Botany 106 – Pteridology
Review of Plant Systematics
What is a plant?
• Defined by the following characteristics:
o Photosynthesis (chlorophyll a and b)
o Cellulosic cell wall
o Produces starch
o Multicellular eukaryotes
• Defined through evolutionary history
• Cladogram
o Photosynthesis provides a niche
• Theory of endosymbiosis
•
o Psilotales (Psilotum)
o Marattiophytes (Angiopteris)
o Polypodiales (Blechnum)
Spermatophytes
Systematics
• Science of organismal diversity
• Entails
discovery,
description,
and
interpretation of biological diversity
• Synthesis of information on diversity in the
form of predictive classification types
• Taxonomy
o Identification,
nomenclature,
classification
• Phylogenetics
o Reconstructing the evolutionary history
and relationships of organisms
Central Problem
• Reconstrct history of the separation of the
lineages and history of their modifications as
accurately as possible bringing as much
relevant information as possible to bear on
the problem
Plants
• Viridiplantae
o Green plants (chlorophyll a and b)
o With green algae
• Embryophytes
o Land plants
• Cryotogams
o Without seeds
• Phanerogams
o Spermatophytes
Aims of Plant Systematics
• To provide a convenient method of
identification and communication
• To provide an inventory of the world’s fern
• To detect evolution at work
• To provide a system of classification which
depicts the evolution within the group
Embryophytes
• Nontracheophytes
o Liverworts, hornworts, mosses
o Can still transport water via hydroids
and leptoids but not as efficient as
xylem and phloem
o Gametophyte dominates the life cycle
o Oogamous (sperm needs to swim and
find egg) → found in damp/wet
environments
o Non-photosynthetic sporophytes
o Rhizoids anchor the body
▪ Not very absorptive (it is the
vegetative body with high SA:V
ratio that absorbs)
• Tracheophytes
o Lycophytes (Selaginella)
o Equisetales (Equisetum)
o Ophioglossales (Ophioglossum)
Evolution
• Descent with modification
• What is being modified?
o Genetic material: DNA
o Through:
▪ Mutation (adaptive or not)
▪ Selection
▪ Genetic drift
Why study systematics?
• Foundation of biology
• Integrative, unifying science
• Practical value – economically important
plants
• Conservation biology – rare/endangered
species
• Intellectually challenging/fun
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Botany 106 – Pteridology
•
General Descriptions of Cryptogams
Alternation of Generations
• Sexual and asexual phases (often
morphologically distinct)
o Alternation of dimorphic forms
o Distinct in number of chromosomes
• Presence of distinct multicellular forms
• Stages of ontogenetic development of an
organism
• Haplo-diplontic life cycle
o Haplo = sexual
o Diplo = asexual
Sporophyte
o Leaves, stems, roots
o Does the vegetative activities of the
plant
Advantage of 2 Forms
• Allows
each
to
exploit
different
environments
o Tiny spores allow genes to travel far
beyond the immediate vicinity of the
parent
o Allows one generation of such
organism exploratory role
• Sporophytes can also disperse due to
gemmae
Fern Life Cycle
• Some have separate sexes of prothallus
• Prothallus
o No vascular tissues (transport via
diffusion)
o No leaves and stems
o Has rhizoids (for anchorage)
o Goal: to form gametes
• Plant that produces separate sexes of
prothallus = HETEROSPOROUS
• Plant that produces just one spore =
HOMOSPOROUS
Cryptogam vs Phanerogam
• Cryptogam
o Zygote germinates directly to plant
• Phanerogam
o Seed is part of sporophyte stage
Morpho-anatomy of Ferns and Fern Allies
(Sporophyte)
• Stem
o No secondary growth
▪ No wood, bark
▪ No increase in girth
▪ No vascular cambium
o Has cells with secondary cell walls and
fibers (sclerenchyma)
o Stellar patterns:
▪ Protostele
▪ Siphonostele
