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W A T E R F R O G N E W S L E T T E R
November 1997
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The Water Frog Information Pool can be reached through its home page at
http://waterfrogs.scs.fsu.edu/waterfrogs.html
You can send email to
frog@genetics.washington.edu
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EDITORAL
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by Thomas Uzzell
(uzzell@acnatsci.org or tuzzell@magainin.com)
Surely someone besides the webmaster for this site must have a
controversial idea to discuss in an editorial!
Since the water frog site was instituted in 1995, there have been over
15,000 hits recorded, excluding those of the webmaster. The counter on
the site was reset most recently on 1 January 1997, and 7850 hits have
been recorded since then. And yet there has been little input from the
members of the water frog research community or from casual visitors to
the site. If you want this site to be vibrant, to reflect the excitement
of water frog research, to serve as a vehicle for sharing ideas and
information, active participation (contributions) is needed, not passive
participation (use of information deposited by others).
We need as a minimum your name and email address. We'd also like a
statement both brief and extended, of your interests. People not
registered can add their address by going to the researcher page and
filling out a simple form. If you're already registered and want to
update your entry, send an email to Peter Beerli
(beerli@scs.fsu.edu) if your last name begins with letters A
through L, or to Dirk Schmeller (dirk@hydra.biologie.uni-mainz.de) if
it begins with M through Z.
Download the bibliography file or browse it on the web and scan it for
missing literature; check especially to see if *your*
publications are included. Help us keep the 'current literature' and
'current abstracts' current: submit titles and abstracts as soon as
papers are published to beerli@scs.fsu.edu; please also send
literature updates to Hansjurg Hotz at hotz@zoolmus.unizh.ch.
It would be nice if notes of jobs or research positions, opportunities
for research, preliminary findings, points of view, and whatever else
might interest your colleagues were also contributed.
If this is going to be a
****water frog information pool,****
it needs information.
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News and Views
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The information here, including links to other relevant sections,
can be found at http://waterfrogs.scs.fsu.edu/waterfrogs.html
L-E versus L-LR terminology
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Hansjurg Hotz (hotz@zoolmus.unizh.ch) sent us the following remarks
as a response to a query:
It has been stated that people are more and more often using the term
'L-LR' rather than 'L-E' for population systems with Rana lessonae and
hybridogenetic Rana esculenta. I think there is some misunderstanding. I
don't think that the term 'L-RL system' or any such construction is
increasingly used. What is often used recently in abstracts and figures
(I and my colleagues do it too, to increase clarity for
readers not familiar with these frogs) are genome abbreviations (L, R,
...) to distinguish parental and hybrid somatic or gametic genome
compositions. This is nothing but a shorthand for easier grasping. I see
no reason whatsoever to replace the very well-established term L-E
system with anything else. In L-E systems, hybridogenetic Rana esculenta
coexist and reproductively depend on the sexual host species Rana
lessonae. This is by far the most widespread population system and it
clearly needs a label for referring to it. 'L-E system' certainly doesn't
mean mere coexistence of Rana lessonae and Rana esculenta. Although
some people may use it that way, this clearly differs from its original
meaning given in 1975, when Uzzell and Berger introduced it. Rainer
Gunther
has created a much more extended terminology to cover the variety of
population compositions observed in his area. These describe in detail
the different situations occurring in different habitats or locales
(although there may be more of a continuum than his classes suggest),
but the gain in precision is counterbalanced by a loss in both
generality and information. L-E system is a term for the most common
host-hybridogen reproductive system, irrespective of hybrid frequency
and other particulars. It can
readily be applied to the exactly analogous perezi-hybridogen system;
"P-RP" was used as a convenient shorthand (Graf and Polls Pelaz 1989,
Hotz et al. 1994) while there was no name for the hybridogen, but now
that it's been described as Rana grafi (Crochet et al. 1995), P-G system
can be used (Pagano et al. 1997) and is clearly better because it
implies reproductive mode of the hybrids rather than just coexistence.
There are two significant disadvantages to using a genome-based
nomenclature for hybridogens and for sexual-hybridogen population
systems. For example, hybrids between Rana ridibunda and Rana lessonae,
genomically RL, may be hybridogenetic and parts of hemiclonal lineages;
or, alternatively, they may be nonhybridogenetic and sterile. This
distinction cannot be made
if RL is used for both; whereas calling the hybridogenetic lineages Rana
esculenta makes this distinction clear.
Similarly, if RL is used
always for the hybrids, L-RL can indicate either
coexistence of Rana lessonae and sterile, non-hybridogenetic
hybrids between Rana ridibunda and Rana lessonae (such
populations do exist in some parts of Rana lessonae's
range); or it can refer to population systems in which such
hybrids are 1) hybridogenetic and 2) sexual parasites on
the host species Rana lessonae.
For the latter, it seems to me far preferable to use L-E
system, with its specification of both reproductive mode and sexual
dependency. It is only watering down information content if special
terms like
"XY system" are used for mere syntopies.
Moreover, given that L-E system has been used in
dozens of publications since 1975, nomenclatural stability almost
requires continued usage of L-E system.
We would like to hear your opinion. Send your thoughts to
frog@genetics.washington.edu.
New literature with abstracts
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Guerrini, F., S. Bucci, M. Ragghianti, G. Mancino, H. Hotz, T. Uzzell,
and L. Berger. 1997. Genomes of two water frog species resist germ line
exclusion in interspecies hybrids. Journal of Experimental Zoology
279(2): 163-176.
