[Odonata-l] Frog legs and odonates - simplistic answer - Occam

Sun Jun 28 07:15:04 PDT 2009

Congratulations on marvelous timing, Marion!

I think that most of us reading this are in agreement that it is foolish to jump to a conclusion based on a small sampling at limited geographic locations, and to use that conclusion to try to explain a very wide ranging phenomena, whether the proposed explanation is simplistic or not. I find it obvious that more research is in order, and it appears most people commentating on this thread, if not all, are in agreement.

I've enjoyed reading all the comments on this discussion!

Now, back to "work".

Glenn Corbiere

Glenn Corbiere 
100 Prospect St. 
Chester, MA. 01011-9657 

www.dragonhunter.net 

________________________________
From: Marion Dobbs <pond_damsel at comcast.net>
To: Odonata-l <odonata-l at listhost.ups.edu>
Sent: Sunday, June 28, 2009 7:41:14 AM
Subject: Re: [Odonata-l] Frog legs and odonates - simplistic answer - Occam

This is straying even farther afield, but today's New York Times has a piece by Nicholas Kristof linking frog abnormalities, as well as those in other amphibians and in fish, to endocrine disruptors, a category of chemicals used in industry and agriculture and also found in some human waste. This sort of canary in the coal mine scenario is making scientists look at a possible connection between these same chemicals and increasing numbers of abnormalities in humans. Further evidence that larval odonates may be only one contributor to frog leg anomalies. 

http://www.nytimes.com/2009/06/28/opinion/28kristof.html

Marion Dobbs
Rome (Floyd Co.) GA
pond_damsel AT comcast.net
http://mamomi.net
http://mariondobbs.smugmug.com
http://ponddamsel.phanfare.com

----- Original Message ----- 
From: Richard Rowe 
To: John Acorn ; Odonata-l 
Sent: Saturday, June 27, 2009 9:49 PM
Subject: Re: [Odonata-l] Frog legs and odonates - simplistic answer - Occam
John Acorn wrote: 
Hi Josh, Odesters, 

Just a wee clarification, since I've been thinking about this myself.  Occam's Razor is a logical concept, not a scientific concept, and it fails to point to the "right answer" not because it is flawed logically, but because it needs sufficient evidence to work correctly.  It simply means choosing the hypothesis that makes the fewest poorly supported, or unsupported assumptions.  The only way to judge these assumptions is with evidence, so a more detailed view of the world makes for a more useful application of parsimony (i.e. Occam's Razor).  To ignore parsimony is to accept unnecessarily complex hypotheses, which is not a good idea either.  It all points not to the weakness of parsimony, but to the limits of science in the face of a very complex world.Precisely. And until you have evidence it is NOT predation you shouldn't seek more complicated explanations (the filmed predators look like libellulids, aeshnids chomp tadpoles but do a complete job,
 Pantala flavescens is a libellulid that chomps tadpoles, so choose your predator carefully). The seeking of complex explanations comes close to Crabtree's bludgeon (q.v.).

On Jun 26, 2009, at 9:19 PM, Joshua Rose wrote:

Occam's Razor actually tends to be wrong in many ecological cases. Academic science favors oversimplification; everyone wants to boil each effect down to a single cause, that being conducive to winning grants, getting published, and receiving tenure. Real life usually does not cooperate.in multivariate situations, and where synergistic processes abound, a little early observation can go a long way to asking the right questions. Asking the wrong question, and worse erecting a bandwagon based on the wrong question, does science no favours.

The publications I read concerning that chytrid indicated that it had been present in many areas without causing any undue harm to amphibians; but that other environmental effects - acidification, UV, and so on - degraded the amphibian's immune responses such that the formerly innocuous chytrid became a threat. To the extent that herpetologists carried the chytrid to isolated populations and helped wipe them out, if that did take place, it was A cause but probably not THE cause. A number of frog populations disappeared that had been well known to herpetologists and under study for many years before the chytrid reared its ugly head.The chytrid in question had been out there for years before it was recognised as a problem, then identified as a previously unrecognised species that had invaded new habitats/species. From memory (treacherous) it was first identified on Dendrobates in the National Zoological Park in Washington DC. First publications were in
 1999. Before that people were looking for complicated causes and ignored the fundamental indications of an infectious agent which would have led them to the correct diagnosis in the late 80s. Batrachochytrium dendrobatidis is not hard to find.

Another study indicated that non-native Bullfrogs were carriers of the chytrid, hosting it but not being killed off by it, and had helped spread it to at least four continents. African Clawed Frogs are carriers as well. One more piece of the complicated puzzle.

Back to the issue relevant to this listserv, the odonate larvae eating the legs off of amphibian larvae. The study in question took place in three ponds in one county in England. The answer may be simple in this one small area. There is a LOT more research to do before odonates can be generally accepted as a single worldwide cause of amphibian limb shortages....

--   Dr Richard Rowe  Zoology & Tropical Ecology  School of Marine & Tropical Biology  James Cook University  Townsville 4811  AUSTRALIA    ph +61 7 47 81 4851  fax +61 7 47 25 1570  JCU has CRICOS Provider Code 00117J 
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