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Discussion Starter #1 (Edited)
Just a quick look at the rich variety of aquatic plants in the Santa Fe River in N. Central Florida. In the first picture you can see Vallisneria, Hydrilla, and a little bit of Najas and a leaf or two of Sagittaria. Also present but not in these pictures were a submersed Cyperus, and a pink Myriophyllum which turned out to be M aquaticum (parrot's feather).



The Sagittaria species and a variety of snails


Hygrophila polysperma in the Santa Fe
 

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Wow :)

That's beautiful. I wish we had rivers planted that way up here! (Detroit)
 

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Thats awesome! Im headed to Austin this weekend, and really want to stop by the San Marcos river.....if so I'll try and get some pics to share.
 

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Discussion Starter #5
Thought I would bump this up because I added some more pictures of plants in the Santa Fe River.
 

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Wow! That's some awesome growth. I can't wait until May around here. Most of the lakes and ponds start showing different variety of plants including some stuff that's harder to find.

Texex94
 

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Beautiful pics! Is that Sagittaria graminea, or is too hard to tell one from another submersed?

-Dave
 

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Discussion Starter #8
It is too hard for me to tell what species of Sag it is. The leaves are very narrow and can get over one foot long. This is what it looked like in my aquarium:

 

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Hello HeyPK,
I think this Sagittaria may belong to the S. subulata complex. The very narrow and long leaves seem to match S. subulata var. gracillima in older aquarium literature. Peter Schneider (CH) describes the leaves as rather hard and wiry: http://www.a-perleverlag.ch/buch/sagittaria.html (in german)
In the Flora of North America several taxa of the S. subulata complex are even considered as species:
http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=129016
http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=222000335
Thus S. subulata var. gracillima is a synonym of S. filiformis. But this species may include different forms because the leaves are stated being 0.1-1.5 cm broad.

Are there inflorescences? In the S. subulata complex, they float along the water surface (not upright and emergent), and the male flowers have mostly about 7 stamens.
 

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Discussion Starter #10
Thanks for all the info.! I found this link from Shawn Winterton's guide:

http://keys.lucidcentral.org/keys/aquariumplants2/Aquarium_&_Pond_Plants_of_the_World/key/Aquarium_&_Pond_Plants/Media/Html/Fact_sheets/sagittaria.html

Winterton says,"The taxonomy of the genus is problematic, with little consensus from recent revisions". I can believe it, having seen some of the variety within a supposed species as well as some of the similarity between supposed species. There seems to be just as much variety in American Vallisneria, but they lump it all into one species, Vallisneria americana. We have a long way to go in taxonomy of some of our aquarium plants.

The key at this link http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=129016 says that subulata is mostly in brackish water and tidal mud flats. The Santa Fe River plant seems closer to Satittaria kurziana, found in Florida springs and clear streams.
 

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Interesting site, thank You! S. sagittifolia a noxious weed in USA :eek:... this only native Sagittaria of Central Europe is not really common in wide parts of Germany.
Maybe S. graminea in the aquarium hobby isn't correctly named - according to the Flora of North America S. graminea lacks stolons and corms but possesses coarse rhizoms :confused:
Also in Vallisneria there will be name changes... Cladistic studies by Les, Jacobs et al. lead to re-establishment and new description of several species: http://www.bioone.org/doi/abs/10.1600/036364408783887483
 

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The key at this link http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=129016 says that subulata is mostly in brackish water and tidal mud flats. The Santa Fe River plant seems closer to Satittaria kurziana, found in Florida springs and clear streams.
OK; I mention not S. subulata in the narrower sense but the S. subulata complex including S. subulata, filiformis and kurziana. As I've understood it, S. kurziana differs from S. filiformis mainly by lack of expanded leaf blades, also in stranded / emersed plants.
 

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Discussion Starter #13
I can't tell from the abstract on Vallisneria whether or not the authors have more than one Vallisneria species in the U.S. There ought to be. While on Tom Barr's Plantfest, 2004, I found an extremely large Vallisneria in the Ichetucknee River that, instead of sending up single female flowers on long, coiled, thin stems, sent up a thick stem with a node and a leaf at the end with several short flower stems coming from the node. Picture 1 is a drawing I made. Picture 2 is of the typical female flower.
 

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Your finding is very interesting because North American Vallisneria populations with "cymes" or umbels with up to 30 female flowers are mentioned: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=134329 (= V. sp. (umbellate) in Les et al.)
According to the paper of Les et al. (2008 ) (I've got a copy) there are 3 distinct taxa in N-America: V. americana (in the narrow sense), V. neotropicalis and V. sp. (umbellate), the latter being closer related to V. neotropicalis. Their V. americana is restricted to America and doesn't include Old World Vallisnerias.
The paper doesn't contain a key for the genus.
Maike Wilstermann, a co-author of the paper, writes that true V. neotropicalis and V. gigantea are not among the different giant vallisnerias in the trade. Instead the latter are to be belonging to the newly described V. australis from Australia: http://www.heimbiotop.de/vallisneria.html
 

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Discussion Starter #15
Most interesting. I am not enough of a taxonomist to know if there is consistency the criteria that are used to define a genus or a species in botany. Ultimately, I think the criteria will be molecular differences and then taxonomists will then try to settle on some morphological differences that agree with the molecular data so that keys can be made so that you don't have to be a molecular biologist with a lot of time on your hands to key out a species. I find it interesting, that in the genus Ludwigia, flowers can have three to seven petals, or no petals at all. and leaves are usually opposite, but can be alternate or in a rosette. I guess we know one when we see one.

I know that molecular taxonomy has made some large revisions in animal taxonomy. For instance, the nematodes are now considered closely related to the arthropods, and the morphological character found to agree with the molecular data is that they both molt. Types of body cavities used to be important in distinguishing major groups (acoelomates, pseudocoelomates and those with 'true' coeloms formed in mesoderm), but are no longer important.
 

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Hello Paul,
that's fine that You've got the Vall paper.
Species delimitation is really a difficult topic... especially in the often character-poor and morphologically plastic water plants.
As I understand it, really new in systematics is not simply the availability of molecular data but the consistent use of the principles of phylogenetic systematics (= cladistics) in the analysis of characters (molecular as well as morphological, ecological, behavioural etc.) and in the delimitation of taxonomic groups. Every grouping should be monophyletic, that means a natural group (a clade), descending from a last common ancestor that is not at the same time an ancestor of taxa outside the grouping. Often morphological and molecular characters are simultaneously analyzed. One of the advantages of molecular data is the potentially high amount of characters. There are mostly no a priori assumptions which characters are more important than others.The results of the analyses are testable hypotheses about the evolutionary history of the studied organisms, displayed as tree diagrams.
 
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