[Taxacom] Forgotting at the edge of miracles

Dr. Antonio Lopez cycas at mnhnc.inf.cu
Sun Apr 26 12:02:07 CDT 2015

If I don't understand bad, I am in great agreement measure with you. I find that in many aspects we are being about flying, and we have not even learned how to walk. At this time single treatment of exposing what I am able to analyze the patterns of current distribution of 2.5 thousand species of plants well identified exclusive of an island that it left the sea in a tectonic small and quite recent tectonic plate.
That contrasts it by the way with the local, very well-known geology advances. Also with vegetable big groups in near regions. Until the molecular genetics, I was interested in a group of species, the tropical pines living at the sea level.
The advances have been numerous, but we feel unable to elaborate global hypothesis of nothing. After 20 years when we try to come closer to that, we finish writing a book on biogeography by the light of the complexity with 700 pages. Pure philosophy.
In real biogeography, we continue analyzing what we have, and that we can understand, being about giving a step every time. Maybe some day we can write something more concrete.

Dr. Antonio López Almirall
Conservador del Herbario 
Museo Nacional de Historia Natural
Obispo 61, Plaza de Armas
Habana Vieja 10100, La Habana 
Email cycas at mnhnc.inf.cu

-----Mensaje original-----
De: Richard Pyle [mailto:pylediver at gmail.com] En nombre de Richard Pyle
Enviado el: domingo, 26 de abril de 2015 10:08 a. m.
Para: 'John Grehan'
CC: 'Anthony Gill'; 'Karl Magnacca'; 'TAXACOM'; 'Dr. Antonio Lopez'
Asunto: RE: [Taxacom] Forgotting at the edge of miracles

> Could you put a bit of meat on your characterization? 

A bit?  Sure.

> What do you mean by a single 'model' that accounts for all distributions. 

Well, we have lots of proposed hypotheses about historical mechanisms to account for modern geographic distribution patterns of organisms.  Some (most?) of these hypotheses involve mechanisms that occur on evolutionary time scales (i.e., the implication being that present-day patterns of geographic occurrence of organisms reflects historical patterns of geographic speciation of organisms). Other hypotheses involve mechanisms that occur on ecological (i.e., sub-evolutionary) time-scales (the implication being that present-day patterns of geographic occurrence does not necessarily reflect historical patterns of speciation).  Good hypotheses show how existing evidence "fits" the proposed mechanism behind how populations of organisms got to be where they are now. Better hypotheses show how the existing evidence "fits" the proposed mechanism behind how populations of organisms got to be where they are now MORE EFFECTIVELY than alternative hypotheses (i.e., in many cases, the same evidence often "fits" multiple different competing hypotheses).  The BEST hypotheses make specific, testable predictions about future (but not yet acquired) evidence, in ways that support one hypothesis over others.

This is all good -- exactly the sort of process by which science SHOULD progress (i.e., using empirical data to support or refute alternate competing hypotheses).

Now, getting to your question, I used the word "model" as a more inclusive term of "mechanisms".  So, one "model" of biogeography, for example, is that organisms occur where they do now because historical vicariant events have shaped patterns of allopatry and subsequent speciation.  Another model of biogeography is that organisms occur where they do now because historical dispersal of organisms has shaped patterns of allopatry and subsequent speciation.  Other models involve mechanisms of extinction and re-colonization, or consequences of both organism-induced and Earth-induced factors, or various other sets of factors.

I was echoing and extending Tony's complaint of "A presumption of dispersal as an explanation for everything makes for uninteresting, and ultimately irrelevant, research",  to replace the word "dispersal" with *any* mechanism that has been proposed to account for modern geographic distribution patterns of organisms; the key phrase being "as an explanation for everything".

The point I was trying to make is that often-times combatants in these biogeopgraphic debates act as though there is necessarily one dominant mechanism to explain modern distribution patterns of most organisms, and the alternate mechanisms only apply to exceptional situations.  Maybe different mechanisms play greater or lesser roles for different kinds of organisms (e.g., coral-reef fishes vs. terrestrial mammals). Maybe in some cases, modern distribution patterns correlate well with historical patterns of speciation. Maybe in other cases, they don't.  My main point is that the word "Maybe" applies here because we are still "SO, SO, SO far away from understanding both evolutionary history and the actual distribution patterns of most living things".

> And what is the basis for your contention that we are 'SO, SO' far away from understanding evolutionary history and distributions of living things. 

That's easy:

1) The most plausible estimates put total diversity at around 10-30 million species. We've only cataloged about 2 million (let's call it 10%). We obviously don't know the distribution patterns of species that we don't even know exist yet. So, at BEST, the evidence to support alternative mechanisms behind patterns of speciation and biogeography are using only 10% of available evidence.

2) We are, of course, far from the "BEST" situation (i.e., 10%) because we have not yet confidently established evolutionary relationships among the 10% of organisms we do know about. For example, molecular evidence strongly supports a phylogeny of ((Humans, Chimps), Orangutans); yet you have shared with this list in the past compelling morphological and other non-molecular evidence to support a phylogeny of ((Humans, Orangutans), Chimps).  If the best we can say about one of the most well-studied examples of evolutionary relationships is, "we have conflicting evidence"; then where does that leave us with the rest of the 2 million species?

3) Even if we ignore our ignorance of evolutionary relationships, and simply trust our assessment of species boundaries to focus on inferring mechanisms of biogeography from observed distribution patterns (without trying to correlate to patterns of speciation), we are still woefully lacking in our documentation of the current distribution patterns of most of the known species (let alone the unknown species).

> Who in biogeography has made claims that we are close to fully understanding it

Well, we have these seemingly endless (and sometimes fierce) arguments about biogeography, and historical mechanisms to explain observed modern patterns of distribution. What are these arguments about, if not, fundamentally "Mechanism 'X' explains most distribution patterns better than mechanism 'Y'"?  My point (again, to echo Tony's), is that such strong convictions about historical mechanisms behind apparent modern distribution patterns of organisms (and especially when those patterns are correlated with inferred patterns of speciation) are wholly unwarranted when they are based on largely incomplete knowledge of current distribution patterns and evolutionary relationships of something like 10% of biota.

I hope that addresses your questions.


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