▪ Plectostele
▪ Dictyostele
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Botany 106 – Pteridology
o
o
o
•
Due to leaf gaps that arise from leaf
traces
Leaves
o Megaphyllous (multiple and several
venations)
o Most familiar:
▪ Compound leaves
▪ Pinnate
o When immature:
▪ Crosiers
o Microphyllous
(just
one
major
vascularization)
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Whisk ferns (Psilotum)
▪ No leaves
▪ Stems are photosynthetic
▪ Have rhizoids
Horsetails
▪ Have leaves but not photosynthetic
▪ Stems are photosynthetic
Botany 106 – Pteridology
Phylogeny of Lycophytes
General Characteristics of Lycophytes
• Tracheophytes
o Xylem and phloem
o Can grow taller due to more efficient
transport
• Cryptogams
• Dominant sporophyte phase
• Common in tropics and subtropics
• Vegetative organs
o Microphyllous leaves
o Dichotomously (dichopodial) branching
stem and roots
• Possess strobili (cones) [sporophylls]
o Bear the sporangia that bear the spores
o Club mosses: homosporous
o Spike
mosses
and
quillworts:
heterosporous
•
Club Mosses (Lycopodiaceae)
• Greek lycos (wolf) + podion (foot), from
resemblance to a wolf’s foot
• Dichotomously branching stem without
secondary growth and with plectostele
o Perennial life span
• Adventitious roots from rhizomes and corms
• Leaves are simple, sessile, spiral or whorled,
the blades are scale-like to acicular, all with
a single midrib
• Sporangia homosporous occurring on short
stalks in axils of leaves (sporophylls)
organized in terminal strobilus (cones)
• Gametophytes are mycorrhizal, either
epiterranean
and
photosynthetic
or
subterranean and saprophytic
• Worldwide, there are 10 to 15 genera and
350 to 400 species
• Sporophytes have bulbil and gemma for
asexual reproduction
• Gametophyte (L. digitatum A. Braun)
o Subterranean, myccorhizal structures
o Externally, they are divided into 3
principal regions:
▪ Tapering base
▪ Ring meristem
▪ Gametangial cap
o Growth of young embryo is parasitic
and will kill the gametophyte
o Aka prothallus
•
Sporophyte dominance
o Lifespan: sporophyte > gametophyte
o Performance of vegetative activities
(photosynthetisis + absorption)
Paraphyletic clade
o Angiosperms and gymnosperms are
embedded within
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Botany 106 – Pteridology
•
•
•
Consists of 5 genera:
o Huperzia (ca. 200 spp., mostly
worldwide)
o Lycopodiella (ca. 40 spp., tropical and
temperate regions)
o Lycopodium (ca. 40 spp., tropical and
temperate regions)
o Pseudolycopodiella
(12
spp.,
worldwide)
o Phylloglossum (2 spp., Australia, New
Zealand)
The family has a worldwide distribution
Economic Importance
o Cultivated ornamentals
o Medicinal plants (e.g., Lycopodiella
spp.; Huperzia selago used as an
emetic; H. serrata experimentally used
to treat Alzheimer’s)
o Fibers: used as stuffing material,
baskets, nets
o Dried spores have been used as a
lubricant (in condoms, rubber gloves)
and, because they are very flammable,
in fireworks and lights, including early
flash photography
•
•
•
Spike Mosses (Selaginellaceae)
• Latin Selago, a mosslike plant of the
Scrophulariaceae + ella (diminutive)
• Perennial herbs
• Roots are adventitious and dichotomously
branching (dichopodial)
• Stems
are
generally
dichotomously
branching
(pseudomonopodial
or
sympodial),
with
erect,
cespitose,
prostrate/repand, or climbing habit
• Stems are protostelic
• Leaves are simple, sessile, spiral, with a
single midrib
• Sporangia heterosporous
o Microsporangia bearing numerous,
small, trilete microsporous
o Megasporangia bearing usually 4, large,
trilete megaspores
• Sporangia subtended by sporophyll on the
axis of terminal strobili
• With endosporic gametophytes
• Some are anisophyllous
1 genus (Selaginella), ca. 700 spp.
