Understanding through Discussion


Welcome! You are not logged in. [ Login ]
EvC Forum active members: 80 (8905 total)
Current session began: 
Page Loaded: 04-19-2019 4:51 AM
27 online now:
PaulK, Phat (AdminPhat), Tangle, vimesey (4 members, 23 visitors)
Chatting now:  Chat room empty
Newest Member: WookieeB
Post Volume:
Total: 849,818 Year: 4,855/19,786 Month: 977/873 Week: 333/376 Day: 10/116 Hour: 2/4


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
1
2Next
Author Topic:   Evolution Occurs Faster at the Equator
melatonin
Member (Idle past 4313 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 1 of 18 (308317)
05-01-2006 8:19 PM


Evolution Occurs Faster at the Equator
By Ker Than
LiveScience Staff Writer
posted: 01 May 2006
05:00 pm ET

Plants and animals living in warm, tropical climates evolve faster than those living in more temperate zones, a new study suggests.

The finding, detailed in the May 2 issue of the journal for the Proceedings of the National Academy of Sciences, could help explain why rainforests have such rich biodiversity compared to other parts of the planet.

A census of all the plants and animals around the world would reveal that species richness is uneven: it is highest in the tropics, the regions of Earth near the equator, and lower the closer one goes toward the planet's poles.

What's going on

To investigate the reasons for this trend, Shane Wright of the University of Auckland, New Zealand, and colleagues looked at the rate of molecular evolution for 45 tropical plants and compared it to that of related species living at more temperate latitudes.

The researchers examined the rate at which DNA bases in the plants' genetic code are substituted. Like characters in a four-letter alphabet, bases are DNA molecules arranged to spell out instructions for building proteins. If one of the letters—A, T, G or C—become substituted with another, the instructions can change and a dysfunctional or entirely new and useful protein can be produced.

The researchers found that tropical plants had more than twice the rate of base substitution compared to their temperate cousins.

How it works

The finding supports a theory put forth by biologist Klaus Rohde in 1992 that climate can have a powerful effect on how fast organisms evolve and branch off into new species. Scientists think it works like this:

Warmer temperatures speed up metabolism by allowing chemical reactions to occur at a faster rate, but this increased efficiency comes at a price: it produces higher quantities of charged atoms or molecules called "free radicals," which can damage proteins—including DNA. Higher metabolism also speeds up DNA replication, which is just another chemical reaction, and this can increase the number of copying mistakes that can occur.

Together, damage to DNA by free radicals and replication mistakes could result in mutations that, over time and through natural selection pressures, can form new species.


http://www.livescience.com/animalworld/060501_tropics_evo.html
Replies to this message:
 Message 4 by macaroniandcheese, posted 05-04-2006 4:48 PM melatonin has responded
 Message 6 by Quetzal, posted 05-04-2006 5:07 PM melatonin has not yet responded
 Message 7 by Quetzal, posted 05-04-2006 6:07 PM melatonin has not yet responded

  
Mespo
Member (Idle past 989 days)
Posts: 158
From: Mesopotamia, Ohio, USA
Joined: 09-19-2002


Message 2 of 18 (309030)
05-04-2006 12:19 PM


...and all along I thought...
...that evolution was faster at the equator because the Earth rotated faster at the equator.

Shucks. Back to the drawing board.

(:raig


Replies to this message:
 Message 3 by Omnivorous, posted 05-04-2006 4:23 PM Mespo has not yet responded

    
Omnivorous
Member (Idle past 1072 days)
Posts: 3808
From: Adirondackia
Joined: 07-21-2005


Message 3 of 18 (309113)
05-04-2006 4:23 PM
Reply to: Message 2 by Mespo
05-04-2006 12:19 PM


Re: ...and all along I thought...
...that evolution was faster at the equator because the Earth rotated faster at the equator.

Heck, I thought it was steeper levels of solar radiation promoting a higher mutation rate.


