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CO2 Connectors - Threaded vs Unthreaded



 
 
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  #41  
Old July 16th 19, 04:16 PM posted to rec.bicycles.tech
Duane[_2_]
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Posts: 401
Default CO2 Connectors - Threaded vs Unthreaded

On 16/07/2019 10:28 a.m., jbeattie wrote:
On Tuesday, July 16, 2019 at 6:56:11 AM UTC-7, Tom Kunich wrote:
On Monday, July 15, 2019 at 5:20:04 PM UTC-7, John B. wrote:
On Mon, 15 Jul 2019 15:20:57 -0700 (PDT), Frank Krygowski
wrote:

On Monday, July 15, 2019 at 6:09:22 PM UTC-4, John B. wrote:
On Mon, 15 Jul 2019 13:05:17 -0000 (UTC), dave
wrote:

On Sat, 13 Jul 2019 17:01:15 +0200, Tosspot wrote:

A discussion down there --v or up there --^ reminded me CO2 cartridges
come in a least two connectors, threaded and not. I've been caught by
this.

Why the difference? Who cam first?

The chicken.

But where did the chicken come from? The Ark :-?

The scientists say the egg came way before the chicken, because animals much
more primitive than chickens had been laying eggs for millions of years
before there were birds of any kind.

But those people saying that are evil evolutionists. They don't understand that
God put fossils in the ground to test our faith. He's infinitely tricky!

- Frank Krygowski

On the other hand if the Christian/Jewish/Moslem God made the universe
and everything in it might he/she/it have created lizards and as
he/she/it rested on the seventh day might that be interpreted as the
period from the creation to modern times giving those pesky lizards
time to grow feathers and learn to fly?
--
cheers,

John B.


Never having read the Bible you can be excused for not having even an inkling what is in it.


I've read the Bible. I've even read the Book of Mormon. O.K., part of it and even parts of the Koran and parts of Buddhist and Hindu texts. I've also read "Horton Hears a Who!" I'm not sure which one is the best scientific text.


Wasn't aware that the bible had anything definitive to say regarding
threaded vs un-threaded CO2 cartridges...

BTW, I stood on Charles Darwin's grave at Westminster Abby. Take that!

And evolution is all around us -- bacteria, viruses, plants and animals. Go to Death Valley and look at the pupfish. https://www.sciencemag.org/news/2016...dred-years-ago I have. Go there and say hello to my little evolving friends.

-- Jay Beattie.


Ads
  #42  
Old July 16th 19, 04:17 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
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Posts: 7,511
Default CO2 Connectors - Threaded vs Unthreaded

On Tuesday, July 16, 2019 at 2:22:27 AM UTC-4, wrote:
On Monday, July 15, 2019 at 5:05:12 PM UTC+2, Frank Krygowski wrote:
On Monday, July 15, 2019 at 10:24:29 AM UTC-4, Tom Kunich wrote:
On Monday, July 15, 2019 at 4:57:15 AM UTC-7, Tom Evans wrote:
On 15/07/2019 08:12, John B. wrote:
On Sun, 14 Jul 2019 22:42:12 -0700 (PDT), Chalo
wrote:

That's grams, not ounces.

And it's a pretty horrendous misuse of resources just to avoid pumping.

Try pumping oh say a 700-25C tire to 90 psi with one of those little
short pocket sized pumps :-)

Framefit pumps still work, quickly, zefal hpx, just because worse
solutions have been invented doesn't mean you have to switch to them.

Someone else telling me what to do with my money. The same person that was supporting electronic shifting?


Sheesh. It's getting to where a person can't state an opinion without triggering
someone else.

You love CO2 cartridges? Fine, use them. If we ever ride together and you need
to use my pump, I'll loan it to you. You won't be the first.

- Frank Krygowski


Like I offer one of my CO2 cartidges after a riding buddy f*cked with 2 or 3 clown pumps (copyright Jay) that don't work and I'm fed up with it and getting cold. Won't be the first time.


I understand. That's why I don't use clown pumps.

Well, the pump for my Bike Friday may qualify. It was chosen so (after a little
filing to reduce some corners on the head) I can slide it into the seat tube of
the bike. It's inconvenient to carry a Zephal HPX on a folding bike.

- Frank Krygowski

  #43  
Old July 16th 19, 04:18 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
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Posts: 7,511
Default CO2 Connectors - Threaded vs Unthreaded

On Tuesday, July 16, 2019 at 10:00:18 AM UTC-4, Tom Kunich wrote:
On Monday, July 15, 2019 at 9:05:15 PM UTC-7, Frank Krygowski wrote:

Yesterday I saw one of my friends - a PhD biologist - wearing a T-shirt that
said "Science is not a liberal conspiracy."

