Desert ferns: Adaptations and possible origin from epiphyti - PowerPoint Presentation

Slide1

Desert ferns: Adaptations and possible origin from epiphytic ancestors

Cheilanthes

gracillima

Slide2

What are the desert ferns?

Desert ferns, often referred to as Cheilanthoids, are all in the family Pteridium

which includes 4 groups: AdiantoidsCheilanthoidsHemiontidoids

P

teroidsSlide3

Cheilanthoids consist of 6 genera

Argyrochosma

- false cloak fernsAspidotis - lace ferns

Astrolepis

- star-scaled cloak

ferns

Cheilanthes

- lip

ferns

Notholaena

- cloak

ferns

Pellaea

- cliff

brakes

All are known to inhabit xeric

enviroments

Source: WikipediaSlide4

Cheilanthoids have developed many adaptations to allow them to survive in very dry environments

Microphylly, or reduced frond and

pinnea size

Argyrochosma

dealbata

Reference: R. H.

HevlySlide5

Adaptations continued…

Partially sunken and fewer stomata, reduces water loss through transpiration Reduced cell size, reduce likelihood of plasmolysis and resulting

plasmadesmata ruptureIncreased palisade tissue, spreads illumination to a larger volume of cells decreasing stress on chloroplasts and improves translocation of water, nutrients and

photosynthates

Reference: R. H.

HevlySlide6

Adaptations continued…

Heavily cutinized epidermis, particularly in glabrous (free of hair/scale) species

Lamina of nonglabrous species partially or completely obscured by hair, scale and gland in various combinations

C

heilanthes

parryi

(hair)

Reference: R. H.

HevlySlide7

Adaptations continued…

Impregnation of epidermal and cortex cell walls with suberin

and lignin particularly in stipe and rhizome. Sclerification

of cell walls extending to the stele as well as epidermal appendages of rhizome and

stipe

.

Cortex cells filled with gum or tannin-like substances

All of these deposits are designed to control water loss from the main plant body

Reference: R. H.

HevlySlide8
Slide9

Some Cheilanthes

have even been found to utilize mycorrhizal VAM relationships that ostensibly help them to better deal with water stress and nutrient uptake

(M. Palmieri, L.T.Swatzell)Slide10

And the most common adaptation to the xeric environment…

Poikilohydry- curling of leaves under drought stress. It has been shown that desert ferns curl differently depending on their morphology. Ferns with coverings on the lower epidermis curl to protect the upper epidermis from exposure, while ferns without lower epidermal coverings curl such that the lower epidermis and stomata are protected

Reference: R. H.

HevlySlide11

Notholaena

standeyi

Maxon

Pellaea

mucronataSlide12

The gametophytes of Cheilanthoids are also adapted to xeric enviroments

The

prothallus is able to recover from desiccation severe enough to destroy all but a few cellsThe mode of reproduction is apomictic

Remember

Cheilanthes

yavapensis

?

(A.L.

Grusz

et al.)Slide13

The southwest is a biodiversity hot spot for CheilanthoidsSlide14

So how do Cheilanthoids fit into the phylogeny of ferns? (What about the epiphyte part of this talk?)

As previously state Cheilanthoids are in the family Pteridaceae.

They are polypods, not eupolypods

Pteridaceae have a false

indusium

, never a true

indusium

, vertical interrupted annulus with mixed development of sporangium

Pteridaceae is the only

polypod

(excluding

eupolypods

) not in the double

indusium

groupSlide15
Slide16

the divergance point (50) was estimated to be 124.92 MYA (K.M. Pryer et al.)Slide17

Divergence of Pteridaceae

The initial divergence point (50 ) was estimated to be 124.92 MYA while the divergence of Pteridaceae proper (52) was 92.03MYA this put the divergence point in the mid to late Cretaceous periodSlide18

Diversification of epiphytes

According to research done by Eric Schuettpelz the bulk of epiphytic radiation occurred after the K/T boundary about 65 MYA

However epiphytism is a trait that has arose independently as well as subsequently lost, several times in fernsSlide19
Slide20

So what does this mean? Maybe nothing, One of the earliest families of ferns to diverge, estimated in

Pryer et al. at 272.89 MYA, during the Permian, was

hymenophyllum, the filmy ferns. This family today has an very high percentage of epiphytes.Slide21

The fact is that desert ferns and epiphytic ferns share many characteristics

Most of these are characteristics that help the plants prevent water loss.

Most epiphytic ferns have also lost their indusium like Cheilanthoids.Slide22

Works cited

Comparative Desiccation Tolerance of Three Desert

Pteridophytes: Response to Long-term Desiccation James B.

Harten

, William G.

Eickmeier

American Midland Naturalist

, Vol. 118, No. 2 (Oct., 1987), pp. 337-347

Published by: The University of Notre Dame

Stable URL: http://www.jstor.org/stable/2425790

Adaptations of Cheilanthoid Ferns to Desert Environments

Richard H.

Hevly

Journal of the Arizona Academy of Science

, Vol. 2, No. 4 (Dec., 1963), pp. 164-175

Published by: Arizona-Nevada Academy of Science

Stable URL: http://www.jstor.org/stable/40026172

Mycorrhizal Fungi Associated with the Fern

Cheilanthes

lanosa

M.

Palmieri

, L. J.

Swatzell

Northeastern Naturalist

, Vol. 11, No. 1 (2004), pp. 57-66

Published by: Humboldt Field Research Institute

Stable URL: http://www.jstor.org/stable/3858543

A Fossil Fern Indicator of

Epiphytism

in a Tertiary Flora

Imogen

Poole, Christopher N. Page

New

Phytologist

, Vol. 148, No. 1 (Oct., 2000), pp. 117-125

Published by: Blackwell Publishing on behalf of the New

Phytologist

Trust

Stable URL: http://www.jstor.org/stable/2588907

Phylogeny and Evolution of Ferns (

Monilophytes

) with a Focus on the Early

Leptosporangiate

Divergences

Kathleen M.

Pryer

, Eric

Schuettpelz

, Paul G. Wolf,

Harald

Schneider, Alan R. Smith, Raymond

Cranfill

American Journal of Botany

, Vol. 91, No. 10 (Oct., 2004), pp. 1582-1598

Published by: Botanical Society of America

Stable URL: http://www.jstor.org/stable/4123853

Schuettpelz

, Eric. "THE EVOLUTION AND DIVERSIFICATION OF EPIPHYTIC FERNS." Diss. Duke University, 2007.

Dukespace

. Web. <http://dukespace.lib.duke.edu/dspace/bitstream/10161/181/1/D_Schuettpelz_Eric_a_052007.pdf>.