What reproductive advantage do superhydrophobic spores bring?

Question

Clubmoss plants produce spores that are superhydrophobic, meaning they will not mix with water. When you drop water on top of a whole bunch of these spores, the water will form tiny water droplets on top of the spore powder instead of being absorbed by it. You can see an example of this in this video. The spore powder is also known as lycopodium powder and is used in fire shows and magic tricks.

To my knowledge clubmoss is the only plantspecies that produces superhydrophobic spores. This made me wonder what the reproductive or evolutionary advantage of a superhydrophobic seed or spore could be.

I personally think the superhydrophobic layer could protect the spores from being digested when the clubmoss plant is eaten by a herbivore. The superhydrophobic layer could also prevent the spores from sinking when they fall into water like a river, instead they would stick to the surface. A river could help disperse the spores accross a larger area pretty easily. Eventually the spores would drift to the shore again where they could settle and become new clubmoss plants.

What do you think the reproductive advantage could be?

Answer 1

This paper seems to agree with you; It says that the spores of the clubmoss plant are likely hydrophobic to spread more easily.

This is also a part of the secret of the well-known Lycopodium powders: the clubmoss-spores (diameter ca 30 μm) are weakly hydrophobic, but as powder, they exhibit remarkable functionalities. Many spores—even of aquatic organisms such as the spores of Isoetes or fungi, or myxomycetes [80] are hydrophobic for dispersal purpose.

[80]
(citation from the paper)
Hoppe T, Schwippert WW. 2014 Hydrophobicity of myxomycete spores: an undescribed aspect of spore ornamentation. Mycosphere 5, 601–606. Crossref, ISI, Google Scholar

Additionally, this article believes spores are hydrophobic to protect against environmental factors.

When spores are carried over a long distance, survival is compromised by exposure to diverse abiotic stressors, such as drought, extreme temperatures, and ultraviolet (UV) radiation [12, 13]. Thus, fitness can be estimated using not only developmental parameters but also spore properties that influence dispersal efficiency in different media and resistance to stressors.

Most filamentous fungi disperse through airborne spores that can be transferred by wind over a long distance [11, 14]. For this reason, fungal spores usually remain dry and hydrophobic [15].

(citations from the article)
[11]
Wyatt TT, Wosten HA, Dijksterhuis J. Fungal spores for dispersion in space and time. Adv Appl Microbiol. 2013;85:43–91.

[12]
Fuller KK, Ringelberg CS, Loros JJ, Dunlap JC. The fungal pathogen Aspergillus fumigatus regulates growth, metabolism, and stress resistance in response to light. mBio. 2013;4.

[13]
Norros V, Karhu E, Norden J, Vahatalo AV, Ovaskainen O. Spore sensitivity to sunlight and freezing can restrict dispersal in wood-decay fungi. Ecol Evol. 2015;5:3312–26.

[14]
Roper M, Seminara A, Bandi MM, Cobb A, Dillard HR, Pringle A. Dispersal of fungal spores on a cooperatively generated wind. Proc Natl Acad Sci USA. 2010;107:17474–9.

[15]
Aimanianda V, Bayry J, Bozza S, Kniemeyer O, Perruccio K, Elluru SR, et al. Surface hydrophobin prevents immune recognition of airborne fungal spores. Nature. 2009;460:1117–21.