It's sad that it's now necessary to say that.

- Frank Krygowski


"Science" like the man-made global warming that doesn't exist?


Wow.

- Frank Krygowski
  #44  
Old July 16th 19, 04:21 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
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Posts: 7,511
Default CO2 Connectors - Threaded vs Unthreaded

On Tuesday, July 16, 2019 at 10:01:14 AM UTC-4, Tom Kunich wrote:
On Monday, July 15, 2019 at 9:06:32 PM UTC-7, Frank Krygowski wrote:
On Monday, July 15, 2019 at 7:10:44 PM UTC-4, Tom Kunich wrote:
On Monday, July 15, 2019 at 3:20:58 PM UTC-7, Frank Krygowski wrote:

The scientists say the egg came way before the chicken, because animals much
more primitive than chickens had been laying eggs for millions of years
before there were birds of any kind.

But those people saying that are evil evolutionists. They don't understand that
God put fossils in the ground to test our faith. He's infinitely tricky!

- Frank Krygowski

Show us ONE proof that ANY evolution ever led to a new species. That has NEVER been found and the theory of evolution is still noting more than a theory.


Wow.

- Frank Krygowski


Rather than show any doubt why don't you show us even a single instance of evolution causing speciation?


What sort of evidence would you accept? I strongly suspect the answer is "none."

- Frank Krygowski
  #45  
Old July 16th 19, 05:03 PM posted to rec.bicycles.tech
Jeff Liebermann
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Posts: 4,018
Default CO2 Connectors - Threaded vs Unthreaded

On Tue, 16 Jul 2019 12:25:53 +0700, John B.
wrote:
Since that rainy morning I carry spare tubes and CO2 cartridges.
And, I used to also carry a pump. But I gave that up after a couple of
years with no punctures at all :-)


That's because your spare tubes and CO2 cartridges act as a talisman
to ward way evil spirits and bad luck. As long as you carry those
spares, you will not have any flat tires. However, should you forget
and ride without them for even one day, you will surely get a flat
tire on that day.

I have two spare tubes and two CO2 cartridges on each bike and (knock
on wood) I haven't , so far, needed the second tube.


My problem is that everything I own leaks. My car radiator leaks, my
A/C coolant leaks, my garbage dolly tires leak, my house plumbing
leaks, all my water bottles drip, etc. Of course, my bicycle inner
tubes also leak. While CO2 is quite practical for refilling empty
tubes after a puncture patch, it's totally useless for dealing with
leaky inner tubes, where "topping off" with a hand or floor pump is
far more practical. Therefore, I do not own a CO2 inflator and only
carry whichever hand pump best color matches my current choice of ride
and atti
http://www.learnbydestroying.com/jeffl/pics/bicycles/misc/slides/bicycle-pumps.html
The situation is unlikely to change because I have a supply of genuine
leaky Nashbar inner tubes. I'll probably never need a CO2 inflator
because it's difficult to get a flat on a partially inflated leaky
tube.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #46  
Old July 16th 19, 05:28 PM posted to rec.bicycles.tech
JBeattie
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Posts: 5,870
Default CO2 Connectors - Threaded vs Unthreaded

On Tuesday, July 16, 2019 at 8:16:25 AM UTC-7, duane wrote:
On 16/07/2019 10:28 a.m., jbeattie wrote:
On Tuesday, July 16, 2019 at 6:56:11 AM UTC-7, Tom Kunich wrote:
On Monday, July 15, 2019 at 5:20:04 PM UTC-7, John B. wrote:
On Mon, 15 Jul 2019 15:20:57 -0700 (PDT), Frank Krygowski
wrote:

On Monday, July 15, 2019 at 6:09:22 PM UTC-4, John B. wrote:
On Mon, 15 Jul 2019 13:05:17 -0000 (UTC), dave
wrote:

On Sat, 13 Jul 2019 17:01:15 +0200, Tosspot wrote:

A discussion down there --v or up there --^ reminded me CO2 cartridges
come in a least two connectors, threaded and not. I've been caught by
this.

Why the difference? Who cam first?

The chicken.

But where did the chicken come from? The Ark :-?

The scientists say the egg came way before the chicken, because animals much
more primitive than chickens had been laying eggs for millions of years
before there were birds of any kind.

But those people saying that are evil evolutionists. They don't understand that
God put fossils in the ground to test our faith. He's infinitely tricky!

