Biogeography and Ecology of Ferns

Geonyzl L. Alviola

Biogeography

factors to be considered:

a) size of geographical ranges, and their

spatial placement; b) the way individual

species attain their distribution ranges

(dispersal, extinction and vicariance);

c) the distribution of species numbers

(alpha diversity);

d) changes in species composition and e) spatial distribution of species traits (beta diversity).

But according to Barrington (1993) that there were three prominent factors relevant to fern biogeography:

a) habitat preferences and distribution;

b) the unique reproductive biology of ferns and

c) long distance dispersal

Ferns are suitable organisms for biogeographic studies because of the following reasons:

a) its worldwide distribution;

b) moderately high but manageable species richness;

and the occurrence of independent gametophytic and

c.) sporophyte generations of ferns, allow direct

comparison of moss-like and angiosperm-like.

Which make them a great model how land plants evolved.

Habitat preferences and Distribution

minute filmy plants whose height might range from 2 mm to 3mm (0.08 to 0.12 inch)

Azolla filiculoides

tree fern in class Polypodiopsida

with an average height of 10 to 25 m.

Geographically ferns are usually found in the tropics, there are only few species could be found in the Arctic and Antarctic regions

A number of families that are exclusive to tropical areas like the:

Marattiaceae , Cyatheaceae,

Blechnaceae Davalliaceae.

Gleicheniaceae,

Schizaeaceae,

Certain genera of ferns could be found in temperate and Arctic regions like the:

Athyrium,

Cystopteris,

Dryopteris and

Polystichum.

From the widespread fern species :

Dispersal and Vicariance

Dispersal of ferns species takes place primarily via dust-like spores, but there are species produces gametophytic gemmae for medium dispersal.

Grandstein and van Zanten (2001) had an

experiment on spore dispersal in extreme

environmental condition exposing the spores on

low temperatures and high UV radiation exposure.

Long-distance dispersal of ferns is effective because most ferns have small, lightweight spores that will develop into a gametophyte capable of producing both egg and sperm.

Factors influencing the potential for long distance

dispersal would be the :

- size,

- shape and

- ornamentation of the spores, and

- spores with or without chlorophyll.

Families with Green spores

Some families of ferns which are chlorophyllus such as:

Equisataceae,

Hymenophyllaceae,

Onocleaceae and

Osmundaeceae

Dispersal to Oceanic Islands

Adenophorus which related to the Grammitis

Vicariance

Latin word vicaries

derived from vicis means for change,

alternation

vicariance may happen due to continental drift

long time ago that resulted to biogeographic

patterns

Range size: Variability and Spatial Distribution

A. Range size and its correlates

Ferns and lycophytes were geographically widespread in

distribution than the flowering plants due to their efficient spore

dispersal.

But other interpretations have also suggest other factors like :

= age,

= ecological requirements,

= availability of suitable habitats and

= the ability of the species to reach these habitats and survive

Cystopteris fragilis

and that occur almost

throughout temperate

regions and tropical

montane ecosystem.

Lycopodium clavatum

Range size may be also correlated with other reproductive and morphological traits.

Japanese ferns =

ranges are larger in species with multiple

reproductive modes (sexual and vegetative

propagation)

Endemism

FACTORS OF ENDEMISM:

= Geographical isolation – separated by barriers like

mountain, or water

= Abiotic factors (nutrient, temperature, humidity,

elevation)

= Species of different life forms and habitat show

distinct patterns. eg. Epipetric ferns

American Hart’s Tongue Fern (Asplenium scolopendrium L.)

Alpha Diversity

Alpha diversity refers to the diversity within a particular area or ecosystem and is usually expressed by the number of species in that ecosystem.

A. Pattern of species richness

Marsilea crenata

aquatic fern

B. Mountains as hot spots of biodiversity

Fern diversity among mountain ranges would vary depending on its elevation, because not all mountain ranges had the same elevation.

It has been observed that fern species have been

dependent on humid microhabitats, mild temperatures, in

ravines , streams rather than slopes.

Beta Diversity

Beta diversity is the change of plant or animal communities along ecological gradients.

While these gradients can cover a wide range of

spatial , temporal and ecological aspects, studies on

the beta diversity of ferns have mostly focused on

change in geological substrates and soils as well as

elevation.

Soil Gradient

Elevational Gradient

1. Families Aspleniaceae and Dryopteridaceae

Found to the lowest to the highest elevation

2. Family Hymenophylleceae

Found at low to the middle elevation

Asplenium platyneuron