Talk:Island gigantism

8 January 2006

I think this page and island dwarfing need to be tied together with a little context and should refer to each other in the main body of text. Can anyone take a crack at that? I don't think I'm qualified. bikeable (talk) 17:35, 8 January 2006 (UTC)

We should make an "In Popular Culture" section for this page, and mention the animals in the King Kong movies. Hehe.  :) King nothing 2 09:45, 2 March 2006 (UTC)

It is by no means certain that Giant tortoises, and many of the other examples listed, represent island gigantism, but instead island refugia. Even larger tortoises inhabited most continental landmasses until the pleistocene, when they became extinct, perhaps due to human predation. Thus these could even be examples of island dwarfism. Regardless the tortoises that colonized the Galagagos and other island systems were likely already giant, a feature which aided in this colonization event (PNAS Caccone et al. 96 (23): 13223). You would need to be relatively certain that the original colonizers of the islands were smaller species which subsequently evolved larger size in order to label it island gigantism. The same may apply to the ratites, komodo dragon, and the weta. Beseekay 06:36, 19 June 2007 (UTC)

This makes no sense!

Why would creatures grow larger in a smaller environment? Food would runout and it would be harder to hide. It would be more efficient to become smaller.

-G

The article already answers this question. The creatures don't simply "grow larger", they evolve. A mutation's popularity is typically determined by how well it's able to reproduce within its environment, this is known as natural selection. In situations where a predator is not present, sexual selection leads to mutations that display more contrast against their environment becoming more popular, and a phenomenon known as Bergmann's Rule leads to gigantism. Observations of both these scenarios have been well documented. However, there are exceptions to this phenomenon; for example, you may be interested to learn about Insular dwarfism. Hope that helps.

jdbartlett (talk) 11:50, 5 May 2008 (UTC)

To elaborate, for very large creatures (e.g., elephants and their relatives), food usually does tend to run out on islands, so they evolve smaller size. In many cases of small creatures on islands, however, the key difference is the reduced presence or absence of predators or larger competitors, resulting in larger sizes. WolfmanSF (talk) 05:31, 26 February 2011 (UTC)

prime apes

wouldnt the Diademed Sifaka and the indri also count. and many peaple say that the indri along with the Diademed Sifaka are the largest lemurs still in existence.--Jasonz2z (talk) 18:20, 25 February 2011 (UTC)

The much larger recently extinct lemurs that are listed are better examples. WolfmanSF (talk) 05:33, 26 February 2011 (UTC)

um yah true but it doesn't matter if it seems as a better species if it suffers from island giganism then it should count as and be given as an exapmle of island gigantism. and how could you say the recently extinct lemurs that are listed are better examples that is not zoologicly practical to say that just because one species is not as large as those other species doesnt mean it shouldnt be classified as one cause aslong as its does suffer from island gigantism then it should count as it not cause some other species of lemurs have grown evan larger, and your supposed to see how this one species is effected you don't compare it (exept in classification) to another species cause your looking and talking about this animal not its other relatives wich dont have much to do with these two species of lemur and i what asked for. and in my opinion if anything should be deamed better i think it should be the Diademed Sifaka and the indri. because their still alive they have survived the disruption of humans while those other island gigantism species you mentioned are now extinct their no longer with us cause they didn't have the power to survive the power of human disruption in their habitat while the lemur i mentioned did, and we should be glad that their the last two island gigantism lemurs, and plus those lemurs don't count anymore since their extinct the indri is the largest lemur now, just like how the cave lion was bigger then the modern day lion however it went extinct and now the modern day lion is now seen as the 2nd biggest feline in the world. only 2nd to the tiger and evan the tiger the biggest cat in the world today is not as big as the cave lion either yet we still see it as a graceful, majestic, powerful, giant and the greatest big cat so you do not compare it to a larger feline that existed previosly alongside it and went exinct. no you must see this one species indiviully as its own species (back to the lemur) cause im not talking about the aye aye or the ring tailed lemur no im talking about these just two species of island gigantism lemurs the others don't matter to me i focus and just study these two and see how it is diffrent from its other relatives and what sets it apart for if it not had been for diffrences and varietys all the lemurs of today would all be the same. And what you said is equivelent to somebody wanting to learn about fox's but isntead they look at its extinct relative the dire wolf so you see my point because then that person is not gonna learn much about fox's when they are instead focusing on a larger and extinct relative that is more closely related to the modern day wolves then the animal that i am trying to tell or learn about. or another comparisson could be if two species of tortiose live on the same island and due to island gigantism both species grow very large. However one species grows much larger then the other but evan though that species grew alot larger then the other, both tortioses did grow large because of island gigantism so both species should be classified as animals that evolved large because of island gigantism. so i insist in putting the two lemurs i mentioned previosly in the beginning, in this articles category because zoologicly they should be because they two aswell becoame very large and contrasted from other lemurs because of island gigantism.--Jasonz2z (talk) 15:32, 26 February 2011 (UTC)