- Frank Krygowski

On the other hand if the Christian/Jewish/Moslem God made the universe
and everything in it might he/she/it have created lizards and as
he/she/it rested on the seventh day might that be interpreted as the
period from the creation to modern times giving those pesky lizards
time to grow feathers and learn to fly?
--
cheers,

John B.

Never having read the Bible you can be excused for not having even an inkling what is in it.


I've read the Bible. I've even read the Book of Mormon. O.K., part of it and even parts of the Koran and parts of Buddhist and Hindu texts. I've also read "Horton Hears a Who!" I'm not sure which one is the best scientific text.


Wasn't aware that the bible had anything definitive to say regarding
threaded vs un-threaded CO2 cartridges...


Ludditicus 2:14 "You shall not use a CO2 inflator as you would a frame pump. It is an abomination." All CO2 cartridges are prohibited. Apparently you do not read the Bible . . . or invest in the stock market!

-- Jay Beattie.
  #47  
Old July 16th 19, 05:53 PM posted to rec.bicycles.tech
Duane[_2_]
external usenet poster
 
Posts: 401
Default CO2 Connectors - Threaded vs Unthreaded

On 16/07/2019 12:28 p.m., jbeattie wrote:
On Tuesday, July 16, 2019 at 8:16:25 AM UTC-7, duane wrote:
On 16/07/2019 10:28 a.m., jbeattie wrote:
On Tuesday, July 16, 2019 at 6:56:11 AM UTC-7, Tom Kunich wrote:
On Monday, July 15, 2019 at 5:20:04 PM UTC-7, John B. wrote:
On Mon, 15 Jul 2019 15:20:57 -0700 (PDT), Frank Krygowski
wrote:

On Monday, July 15, 2019 at 6:09:22 PM UTC-4, John B. wrote:
On Mon, 15 Jul 2019 13:05:17 -0000 (UTC), dave
wrote:

On Sat, 13 Jul 2019 17:01:15 +0200, Tosspot wrote:

A discussion down there --v or up there --^ reminded me CO2 cartridges
come in a least two connectors, threaded and not. I've been caught by
this.

Why the difference? Who cam first?

The chicken.

But where did the chicken come from? The Ark :-?

The scientists say the egg came way before the chicken, because animals much
more primitive than chickens had been laying eggs for millions of years
before there were birds of any kind.

But those people saying that are evil evolutionists. They don't understand that
God put fossils in the ground to test our faith. He's infinitely tricky!

- Frank Krygowski

On the other hand if the Christian/Jewish/Moslem God made the universe
and everything in it might he/she/it have created lizards and as
he/she/it rested on the seventh day might that be interpreted as the
period from the creation to modern times giving those pesky lizards
time to grow feathers and learn to fly?
--
cheers,

John B.

Never having read the Bible you can be excused for not having even an inkling what is in it.

I've read the Bible. I've even read the Book of Mormon. O.K., part of it and even parts of the Koran and parts of Buddhist and Hindu texts. I've also read "Horton Hears a Who!" I'm not sure which one is the best scientific text.


Wasn't aware that the bible had anything definitive to say regarding
threaded vs un-threaded CO2 cartridges...


Ludditicus 2:14 "You shall not use a CO2 inflator as you would a frame pump. It is an abomination." All CO2 cartridges are prohibited. Apparently you do not read the Bible . . . or invest in the stock market!

-- Jay Beattie.


Ludditicus? Must be new testament. Fake news. Old testament is the
juicy testament.
  #48  
Old July 16th 19, 07:51 PM posted to rec.bicycles.tech
Tosspot[_3_]
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Posts: 1,563
Default CO2 Connectors - Threaded vs Unthreaded

On 15/07/2019 15:05, dave wrote:
On Sat, 13 Jul 2019 17:01:15 +0200, Tosspot wrote:

A discussion down there --v or up there --^ reminded me CO2 cartridges
come in a least two connectors, threaded and not. I've been caught by
this.

Why the difference? Who cam first?


