The Tree Fern Tree - Continued

Do you remember the core tree fern clade from last fortnight? How many families do you remember? Hopefully all of them. This week you get to build on what you already know by investigating the rest of the order.

Tree Fern Fronds
http://wpnature.com/ferns-look-fractals-shaped-view-desktop-photo/
Viewed on 20/4/2018

The sori of Thyrsopteris elegans
https://commons.wikimedia.org/wiki/File:Thyrsopteris_elegans01.jpg
Viewed on 20/4/18

The “Lonely Lenny” of this order is Thyrsopteridaceae. It has only one genus and one species, and boy what a species. Thyrsopteris elegans is the only living fern today that produced spherical "grape like" sori (Smith et al., 2006). It can only be found on a group of volcanic islands off the coast of Chile. However,Thyrsopteris fossils have been found from the Mesozoic and Cretaceous periods (Korall et al., 2006). This species grows on a "trunk like" rhizome similarly to Cyathea and Dicksonia. I really want one of these guys so please, if you have one spare could you let me know. 

The visibly larger fertile fronds of Plagiogyria tuberculata
https://commons.wikimedia.org/wiki/File:8460-Plagiogyria_tuberculata-Kemiri.JPG
Viewed on 20/4/18

Plagiogyria is another “single genus” order. The ferns of the plagiogyria family produce two kinds of fronds. The fertile fronds are visibly much larger than the smaller sterile fronds (Korall, 2006). Most are found in Asia but one is found in America. This fern grows on a creeping rhizome and lacks both hairs and scales. That last detail resonates with me, I have a "bald bias".

Culcitaceae houses a single genus called “Culcita” with two species (Smith et al., 2006) and is closely related to Plagiogri. They can have a creeping or ascending rhizome, so no trunk. there's no way to put it nicely, this is an all round boring plant.

Culcita macrocarpa
https://commons.wikimedia.org/wiki/File:089._R%C3%ADo_de_la_Miel_-_Helecho_de_colchonero_(Culcita_macrocarpa)_(12858470513).jpg
Viewed on 20/4/18

Loxsoma cunninghamii
http://www.fernsoftheworld.com/2014/09/18/loxsoma-cunninghamii/
Viewed on 20/4/18

Loxsomataceae is considered to be the sister group to Culcita and plagiogyria. There are only two known Loxsomata species, both of which have a creeping rhizomes (Korall et al., 2006).  The gametophytes of this family have "scalelike" hairs which also occur in Cyatheacea (Smith et al., 2006).

So why are Plagiogyria, Culcita and Loxsomata grouped with the core tree fern clade if they don’t have trunk-like rhizomes? Wouldn’t they be better grouped with other creeping ferns? Well it actually makes more sense that the morphological similarities in their sporangia alannuli and spore wall is a result of  a common ancestor shared with the core tree fern clade (Hasebe et al., 1994). 

A diagram indicating the function of sporangia alanulihttp://www.naturalhistorymag.com/biomechanics/172095/spore-launchers
Viewed on 20/4/2018

Well folk, I think that's quite enough about the tree fern tree for one life time. Please keep in mind that this tree is always subject to change and will be regularly reviewed. As a famous genealogist never once said "Done! everything in the family tree has been found and is completely organised" 

Until next time, Keep your trunk wet.

Image taken from
https://www.maxpixel.net/Flora-Tree-Fern-Huge-Of-Giant-Nature-Filigree-420073
Viewed on 28/4/2018

Reference list

Hasebe, M., Omori, T., Nakazawa, M., Sano, T., Kato, M. & Iwatsuki, K. 1994, "rbcL Gene Sequences Provide Evidence for the Evolutionary Lineages of Leptosporangiate Ferns", Proceedings of the National Academy of Sciences of the United States of America, vol. 91, no. 12, pp. 5730-5734.

Korall, P., Pryer, K.M., Metzgar, J.S., Schneider, H. & Conant, D.S. (2006) "Tree ferns: Monophyletic groups and their relationships as revealed by four protein-coding plastid loci", Molecular Phylogenetics and Evolution, vol. 39, no. 3, pp. 830-845.

Smith, A.R., Pryer, K.M., Schuettpelz, E., Korall, P., Schneider, H. & Wolf, P.G. (2006) "A classification for extant ferns", Taxon, vol. 55, no. 3, pp. 705-731.