You should look at a different comparison. The extinct lemurs are good examples of island gigantism because they're bigger than nearly all the primates on the neighboring continent of Africa. The same cannot be said of the indri or the diademed sifaka, so it really isn't clear that they are examples of gigantism. The fact that the latter are the largest surviving lemurs is less relevant. By the way, it's helpful to others if you condense your arguments as much as possible. WolfmanSF (talk) 18:40, 26 February 2011 (UTC)

Ok , and i kind of have a problem with condencing but i'll work on it.--Jasonz2z (talk) 21:22, 26 February 2011 (UTC)

Oh and another thing

i can understand how the tortiose grew so large in madagascar and some parts of southern asia such as sumatra phillipens and bornea and other island, but just because their are giant tortioses found on main lands doesnt mean that the ones on islands were already large. and plus that makes no sence the galapagos were created actually geologicly quite recently i think some time after the ice age and then think its takes time until migratory bids and plants can get their so it will take alot of time until their will enough habitat to sustain multi celluler life so by the time the island could sustain life i think the giant torioses that existed on the mainland were already endangered and much of them extinct. and another thing the galapgos tortioses are not adapted to swim, evan though they live on isalnds you can see that their bulk and heavy-ness allows the to be boyant but do to their legs their not really adapted to swim they can drift to nearby island but a large portion of tortioses have to drift to the same island and mate their to sustain life and the length from the galapagos to the mainland of south america is pretty far so if some how back durring that time with the few giant tortioses left in south and north america some how got on the water and drifted to the galapagos doesn't sound right cause thats a very far distance the tortioses would have died of starvation by then and if somehow lets just say it did survive their would have to have been a large number of giant tortiose of the same species that did the same thing. and not that many tortioses are adapted to be able to swim, most are more adapted to walking on solid dry land of deserts. evan the the galapagos tortiose more adapted to the rough terrain of the galapagos. what sounds more believable is back then some semi-aquitic terrapins swam to the island and evolved to live more on land and then evolved to beome large and more land based. and evoltion is spead up due to island gigantism so it may only of taken like some thousands of years to adapt to the island with plenty of time to do so and makes more sence. And let me just see your point of view its the equivelent of saying if a galapagos giant tortiose drifted back to the mainland of south america so if your saying if its possible then it should be possible to happen the oppisite way aswel yet we don't find any galapagos tortios washed up on the coasts of south america cause they would already be dead by then. and just because their are giant tortiose on the mainland doesnt mean their the desendents of the galapagos tortiose either cause their were also smaller tortioses that existed alongside them aswell prehistoricly so they could have been the desdents of any terrapin thousands of years ago cause who knows what kind of terripen they could of evolved from with that much time to evolve.so you just think that just cause two animals are related just cause they are closely the same size makes the other one the desendent but that is not always zoologicly plausable.Like how some crocodiles are closely the same size as the american alligator but the american alligator is more related to the much smaller spectacle caimon from far away south america then it is to its other same size reltives such as the american crocodile thats lives closer and sometimes along with the american aligator. and i see another flaw in your hypothosis is that the tortioses native to the americas werent the same size as the galapagos toriose they were either much larger or much smaller they werent the same size.--Jasonz2z (talk) 16:51, 26 February 2011 (UTC)

