Can someone help me how to show this on a cladic chart, and
perhaps why such breeding does not occur at the molecular
level. Please help, Frank

Can someone help me how to show this on a cladic chart, and perhaps why such
breeding does not occur at the molecular level.
I don't know anything about cladic charts or what you mean by a molecular
level, but I can tell you breeding between species goes on all the time.


Iris,
Central NY, Zone 5a, Sunset Zone 40
"The trouble with people is not that they don't know but that they know so much
that ain't so."
Josh Billings (Henry Wheeler Shaw), 1818-1885

Frank Martin schreef
Can someone help me how to show this on a cladic chart, and
perhaps why such breeding does not occur at the molecular
level. Please help, Frank

Iris Cohen schreef
I don't know anything about cladic charts or what you mean by a molecular
level, but I can tell you breeding between species goes on all the time.
Iris,

+ + +
It does not show on a 'cladic chart' because cladism analyses descent.
Cladism assumes gene exchange across species borders is not a contributing
factor to genetic make-up of species.
A 'cladic chart' that showed this would not be a 'cladic chart'.

As to the molecular level:
the short answer is that molecules are not plant species.
PvR

Many plant species have mechanisms to prevent self-fertilization:
http://www.news.cornell.edu/releases...tigma.bpf.html
http://www.news.cornell.edu/releases...stils.bpf.html

Self-fertilization can be a disadvantage because it often causes
inbreeding depression in outcrossing species. However, there can be an
advantage to allow fertilization with other species because crossing
between two species may produce a superior hybrid. Thus, interspecific
hybridization may lead to a new species (Arnold 1997). Levin (2002)
gives a figure that between 6 and 16% of plant genera are capable of
crossing between species but doesn't indicate a source of that
statistic. Many important cultivated plants are interspecific hybrids
including grapefruit (Citrus x paradisi) and strawberry (Fragaria x
ananassa).

A lot of breeding between plant species occurs because people have
removed geographical barriers or use hand pollination to overcome time
of flowering differences or lack of pollinators. Orchids often prevent
breeding with other species because an orchid species has coevolved
with a single insect species that will carry pollen just for that
species. However, there are hundreds of intergeneric orchid hybrids
developed by hybridizers:
http://www.orchids.mu/Glossary/Glossary_A.htm

If breeding between two species occurs at a high frequency, it may
result in extinction of one parent even if the hybrids are infertile
(Levin 2002). This can happen naturally but more frequently occurs
when one species is introduced. For example the English bluebell
(Hyacinthoides non-scriptus) [synonyms: Scilla non-scripta, Endymion
non-scripta] readily crosses with the introduced and larger, more
vigorous Spanish bluebell (Hyacinthoides hispanica) to form hybrids.
Hyacinthoides non-scriptus has become rare in the wild as the hybrids
have crowded it out. Levin (2002) gives other examples of introduced
plants that may eventually cause extinction of native species, such as
cultivated sunflowers (Helianthus annuus) breeding with wild
sunflowers to produce fertile hybrids.

In other cases, cross-breeding between species occurs fairly
frequently but both parents maintain their populations. This is
apparently the case in some of the natural interspecific hybrids in
oaks.

In some oaks and pines, the frequency of crossing between species is
sometimes low so the hybrids are rare. For example, Jeffrey pine can
naturally cross with Coulter pine or Ponderosa pine but hybrids are
rare even under artificial conditions:
http://www.na.fs.fed.us/spfo/pubs/si...s/jeffreyi.htm

References

http://waynesword.palomar.edu/hybrids1.htm

Arnold, M.L. 1997. Natural Hybridization and Evolution. New York:
Oxford University Press.

Levin, D.A. 2002. Hybridization and extinction. American Scientist.
90: 254-261.


"Frank Martin" wrote in message ...
Can someone help me how to show this on a cladic chart, and
perhaps why such breeding does not occur at the molecular
level. Please help, Frank

Not to mention introgression and polyploidy
PvR

====================
David Hershey schreef
Many plant species have mechanisms to prevent self-fertilization:
http://www.news.cornell.edu/releases...tigma.bpf.html
http://www.news.cornell.edu/releases...stils.bpf.html

Self-fertilization can be a disadvantage because it often causes
inbreeding depression in outcrossing species. However, there can be an
advantage to allow fertilization with other species because crossing
between two species may produce a superior hybrid. Thus, interspecific
hybridization may lead to a new species (Arnold 1997). Levin (2002)
gives a figure that between 6 and 16% of plant genera are capable of
crossing between species but doesn't indicate a source of that
statistic. Many important cultivated plants are interspecific hybrids
including grapefruit (Citrus x paradisi) and strawberry (Fragaria x
ananassa).