Mostly distributed in tropical and warm
regions, worldwide
Economic importance includes cultivated
ornamentals and local medicinal plants
o Wound injury
o Menstrual disorder
o Post childbirth
o Itchy skin
o Liniment
Quillworts (Isoëtaceae)
• Greek isos (ever) + etas (green), in reference
to apparent duration of some primarily
aquatic, perennial herbs
• Stems are protostelic, vertically oriented,
rarely rhizomatous
• Leaves are simple, spiral, in a basal rosette,
the blades basically widened, sheathing,
apically linear to acicular, flat to terete
(generally short, but >50 cm in some
species), with a single midrib, mostly
sporophyllous
• Sporangia are heterosporous, and are located
on the adaxial side of leaf (sporophyll) bases
o Megasporangia occur on outer leaves of
a flush of growth, the megaspores large
(50-300 per sporangium), trilete, spore
sculpturing
used
in
species
identification
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Botany 106 – Pteridology
o
o
o
o
o
o
o
o
o
Microsporangia occur on inner leaves
(or in alternating cycle with
megasporangia), the microspores small,
monolete, very numerous (up to 1
million per sporangium)
Both sporangia are marginally covered
by a membrane, the “velum,” and are
internally traversed by sterile strands
(“trabeculae”)
Plants have CAM photosynthesis, air
chambers occur in roots and leaves
Freshwater plants
Isoetes unique characteristics:
▪ Has a lateral meristem (not
woody)
▪ Stem
is
continuous
with
rhizomorph
1 genus (Isoetes), ca. 200 spp.
Distributed all around the world and are
found on all continents excluding
America, they are however often
naturally rare or uncommon in many
areas
Rely heavily on an abundance of water
in order to survive, many species live
permanently submerged in lakes and
slow moving rivers, other species
inhabit estuaries and wetlands where
they often encounter periods of
flooding
Isoetes plants are often used as
indicators of water quality because they
do not like to grow in poor water
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Botany 106 – Pteridology
Monilophytes
• Review on phylogeny:
•
Leptosporangiate
o Small sporangium develops from a
single initial cell and produces a small
definite number of spores (< 128)
•
Leptosporangia are more recent than
eusporangia
There are no leptosporangiate fern allies
Leptosporangiate
Eusporangiate
• Sporangia small • Sporangia large
(ca
0.2
mm
(ca 0.5 mm
diameter)
diameter)
• Sporangial walls • Sporangial
one cell layer
walls
several
thick plus
cell layer thick
• Develop from a • Develop from a
single sporangial
group
of
•
•
sporangial
initials
Produce a large
number
of
spores
Equisetales (Horsetails)
• Aka sphenopsids and scouring rushes
• Perennial herbs growing in or near wet
habitats
• Upright and distinctly articulate and
typically hollow stems that are ridged
arising from horizontal rhizomes
• The aerial stems are photosynthetic (called
phylloclade/cladophyll), with an epidermis
containing silica inclusions
• Branches and leaves are born in whorls at
the nodes
• Extant plants are homosporous with
terminal, mostly abaxial sporangia, born on
peltate, scaly sporophylls that are arranged
in terminal, ellipsoid cones
• Spores are spherical, green (with
chloroplasts), each bearing hygroscopic
elaters
o Structures on spore wall
o Springlike, absorb water and expand for
spore dispersal
• Strobili
are
sporangiophores
with
sporophylls wherein there are sporangia
Eusporangiate vs Leptosporangiate Ferns
• Eusporangiate
o Large sporangium develops from many
initial cells and produces many spores
•
initial
Produce
relatively
few
spores
(commonly 64)
Psilotales (Whisk Ferns)
• Greek psilos (naked), alluding to leafless
stems
• Consisting of the single family Psilotaceae,
with 2 genera (Psilotum and Tmesipteris)
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Botany 106 – Pteridology
•
•
•
•
•
•
Sporophyte consists of horizontal rhizomes
that give rise to aerial, photosynthetic,
generally dichotomously branching stems
Lack true roots, an apomorphy for the
group; only absorptive rhizoids (typically
unicellular) arise from the rhizome
Rhizomes having symbiotic myccorhizal
associations
Leaves are very reduced and peglike and
may lack a vascular strand, in which case
they are termed enations
Sporangia are eusporangiate, homosporous,
2- or 3-lobed which is interpreted as a
synangium, a fusion product of 2 or 3
sporangia arising from short, lateral
branches
Gametophytes
are
non-photosynthetic,
cylindrical, saprophytic, and myccorhizal;
sperm are multiflagellate
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Botany 106 – Pteridology
Eusporangiate Ferns
Ophioglossaceae
• CN: Adder’s Tongue family
• Greek ophis (snake) + glossa (tongue), in