Tortoises can't swim very well, but they can float. That's how they've reached islands around the world. South American tortoises are descended from African tortoises that floated across the Atlantic Ocean (with the aid of ocean currents). We know from genetic studies that the closest relatives of Galápagos tortoises are mainland South American tortoises. I'm not saying the ancestors of Galápagos tortoises were the same size as they are, just that there were tortoises of similar size in South America before the arrival of humans. WolfmanSF (talk) 18:58, 26 February 2011 (UTC)

what about salamanders

the Japanese giant salamander as its name states is native to the island of japan and is the largest amphibian in existence today. And i know what ur thinking their aquitic and therfor don't count. but thats not always the case the komodo dragon is a good swimmer and is known to swim long distances to reach other island and its believed thats how it got to nearby islands such as komodo and the giant ducks in hawaii and the spectacled cormorant were also very aquitic yet they still evolved to become very large due to island gigantism. and japan lacks many predators and its an amphibian meaning it can come out of water aswell.--Jasonz2z (talk) 19:15, 27 February 2011 (UTC)

The Japanese giant salamander would be a good example if it was bigger than the Chinese giant salamander. However, the Chinese giant salamander is actually larger. (The fact that it is aquatic is not relevant.) WolfmanSF (talk) 19:27, 27 February 2011 (UTC)

ok but its close to that size. and it doesnt matter that, that one species of salamander is bigger then the other it has nothing 2 do with it cause i wasnt talkin bout the chinese giant salamander and it didnt evan grow so giant cause of island gigantism it doesnt count but the japanese one does. and thats just like saying u can't count the galapagos tortiose cause its smaller then the leatherback sea turtle yet u still count it as an example and evan thoguh the japanese giant salamander isn't as famous as the galapagos tortiose i think its a better example of island gigantism.--Jasonz2z (talk) 19:38, 27 February 2011 (UTC)

what about another species of giant eagle

the philippines monkey eating eagle wich is like the 2nd biggest eagle in the world that is still in existence today.--Jasonz2z (talk) 16:56, 2 March 2011 (UTC)

Both the New Guinea Harpy Eagle and the Philippine Eagle might be valid examples, but they aren't the best examples because the Harpy Eagle is similar in size. In contrast, Haast's Eagle was significantly larger that all living continental eagles. Note that we aren't trying to put together a comprehensive list of insular giants, only a list of some of the more notable and obvious examples. WolfmanSF (talk) 20:02, 2 March 2011 (UTC)

i know, im just trying to help out. and ok--Jasonz2z (talk) 20:48, 2 March 2011 (UTC)

just asking, no need 2 add this as an example

would a kodiac bear be considered to be an animal of island gigantism or no?, mabie since one specimen was the largest bear recorded in history but normally it isn't as large as the poler bear but very close and sometimes the same size, and it is believed that the kodiac bear is the largest brown bear subspecies in the world.--Jasonz2z (talk) 00:20, 5 March 2011 (UTC)

This is not clear. It would certainly not be a typical example, because large mammalian predators typically evolve smaller sizes on islands. According to the Brown Bear article, other coastal brown bears reach a similar size. Maybe the abundant salmon of coastal habitats allows brown bears to grow larger, and the isolation of the Kodiak Archipelago means the bears there don't mix with noncoastal populations. WolfmanSF (talk) 01:07, 5 March 2011 (UTC)

ok.--Jasonz2z (talk) 01:31, 5 March 2011 (UTC)

bats

the Giant Golden-crowned Flying Fox wich is the largst bat species in the world and is only native to the islands of the phillipenes.--Jasonz2z (talk) 15:40, 20 March 2011 (UTC)

This might be a valid example, and if so it's an interesting one, but this isn't entirely clear because Pteropus vampyrus apparently reaches a similar size. I think we're better off sticking with the most obvious examples. WolfmanSF (talk) 05:08, 21 March 2011 (UTC)

giant tortoises

The line "...humans reached these islands too recently to finish the job of exterminating them" doesn't seem like the right tone for an encyclopedia, and has no cite (though at least it says [i]may[/i]). --89.206.228.155 (talk) 16:40, 23 June 2011 (UTC)

Title

Should the article title be changed to Insular Gigantism, to mesh with the Insular Dwarfism article? "Insular" seems like a better term because it's unambiguously an adjective. — Preceding unsigned comment added by Sarcoidjohn (talk • contribs) 14:22, 3 December 2011 (UTC)