This message is a reply to:
 Message 2 by Mespo, posted 05-04-2006 12:19 PM Mespo has not yet responded

Replies to this message:
 Message 5 by Parasomnium, posted 05-04-2006 4:52 PM Omnivorous has not yet responded

    
macaroniandcheese 
Suspended Member (Idle past 2032 days)
Posts: 4258
Joined: 05-24-2004


Message 4 of 18 (309120)
05-04-2006 4:48 PM
Reply to: Message 1 by melatonin
05-01-2006 8:19 PM


hmm. if that's the case, then all our antioxidants could be slowing our evolution? that's very interesting. by wanting to look younger, we could be reducing our mutability.
This message is a reply to:
 Message 1 by melatonin, posted 05-01-2006 8:19 PM melatonin has responded

Replies to this message:
 Message 8 by melatonin, posted 05-04-2006 6:14 PM macaroniandcheese has not yet responded

  
Parasomnium
Member (Idle past 800 days)
Posts: 2191
Joined: 07-15-2003


Message 5 of 18 (309122)
05-04-2006 4:52 PM
Reply to: Message 3 by Omnivorous
05-04-2006 4:23 PM


Finally: the synthesis between Evolution and Relativity
No, the reason is that, due to its rotation, the earth bulges at the equator, so that organisms there are located a bit higher up the gravity well. This means that time runs slightly faster for them. Hence a faster evolution rate.

This message has been edited by Parasomnium, 04-May-2006 10:07 PM


This message is a reply to:
 Message 3 by Omnivorous, posted 05-04-2006 4:23 PM Omnivorous has not yet responded

  
Quetzal
Member (Idle past 3976 days)
Posts: 3228
Joined: 01-09-2002


Message 6 of 18 (309126)
05-04-2006 5:07 PM
Reply to: Message 1 by melatonin
05-01-2006 8:19 PM


Hi Melatonin,

Interesting article. Actually, I'm not sure I agree with the authors' conclusion, however. I'm going to try and dig up the original PNAS article and see what it says. I think the conclusion is erroneous from the simple fact that the highest biodiversity hotspot on the planet is the tropical Andes - 15,000 endemic species of plants, mostly located in cloud forests above 2000 m (representing 1/6 of all plant species in Earth in less than 1% of the surface area). I guaran-damn-tee you that heat is not the operative factor here (I live less than 30 min drive from three of the Ecuadorian biggies: Pasachoa, Antisana and Cayambe-Coca). The cloud forests are perpetually cool and often mist-shrouded. Their upper ends at 3800-4000 m are actually cold.

Omni was closer to the mark, I think. The rapidity of molecular change has more to do with levels of ionizing radiation than heat. I readily agree with their observation on the rate, but disagree with their causal explanation.


This message is a reply to:
 Message 1 by melatonin, posted 05-01-2006 8:19 PM melatonin has not yet responded

Replies to this message:
 Message 10 by Mespo, posted 05-05-2006 3:19 PM Quetzal has responded
 Message 12 by MangyTiger, posted 05-11-2006 9:40 PM Quetzal has responded
 Message 15 by fallacycop, posted 05-16-2006 12:29 AM Quetzal has responded

  
Quetzal
Member (Idle past 3976 days)
Posts: 3228
Joined: 01-09-2002


Message 7 of 18 (309160)
05-04-2006 6:07 PM
Reply to: Message 1 by melatonin
05-01-2006 8:19 PM


quote:
We selected a total of 45 tropical woody plant taxa with latitudinal/altitudinal ranges coinciding with the warmest sectors of the total climatic ranges of their respective genera.

Here's one problem with their study. Actually, it's not a "flaw" in the sense that it represents sloppy methodology or something, but rather provides a key to understanding why they got the results they did. It was a MUCH narrower study than the livescience article would lead you to believe. They deliberately chose samples from the "warmest sectors". Which is okay if all they were trying to show was the effect of relative warmth on the evolution of congeneric plants. Which, in fact, appears to be what they were trying to do based on the full abstract:
quote:
Using an appropriately designed and replicated study of a latitudinal influence on rates of evolution, we test the prediction by K. Rohde [(1992) Oikos 65, 514–527] that the tempo of molecular evolution in the tropics is greater than at higher latitudes.
In other words, although they demonstrated a higher-rate of molecular evolution in tropical vs. temperate closely-related plant genera, nowhere in their study did they allow for "other" factors in developing their conclusion. They wanted to find a heat difference, so the samples and methods used were predicated on heat difference. Hence the conclusion that heat difference was the cause. The logical flaw here is obvious, I would think. IOW, it's an interesting study, and adds to the literature on the latitudinal stratification of biodiversity, but doesn't support the interpretation in the cited article.