reference to shape of fertile segments
• 4 genera: Ophioglossum, Botrychium,
Helminthostachys, and Mankyua, ~70
species of temperate to boreal distribution,
terrestrial, perennial herbs
• The roots are fleshy, mycorrhizal, lacking
root hairs, sometimes bearing adventitious
buds (that may grow into a new plantlet)
o Root hairs usually function for water
absorption
o Plant relies on mycorrhiza for water
absorption
o Adventitious buds grow into a new
plantlet = asexual reproduction
• The stems are subterranean, erect; the
vasculature is a protostele or ectophloic
siphonostele
• The leaf is often solitary, lacking circinate
vernation, the blade simple and unlobed or
compound to divided (1-2 pinnatifid);
venation is open-dichotomous or reticulate
• Ophioglossum reticulatum has the highest
recorded chromosome count of any
organism: n = 760, the latter 2n = 1520
• Sori are lacking
o Sorus: a cluster of sporangia on the
underside of a fern frond)
• Gametophytes are nonphotosynthetic and
mycorrhizal or mycotrophic
o Mature gametophytes are cylindrical
and branched with sunken antheridia
and short-necked archegonia
Marattiaceae
• After G. F. Maratti, Italian botanist (17231777), 6 genera/ca. 111 species
• Large rhizomatous or arborescent, perennial,
terrestrial ferns
• Stems with mucilage canals
• Leaves develop by circinate vernation,
mature leaves large, simple, or 1-4 pinnate,
the petioles and rachillae with swollen
pulvini and prominent pneumatodes
(lenticels)
• Sporangia are eusporangiate , homosporous,
distinct, vertically dehiscent, and located on
the abaxial surface of leaflets, which may or
may not be fused into a synangium
o Separate: Angiopteris
o Fused: Marattia, Danaea
• Gametophytes are large, thalloid, and
photosynthetic
• Distributed in tropical and warm regions
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Botany 106 – Pteridology
Leptosporangiate Ferns
Osmundales
• Mindanao
• Ex: Osmunda cinnamonea
• 2 types of fronds:
o Fertile
o Sterile
Polypodiidae
• From Greek polys (many) + pous (foot), in
reference to knob-like petiole bases left after
leaf abscission
• Largest group of living ferns, including
some 11,000 species worldwide
• Indusiate (laterally or centrally attached) or
exindusiate
o Indusium: covering of sporangia
o False indusium: flaps do not arise from
lamina but it is the folded lamina
• Sporangia
o Distinctive in having a thin, generally
long stalk, a lateral stomium, and an
annulus
▪ Annulus: single layer of cells that
incompletely the circumference of
the sporangial wall
▪ Stomium: weak portion; an
opening
o Annular cells are dead at maturity
•
Gametophytes
o Green, usually cordate, and superficial
Hymenophyllales
• Filmy ferns and bristle ferns
• Found in mountains, mossy forests
• Delicate and thin
• Mainly epiphytic but some are terrestrial
• Prone to desiccation due to high SA:V ratio
• Ex: Cephalomanes javanicum
Gleicheniales
• Thick cutin
• Tough structure
• Ex: Dipteris conjugata,
linearis
• Branching foliage
Dicranopteris
Schizaeales
• CN: climbing fern
• Ex: Lygodium japonicum
o CN: nito
Salviniales
• Strictly aquatic
• High N content
• Ex: Salvinia minima, Azolla rubra
Cyatheales
• Arborescent
• No secondary growth
• Ex: Cyathea contaminans
• Angiopteris (Marattiales) vs Cyatheales
o Stem girth is wider in Angiopteris
o Frond length is longer in Angiopteris
o Stem height is shorter in Angiopteris
Polypodiales
• Divided into 3 groups by the Pteridophyte
Phylogeny Group (PPG)
Basal Polypods
• Dennstaedtiaceae
o Ex: Pteridium aquilinum (bracken fern)
o Compound leaves
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Botany 106 – Pteridology
o
•
•
Common in many tropical regions in
the world
Lindsaeaceae
o Ex: Lindsaea fissa
o Endemic to the Philippines
o Ornamental ferns
o Sori on the tips
o Many epiphytic
o Thin fronds
Pteridaceae
o Ex: Adiantum sp. (maiden hair fern)
o Some say that Adiantum belongs to its
own family (Adiantaceae)
Eupolypods 1 (Polypodiineae)
• Nephrolepidaceae
o Ex: Nephrolepis cordifolia
o Simple pinnately compound
o Can be on soil or epiphytic
• Davalliaceae
o Ex: Davalia griffithiana, Davallia
denticulata
o Commonly epiphytic
o Common for horticultural purposes
• Polypodiaceae
o Ex: Platycerium grande (staghorn fern)
o Dimorphic leaves (fertile fronds below
and sterile on top)
o Epiphytic
Aspleniineae
• Biggest group
• Aspleniaceae
o Ex: Asplenium nidus (bird’s nest fern)
o Epiphytic
o Arranged as a rosette
o 2-3 m in diameter
o A frond can be as long as 1 m
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Botany 106 – Pteridology
Fern Population Dynamics
• Population: group of individuals of the same
species that occupy a specific area over a
certain period of time
o Why do you need to understand?
