Fauchea: Evolution and Morpholgy of F. laciniata
While the literature on F. laciniata is sparse, several theories exist that help to explain parasitism, and the evolution of F. laciniata. Additionally, early after its initial description by Agardh, there was some confusion surrounding different morphologies and the possibility that they were other species.
Setchell was the first person to put forth the hypothesis that red adelphoparasitic red algae that share morpohological traits with their hosts in fact evolved from their specific hosts. Goff, et al, reviewed small sub-unit 18S nuclear ribosomal DNA to explore this hypothesis. Their results as they apply to Fauchea are described below. For further reading, see the Acknowledgements section.
Using 18S ribsomal DNA and the internal transcribed spacer regions (ITSs), this group analyzed Faucheocolax, a species found parasitizing many species of Fauchea, but specifically, in this study, found on Fauchea fryeana and Fauchea laciniata. They determined that Faucheocolax evolved from either F. fryeana or F. laciniata.
The mechanism for this evolution is undetermined, but it possible may have been something similar to neotony. Neotony is a speciation event in which a genetic change affects the rate of maturation that results in a species reaching sexual maturity before growing to full adult size. The result is a sexually mature organism with juvenile appearance that goes on to become a new species. Neotony can be seen in many animals and is a common occurance in the domestication of animals. It is also considered significant in the evolution of humans, especially females.
Neotony, or another mechanism, resulted in Faucheocolax evolving from a common ancestor with Fauchea. It retains many of the characteristics of Fauchea, which was the initial reason for believing the two to be so intimately related.
In Dawson's 1950 report on Pacific cost algae, he expressed surprise at finding F. laciniata in full reproductive phase in April of 1946. He then went on to discuss Setchell and Kylin's ideas about a species separate from F. laciniata called F. laciniata f. pygmaea , the latter being a smaller species that matured before it reached 4 cm while the former being the only previously recognized Fauchea that matured around 10 - 12 cm. Sounds a bit esoteric, does it?
In the end, all this discussion was for naught. Today, the f. pygamaea morph is simply considered a small morph of F. laciniata as is F. media, what was once considered an intermediate between the tiny F. laciniata f. pygmaea and F. laciniata.