Scott,
When I started to prepare for my May 1997 trip to Eastern Indonesia, it was
suggested that I read "The Malay Archipelago" by Alfred Russell Wallace.
It was that book that got me hooked on the evolutionary concepts that
influence variability in land shells and other living organisms. And his
paper "On The Tendency of Varieties to Depart Indefinitely From The
Original Type " is also essential reading. Excerpts of the latter and
others are available on the Internet (see below).
Wallace, a protégé of Darwin, came up with his own independent theory of
evolution and ideas on natural selection during an eight year sojourn to
the Maluku region of Indonesia in the mid-1850's. His narrative of
misfortunes, illness and deception during the excursion is fascinating. He
waxes eloquently about the extraordinary wildlife and beauty of the
islands. This book along with Darwin's Origins of Species, and a number of
other papers dealing with evolutionary theory are available on the
Internet, were essential reading before I began to learn more about these
biological concepts.
Gary Rosenberg and Tim Pearce have both been a tremendous help in
explaining many of these concepts that ultimately became the basis for the
Amphidromus article. Gary mentioned a couple of references dealing with
variation, on Conch-L today which I am going to seek out. I'm sure a large
library would have books dealing with evolutionary biology which may
explain in more detail, frequency dependent selection, genetic drift, and
the founder effect.
And search the Internet. I've found excellent Web sites dealing with a
host of biological concepts. A few, including some Wallace references are
listed below, as well as some print references.
Let us know if you come across anything related to mollusks in particular.
Rich
PRINT:
Alfred Russel Wallace: An Anthology of His Shorter Writings. Charles H.
Smith, ed. Oxford/ New York: Oxford University Press, 1992.
Brooks, John Langdon. Just Before the Origin: Alfred Russell Wallace's
Theory of Evolution. New York: Columbia University Press, 1984.
McKinney, H. Lewis. Wallace and Natural Selection. Yale Studies in the
History of Science and Medicine. New Haven / London: Yale University Press,
1972.
INTERNET:
http://www.literature.org/Works/Charles-Darwin/origin/
Darwin
gopher://gopher.vt.edu:10010/02/69/2
Darwin - Origin of Species (tough to read on the computer)
http://www.stg.brown.edu/projects/hypertext/landow/victorian/science/lamarck
1.html
Commentary on Lamarck's theories of evolution.
http://www.uib.no/zoo/classics/new_species.txt
Wallace - February, 1855 / "On The Law Which Has Regulated The
Introduction of New Species"
http://www.uib.no/zoo/classics/varieties.html
Wallace - 1858 "On The Tendency of Varieties to Depart Indefinitely From
The Original Type "
At 12:44 AM 2/3/98 -0500, you wrote:
>-- [ From: Scott Jordan * EMC.Ver #2.5.3 ] --
>
>Dear Rich,
>
>Do you recommend any particular books that delve into these biological
>concepts? I realize that these are hardly new but perhaps you are aware
>of a text that would be of help to the interesed layperson.
>
>Thanks in advance,
>
>Scott Jordan
>
>-------- REPLY, Original message follows --------
>
>> Date: Tuesday, 03-Feb-98 12:08 AM
>>
>> From: Worldwide \ Internet: ([log in to unmask])
>> To: conch-l \ Internet: ([log in to unmask])
>>
>> Subject: Re: color and pattern variation
>>
>> Ross,
>>
>> Your explanation of variation seems to be related to natural selection
>and
>> frequency dependent selection, and are well taken. These biological
>concepts
>> were covered in the article I co-authored on the isolation and
>evolution of the
>> land shell genus Amphidromus in Indonesia [Am.Conch. June 1997 (on
>Conch-Net:
>> http://coa.acnatsci.org/conchnet/gold697.html )]. What I was
>interested to
>> know is whether the biological concepts which may influence variation
>in land
>> shells would also hold true for marine species?
>>
>> For instance, marine mollusks are often encrusted with marine
>organisms, or
>> periostracum which completely obscure color and pattern. Would
>natural
>> selection, or frequency dependent selection then apply to a group such
>as the
>> Cones where the periostracum obscures the color and pattern? Since
>predators
>> are not developing a search image of the color/pattern, would genetic
>drift
>> (described in the above article) be a more appropriate theory
>explaining
>> variation? -- e.g. Conus cedonulli shows extreme variation within one
>> population. The Amphidromus article states that genetic drift tends
>to
>> eliminate variation within a population and increases differences
>between
>> populations. Confusing!
>>
>> Another instance where a species exhibits a great deal of color
>variation
>> within a population is Spondylus linguaefelis. It inhabits water deep
>enough
>> to filter out most of the warm color range that Ross refers to. Also,
>the
>> species is almost always encrusted with sponge and other organisms,
>totally
>> obscuring the color. Yet the species which lives its life anchored in
>one
>> position is found in a broad range of colors. Do these colors have
>any
>> function?