The chicken.


folds

  #49  
Old July 16th 19, 07:52 PM posted to rec.bicycles.tech
Mark J.
external usenet poster
 
Posts: 840
Default CO2 Connectors - Threaded vs Unthreaded

On 7/16/2019 9:53 AM, Duane wrote:
On 16/07/2019 12:28 p.m., jbeattie wrote:
On Tuesday, July 16, 2019 at 8:16:25 AM UTC-7, duane wrote:
On 16/07/2019 10:28 a.m., jbeattie wrote:
On Tuesday, July 16, 2019 at 6:56:11 AM UTC-7, Tom Kunich wrote:
On Monday, July 15, 2019 at 5:20:04 PM UTC-7, John B. wrote:
On Mon, 15 Jul 2019 15:20:57 -0700 (PDT), Frank Krygowski
wrote:

On Monday, July 15, 2019 at 6:09:22 PM UTC-4, John B. wrote:
On Mon, 15 Jul 2019 13:05:17 -0000 (UTC), dave

wrote:

On Sat, 13 Jul 2019 17:01:15 +0200, Tosspot wrote:

A discussion down there --v or up there --^ reminded me CO2
cartridges
come in a least two connectors, threaded and not.Â* I've been
caught by
this.

Why the difference?Â* Who cam first?

The chicken.

But where did the chicken come from? The Ark :-?

The scientists say the egg came way before the chicken, because
animals much
more primitive than chickens had been laying eggs for millions of
years
before there were birds of any kind.

But those people saying that are evil evolutionists. They don't
understand that
God put fossils in the ground to test our faith. He's infinitely
tricky!

- Frank Krygowski

On the other hand if the Christian/Jewish/Moslem God made the
universe
and everything in it might he/she/itÂ* have created lizards and as
he/she/itÂ* rested on the seventh day might that be interpreted as the
period from the creation to modern times giving those pesky lizards
time to grow feathers and learn to fly?
--
cheers,

John B.

Never having read the Bible you can be excused for not having even
an inkling what is in it.

I've read the Bible.Â* I've even read the Book of Mormon.Â* O.K., part
of it and even parts of the Koran and parts of Buddhist and Hindu
texts.Â* I've also read "Horton Hears a Who!"Â* I'm not sure which one
is the best scientific text.


Wasn't aware that the bible had anything definitive to say regarding
threaded vs un-threaded CO2 cartridges...


Ludditicus 2:14 "You shall not use a CO2 inflator as you would a frame
pump. It is an abomination."Â* All CO2 cartridges are prohibited.
Apparently you do not read the Bible . . . or invest in the stock market!

-- Jay Beattie.


Ludditicus?Â* Must be new testament. Fake news. Old testament is the
juicy testament.


I think Jay was thinking of the book of Hezekiah. Easy to get those
citations wrong.

Mark J.
  #50  
Old July 16th 19, 08:11 PM posted to rec.bicycles.tech
Zen Cycle
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Posts: 194
Default CO2 Connectors - Threaded vs Unthreaded

On Tuesday, July 16, 2019 at 10:01:14 AM UTC-4, Tom Kunich wrote:
On Monday, July 15, 2019 at 9:06:32 PM UTC-7, Frank Krygowski wrote:
On Monday, July 15, 2019 at 7:10:44 PM UTC-4, Tom Kunich wrote:
On Monday, July 15, 2019 at 3:20:58 PM UTC-7, Frank Krygowski wrote:

The scientists say the egg came way before the chicken, because animals much
more primitive than chickens had been laying eggs for millions of years
before there were birds of any kind.

But those people saying that are evil evolutionists. They don't understand that
God put fossils in the ground to test our faith. He's infinitely tricky!

- Frank Krygowski

Show us ONE proof that ANY evolution ever led to a new species. That has NEVER been found and the theory of evolution is still noting more than a theory.


Wow.

- Frank Krygowski


Rather than show any doubt why don't you show us even a single instance of evolution causing speciation?


You really are a spectacularly stupid troll, kunich

https://blogs.scientificamerican.com...-observations/

https://www.pnas.org/content/114/23/6074

http://blog.pnas.org/2014/01/evidenc...lution-canyon/

https://biomed.brown.edu/Courses/BIO48/23.Cases.HTML

https://www.frontiersin.org/articles...018.00144/full

http://www.talkorigins.org/faqs/speciation.html

and from http://www.talkorigins.org/faqs/faq-speciation.html


5.0 Observed Instances of Speciation
The following are several examples of observations of speciation.

5.1 Speciations Involving Polyploidy, Hybridization or Hybridization Followed by Polyploidization.

5.1.1 Plants
(See also the discussion in de Wet 1971).

5.1.1.1 Evening Primrose (Oenothera gigas)
While studying the genetics of the evening primrose, Oenothera lamarckiana, de Vries (1905) found an unusual variant among his plants. O. lamarckiana has a chromosome number of 2N = 14. The variant had a chromosome number of 2N = 28. He found that he was unable to breed this variant with O. lamarckiana. He named this new species O. gigas.