Abstract: Abundant natural interspecies hybrids between the European
water frog Rana ridibunda and at least three other taxa reproduce
hemiclonally, by hybridogenesis: the non-ridibunda genome is excluded in
the germ line before meiosis, and the unrecombined ridibunda genome is
transmitted to haploid gametes. In contrast, natural hybrids between
Rana ridibunda and either of two Balkan species (Rana shqiperica and
Rana epeirotica) do not show such genome exclusion. This plausibly
results from failure of Balkan Rana ridibunda genomes to "induce" such
exclusion in the germ line of hybrids, from "resistance" of Rana
shqiperica and Rana epeirotica genomes to such exclusion in hybrids with
an "inducing" Rana ridibunda genome, or both. We tested the second
hypothesis by examining lampbrush chromosome patterns in oocytes of
hybrids that in the soma contain one "inducing" ridibunda genome and one
genome of either of the two Balkan species. Several lampbrush chromosome
markers (e.g., presence and location of certain giant loops and
conspicuousness and width of centromeres) discriminate sets of Rana
ridibunda chromosomes from those of Rana shqiperica and Rana epeirotica.
Based on such markers, nine diploid female hybrids between Rana
ridibunda or Rana esculenta from natural hybridogenetic lineages (Rana
ridibunda x Rana lessonae, making ridibunda gametes) from central Poland
and either Rana shqiperica or Rana epeirotica each contained both
parental genomes in primary oocytes; the bivalents showed reduced
numbers of chiasmata compared with parental species. It follows that
none of these hybrids was hybridogenetic. This conclusion is confirmed,
for two hybrids between Rana epeirotica and either Rana ridibunda or
Rana esculenta, by protein electrophoretic comparison of somatic tissues
with primary oocytes, all of which evidenced allelic markers of both
parental species. Because Rana ridibunda genomes that are known to
induce germ line genome exclusion when combined in hybrids with markers
of both parental species. Because Rana ridibunda genomes that are known
to induce germ line genome exclusion when combined in hybrids with Rana
lessonae genomes were used, these data provide the first compelling
evidence for resistance of Rana shqiperica as well as Rana epeirotica
genomes to such exclusion.
Pagano, A., P. Joly, and H. Hotz. 1997. Taxon composition and genetic
variation of water frogs in the Mid-Rhone floodplain. C.R. Acad.Sci.
Paris, Life sciences, 320: 759-766.
Abstract: Natural hemiclonal hybrid lineages of water frogs reproduce by
hybridogenesis, excluding one parental genome in the germ line and
mating with the coexisting same parental species. Two such sexual
host-hybridogen systems occur in the Rhone valley: the L-E system in the
north, the P-G system in the south. Although these hybridogenetic
complexes may overlap along the Rhone river, there is no evidence for a
contact zone in our samples: only Rana ridibunda and R. esculenta were
identified using protein electrophoresis. Whether the absence of R.
perezi reflects a more southern distribution or its exclusive occurrence
in other habitats, remains to be tested. Comparison of somatic and
gonadal tissues reveals that gametogenesis of R. esculenta is of the L-E
type: gametes carry ridibunda genomes. R. ridibunda apparently is not
native, but was introduced by humans, and R. esculenta of our samples
are probably immigrants from nearby L-E systems.
Older abstracts newly added
---------------------------
Beerli, P., H. Hotz, E., and T. Uzzell. 1996. Geologically dated sea
barriers calibrate a protein clock for Aegean water frogs. Evolution
50(4): 1676-1687.
Hotz, H., T. Uzzell, P. Beerli, and G.-D. Guex. 1996. Are hybrid clonals
species? A case for enlightened anarchy. Amphibia-Reptilia 17: 315-320.
Schmeller, D., A. Crivelli, and M. Veith. 1997. Genetic and demographic
structure of populations of hybridogenetic water frogs (Rana perezi, R.
ridibunda) in the Rhone-delta (Camargue, France). 3rd World Congress of
Herpetology, Prague.
Other Changes
--------------
The Water Frog Information Pool (WIP) web site continues to develop, and
several small changes have recently been made including:
-Addition of a section 'literature' with links to abstracts,
the bibliography, updates to the bibliography provided by
Hansjurg Hotz, and past newsletters.
-Inclusion of additional interesting sites to 'Other sites'.
-Redesign of the layout for abstracts [not yet finished].
-Addition of several search utilities.
More extensive literature coverage
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Although the original file for water frog literature was restricted to
research on western Palearctic water frogs, it has been expanded to
include publications on the eastern Palearctic water frogs as well.
Research on this group, especially by the students and staff at
Hiroshima University's Laboratory of Amphibian Biology, often provides
interesting parallels or alternatives to work on the western Palearctic
forms. Look for a more inclusive literature file on WIP in the near
future.
But we would also like to hear your opinions: what else should be
covered? Send your thoughts to frog@genetics.washington.edu.
A water frog session or workshop at the SEH conference
in Chambery, France, August 27-29 1998.
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As was discussed at the 3rd World Congress of Herpetology in Prague,
having a water frog session of workshop at the upcoming conference
would be useful, but we still have received no
suggestions or ideas.
If you have ideas or thoughts about organizing a special water frog
program at the SEH meetings, send them to Dirk Schmeller
(dirk@hydra.biologie.uni-mainz.de or frog@genetics.washington.edu).
What topics should be covered? Send your ideas as soon as possible so
that the water frog community has enough time to discuss them and get
something going. The first call for papers will be in a few weeks.
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Researcher list
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to hear more). And check your entry in the researcher list for accuracy
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If you receive this newletter more than once, then other people share
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