>>
>> So again, the question restated is, "Do the biological concepts
>maintained for
>> intra and inter-population variability of land snails like frequency
>dependent
>> selection, genetic drift, and the founder effect hold true for marine
>species?
>> Carol mentioned that she has not come across any specific mention in
>the
>> literature. Neither have I. Does anyone know of recent papers
>related to
>> these concepts? Gary? Tim? Others? Are there any easy answers?
>Lot's of
>> questions...
>>
>> Rich
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Richard L. Goldberg
>> Worldwide Specimen Shells
>> email: [log in to unmask]
>> homepage: http://www.erols.com/worldwide
>> ------------------------------------------------------------------
>> "The shortest distance between two points
>> is under construction." Noelie Alito
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>>
>>
>> At 05:32 AM 2/2/98 -0400, Mayhew wrote:
>> >Did anybody see which way January went?? Talk about warp-speed time
>> >travel!!
>> >
>> > A week or so ago, someone asked about the feature i admire
>the most
>> >about Mollusc shells: the incredible range of variation many
>populations
>> >exhibit, regarding color and patterns, especially in many of the most
>> >common spp, and the most successful and diverse families, such as
>> >Pectinidae, Neritidae, and of course Conidae. It is highly probale
>> >that these spp and families BECAME so successful because of their
>> >adaptability, which included their ability to blend in with their
>> >visible surroundings whenever nessessary -ie, whenever predatory
>> >pressure based upon color and/or pattern occurs. I believe that many
>> >spp maintain a genetic "pool"
>> >of visually-related variation, based partly upon past episodes of
>> >visual predation which enhanced the relative survival rate of certain
>> >colors and pattern-types, and partly upon simple genetic drift, which
>> >often produces morphs of limited or no survival value (as in shocking
>> >orange Nucella lapillus L., or violet Neptunea lyrata decemcostata-
>> >beautiful from our perspective, but not corresponding to any feature
>in
>> >their environment that i have ever seen!). The more varied a given
>> >species' pool of visual possibilities, the better their chances of
>> >surviving in different portions of their total niche, if and when
>> >visual predation becomes intense locally or regionally.
>> >A "local" example would be Littorina obtusata L.. In situations where
>> >crabs can easily pick them off their Fucus habitat, they are
>> >marvellously camoflaged, being mainly green and pale yellow, these
>> >being the colors of the blades and bladders of the algae they live
>on.
>> >In other localities, where crabs are less able to get at them, they
>are
>> >orange, black-striped, and a good variety of morphs or quite scarce
>in
>> >the crab-harrased populations.
>> > Some of the variation we humans easily notice in sunlight,
>with eyes
>> >capable of differentiating many thousands of colors, hues, and
>pattern
>> >subteties, may be due to the differing visual charactaristics of the
>> >bakground, the medium (air vs water of varying depth) the shell is
>> >viewed in, as well as the visual capabilities of the relevant
>> >predator(s): Water filters out certain wavelengths, and most marine
>> >predators cannot distinguish as wide a range of colors as we can-
>some
>> >indeed are color-blind, and rely upon form, pattern, refleciveness,
>> >etc., to discern their lunches from surrounding inedible materials.
>> >So, what may look like very different colors and hues to our
>discerning
>> >eyes, may be nearly identical to the predator(s) which help determine
>> >their relative frequencies by eating the inhabitants of the shells
>> >they can more easily find. Likewise, some patterns may be just as
>> >difficult for predators to discern as others which seem to us, under
>> >very different circumstances, to be radically dissimilar (Neritidae
>> >would seem to be masters at producing "visually-equivilant" patterns!
>!).
>> > Any other theories, or comments and critisisms on the ideas
>above,
>> >would be most welcome! -Ross Mayhew
>> >(Schooner Specimen Theories)
>> >
>>
>>
>> >At 11:00 PM 1/27/98 -0600, Goldberg wrote:
>> >Here's a topic for discussion. Color variation within a species has
>always
>> >interested me; both aesthetically and scientifically. Marine species
>like
>> >Pecten and Spondylus are prime examples. What are the accepted
>theories
>> >for particular marine species varying widely in color? Is it
>adaptive
>> >coloring? Genetic? Spondylus and Pectens are quite often encrusted
>or
>> >coated with marine growths which obscure the external coloring. So
>> >adaptive coloring seems a less likely theory. A number of Murex,
>Chitons
>> >and other groups have species that also exhibit a wide range of
>colors.
>> >Color variation in land shells is often an adaptive characteristic.
>What
>> >about marine shells? Anyone takers?
>> >
>> >Rich
>> >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> >Richard L. Goldberg
>> >Worldwide Specimen Shells
>> >email: [log in to unmask]
>> >homepage: http://www.erols.com/worldwide
>> >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>
>-------- REPLY, End of original message --------
>
>
>
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