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By Maribel Esperanza Agoo
CYCADS are the oldest living seed
plants on earth. Fossil records show that the cycads originated
during the Lower Permian, about 270 to 280 million years ago, much
earlier than the Dinosaur Age. They have also been considered the
“missing link” as they exhibit characteristics intermediate
between vascular nonseed plants and the more derived seed plants.
These have also shown insignificant morphological changes through
these years.
Today, the cycads are classified
under three families, 11 genera and 250 species, 90 of which are
Cycas species. The Cycas species are found in tropical and
subtropical areas around the world, particularly in Indo-China,
Japan, Southeast Asia, the Malesian Region (where the Philippines is
part of), Micronesia, Polynesia, Australia, Madagascar and East
Africa.
In the horticultural trade, the
plant is commonly referred to as the “Sago Palm.” It has a
single trunk, which sometimes branches out, with little woody
tissue. Its leaves are large and divided, resembling those of palms
and tree ferns, thus the basis for its name Cycas (the Greek word
for koikas, a name used by Theoprastus for a palm species). It is
dioecious (meaning separate male and female plants). It bears naked
seeds on sporophylls. Its pollens are also borne on microsporopylls
forming a cone. The coralloid roots are symbiotically associated
with nitrogen fixing bacteria, which contribute to the fertilization
of the soil and nutrition of the plant.
Cycas have great ornamental
value. Owing to its demand for horticultural trade, the group has
been listed under CITES Appendix II. Cycas are also prominent
elements in the religious and cultural lives of local people. These
plants, however, possess very toxic substances—cycasin and BMAA—,
which are linked to Guam’s disease, a combination of
Alzheimer’s, Parkinson’s and Motor Nueron Disease.
In the 2004 Global Assessment of
Species, the cycads (Cycadaceae, Stangeriaceae, Zamiaceae) were
identified as the most threatened plant group with a total of 151
species included in the 2004 IUCN Red List. This represents 75
percent of the total number of cycads: 52 percent as
“Threatened” and 23 percent as “Near Threatened.”
In the Philippines, cycads are
among these species, which may serve as an indicator for the status
of plant conservation in the country. It is a group, which is poorly
documented in the country in terms of taxonomy, biology,
conservation, ethnobotany and drug source potential.
Cycas chamberlainii, a cycad
known as C. riuminiana, is listed as EN (Endangered). Two other
Philippine endemics, C. wadei and C. curranii and a widespread
species, C. edentata are categorized as DD (Data Deficient).
In 2004, field surveys on C.
riuminiana—initiated under the Threatened Species Program of
Haribon—were conducted by researchers and students of the De La
Salle University-Manila and the Philippine National Herbarium to
gather specimens, determine the distribution and describe the
biology and the threats to the species. Localities visited were
Pampanga (Mount Arayat), Bataan (Bagac and Morong), Zambales (San
Antonio, Subic, Botolan), Batangas (San Juan and Lobo), and Mindoro
(Iling Island and Bongabon Magsalay). Its center of distribution was
identified as Mt. Arayat, Pampanga.
The surveys of species in their
natural habitats around the country yielded fresh insights on the
taxonomy of Cycas in general.
Cycas riuminiana, in particular,
occurs at altitudes of 400 m.a.s.l. near forest edges. Most often,
they occur in very small groups and becoming denser as altitude
increases. In Pampanga and Bataan, the species occurs in a lowland
evergreen rainforest type in association with species belonging to
the families Combretaceae, Euphorbiaceae, Myristicaceae, Myrsinaceae,
Myrtaceae, Meliaceae, and Moraceae, Rutaceae, and Sterculiaceae.
It has also been observed that
seeds are dispersed close to the mother tree. These germinate
densely but die off as they compete for space and light in forest
habitats. It has also been noted that the seeds are probably eaten
by mammals, leaving them clean and bare on the ground. Threats to
the population of cycads include the collection of the plants for
horticultural trade and conversion of the natural habitat to other
land uses.
Though other cycads like C. wadei
and C. curranii appear to be resilient to fire, the constant burning
of the grasslands to regenerate growth of grass for cattle is also
becoming a threat to the species.
It is also recognized that the
taxonomy of the Cycas of the Philippines clearly presents a problem
in the conservation of this group. It is a potentially challenging
subject, which provides good insight on the state of taxonomy in the
Philippines, in general, and its implications on the difficulties
towards the conservation of cycads and other plants in the
Philippines.
To resolve some problems in the
taxonomy of Cycas, in general, a comparison of the vegetative and
sporophyll characters of cycads based on literature, herbarium
specimens available at the PNH, and recent collections from various
localities of the same or different species, were also made.
Difficulties were encountered in reconciling keys and taxonomic
descriptions with specimens. It is surmised that erroneous taxonomic
decisions by authors can be attributed to the mere examination of
herbarium materials or limited herbarium materials. Thus, the wider
range of variation in important morphological characters of the
leaves, seeds, and sporophylls, oftentimes observed in living
specimens, were overlooked. This underlines the need for field
surveys and collection of specimens for study materials for
taxonomic and conservation research.
To date, six species have been
delineated and recognized for the Philippines namely C. wadei, C.
curranii, C. silvestris, C. edentata, C. riuminiana, and C.
zambalensis, which is a probable new species. C. saxatilis is
excluded, as neither description nor specimen is available for
review.
It can also be noted that more
recent discoveries include species from poorly known habitats, i.e.
forest over limestone (C. saxatilis nom. nud.) and forest over
ultramafic soils (C. zambalensis sp. nov.).
Molecular techniques are also
applied to resolve the genetic distinctiveness of the cycad
population in Mt. Arayat, which to some authors should stand as a
separate species.
A species management plan for
Cycas chamberlainii (= Cycas riuminiana) is now being drafted by the
stakeholders, which include representatives of the local government
units (mayors and barangay captains), secondary and tertiary
schools, government units (Department of Environment and Natural
Resources, Department of Science and Technology, and Department of
Tourism), and NGOs (local farmer’s cooperative groups) in the area
of Mount Arayat. It is anticipated that with the concerted effort of
the local people, a significant proportion of the gene pool of the
species in the Philippines can be conserved and sustainably managed.
This may also serve as a model for the management of other cycad
species with narrow distribution in the Philippines like C. wadei,
C. curranii, and C. zambalensis.
About the author: Esperanza
Maribel G. Agoo is a Haribon Threatened Species Program Conservation
Research Grantee. Her project is called “A Conservation Statue
Assessment of cycas Chamberlainii BR & KINH Towards the
Development of a Species Management Plan.”
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