Co-evolution of ferns and mycorrhizae: Phylogenic and

morphological trends.

Timothy Perez

5/4/10

Overview

• Background

• Why?

• Evidence?

• Patterns?

• Conclusions that can be drawn

Background

(Read et al. 2000)

(Read et al. 2000)

(Selosse and Le Tacon, 1998)

Why would mycorrhizae co-evolve with ferns?

• Increased absorption into fern rhizomes (2)

• Subterranean gametophyte nutrients (2)

(Smith et al. 2006)

What is Evidence for co-evolution?

• Read et al. 2000: down regulation pathogen response in plants

• Simon et al. 1993 determined approximate VAM origin to be 462-353 Myr. (3)

Methods:

• SSU rRNA from 12 Glomalean VAM species

• Homogeneity rate

• Calibration checkpoints of 200Myr and 1000Myr.

Results:

(Simon, Luc et al. 1993)

Conclusion:

• Within range of 462-353 Myr. land plants also evolved suggesting VAM importance in land colonization

(Simon, Luc et al. 1993)

What pattern and/or generalizations can be made?

•Boullard’s, 1979 observations

What patterns and generalizations can be made? • B. Boullard, 1979: Considerations sur la

symbiose fongique chez les pteridophytes– Primitive ferns had higher frequency of

mycorrhizae than derived.– From primitive to ‘higher’ fern gametophytes

we see reduction in mycorrhizal association, reduction is size, and chlorophyll

• Read et al, 2000, and Brundrett, 2002 support

To good to be true?

• Gemma et al. 1992. Mycorrhizae in Hawaiian Pteridophtyes: Occurrence and Evolutionary Significance

Asplenium adiantum-nigrum vesicles, hyphal coils and arbuscles (Gemma et al,1993)

Methods

• Sampled 45% of HI fern species for mycorrhizae

• Stained roots to determine mycorrhizal colonization density (scale of 1.0-3.0)

• Mycorrhizal index (MI) was determined by averaging colonization for each species and for each family (MIF)

Results and Conclusions:

• Highest VAM frequency occurred in Dicksoniacea, Dryopteridaceae, Dennstaedtiaceae and Lindsaeaceae

• Greatest MI in terricolous species, with next highest frequencies in epiphytic and epilithic ferns

• None in Polypodiaceae• Equal distribution of mycorrhizae within

‘primitive’ and ‘higher’ ferns

Conclusions on Generalizations:

• A proposed HI phylogeny based on mycorrhizae isn’t consistent with Smith et al. 2006.

• Contradicting evidence discounts Boullard, 1979

• More information is needed.

(Gemma et al. 1993)

Works Cited:

1: Read, D.J. et al. 2000. Symbiotic fungal associations in ‘lower’ land plants. Philosophical Transactions of the Royal Society B: Biological Sciences. 335: 815-831.

2:Mark C. Brundrett. 2002. Coevolution of roots and mycorrhizas of land plants. New Phytologist. 154: 275-304.

3: Simon, Luc et al. 1993. Origin and diversification of endomycorrhizal fungi and coincidence with vascular plants. Nature. 363: 67-69.

4: Boullard, Bernard. 1979. Considerations sur la symbiose fongique chez les Pteridophytes. Syllogeus. 19.

5: Gemma et al. 1992. Mycorrhizae in Hawaiian Pteridophtyes: Occurrence and Evolutionary Significance. J. Am. Botany. 79:8, 843-852.

6: M-A Selosse and F. Le Tacon. 1998. The land flora: a photroph-fungus partnership? TREE. 13:1, 15-20.

7: Smith et al. 2006. A classification for extant ferns. Taxon. 55:3, 705-731.

Questions?