5.1.1.2 Kew Primrose (Primula kewensis)
Digby (1912) crossed the primrose species Primula verticillata and P. floribunda to produce a sterile hybrid. Polyploidization occurred in a few of these plants to produce fertile offspring. The new species was named P. kewensis. Newton and Pellew (1929) note that spontaneous hybrids of P. verticillata and P. floribunda set tetraploid seed on at least three occasions. These happened in 1905, 1923 and 1926.

5.1.1.3 Tragopogon
Owenby (1950) demonstrated that two species in this genus were produced by polyploidization from hybrids. He showed that Tragopogon miscellus found in a colony in Moscow, Idaho was produced by hybridization of T. dubius and T.. pratensis. He also showed that T. mirus found in a colony near Pullman, Washington was produced by hybridization of T. dubius and T. porrifolius. Evidence from chloroplast DNA suggests that T. mirus has originated independently by hybridization in eastern Washington and western Idaho at least three times (Soltis and Soltis 1989). The same study also shows multiple origins for T. micellus.

5.1.1.4 Raphanobrassica
The Russian cytologist Karpchenko (1927, 1928) crossed the radish, Raphanus sativus, with the cabbage, Brassica oleracea. Despite the fact that the plants were in different genera, he got a sterile hybrid. Some unreduced gametes were formed in the hybrids. This allowed for the production of seed. Plants grown from the seeds were interfertile with each other. They were not interfertile with either parental species. Unfortunately the new plant (genus Raphanobrassica) had the foliage of a radish and the root of a cabbage.

5.1.1.5 Hemp Nettle (Galeopsis tetrahit)
A species of hemp nettle, Galeopsis tetrahit, was hypothesized to be the result of a natural hybridization of two other species, G. pubescens and G. speciosa (Muntzing 1932). The two species were crossed. The hybrids matched G. tetrahit in both visible features and chromosome morphology.

5.1.1.6 Madia citrigracilis
Along similar lines, Clausen et al. (1945) hypothesized that Madia citrigracilis was a hexaploid hybrid of M. gracilis and M. citriodora As evidence they noted that the species have gametic chromosome numbers of n = 24, 16 and 8 respectively. Crossing M. gracilis and M. citriodora resulted in a highly sterile triploid with n = 24. The chromosomes formed almost no bivalents during meiosis. Artificially doubling the chromosome number using colchecine produced a hexaploid hybrid which closely resembled M. citrigracilis and was fertile.

5.1.1.7 Brassica
Frandsen (1943, 1947) was able to do this same sort of recreation of species in the genus Brassica (cabbage, etc.). His experiments showed that B. carinata (n = 17) may be recreated by hybridizing B. nigra (n = 8) and B. oleracea, B. juncea (n = 18) may be recreated by hybridizing B. nigra and B. campestris (n = 10), and B. napus (n = 19) may be recreated by hybridizing B. oleracea and B. campestris.

5.1.1.8 Maidenhair Fern (Adiantum pedatum)
Rabe and Haufler (1992) found a naturally occurring diploid sporophyte of maidenhair fern which produced unreduced (2N) spores. These spores resulted from a failure of the paired chromosomes to dissociate during the first division of meiosis. The spores germinated normally and grew into diploid gametophytes. These did not appear to produce antheridia. Nonetheless, a subsequent generation of tetraploid sporophytes was produced. When grown in the lab, the tetraploid sporophytes appear to be less vigorous than the normal diploid sporophytes. The 4N individuals were found near Baldwin City, Kansas..

5.1.1.9 Woodsia Fern (Woodsia abbeae)
Woodsia abbeae was described as a hybrid of W. cathcariana and W. ilvensis (Butters 1941). Plants of this hybrid normally produce abortive sporangia containing inviable spores. In 1944 Butters found a W. abbeae plant near Grand Portage, Minn. that had one fertile frond (Butters and Tryon 1948). The apical portion of this frond had fertile sporangia. Spores from this frond germinated and grew into prothallia. About six months after germination sporophytes were produced. They survived for about one year. Based on cytological evidence, Butters and Tryon concluded that the frond that produced the viable spores had gone tetraploid. They made no statement as to whether the sporophytes grown produced viable spores.

5.1.2 Animals
Speciation through hybridization and/or polyploidy has long been considered much less important in animals than in plants [[[refs.]]]. A number of reviews suggest that this view may be mistaken. (Lokki and Saura 1980; Bullini and Nascetti 1990; Vrijenhoek 1994). Bullini and Nasceti (1990) review chromosomal and genetic evidence that suggest that speciation through hybridization may occur in a number of insect species, including walking sticks, grasshoppers, blackflies and cucurlionid beetles. Lokki and Saura (1980) discuss the role of polyploidy in insect evolution. Vrijenhoek (1994) reviews the literature on parthenogenesis and hybridogenesis in fish. I will tackle this topic in greater depth in the next version of this document.