▪ Change in population structure, in
interaction between individuals in
the population, and interaction of
entire
population
to
other
populations that compose the
community
• Population dynamics: how populations of a
species change over time and descriptions of
current and previous states for comparison
• Changes in individual success in:
o Mating and reproducing
o Finding and exploiting resources
o Avoiding mortality agents determine
numbers of individuals
o Their spatial distribution
o Genetic composition
•
Gametophyte Growth and Reproduction
• Small, independent, usually haploid
• Short-lived compared to sporophyte (~3
months – 2 years)
o Depends on suitability of environment
o Sporophyte:
thicker
cutin
with
trichomes, thicker tissues
• Photosynthetic or saprotrophic
• Above or below ground
• Unisexual or bisexual
Ways of Sexual Reproduction
• Gametophyte selfing
o Happens only to bisexual gametophytes
o Only in homosporous plants
• Sporophytic selfing
o Still entails the gametophyte
o Sperm produced by a sporophyte
fertilizes the egg that came from the
same plant
o Both gametophytes come from the
same plant
• Outcrossing
o Different plants combine their spores
*Antheridiogens
• Hormone released from gametophytes
with archegonia to induce the
production of antheridia in surrounding
gametophytes
• Promote outcrossing
Sexual Reproduction
•
Heterospory
o Bisexual sporophyte
o Mono/unisexual gametophyte
Homospory
o Mono/unisexual sporophyte
o Bisexual gametophyte
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Botany 106 – Pteridology
Apospory
•
•
•
•
Without spores
Gametophytes form without formation of
haploid spores
Consequence: diploid gametophytes
No meiosis → diploid spores
Sporophyte Reproduction
• Sporophyte
o Diploid phase
o Not capable of secondary growth
o Produces spores
o Capable of asexual reproduction
• Vegetative Reproduction
o Genets vs ramets
▪ Genets: the “genetic individual”;
the collection of all modules
derived from a single zygote
▪ Ramets: a module with the
potential for a separate existence
Apogamy
• Development
of
sporophyte
from
gametophyte without fertilization
• Thus, does not require water for the
formation of the sporophyte
• Occurs in ~10% of fern species
• Mature faster and develop leaves first
• Advantageous in dry regions with a short
growing season
• Is the only way of reproduction for
sterile/hybrid ferns
Bud Production and Rhizome Branching
• May be from the roots and stems
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Botany 106 – Pteridology
Nutrient Ecology of Ferns
How do ferns acquire nutrients?
