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Chris, Angus, others...
Chris' comment in reply raises a very interesting general =20
evolutionary issue that someone else must have considered but I haven't =20=
ever seen mentioned. The original observation is that, as Chris =20
points out, many or most of the family Syrphidae ("hoverflies"), Order =20=
Diptera (true flies) are considered to be mimics of some member or =20
other of the wasp and bee branches of the Order Hymenoptera (bees, =20
wasps, sawflies, etc).
I believe this is correct. It's also is correct for many of one =20=
other family of flies, the lesser-known Stratiomyidae ("soldier =20
flies"). This perhaps would be less surprising if the two families of =20=
fly were phylogenetically close together, but they're not, they are =20
very distantly related. The syrphids fall at the primitive beginnings =20=
of the huge group of advanced muscomorph families of flies, none of =20
which are known from fossils from Canadian amber deposits (Cedar Lake =20=
~90 million years old), but all of which are found later in Baltic =20
amber ~50 MYr or so old: they probably all evolved between 90 and 50 =20=
Myr ago, so are 'recent'. By contrast, the stratiomyids are =20
'ancient', classified in the most basal group of Brachyceran flies, =20
close to the tabanids (horse- and deerflies), some members of which =20
general group are known from Cretaceous fossils maybe ~130 Myr old =20
(from memory). Since the mimicry is superficial, extending to =20
external bodily appearance and perhaps to some behaviour, it is unclear =20=
why mimicry is not distributed more or less evenly among other groups =20=
of flies, or why it is so common in syrphids and strats: it is hard to =20=
imagine that either group would have had some special 'preadaptation' =20=
not found in other families of fly, that would make mimicry a likely =20
evolutionary strategy for the whole family -- at least I can't think of =20=
anything.
The only thing that seems to make sense is (1) that mimicry must =20
have developed independently (obviously) in the two families, and (2) =20=
that in both cases mimicry is very old, such that as the models (the =20
bees, wasps) diverged to form new species during evolution, the mimics =20=
diverged and evolved to match them. If so, it would be two very =20
interesting cases of co-evolution of models and their mimics. I don't =20=
know if anyone has looked further into this, for instance trying to =20
match up a phylogenetic tree of mimics, to see if it could be =20
superimposed upon the tree for the models. Probably much too =20
ambitious and difficult, and also would require a taxonomist who knew =20=
both dipterans and hymenopterans intimately -- probably no-one anywhere =20=
specializes in both.
Has anyone come across this idea of co-evolution of these two =20
groups, or seen any evidence for it?
Steve
On 20-Oct-06, at 12:52 AM, c.majka@ns.sympatico.ca wrote:
> My=A0knowledge of syrphids is pretty slender, however, I think many =20=
> (maybe even most?) species, however, are considered to be wasp or bee =20=
> mimics. I've no idea what wasp=A0Sphaerophoria imitates in particular; =
=20
> could be a potter wasp or some other vespid. I've no idea if this is =20=
> even known.
> Cheers,
> =
Chris_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._.=20=
> _._._._.
> Christopher Majka - Nova Scotia Museum of Natural History
> 1747 Summer Street, Halifax, Nova Scotia, Canada=A0 B3H 3A6
> (902) 424-6435 =A0 Email <c.majka@ns.sympatico.ca>
> =
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._=20=
> ._.
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Chris, Angus, others...
Chris' comment in reply raises a very interesting general
evolutionary issue that someone else must have considered but I
haven't ever seen mentioned. The original observation is that, as
Chris points out, many or most of the family Syrphidae ("hoverflies"),
Order Diptera (true flies) are considered to be mimics of some member
or other of the wasp and bee branches of the Order Hymenoptera (bees,
wasps, sawflies, etc). =20
I believe this is correct. It's also is correct for many of one
other family of flies, the lesser-known Stratiomyidae ("soldier
flies"). This perhaps would be less surprising if the two families
of fly were phylogenetically close together, but they're not, they are
very distantly related. The syrphids fall at the primitive
beginnings of the huge group of advanced muscomorph families of flies,
none of which are known from fossils from Canadian amber deposits
(Cedar Lake ~90 million years old), but all of which are found later
in Baltic amber ~50 MYr or so old: they probably all evolved between
90 and 50 Myr ago, so are 'recent'. By contrast, the stratiomyids
are 'ancient', classified in the most basal group of Brachyceran
flies, close to the tabanids (horse- and deerflies), some members of
which general group are known from Cretaceous fossils maybe ~130 Myr
old (from memory). Since the mimicry is superficial, extending to
external bodily appearance and perhaps to some behaviour, it is
unclear why mimicry is not distributed more or less evenly among other
groups of flies, or why it is so common in syrphids and strats: it is
hard to imagine that either group would have had some special
'preadaptation' not found in other families of fly, that would make
mimicry a likely evolutionary strategy for the whole family -- at
least I can't think of anything.
The only thing that seems to make sense is (1) that mimicry must
have developed independently (obviously) in the two families, and (2)
that in both cases mimicry is very old, such that as the models (the
bees, wasps) diverged to form new species during evolution, the mimics
diverged and evolved to match them. If so, it would be two very
interesting cases of co-evolution of models and their mimics. I
don't know if anyone has looked further into this, for instance trying
to match up a phylogenetic tree of mimics, to see if it could be
superimposed upon the tree for the models. Probably much too
ambitious and difficult, and also would require a taxonomist who knew
both dipterans and hymenopterans intimately -- probably no-one
anywhere specializes in both. =20
Has anyone come across this idea of co-evolution of these two
groups, or seen any evidence for it?
Steve =20
=20
On 20-Oct-06, at 12:52 AM, c.majka@ns.sympatico.ca wrote:
<excerpt>My=A0knowledge of syrphids