A lot of breeding between plant species occurs because people have
removed geographical barriers or use hand pollination to overcome time
of flowering differences or lack of pollinators. Orchids often prevent
breeding with other species because an orchid species has coevolved
with a single insect species that will carry pollen just for that
species. However, there are hundreds of intergeneric orchid hybrids
developed by hybridizers:
http://www.orchids.mu/Glossary/Glossary_A.htm

If breeding between two species occurs at a high frequency, it may
result in extinction of one parent even if the hybrids are infertile
(Levin 2002). This can happen naturally but more frequently occurs
when one species is introduced. For example the English bluebell
(Hyacinthoides non-scriptus) [synonyms: Scilla non-scripta, Endymion
non-scripta] readily crosses with the introduced and larger, more
vigorous Spanish bluebell (Hyacinthoides hispanica) to form hybrids.
Hyacinthoides non-scriptus has become rare in the wild as the hybrids
have crowded it out. Levin (2002) gives other examples of introduced
plants that may eventually cause extinction of native species, such as
cultivated sunflowers (Helianthus annuus) breeding with wild
sunflowers to produce fertile hybrids.

In other cases, cross-breeding between species occurs fairly
frequently but both parents maintain their populations. This is
apparently the case in some of the natural interspecific hybrids in
oaks.

In some oaks and pines, the frequency of crossing between species is
sometimes low so the hybrids are rare. For example, Jeffrey pine can
naturally cross with Coulter pine or Ponderosa pine but hybrids are
rare even under artificial conditions:

http://www.na.fs.fed.us/spfo/pubs/si...s/jeffreyi.htm

References

http://waynesword.palomar.edu/hybrids1.htm

Arnold, M.L. 1997. Natural Hybridization and Evolution. New York:
Oxford University Press.

Levin, D.A. 2002. Hybridization and extinction. American Scientist.
90: 254-261.

======================
"Frank Martin" wrote
Can someone help me how to show this on a cladic chart, and
perhaps why such breeding does not occur at the molecular
level. Please help, Frank

I can assure you that, although in Britain there is a problem with the
introduced spanish bluebell, the native ones are by no means rare. Of
course, this may not be the case world-wide.

Regarding the wider question, although I appreciate that species do
interbreed, isn't the fact that they can't one of the things that make them
species? whoops, not good English I mean, shouldn't we restrict the
artificial term 'species' to organisms which can only breed within that
species?

And, on a tangent, shouldn't we use the word specie for one species (not
that I do)?

--
David Brear

Conserv@tion
http://www.habitat.org.uk/news1.htm

The Wild Flower Page
http://www.habitat.org.uk/wildflwr.htm
"David Hershey" wrote in message
om...

If breeding between two species occurs at a high frequency, it may
result in extinction of one parent even if the hybrids are infertile
(Levin 2002). This can happen naturally but more frequently occurs
when one species is introduced. For example the English bluebell
(Hyacinthoides non-scriptus) [synonyms: Scilla non-scripta, Endymion
non-scripta] readily crosses with the introduced and larger, more
vigorous Spanish bluebell (Hyacinthoides hispanica) to form hybrids.
Hyacinthoides non-scriptus has become rare in the wild as the hybrids
have crowded it out. Levin (2002) gives other examples of introduced
plants that may eventually cause extinction of native species, such as
cultivated sunflowers (Helianthus annuus) breeding with wild
sunflowers to produce fertile hybrids.

shouldn't we restrict the artificial term 'species' to organisms which can
only breed within that species?
That is only part of the definition of a species, & is largely ignored
nowadays.

shouldn't we use the word specie for one species
Absolutely not. The term specie refers only to currency. In biology, species is
both singular & plural, like thrips & a few other words.


Iris,
Central NY, Zone 5a, Sunset Zone 40
"The trouble with people is not that they don't know but that they know so much
that ain't so."
Josh Billings (Henry Wheeler Shaw), 1818-1885

I guess I was misled by a save-the-bluebells website. One government
site lists it as "conservation concern" which is well below endangered
status: http://www.leeds.gov.uk/downloads/20011213_9402102.pdf

It depends how you define a species. There are many "species concepts"
such as morphological, biological and phylogenetic. The morphological
concept is the oldest and is still useful and widely used,
particularly in horticulture.

http://216.239.39.100/search?q=cache...hl=en&ie=UTF-8

Species is used as both singular and plural.


David R. Hershey



"David Brear" wrote in message ...
I can assure you that, although in Britain there is a problem with the
introduced spanish bluebell, the native ones are by no means rare. Of
course, this may not be the case world-wide.

Regarding the wider question, although I appreciate that species do
interbreed, isn't the fact that they can't one of the things that make them
species? whoops, not good English I mean, shouldn't we restrict the
artificial term 'species' to organisms which can only breed within that
species?

And, on a tangent, shouldn't we use the word specie for one species (not
that I do)?

--
David Brear

Conserv@tion
http://www.habitat.org.uk/news1.htm

The Wild Flower Page
http://www.habitat.org.uk/wildflwr.htm
"David Hershey" wrote in message
om...

If breeding between two species occurs at a high frequency, it may
result in extinction of one parent even if the hybrids are infertile
(Levin 2002). This can happen naturally but more frequently occurs
when one species is introduced. For example the English bluebell
(Hyacinthoides non-scriptus) [synonyms: Scilla non-scripta, Endymion
non-scripta] readily crosses with the introduced and larger, more
vigorous Spanish bluebell (Hyacinthoides hispanica) to form hybrids.
Hyacinthoides non-scriptus has become rare in the wild as the hybrids
have crowded it out. Levin (2002) gives other examples of introduced
plants that may eventually cause extinction of native species, such as
cultivated sunflowers (Helianthus annuus) breeding with wild
sunflowers to produce fertile hybrids.