5.2 Speciations in Plant Species not Involving Hybridization or Polyploidy

5.2.1 Stephanomeira malheurensis
Gottlieb (1973) documented the speciation of Stephanomeira malheurensis. He found a single small population ( 250 plants) among a much larger population ( 25,000 plants) of S. exigua in Harney Co., Oregon. Both species are diploid and have the same number of chromosomes (N = 8). S. exigua is an obligate outcrosser exhibiting sporophytic self-incompatibility. S. malheurensis exhibits no self-incompatibility and self-pollinates. Though the two species look very similar, Gottlieb was able to document morphological differences in five characters plus chromosomal differences. F1 hybrids between the species produces only 50% of the seeds and 24% of the pollen that conspecific crosses produced. F2 hybrids showed various developmental abnormalities.

5.2.2 Maize (Zea mays)
Pasterniani (1969) produced almost complete reproductive isolation between two varieties of maize. The varieties were distinguishable by seed color, white versus yellow. Other genetic markers allowed him to identify hybrids. The two varieties were planted in a common field. Any plant's nearest neighbors were always plants of the other strain. Selection was applied against hybridization by using only those ears of corn that showed a low degree of hybridization as the source of the next years seed. Only parental type kernels from these ears were planted. The strength of selection was increased each year. In the first year, only ears with less than 30% intercrossed seed were used. In the fifth year, only ears with less than 1% intercrossed seed were used. After five years the average percentage of intercrossed matings dropped from 35.8% to 4.9% in the white strain and from 46.7% to 3.4% in the yellow strain.

5.2.3 Speciation as a Result of Selection for Tolerance to a Toxin: Yellow Monkey Flower (Mimulus guttatus)
At reasonably low concentrations, copper is toxic to many plant species. Several plants have been seen to develop a tolerance to this metal (Macnair 1981). Macnair and Christie (1983) used this to examine the genetic basis of a postmating isolating mechanism in yellow monkey flower. When they crossed plants from the copper tolerant "Copperopolis" population with plants from the nontolerant "Cerig" population, they found that many of the hybrids were inviable. During early growth, just after the four leaf stage, the leaves of many of the hybrids turned yellow and became necrotic. Death followed this. This was seen only in hybrids between the two populations. Through mapping studies, the authors were able to show that the copper tolerance gene and the gene responsible for hybrid inviability were either the same gene or were very tightly linked. These results suggest that reproductive isolation may require changes in only a small number of genes.

5.3 The Fruit Fly Literature

5.3.1 Drosophila paulistorum
Dobzhansky and Pavlovsky (1971) reported a speciation event that occurred in a laboratory culture of Drosophila paulistorum sometime between 1958 and 1963. The culture was descended from a single inseminated female that was captured in the Llanos of Colombia. In 1958 this strain produced fertile hybrids when crossed with conspecifics of different strains from Orinocan. From 1963 onward crosses with Orinocan strains produced only sterile males. Initially no assortative mating or behavioral isolation was seen between the Llanos strain and the Orinocan strains. Later on Dobzhansky produced assortative mating (Dobzhansky 1972).

5.3.2 Disruptive Selection on Drosophila melanogaster
Thoday and Gibson (1962) established a population of Drosophila melanogaster from four gravid females. They applied selection on this population for flies with the highest and lowest numbers of sternoplural chaetae (hairs). In each generation, eight flies with high numbers of chaetae were allowed to interbreed and eight flies with low numbers of chaetae were allowed to interbreed. Periodically they performed mate choice experiments on the two lines. They found that they had produced a high degree of positive assortative mating between the two groups. In the decade or so following this, eighteen labs attempted unsuccessfully to reproduce these results. References are given in Thoday and Gibson 1970.

5.3.3 Selection on Courtship Behavior in Drosophila melanogaster
Crossley (1974) was able to produce changes in mating behavior in two mutant strains of D. melanogaster. Four treatments were used. In each treatment, 55 virgin males and 55 virgin females of both ebony body mutant flies and vestigial wing mutant flies (220 flies total) were put into a jar and allowed to mate for 20 hours. The females were collected and each was put into a separate vial. The phenotypes of the offspring were recorded. Wild type offspring were hybrids between the mutants. In two of the four treatments, mating was carried out in the light. In one of these treatments all hybrid offspring were destroyed. This was repeated for 40 generations. Mating was carried out in the dark in the other two treatments. Again, in one of these all hybrids were destroyed. This was repeated for 49 generations. Crossley ran mate choice tests and observed mating behavior. Positive assortative mating was found in the treatment which had mated in the light and had been subject to strong selection against hybridization. The basis of this was changes in the courtship behaviors of both sexes. Similar experiments, without observation of mating behavior, were performed by Knight, et al. (1956).