• Roots and rhizomes
o Analogous
o Roots are more efficient due to high
SA:V ratio
• Litter trapping
o Due to epiphytic habit → less in
nutrients
o Ex:
▪ Asplenium nidus
• In a rosette manner as a
funnel
▪ Drynaria quercifolia
• Leaf
dimorphism
(chlorophyllous
and
sclerophyllous)
• Sclerophyllous leaves act as a
trap
• Sclerophyllous leaves clasp
chlorophyllous leaves on
substratum
to
lower
evaporation rate
• Mutualisms
o Nitrogen fixation
▪ Azola
with
a
mutualistic
relationship with Anabaena
• N2 into NH4+, NO3-, NO2o Gametophyte
mycorrhizae
→
arbuscular (branched)
▪ More efficient than rhizoids
▪ Gametophyte
cells
contain
mycelia/hyphae which are not
pathogenic (Ogura-Tsujita et al.,
2016)
▪ With
plasma
membrane
invaginations for exchange
▪ Share absorbed water and nutrients
with host plant which shares
photosynthates
o Sporophyte mycorrhizae → vesicular
(may also be VAM – vesiculararbuscular mycorrhiza)
▪ More pronounce in environments
where water and nutrients are
limiting (e.g., rocks, epiphytes,
aquatic)
Fern Adaptations to Xeric Environments
• Xeric: dry conditions or low atmospheric
humidity and lack of precipitation
Adaptations to Drought
• Water transport: water potential (Ψ)
o Difference in quantity of water
o Higher solute concentration = lower Ψ
o Water always moves to lower Ψ
o
•
•
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Why is xylem more efficient than
hydroids?
▪ Strength of xylem cell wall
provides rigidity to prevent the
collapse of the entire xylem
column
▪ Hydroids do not have secondary
cell wall thickenings
▪ Can manage differences in Ψ
Water transport: adhesion-cohesion
o Adhesion: attraction of water molecules
onto the xylem walls
▪ Because xylem tissue is dead,
water molecules have direct access
to cell wall materials (e.g.,
cellulose, lignin, etc.)
o Cohesion: attraction between different
water particles
Control of water loss
o Presence of cuticle
▪ Prevents and limits escape of
water vapor through epidermis
▪ Acts as a reflecting surface
• Prevents excess heat energy
to limit water evaporation
o Trichomes
▪ Limit escape of water
Botany 106 – Pteridology
▪
•
Act as structures that stabilize air
movement (boundary air layer) for
lesser water loss
▪ Thicker rhizomes = more stable
boundary air layer = lesser water
loss rate
Water uptake
o
•
Mycorrhiza can reach further than bulk
soil
Water storage: parenchyma
Desiccation Tolerance
• Desiccation tolerance of sporophytes:
resurrection plants (Selaginella)
o
o
o
o
o
In some ferns that cannot curl up, they
lose their leaves and the rhizome
remains dormant → leaves grow back
during favorable conditions
Expansins: cell wall loosening enzymes
LEA: late embryonic abundant
proteins; accumulate to high levels
during the late stages of embryogenesis
in seeds when desiccation tolerance is
acquired or in vegetative and
reproductive tissues under dehydration
suggesting a role in adaptation during
desiccation
Carbohydrates: protect membranes and
stabilize biomolecules
CDT-1: a dehydration and ABAinducible gene related to desiccation
tolerance
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Botany 106 – Pteridology
•
Diversity and Biogeography of Ferns and
Fern Allies
• Diversity: estimated of 12 000 to 15 000
species (relatively small)
Prediction of species in drier and wetter
sites:
Latitudinal Diversity Gradient
• As one goes from the pole toward the
equator, the number of species per unit area
increases
o
When drier, graph shifts to the right and
wetter to the left
Altitudinal Endemism Gradient
o
o
Americas = neotropics
Asia = paleotropics
•
•
•
•
Fern Dispersal
• Ferns have lightweight, dust-like spores
generally 30-70 µm long
• Expected to be picked up by winds and
dispersed readily over long distances
• Once airborne, fern spores can tolerate the
low temperatures and high UV light in the
upper atmosphere
o Determine the extent of fern
distribution across the globe
Altitudinal Diversity Gradient
•
•
Lower elevation = lower number of endemic
plants
Higher elevation = higher number of
endemic plants (peak)
Increasing elevation = lower number of
endemic plants
Humpback distribution
Humpback distribution
Temperature can affect availability of water,
hence higher elevation can decrease
diversity
Evidence of Long-distance Dispersal
• Volcanic and of relatively recent in origin
