Co-EvolutionStarring Ferns

Fern-Environment Interactions

• How do ferns interact with animals?

• With other plants?• With the soil around

them?

Ferns: Kickin’ it Old School

• Herbivore deterrents.• Fierce competitors.• Ancient Warriors trained in the school of hard-

knocks.

Toxin Accumulation

• Ferns are known for their ability to uptake toxins, particularily arsenic.

• Chinese Brake Fern (Pteris Vittata), a hyper-accumulator of arsenic can even absorb arsenic through its foliage (Bondada, 61-70)

• Arsenic is stored in the form of arsenate, the most oxidized and most toxic structure of arsenic.

Null Hypothesis:

• Ferns do not exhibit any of the co-evolutionary trends seen in the angiosperms.

Such As:

• Seed (spore) dispersal by herbivores.• Symbiotic relationships with bacteria and

fungi.• Pollination by external agents (birds, bees,

etc.)

Things may not be as simple as they seem….

• Numerous case studies of ferns have found many such plant-environment interactions such as:– Bacterial and fungal symbiotic relationships.– Spore consumption by herbivores.– Mutually beneficial insect interactions.

Spore Consumption• First reported case of fern spore consumption by a

small mammal (Arosa, 115). • Spores of Culcita macrocarpa eaten by woodmouse

in Northwest Spain.• Fertile fronds purposefully targeted.• Spore disporsal through droppings is a possibility,

though most spores are ingested.

Methods:• Two separate populations studied, Eume and Capelanda.• 90 individuals selected, one fertile frond per plant marked

at random.• Sterile and fertile pinnae for each frond were recorded, as

well as any marks of consumption.• Marked leaves were observed every 15 days for 3.5

months.• Droppings were collected from feeding sites.• DNA analysis of droppings determined herbivore identity.• Possible herbivores were captured at the sites and brought

to the lab to see if they exhibited the same consumption patterns.

Results:

• Fern consumption found exclusively on fertile fronds.

• Max consumption rates occurred in December and was practically finished by mid-February.

Results cont.

• Consumer identified as the woodmouse.• Droppings placed in petri dishes showed

germination in 2 of 14 dishes. • Between 14% and 69% of spores remained

unbroken by digestion.

Azolla-Cyanobacteria• Symbiotic relationship between the floating water

fern Azolla and nitrogen-fixing cyanobacteria.• Recent studies show that the cyanobiont in Azolla

ferns is neither Anabaena nor Nostic yet cannot be classified as a distinct genera (Baker, 43)

• Signifies evolution of the cyanobacteria within Azolla.

• Phylogenetic relationship was determined using genomic sequencing of the 16S ribosomal RNA gene.

Mycorrhizae• Ferns have them too!• Arbuscular mycorrhizae increase the arsenic

uptake in Pteris vittata (Trotta, 74).• More on this from Tim and others.

Epiphytism

• Little fossil evidence of epiphytes.• Numerous rapid radiations could coincide with

the establishment and diversification of tropical forests.– Humus collection (Bird’s Nest Fern)– Ant Mutualism (Lecanopteris sp.– Water entrapment (Staghorn fern)

• New evidence from Schuettpelz suggests development of major living epiphyte groups in Tertiary not Carboniferous.

• New evidence shows that fern epiphyte diversification may have been linked to the development of the flowering plants.

What’s it all mean?

• Ferns do not exist as an entity separate from their surroundings.

• The evolution of ferns is in a direct relationship with the evolution of their surroundings.

• All evolution occurs as such, they dynamic interplay of the sum of all parts.

• Even non-biological factors have a role to play in evolution.

Where does that put us?

Works Cited•

Baker J.A., Entsch B., McKay D.B. The cyanobiont in an Azolla fern is neither Anabaena nor Nostoc (2003) FEMS Microbiology Letters, 229 (1), pp. 43-47.

•Dubuisson J.-Y., Schneider H., Hennequin S. Epiphytism in ferns: diversity and history (2009) Comptes Rendus - Biologies, 332 (2-3), pp. 120-128.

• Arosa, M.L., J.A. Ramos, L.G. Quintanilla, and D. Brown. "First report of fern (Culcita macrocarpa) spore sonsumption by a small mammal (Apodemus sylvaticus)." Mammalian Biology 75.2 (2010): 115-121. Web. 25 Apr 2010.

•Bondada B.R., Tu S., Ma L.Q. Absorption of foliar-applied arsenic by the arsenic hyperaccumulating fern (Pteris vittata L.) (2004) Science of the Total Environment, 332 (1-3), pp. 61-70.