Question about Evolution of early Angiosperms - (Sep/17/2006 )

Hi, my name is Rhonda Wilson. I write a monthly column on aquarium plants for Tropical Fish Hobbyist magazine. I also have quite a few planted aquariums. I'm doing research for a few columns and am a bit confused. I hope it's ok if I ask some questions here. I had read in the past that angiosperms first came on land and then went back in to the water. I was wondering why Ceratophyllum didn't have roots. I've been reading articles and doing internet searches for several days and still have some questions. Because I'm reading things written in different years and not all are dated it's a bit hard to find out exactly what the general thoughts are at this time.

So what is the relationship between Nymphaeaceae and Ceratophyllum? Are these oldest or among the second oldest with ancestor(?) of Amborella being oldest? Did Ceratophyllum and Nymphaeaceae evolve in the water or were out and went back in? And when did roots come in to the picture? Should I understand that all the ancestors of these plants were rootless and that while the others evolved roots later Ceratophyllum just stayed more the same?

And finally does Utricularia fit in to this somewhere as it doesn't have roots either? Should I assume the insect catching abilities of different plants developed independently?

Sorry for the questions and I'm sure my lack of the correct terminology.

Thank you, Rhonda

Unfortunately, most of the discussion on such topics is quite scientific, and involves knowledge of the various forms of analysis used to generate phylogenetic trees. From what I can find on the net, Amborella is thought to be the one of the more "primitive" types of angiosperm, however, opinions change quite rapidly, and different analyses have given different results.

Nymphaea and Ceratophyllum don't appear to be very closely related, however, the "support" for their relationships to the other angiosperms is weak, especially for the ceratophyllum (this means that the analysis showed a sort of low probability for the branch in the tree). See link below for more information. Note that the relationship trees do NOT show an evolutionary timeline, they are merely a representation of the similarity between the different characteristics measured for the analysis.

I think it is safe to assume that of the higher land plants (Ferns, angiosperms, gymnosperms) evolved with roots, and some groups have lost them as time goes on. Botanical tree

Yes, there was a transition to aquatic life sometime, either prior to the evolution of angiosperms (but then reversing) or independently in Nymphaceae (and Nelumboniaceae, Ceratophyllum, Lemnaceae, etc.) Definitely a recurring theme.

Some people think that certain Chinese fossils represent an aquatic ancestor of all angiosperms, but Amborella is solidly the first branch on the Angiosperm tree. Without getting too technical, don't assume that the first Angiosperm looked like Amborella! That genus has been evolving exactly as long as every other extant flowering plant, and almost certainly is NOT what the first angiosperm looked like. Amborella just happens to be the only surviving species that is decended from the earliest lineage to split from everything else that still has any surviving species.

Shifts to aquatic life also happened in ferns (Azolla, Salvinia, Marsilia, etc), and lycophytes (Isoetes). No gymnosperms that I'm aware of, unless you want to count bald cypress or something!

Utricularia is related to other carnivorous plants, butterworts, in Lentabulariaceae. These are quite a derived group (not "primitive" in any sense), and all of their relatives are terrestrial, so yet another example of a shift to the water.