from the sea floor (generally within the past
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Botany 106 – Pteridology
•
•
•
o
10 MY), most oceanic islands have never
been connected to continents
The species occurring on them must have
arrived by long-distance dispersal
Case of Anak Krakatoa (1883)
o 3 years after the eruption, 11 species of
ferns
were
thriving,
including
widespread
species
such
as
Pityrogramma calomelanos, Blechnum
orientale, Pteris vittata, Nephrolepis
exaltata, and Pteridium aquilinum
o After 25 years, 15 fern species and 1
lycophyte (Lycopodiella cernua) had
established and after 40 years, 2 species
of Trichomanes abounded on the musty
summit
o After 53 years, a total of 60 species
were present
A striking feature of oceanic island floras is
their high percentage of ferns and
lycophytes, generally 16-60%
•
o
Compared to continental environments:
•
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Ferns and fern allies establish easier in
islands
▪ Disperse faster than angiosperms
→ less competition
o Lower in continents due to the
possibility of competitive exclusion →
angiosperms dominate
o Although oceanic islands show a high
percentage of ferns and lycophytes in
their floras, the endemism of these
plants is lower than for angiosperms
▪ Speciation is slower in ferns,
resulting in lower endemics
• Might be slower because they
lack many of the prezygotic
isolating mechanisms found
in angiosperms, such as
differences in flowering time,
structural differences of the
flowers,
incompatibility
between the pollen and
stigmatic surface, and the
potential to switch to different
pollinators
• Repeated migration from the
source areas maintains gene
flow so that speciation of the
island populations does not
occur → speciation occurs
when gene flow halts
Disjunct Distribution
o Disjunct distribution without evidence
of local extirpation of intervening
distributions
o i.e., Asplenium platyneuron, disjunct
between eastern North America and
South Africa
o i.e., A. subglandulosum has 3
subspecies, one each in Australia and
New Zealand, southern South America,
and Spain and Morocco
Trade Wind Direction
o Of the species occurring on 2 or more
of the southern continents, 22 are
completely circum-Antarctic, 39 occur
in Australia and New Zealand and
Africa but not in South Africa, 29 occur
in Africa and South America but not
elsewhere
Botany 106 – Pteridology
o
Floristic similarity correlates more
strongly with wind direction from
source areas than with geographical
proximity to continents, supporting the
idea that wind is the main dispersal
agent for these widespread ferns
Vicariance in Ferns
• Vicariance Biogeography
o Attempts to explain the distribution of
organisms that have narrow ecological
tolerance by assuming that they
achieved their modern distributions
while riding on tectonic plates and
tracing the geological history of the
continents’ movements
Evidence of Vicariance
• Hokkaido, the northernmost island of Japan,
has roughly the same number of fern species
as are found in north-eastern North America:
122 and 116, respectively
o Of these species, 47 (40%) are common
to both regions
• Huperzia partitioned into Neotropical and
Paleotropical clades
o The 2 clades are estimated to have
diverged before the breakup of Africa
and South America
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Botany 106 – Pteridology
o
Conservation of Ferns and Fern Allies
Conservation Importance of Lycophytes and
Ferns
• Conservation
biology
responds
to
environmental degradation across the globe,
with increased human impacts to vulnerable
ecosystems causing alarming rates of
species extinction and habitat loss
• Approximately 13 600 species of ferns and
lycophytes globally
o Species continue to be described and
because of persistent regional gaps in
floristic treatments, the real number of
fern and lycophyte species is not yet
known
• Ferns and lycophytes are considered
extremely vulnerable to extinction
o High fidelity to their ecological niche
▪ Cannot adjust to changing
environment
o Rate of habitat fragmentation and
deforestation
• Fern and lycophyte ecosystem functions:
o Ferns and lycophytes may be
considered habitat enhancers for other
plants and animal species (i.e., litter
traps, fern trunks for epiphytes,
mycorrhizal symbionts, etc.)