Phasmids and roaches

The inclusion of phasmids in this list makes no sense. Their gigantism is clearly not island gigantism. Phobaeticus chani, for example, is only slightly longer than P. serratipes, a closely related species occurring from Sumatra to Peninsular Malaysia and Thailand. Dryococelus australis' genetic whereabouts seem to be under scrutiny at the moment, but it doesn't much differ in size or weight from phasmids in similar ecological niches that live on bigger islands as well as the Asian and Australian mainland (Eurycantha and Haaniella, just to name two). I also doubt that the Madagascar hissing roaches have something to do with island gigantism. Like big ground-living phasmids, remotely related roach species of similar size and behaviour can be found on several continents, such as Australia (Macropanesthia) or South America (Blaberus giganteus). More accurate examples of island gigantism in insects would be the giant wetas from New Zealand and New Caledonia. Generally, it can be said that gigantism in insects can have a lot of reasons and that the term "island gigantism" has to be used very carefully. 178.192.248.88 (talk) 23:22, 25 December 2012 (UTC)

It is tempting to suspect that island gigantism is involved when the largest member of a widespread taxon is found on an island, but as you point out, a marginal size differential makes the situation murky. What do you think about the giant Fijian long-horned beetle, one of the largest insects? WolfmanSF (talk) 01:24, 26 December 2012 (UTC)

As for Eurycantha, bigger islands are still islands. To look at the situation differently, what was the average size on an insect on Lord Howe Island before the introduction of rats, compared to the average size of insects elsewhere? Quite a bit larger, I would think. WolfmanSF (talk) 00:48, 1 August 2015 (UTC)

Or to put it another way, how does the former average size of phasmids on Lord Howe Island compare with the average size of phasmids on continental land masses? WolfmanSF (talk) 18:43, 1 August 2015 (UTC)

Extra information that could be added

1. It is not mentioned in the article that increased size has its benefits in the animal being able to go long distances without food and water, such as with groups of land dwelling chelonians (e.g. Giant Tortoise). This could also be used as a start to a section called "possible benefits to gigantism, as most things in the article are about causes.
2. There is no mention of how territorialism is linked with gigantism. Some species need to be territorial to get their abundance of resources, and if extra defense mechanisms or behaviors are needed to do this, and this so happens to be linked to larger sizes, the population could evolve to push towards this bigger size.
3. The article doesn’t explain why larger animals can make it to populate a new island in the first place. It only says that they are better at colonizing islands. A lot of times, larger bodies are more helpful to animals for immigration to islands and, as a result, the populating species of the island is already larger than its mainland counterparts. As they continue to breed, generations later the organism has grown quite larger than its founding ancestors. — Preceding unsigned comment added by Bellisario.4 (talk • contribs) 19:51, 29 September 2014 (UTC)

Good rewording and movement of tortoise information

The movement of the information on possible benefits of island gigantism to the middle of the section helps with the flow of the article. It makes it seem like it isn't an afterthought. The rewording also makes the information much clearer. Bellisario.4 (talk) 23:40, 13 October 2014 (UTC)Bellisario.4

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Kiwis?

Hello, I noticed that Kiwis are included in the island gigantism list of animals but, can someone tell me why? I mean ratites usually adopt big sizes but the biggest species of kiwis are the same size of a chicken. Thanks.

It's based on the size comparison with their presumably continental-sized ancestor, Proapteryx. WolfmanSF (talk) 19:04, 13 February 2018 (UTC)

Thanks! — Preceding unsigned comment added by 201.235.196.121 (talk) 23:57, 13 February 2018 (UTC)

"Island Effect" could simply be 'novelty bewilderment'

The opening reads like Island Gigantism is a scientifically endorsed, irrefutable law of nature...

"island effect" or "Foster's rule" posits that when mainland animals colonize islands, small species get bigger, and large species become smaller.

I think this leads the reader to believe there is something special about islands that changes the size of animals. In reality, all that's happening here is, once upon a time members of a species got spatially isolated from one another, and thenceforth evolved independently. It's certainly fun to speculate about what environmental pressure did this or that to an animal's phenotype; that much is clear in the article. However, so far this article presents no cited evidence to suggest divergent species that went from continent->island changed body size any more rapidly or directionally than species that went from continent->continent or island->continent.

Of course there are examples where "big animals" are smaller and "small animals" are bigger on islands. There are also hundreds of examples where the species are roughly the same size, or where there is a small island animal and both a bigger and smaller-yet continental version.