For the full text, see Wright, et al 2006, The Road from Santa Rosalia: A faster tempo of evolution in tropical climates, PNAS 103:7718-7722


This message is a reply to:
 Message 1 by melatonin, posted 05-01-2006 8:19 PM melatonin has not yet responded

  
melatonin
Member (Idle past 4313 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 8 of 18 (309170)
05-04-2006 6:14 PM
Reply to: Message 4 by macaroniandcheese
05-04-2006 4:48 PM


Article Preview
How chemicals can speed up evolution
06 May 2006
Andy Coghlan
Magazine issue 2550
The mystery of how human DNA evolves during someone's lifetime looks a step closer to being solved

Researchers in Japan have found evidence that environmental agents that cause chemical changes to our DNA throughout life may increase the amount of shuffling and mutation that occurs within our DNA during the formation of egg and sperm cells. So exposure of our DNA to reactive chemicals may actually drive evolution by promoting genetic diversity in our children.

Yusaku Nakabeppu and his colleagues at Kyushu University in Fukuoka have shown that, if unrepaired by enzymes, a type of chemical damage called oxidation can reshuffle DNA's four basic building blocks - adenine, thymine, cytosine and guanine.

Normally, cytosine always pairs with guanine, and adenine with thymine, but unrepaired oxidation can disrupt these pairings, so that when a cell multiplies, the DNA sequence handed down to "daughter" cells is subtly altered...


http://www.newscientist.com/channel/life/mg19025504.600.html

It is possible that oxidative damage from environmental agents may speed up evolution. So, maybe anti-oxidants do slow evolution.

....

Hi Quetzal,

I guess it's just one hypothesis as to why these areas have greater diversity than more temperate regions. Just thought it was interesting.

And I'm quite envious of the fantastic location you find yourself in. I love south america. I'm sure it beats the view of Snowdon I have here in wales.


This message is a reply to:
 Message 4 by macaroniandcheese, posted 05-04-2006 4:48 PM macaroniandcheese has not yet responded

Replies to this message:
 Message 9 by Quetzal, posted 05-04-2006 8:58 PM melatonin has not yet responded

  
Quetzal
Member (Idle past 3976 days)
Posts: 3228
Joined: 01-09-2002


Message 9 of 18 (309229)
05-04-2006 8:58 PM
Reply to: Message 8 by melatonin
05-04-2006 6:14 PM


I guess it's just one hypothesis as to why these areas have greater diversity than more temperate regions. Just thought it was interesting.

As did I. I just don't agree with them. :D


This message is a reply to:
 Message 8 by melatonin, posted 05-04-2006 6:14 PM melatonin has not yet responded

  
Mespo
Member (Idle past 989 days)
Posts: 158
From: Mesopotamia, Ohio, USA
Joined: 09-19-2002


Message 10 of 18 (309434)
05-05-2006 3:19 PM
Reply to: Message 6 by Quetzal
05-04-2006 5:07 PM


Altitude vs. Latitude
Omni was closer to the mark, I think. The rapidity of molecular change has more to do with levels of ionizing radiation than heat. I readily agree with their observation on the rate, but disagree with their causal explanation.

If what you're saying is so Quetzal, wouldn't it follow then that one should find a higher rate of bio-diversity in the Rocky Mountains (higher elevation) as opposed to the Eastern Seaboard at the same latitudes?