• Fern and lycophyte ecosystem services:
o For treating ailments and illnesses, and
in various traditional rituals and
ceremonies: Macia (2004) recorded the
use of 24 species of ferns in 2 groups of
Amerindians from Amazonian Bolivia
and Ecuador, mostly medicinal
purposes
o As pollution and habitat quality
indicators
o As genetic resources to aid the
development of stress tolerance in
commercial crops
•
•
Changes in trade wind directions,
atmospheric conditions, temperature,
and water availability
o Increased UV-B solar radiation
▪ Effects on long-distance transport
▪ Azolla
microphylla
exhibited
related growth and reduction in its
cyanobacterial nitrogen
Over-collection of ferns from the wild for
the florist industry, landscaping, collectors’
items
Tree ferns (Cyathea, Dicksonia) are
important in the horticultural trade for
landscaping, while trunks are valued for
orchid-growing medium and substrate
Approaches to Conservation
• Ecosystem Approach
o A geographic area where plants,
animals, and other organisms, as well
as weathers and landscapes, work
together to form a bubble of life
o RA 7586
▪ National Integrated Protected
Areas System (NIPAS) Act of
1992
• Protected Area Management
Board approves proposals,
projects
on
biodiversity
conservation and sustainable
development
and
issues
permits or clearances for the
conduct of such
• Establishment of management
zones, i.e., strict protection
zones where no human
activity is allowed except for
scientific or religious use
• Preparation of management
plant
where
sustainable
tourism is a management
strategy
• Taxon-specific Approach
o Ex-situ conservation
▪ Ex-situ collections of sporophytes
and spores provide a genetic safety
net helping to prevent species
extinction
▪ Ex-situ horticultural propagation
of endangered fern and lycophyte
Threats to Global Fern and Lycophyte Diversity
• Habitat fragmentation, degradation, and
destruction
o Commercial timber harvesting
o Tree plantations
o Conversion to land use
• Climate change
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Botany 106 – Pteridology
▪
species may also reduce harvesting
pressures on wild populations if
they are made commercially
available
Micropropagation techniques
due to their vulnerability to
over-collection and distribution
Future Directions in Fern and Lycophyte
Conservation
• “…it is an inescapable fact that survival for
most species is inextricably dependent on
conservation of forests worldwide,” (Page,
1985, p. 441)
• Conservation of ferns in the tropics of high
priority due to the concentration of fern and
lycophyte diversity in countries with limited
funding for research, limited protection for
threatened areas, and limited means to
enforce existing protections
• Adopting an ecosystem approach to species
conservation, while also considering
regional approaches to in-situ and ex-situ
methods of protection and restoration, are
considered the way forward in fern and
lycophyte conservation biology (Jermy &
Ranker, 2002)
Conservation of Fern and Lycophyte Taxa
• International Union for Conservation of
Nature (IUCN) Conservation Criteria of
Biodiversity
o IUCN Red List 2004 categorized
approximately 67% of the evaluated
species of ferns and allies as threatened
(140 out of 210 evaluated species)
o Species evaluated by IUCN only
represented 1.6% of the total described
species (13 025)
o Ferns and lycophytes as a highly
diverse
group
are
substantially
underrepresented on the IUCN Red List
• Isoetes spp.
o Noted as rare and threatened across
several regions and countries
o All 4 species of Isoetes in China (I.
hypsophila, I. sinensis, I. yunguiensis,
and I. taiwanensis) are critically
endangered and at risk of extinction due
to habitat loss and degradation, water
pollution, and competitive exclusion by
invasive species
o Only 2 natural population of I. sinensis
are known to exist and both are
threatened in mainland China, where
populations have decreased by 50%
within the last 4 years
• Restricted Distribution and Reduced
Population Sizes
o Ferns and lycophytes with restricted
distribution and reduced population
sizes are of highest risk of extinction,
especially
within
degraded
or
vulnerable landscapes
▪ 6 species of the endemic fern
Diellia
are
considered
of
conservation priority due to their
restricted distribution (5 species
are single-island endemics) and
small population sizes in Hawaii
▪
New Zealand fern Asplenium
cimmeriorum of cave entrances,
are of high conservation priority
•
•
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Encourage biologists, land managers, and
conservationists to expand everyone’s
knowledge of the functional and structural
roles performed by ferns and lycophytes in
the Earth’s biomes
Public awareness is crucial in conservation
efforts
o Consumer demand is often driving
exploitative resource extraction
o The collection industry is causing a
decline in certain fern and lycophyte
taxa
o Consumer product awareness and seller
accountability are crucial in today’s
market economy