I think a more appropriate term would be Foster's fallacy or Foster's fantasy, since we are cognitively prone to fixate and over-represent items that strike us as bazzar, absurd, freakish, or fantastical. Seems like Foster saw a big lizard in Jamaica once and now he's gone around getting everyone hot and bothered thinking about huge island dragons of guam and caribbean birds the size of houses, and an archipelago off the coast of Chile exists the floating island of Patagonia where tiny little elephants sing tales of the great shrinkage. Niubrad (talk) 09:31, 4 April 2018 (UTC)

Given that there are numerous examples where the island form is larger than any continental form, despite vastly greater continental populations, the effect doesn't appear to be random, and the field assumes that it is not random. However, if the field ever changes the preferred terminology to "Foster's Fallacy", we will follow suit. WolfmanSF (talk) 18:30, 4 April 2018 (UTC)

Possible giant earthworm example

Spenceriella gigantea is 1.4 m long, and found only in New Zealand's Little Barrier Island. Name implies it's the largest of its genus. No information on the length of other species.--Menah the Great (talk) 20:21, 2 May 2018 (UTC)

Little Barrier Island is the type locality, but this story indicates it is also on (at least) the North Island of New Zealand. You might want to look over the other examples in the Giant earthworm list. WolfmanSF (talk) 21:30, 2 May 2018 (UTC)

Plants as examples of island gigantism

If you look at the literature on island gigantism or the "island rule", I think you will find that the terms are generally conceived of as applying to animals. Try this or this. While it doesn't hurt to add some examples of "island woodiness" to the article, I don't think we should imply in the intro that this is exactly the same phenomenon as island gigantism. WolfmanSF (talk) 19:20, 13 December 2018 (UTC)

Flores flightless stork

It has been suggested that this bird descended from the widespread and larger species Leptoptilos falconeri, in which case it might not be an insular giant after all. WolfmanSF (talk) 00:43, 10 December 2019 (UTC)

There should be a citation regarding this. There are reasons to belive L. robustus is gigantism after all. It lived after L. falconeri so descent is at least questionable, and it shows other island adaptations like increased robustness and flightlesness.--Menah the Great (talk) 04:51, 20 December 2019 (UTC)

Flightlessness and increased robustness, sure, that would not be unexpected for an island species. The only question is, what was the size of it's immediate ancestors? It appears we don't know yet and they might have been larger. So, I think we need a source to resolve that before we list it. WolfmanSF (talk) 06:04, 20 December 2019 (UTC)

Lord Howe Stick Insect

According to this phylogeny, the Lord Howe Island stick insect's closest relatives are in the genus Eurycnema. This includes Eurycnema goliath, the largest stick insect in Australia which actually beats LHI's by 5 cm in length. On the other hand, LHI's is noticeably more robust and adapted to a ground dwelling life which may be the result of island colonization... or not.--Menah the Great (talk) 00:58, 12 December 2019 (UTC)

The other Australian member of the genus, Eurycnema osiris, is up to 30 cm long. So, I think this species should be relisted as an example of insular dwarfism (kidding). WolfmanSF (talk) 01:57, 12 December 2019 (UTC)

Also, maybe it's not relevant, but I feel it should be mentioned somewhere that LHISI doesn't live in LHI anymore but in Ball's Pyramid only.--Menah the Great (talk) 01:12, 12 December 2019 (UTC)

That's mentioned in the first paragraph of the species article. WolfmanSF (talk) 01:57, 12 December 2019 (UTC)

Komodo dragon-sized lizards

A few comments on this issue based on the "Dragon's Paradise Lost" article: the authors argue against the insular giantism explanation, which makes it hard to advocate strongly to the contrary. They say, "The fossil record suggests that giant varanids evolved independently on mainland Asia and the island-continent of Australia during the Pliocene..." They point to V. sivalensis ("This record alone demonstrates that varanids can evolve giantism on continental landmasses with competition from large placental carnivores.") in India and remains of V. komodoensis from Java ("... V. komodoensis dispersed from east to west, perhaps reaching Java during a period of lowered sea-level. At the time of Kedung Brubus, Java was part of the Asian mainland..." i.e., Sundaland) as examples of similarly sized mainland lizards. Given the paucity of fossil remains of some of these examples, it's generally hard to reach strong conclusions about their relative sizes. However, it is indisputable that the Australian megalania was larger than any lizard from any larger continental land mass. WolfmanSF (talk) 00:21, 19 March 2020 (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)

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Kiwi

Wait, why is the kiwi mentioned as an example of island gigantism? The tiny kiwi, part of the ratite family which also includes ostriches, emus, and rheas? To me, this bird seems an excellent example of island dwarfism... Steinbach (talk) 19:39, 20 November 2024 (UTC)