>Look at the cichlids (fish)of Lake Victoria(?) in Africa.  Introduction of new
>species by people made the water cloudy and prevented closely related species
>from distinguishing each other (they were dependant on color patterns).  Now
>there are fewer, blander species.  Not sure if this is at all applicable to
>marine mollusks which probably use chemical cues to distinguish
>species, but at
>the rate we are spreading pollutants into the environment, we may eventually
>screw them up too.

It is possible that the cichlids' (Cichlididae) apparent loss of
diversity is in part due to adaptation to murky waters (analogous to
pale English moths developing a dark form during the Industrial
Revolution). Many of these cichlids differ mainly in color, and quite
a few may not be good species. Dull-colored fish might be more likely
to hybridize, too, especially those which have color-coded (visual)
recognition.

>>>I don't understand: what are the intermediate specimens between Lambis
>>>lambis and Lambis millipeda if they are not hybrids?
>>
>>Certainly they are.

>Thankyou...of course they are. What else could they be??

>I agree with you , Andrew . Maybe in some cases being desperate to mate
>because of too small a population of its own species at the boundaries of
>its range is not the only reason for a specimen of a species A to mate with
>a specimen of a species B instead of a specimen of its own species .

I wrote a good reply to this, then before saving it it disappeared
from my HD! So I'll try again...

Imagine you were a snail called Lambis lambis. You would not
consciously look for a mate, thinking "I just gotta have a ***, I
just GOTTA have a ***!!" Humans are probably the only species which
DESIRES to have sex, and if it can't have it, may become desperate to
do so. Gastropods will mate given the opportunity, but will not go
hunting for it, nor will they become desperate if they don't get it.
This has the corollary that it doesn't make any difference where the
hybridization takes place; it is just as likely to occur anywhere in
the two species' zone of distributional sympatry. And these critters
probably use chemosensory stimuli to find one another; just WHY
crossspecies/crossgenus mating occurs is uncertain, but here's an
idea - perhaps it could be that one of the individuals concerned
produces species-inappropriate pheremones?

Another thing to note: if hybrids begin to breed true and result in a
new species, the offspring of two hybrid specimens will no longer be
a hybrid, as its parents have identical specific genetic makeup.
Nevertheless there will still occur hybridization between the parent
species, so the population of "wheelwrighti", for instance, will
contain first-generation hybrids as wel as second-generation
nonhybrid specimens. That it, a hybrid is a specimen which is
offspring of two different species; two L. wheelwrighti mating are
not hybridizing, as they are conspecific. Nothing is straightforward
in nature!

This sort of discussion is useful; it makes us THINK about the
subjects/issues involved.

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