(:raig


This message is a reply to:
 Message 6 by Quetzal, posted 05-04-2006 5:07 PM Quetzal has responded

Replies to this message:
 Message 11 by Quetzal, posted 05-05-2006 6:05 PM Mespo has not yet responded

    
Quetzal
Member (Idle past 3976 days)
Posts: 3228
Joined: 01-09-2002


Message 11 of 18 (309485)
05-05-2006 6:05 PM
Reply to: Message 10 by Mespo
05-05-2006 3:19 PM


Re: Altitude vs. Latitude
Not necessarily. Insolation is only one factor, albeit a big one. Moisture is another. Topography, climate, geology, etc also all play a role. As does heat (they weren't wrong, I'm quibbling with their conclusion on relative strength of heat vs other factors). In any event, to directly address your point, most conservation organizations list the Colorado Plateau, for instance as a biodiversity hotspot due to the very high level of endemism. Only on the Olympic Penninsula and in the California Floristic Province (which is a global biodiversity hotspot) is there an equivalent level of biodiversity - which is interesting in its own right. The eastern seaboard (as far as I can determine - I could be wrong) has a lower level of biodiversity overall at the same latitudes. You might find this article: DT Rutledge, CA Lepczyk, J Xie and J Liu, 2001 "Spatiotemporal Dynamics of Endangered Species Hotspots in the United States", Conservation Biology 15:475-487. Although the paper doesn't deal with your question directly (don't just read the abstract, they were looking at something else), there is a very interesting graphic on page 480 that seems to support my contention (note the hotspots in the southern Rockies).

I admit number of endangered species doesn't directly translate to high biodiversity. OTOH, endangered species are an indicator. You'd have to find a floristic study that compared Rocky Mountain and Eastern Seaboard species numbers to be sure. I'm not sure that's been done. It would be an interesting comparison in any event.

I base my contention on a few, demonstrated facts:

1. The tropical Andes region contains some 30-35,000 species of plants with over 50% endemism, making it one of if not the highest biodiversity hotspots on the planet.

2. By comparison, the Atlantic coastal rainforest of Brazil (representing sort of the southern end of the latitudes encompassing the Tropical Andes), also a global biodiversity hotspot, contains only ~20,000 species of plants in spite of being substantially hotter and wetter than the Andes.

3. An additional comparison, with the Upper Amazon Basin (specifically, the Upper Rio Negro - which puts it smack in the middle of the Tropical Andean latitudes) contains only ~15,000 plant species. This area is also hotter and wetter than the Andes.

I'm open to a different explanation, of course. However, to me the simple comparison of species numbers is an indicator that heat, per se, although possibly a factor, is not the major criteria for biodiversity - in spite of what was published in the PNAS article.

edited 'cause I kant spel

This message has been edited by Quetzal, 05-05-2006 06:07 PM


This message is a reply to:
 Message 10 by Mespo, posted 05-05-2006 3:19 PM Mespo has not yet responded

Replies to this message:
 Message 14 by scoff, posted 05-15-2006 6:54 PM Quetzal has not yet responded

  
MangyTiger
Member (Idle past 4458 days)
Posts: 989
From: Leicester, UK
Joined: 07-30-2004


Message 12 of 18 (311220)
05-11-2006 9:40 PM
Reply to: Message 6 by Quetzal
05-04-2006 5:07 PM


I think the conclusion is erroneous from the simple fact that the highest biodiversity hotspot on the planet is the tropical Andes - 15,000 endemic species of plants, mostly located in cloud forests above 2000 m

Having no biological education beyond schoolboy level (back in the '70s!) I may be completely wrong here but it seems to me there is a potential hole in your argument.

You are equating current biodiversity in two or more locations with rate of evolution in those locations. Although this may well be valid it is not guaranteed to be.

Suppose in one location you have evolution happening at a rate x and it has been happening for a period of time t. In a second location place the rate of evolution is x/2 - i.e. half the rate - but it has been happening for 10*t - i.e. ten times as long.

All other things being equal - which of course they never are - you could reasonably expect the second location which has half the rate of evolutionary change but has been doing it for ten times as long to have the higher current biodiversity.


Never put off until tomorrow what you can put off until the day after
This message is a reply to:
 Message 6 by Quetzal, posted 05-04-2006 5:07 PM Quetzal has responded

Replies to this message:
 Message 13 by Quetzal, posted 05-12-2006 9:04 AM MangyTiger has not yet responded

    
Quetzal
Member (Idle past 3976 days)
Posts: 3228
Joined: 01-09-2002


Message 13 of 18 (311360)
05-12-2006 9:04 AM
Reply to: Message 12 by MangyTiger
05-11-2006 9:40 PM


You are equating current biodiversity in two or more locations with rate of evolution in those locations. Although this may well be valid it is not guaranteed to be.