5.3.4 Sexual Isolation as a Byproduct of Adaptation to Environmental Conditions in Drosophila melanogaster
Kilias, et al. (1980) exposed D. melanogaster populations to different temperature and humidity regimes for several years. They performed mating tests to check for reproductive isolation. They found some sterility in crosses among populations raised under different conditions. They also showed some positive assortative mating. These things were not observed in populations which were separated but raised under the same conditions. They concluded that sexual isolation was produced as a byproduct of selection.

5.3.5 Sympatric Speciation in Drosophila melanogaster
In a series of papers (Rice 1985, Rice and Salt 1988 and Rice and Salt 1990) Rice and Salt presented experimental evidence for the possibility of sympatric speciation. They started from the premise that whenever organisms sort themselves into the environment first and then mate locally, individuals with the same habitat preferences will necessarily mate assortatively. They established a stock population of D. melanogaster with flies collected in an orchard near Davis, California. Pupae from the culture were placed into a habitat maze. Newly emerged flies had to negotiate the maze to find food. The maze simulated several environmental gradients simultaneously. The flies had to make three choices of which way to go. The first was between light and dark (phototaxis). The second was between up and down (geotaxis). The last was between the scent of acetaldehyde and the scent of ethanol (chemotaxis). This divided the flies among eight habitats. The flies were further divided by the time of day of emergence. In total the flies were divided among 24 spatio-temporal habitats.

They next cultured two strains of flies that had chosen opposite habitats. One strain emerged early, flew upward and was attracted to dark and acetaldehyde. The other emerged late, flew downward and was attracted to light and ethanol. Pupae from these two strains were placed together in the maze. They were allowed to mate at the food site and were collected. Eye color differences between the strains allowed Rice and Salt to distinguish between the two strains. A selective penalty was imposed on flies that switched habitats. Females that switched habitats were destroyed. None of their gametes passed into the next generation. Males that switched habitats received no penalty. After 25 generations of this mating tests showed reproductive isolation between the two strains. Habitat specialization was also produced.

They next repeated the experiment without the penalty against habitat switching. The result was the same -- reproductive isolation was produced. They argued that a switching penalty is not necessary to produce reproductive isolation. Their results, they stated, show the possibility of sympatric speciation.

5.3.6 Isolation Produced as an Incidental Effect of Selection on several Drosophila species
In a series of experiments, del Solar (1966) derived positively and negatively geotactic and phototactic strains of D. pseudoobscura from the same population by running the flies through mazes. Flies from different strains were then introduced into mating chambers (10 males and 10 females from each strain). Matings were recorded. Statistically significant positive assortative mating was found.

In a separate series of experiments Dodd (1989) raised eight populations derived from a single population of D. Pseudoobscura on stressful media. Four populations were raised on a starch based medium, the other four were raised on a maltose based medium. The fly populations in both treatments took several months to get established, implying that they were under strong selection. Dodd found some evidence of genetic divergence between flies in the two treatments. He performed mate choice tests among experimental populations. He found statistically significant assortative mating between populations raised on different media, but no assortative mating among populations raised within the same medium regime. He argued that since there was no direct selection for reproductive isolation, the behavioral isolation results from a pleiotropic by-product to adaptation to the two media. Schluter and Nagel (1995) have argued that these results provide experimental support for the hypothesis of parallel speciation.

Less dramatic results were obtained by growing D. willistoni on media of different pH levels (de Oliveira and Cordeiro 1980). Mate choice tests after 26, 32, 52 and 69 generations of growth showed statistically significant assortative mating between some populations grown in different pH treatments. This ethological isolation did not always persist over time. They also found that some crosses made after 106 and 122 generations showed significant hybrid inferiority, but only when grown in acid medium.

5.3.7 Selection for Reinforcement in Drosophila melanogaster
Some proposed models of speciation rely on a process called reinforcement to complete the speciation process. Reinforcement occurs when to partially isolated allopatric populations come into contact. Lower relative fitness of hybrids between the two populations results in increased selection for isolating mechanisms. I should note that a recent review (Rice and Hostert 1993) argues that there is little experimental evidence to support reinforcement models. Two experiments in which the authors argue that their results provide support are discussed below.

