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Co-Evolution Starring 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 hardknocks. 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 coevolutionary 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.