Actually, the original article (which I linked to above) is the one that made the case that rate of evolution = biodiversity. I was arguing on their terms. I agree with you that rate does not necessarily equal biodiversity. In fact, that's at the heart of one of my key arguments against the conclusions in the paper (although I admit I didn't phrase it this directly). The paper (to recap) claims that heat = higher metabolism = higher rate of evolution = higher biodiversity. I completely agree with the first three terms. It's the equivalancy they make at the end that I disagree with. My counter examples were intended to show that this isn't necessarily the case. So you're right. Not bad for someone who hasn't taken biology since the '70s. :D

All other things being equal - which of course they never are - you could reasonably expect the second location which has half the rate of evolutionary change but has been doing it for ten times as long to have the higher current biodiversity.

Logically you'd be correct. However, as you noted, "All other things being equal" is the real kicker. This is a case that very rarely happens in the real world. For example, much of South America is fairly "young" - the Andes are ~3-5 my old in most places. However, the Guyanan Shield is part of old Gondwana and dates to around 300 my. This one fact alone has huge implications for the flora and fauna of the two regions due to nutrient availablility, etc. Compare the tepuis of the Shield to the equivalent kind of geologic formation in the Cordillera del Condor region of southern Ecuador/northern Peru. The older formation is actually biodiversity-impoverished compared to the "newer" parts of the upper Amazon basin which drains the much younger Andes. Heterogeneity of habitat, historical climatic fluctuations, topography, etc etc etc are also implicated in relative biodiversity. Islands also generally show a higher rate of evolutionary change, as evidenced by the proportion of endemics, with an almost invariant lower degree of overall biodiversity. Ergo, in my opinion, the paper was rather poor quality (although interesting), and doesn't reflect the main factors in biodiversity.

I toyed with the idea of sending in a comment to PNAS, but they probably wouldn't accept it because I'm not affiliated with any academic institution. Journals tend to be sticky about those kinds of things. Ah, well. Take it for what it's worth, and ignore the rest, I guess. It's not all bad, by any means.


This message is a reply to:
 Message 12 by MangyTiger, posted 05-11-2006 9:40 PM MangyTiger has not yet responded

  
scoff
Member
Posts: 36
Joined: 01-20-2006


Message 14 of 18 (312135)
05-15-2006 6:54 PM
Reply to: Message 11 by Quetzal
05-05-2006 6:05 PM


Re: Altitude vs. Latitude
The eastern seaboard (as far as I can determine - I could be wrong) has a lower level of biodiversity overall at the same latitudes.

I find it interesting that all the spots you mentioned are also comparatively young in geological terms. As with Galapagos, I would think the availability of open niches might play a part in the levels of biodiversity found there.


This message is a reply to:
 Message 11 by Quetzal, posted 05-05-2006 6:05 PM Quetzal has not yet responded

  
fallacycop
Member (Idle past 3625 days)
Posts: 692
From: Fortaleza-CE Brazil
Joined: 02-18-2006


Message 15 of 18 (312285)
05-16-2006 12:29 AM
Reply to: Message 6 by Quetzal
05-04-2006 5:07 PM


Quetza writes:

The rapidity of molecular change has more to do with levels of ionizing radiation than heat. I readily agree with their observation on the rate, but disagree with their causal explanation.

I don't agree with either their explanations or with your's. Most probably, the raw rate of mutation has nothing to do with it. I would look into an explanation based in the larger number of niches available, and larger number of species to interact with/adapt to, etc...
this possibly creates a more fluid eviroment that leads to a larger number of adaptations.
In other words, more oportunities for mutations to become fixed in the populations. By the way, it may also be due to faster genetic drift due to smaller populations.


This message is a reply to:
 Message 6 by Quetzal, posted 05-04-2006 5:07 PM Quetzal has responded

Replies to this message:
 Message 16 by Quetzal, posted 05-16-2006 9:35 AM fallacycop has not yet responded

  
1
2Next
Newer Topic | Older Topic
Jump to:


Copyright 2001-2018 by EvC Forum, All Rights Reserved

™ Version 4.0 Beta
Innovative software from Qwixotic © 2019