Ehrman (1971) established strains of wild-type and mutant (black body) D. melanogaster. These flies were derived from compound autosome strains such that heterotypic matings would produce no progeny. The two strains were reared together in common fly cages. After two years, the isolation index generated from mate choice experiments had increased from 0.04 to 0.43, indicating the appearance of considerable assortative mating. After four years this index had risen to 0.64 (Ehrman 1973).

Along the same lines, Koopman (1950) was able to increase the degree of reproductive isolation between two partially isolated species, D. pseudoobscura and D. persimilis.

5.3.8 Tests of the Founder-flush Speciation Hypothesis Using Drosophila
The founder-flush (a.k.a. flush-crash) hypothesis posits that genetic drift and founder effects play a major role in speciation (Powell 1978). During a founder-flush cycle a new habitat is colonized by a small number of individuals (e.g. one inseminated female). The population rapidly expands (the flush phase). This is followed by the population crashing. During this crash period the population experiences strong genetic drift. The population undergoes another rapid expansion followed by another crash. This cycle repeats several times. Reproductive isolation is produced as a byproduct of genetic drift.

Dodd and Powell (1985) tested this hypothesis using D. pseudoobscura. A large, heterogeneous population was allowed to grow rapidly in a very large population cage. Twelve experimental populations were derived from this population from single pair matings. These populations were allowed to flush. Fourteen months later, mating tests were performed among the twelve populations. No postmating isolation was seen. One cross showed strong behavioral isolation. The populations underwent three more flush-crash cycles. Forty-four months after the start of the experiment (and fifteen months after the last flush) the populations were again tested. Once again, no postmating isolation was seen. Three populations showed behavioral isolation in the form of positive assortative mating. Later tests between 1980 and 1984 showed that the isolation persisted, though it was weaker in some cases.

Galina, et al. (1993) performed similar experiments with D. pseudoobscura. Mating tests between populations that underwent flush-crash cycles and their ancestral populations showed 8 cases of positive assortative mating out of 118 crosses. They also showed 5 cases of negative assortative mating (i.e.. the flies preferred to mate with flies of the other strain). Tests among the founder-flush populations showed 36 cases of positive assortative mating out of 370 crosses. These tests also found 4 cases of negative assortative mating. Most of these mating preferences did not persist over time. Galina, et al. concluded that the founder-flush protocol yields reproductive isolation only as a rare and erratic event.

Ahearn (1980) applied the founder-flush protocol to D. silvestris. Flies from a line of this species underwent several flush-crash cycles. They were tested in mate choice experiments against flies from a continuously large population. Female flies from both strains preferred to mate with males from the large population. Females from the large population would not mate with males from the founder flush population. An asymmetric reproductive isolation was produced.

In a three year experiment, Ringo, et al. (1985) compared the effects of a founder-flush protocol to the effects of selection on various traits. A large population of D. simulans was created from flies from 69 wild caught stocks from several locations. Founder-flush lines and selection lines were derived from this population. The founder-flush lines went through six flush-crash cycles. The selection lines experienced equal intensities of selection for various traits. Mating test were performed between strains within a treatment and between treatment strains and the source population. Crosses were also checked for postmating isolation. In the selection lines, 10 out of 216 crosses showed positive assortative mating (2 crosses showed negative assortative mating). They also found that 25 out of 216 crosses showed postmating isolation. Of these, 9 cases involved crosses with the source population. In the founder-flush lines 12 out of 216 crosses showed positive assortative mating (3 crosses showed negative assortative mating). Postmating isolation was found in 15 out of 216 crosses, 11 involving the source population. They concluded that only weak isolation was found and that there was little difference between the effects of natural selection and the effects of genetic drift.

A final test of the founder-flush hypothesis will be described with the housefly cases below.

5.4 Housefly Speciation Experiments

5.4.1 A Test of the Founder-flush Hypothesis Using Houseflies
Meffert and Bryant (1991) used houseflies to test whether bottlenecks in populations can cause permanent alterations in courtship behavior that lead to premating isolation. They collected over 100 flies of each sex from a landfill near Alvin, Texas. These were used to initiate an ancestral population. From this ancestral population they established six lines. Two of these lines were started with one pair of flies, two lines were started with four pairs of flies and two lines were started with sixteen pairs of flies. These populations were flushed to about 2,000 flies each. They then went through five bottlenecks followed by flushes. This took 35 generations. Mate choice tests were performed. One case of positive assortative mating was found.. One case of negative assortative mating was also found.
 




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