 5 March 2011 (UTC)

Bali is a much smaller island than Sumatra. Also, Hokkaido and Honshu are separate islands. WolfmanSF (talk) 18:45, 5 March 2011 (UTC)

true, but honshu wolf was only named that because it was discovered there it was still found on other nearby islands and aswell for the hokkaindo wolf aswel. just like the komodo dragon it was discovered on the island of komodo and was named after where it was discovered but it was also found on other nearby islands aswell, and its the same story for many other animals too, just like the javan rhino was discovered on the island of jave but is also found on a small area on the mainland of asia called cat tien aswell and it probably existed on other islands aswell with a wider range b4 peaple started hunting and killing them off its former territory.--Jasonz2z (talk) 20:25, 5 March 2011 (UTC)

Yes, but my point was that the Hokkaido and Honshu wolves did not coexist on the same island(s), in contrast to the Dwarf and Northern cassowaries. WolfmanSF (talk) 22:10, 5 March 2011 (UTC)

oh i know what u ment its just that at one point in history i ment they were the same species cause they didn't magically just appeared on the island or swam hundreds of miles to their i believe somehow some way a wolf got their perhaps pregnent and took advantage of the predator-less island full of easy prey and eventually diverged and became their own to subspecies, and when wolves 1st came into existence their was just one type of species and evutally they evolved and became diffrent subspecies and their range grew and they had to adopt to new habitat and i now realize im getting a bit off topic but still the islands that the two species of wolves weren't so far apart so the environment would have been pretty much the same so all because they both grew up on two diffrent islands doesn't always account for their diffrences plus both wolves existed on an island wich like i said b4 pretty much the same habitat and same food source its not like they were thousands of miles apart or like one was of desert and the other was of ice or one was rich with plentyful food while the other scarce of life no they would have been much the same and so if both species wolf lived in an island with an environment pretty much the same and would go through the same seasons and were actually nearby eachother then why didnt both the wolf subspecies became small then only one did while the other stayed the same. and to me its like having a rabbit population (the same species) on the same island then all of a sudden u have a gigantic river flooding and seperating the rabbit population on now two islands but nothing changed their, their is just a body of water seperating the two populations now but the environment should still be the same so then what would be the cause of one of the rabbits populations on the other side of the river to shrink in size while the other population stays the same, who knows it just happens. and anyways i do believe that the dwarf cassowary became small due to island dwarfism. And how about this then the giant lemurs where native to madagascar along with their smaller lemur relatives yet they grew large while other shrannk a bit or stayed the same or just slightly grew larger over time, so evan though both many species of lemurs did coexist with one another we still have so many varietys of them that seperate them from each other like you could easily tell the diffrence between an aye aye and a mouse lemur yet both lived in the same habitat and went through the same process's such as predators, weather, food, etc yet they both drasticly changed from one another the aye aye became darked furred, nocturnel, grew long finger nails, large ears, and a fox-like tail while the mouse lemur stay duirnal(some species) shrinked in size and fed on other types of food available such as becoming a pollinator instead of an insectavore(usually), so u c my point now.--Jasonz2z (talk) 22:55, 5 March 2011 (UTC)

other wolves

defanatly the Baffin Island wolf cause its unuasyually small especially compared to Arctic wolves and tundra wolves. 2 other small island wolves are the Greenland wolf and the Alexander Archipelago wolf.--Jasonz2z (talk) 18:18, 6 March 2011 (UTC)

Maybe, but the size difference from mainland wolves appears modest, so not the best examples. WolfmanSF (talk) 18:40, 6 March 2011 (UTC)

what about deer?

like the smallest red deer subspecies being Corsican Red Deer and the 2nd smallest the scottish red deer.--Jasonz2z (talk) 16:27, 20 March 2011 (UTC)

The Corsican red deer appears to be a valid example (I don't have weight data on the Scottish red deer). However, it's not as good as the subspecies examples we already have. If we compare average adult male body weights of the dwarfed to the undwarfed forms, then the ratios are 0.3 (65 lb./ 215 lb.) for Key deer, 0.17 (1/6) for the extinct Jersey red deer, and 0.5 (230/440) for the Corsican red deer. I think we're better off sticking with the more extreme examples. WolfmanSF (talk) 19:02, 20 March 2011 (UTC)

the Ibis

what about the São Tomé Ibis wich is the smallest Ibis in the world and is native to São Tomé .--Jasonz2z (talk) 20:50, 5 April 2011 (UTC)

Do we know the ratio of its weight to that of its relative, the Olive Ibis? WolfmanSF (talk) 05:38, 6 April 2011 (UTC)

well not on wikipedia but im sure it mentions it else where on the internet but i havn't been able 2 find it.--Jasonz2z (talk) 20:18, 6 April 2011 (UTC)

It would be nice to have more examples of birds, if we can locate the relevant supporting data. WolfmanSF (talk) 00:27, 7 April 2011 (UTC)

plot of body mass of largest species in a land mass vs land mass size

The article states that a plot of y = log(body mass/kg) vs x = log(land area/km2) has a slope of about 0.5. What is missing? WolfmanSF (talk) 16:08, 17 May 2013 (UTC)

Standards for inclusion

I think it would be useful to have some sort of set of standards for inclusion. Say, a ref. citing the species in question as an example of the phenomenon, or dimensions ≤ 80% of the mainland form, or body mass ≤ 50% of the mainland form (0.8³ ≈ 0.5). How does that sound? WolfmanSF (talk) 07:39, 5 August 2017 (UTC)

That's original research.--Menah the Great (talk) 00:50, 12 August 2017 (UTC)

No, that isn't original research, because it states nothing about the definition of insular dwarfism. It is simply addressing a question that we have to address if we are going to list examples: what sort of examples, based on what sort of evidence, do we want to include? WolfmanSF (talk) 02:09, 12 August 2017 (UTC)

It's very unlikely that any two species will be exactly the same same. So, without standards, virtually any endemic insular species could be listed as an example of either an insular dwarf or giant. That's obviously not a situation that makes sense. WolfmanSF (talk) 02:28, 13 August 2017 (UTC)

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Crocodiles

It might be interesting to check if the Cuban crocodile and the New Caledonian Mekosuchus species qualify as examples.--Menah the Great (talk) 02:34, 22 December 2018 (UTC)

The Cuban crocodile appears to be similar in size to Morelet's crocodile. Both are freshwater, suggesting they are also ecologically similar. Mekosuchus and Trilophosuchus seem to have been generally similar in size at 1.5-2 m, although smaller than Quinkana at ~3 m. The data for some of these extinct forms might be limited. WolfmanSF (talk) 06:20, 22 December 2018 (UTC)

Defenition expansion

This defention should be expanded for lakes and any other isolated environment as explained in this video https://www.youtube.com/watch?v=4OqUjXEqUtc — Preceding unsigned comment added by 185.175.34.162 (talk) 12:12, 6 May 2022 (UTC)