Thursday, June 22, 2006

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* Succulent Plant Research * Other titles available * Secondhand books

The New Cactus Lexicon

The New Cactus Lexicon

Planned as a successor to Backeberg's Cactus Lexicon, The New Cactus Lexicon will be the most scientifically authoritative conspectus of the Cactaceae published for nearly a century. It will be comprehensively illustrated in colour and is confidently expected to become the benchmark reference for all those with amateur or professional interests in the diversity, identification and conservation of cacti:

A concise compendium of information on cactus genera, species and subspecies accepted in the standard literature on cacti since Britton & Rose's famous monograph (1919-23), with references to places of publication, principal synonyms, geographical distribution, diagnostic features and brief commentary;

More than 2500 colour illustrations in a companion 'Atlas' (not available separately), mostly of plants in habitat or from documented plants in cultivation, covering nearly all currently recognized species and subspecies.

Preparation is being undertaken on behalf of the International Cactaceae Systematics Group (ICSG), an informal group founded in Zurich in 2000 to supersede the former Cactaceae Working Party of the International Organization for Succulent Plant Study (IOS).

Editorial Committee: David Hunt, Nigel Taylor and Graham Charles, supported by a team of more than 130 contributors of illustrations, text and comments.

For pre-publication subscription offers please contact

Publication June 2006

Price (2 volume set, incl. carriage) £100 (UK only) €150 (Eurozone only). Available in North America (from July from Rainbow Gardens Bookshop)

Evolution and Phylogeny of Cacti

Cactus Evolution

Cactus Phylogeny

Cactus Evolution

Perhaps about 50 million years ago, the Cenozoic cooling resulted in regionally arid conditions within which various xerophytes evolved. Among such xerophytes was a particular jungle thorn bush, which bore the seven characteristics by which all cacti are defined. This was defined as the ancestor of all cacti. Its descendants diversified, bit by bit, as each evolved successful survival responses to changing conditions in its own habitat. The popular Pereskia aculeata var. godsefiana, (Lemon Vine), a hardy woody shrub with succulent leaves which produces the delicious "Barbados Gooseberry", is thought to resemble the ancestor closely.

This ancestor was the first to evolve the Areole, the specialized Axillary Bud, unique to and a very important definer of the Cactaceae. Each axillary bud carries the spines and a bud which may (or may not) differentiate to become a flower o r a side shoot, depending upon many local factors.

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Cactus Phylogeny

Finding a series of characteristics common to a plant of interest, and following the line of development, reveals the phylogeny or evolutionary history of a plant family.

In the Cactaceae, the process of developing a phylogenetic scheme rarely identifies clear definable groups, as the descriptions of many genera and most species of cactus are incomplete. The extent of cactus variation and geographical distribution is insufficiently known due to the poor fossil record. No fossil cacti are known to exist and most cases of natural hybrids have only been observed as isolated examples. For this reason, groups within the cactus family are continually split up, re-united and definitions are modified. To make some general conclusions about the evolutionary history of cacti, scientists today must rely on the external form of present day cacti and more commonly, on biochemical, chromosomal and DNA data.

Genealogical Tree of the Family Cactaceae
(Adapted from Barthlott, 1979)

There are over 2000 species of cacti, and these can be arranged in a system based on their presumed degrees of relationship. Within the cactus family it is generally accepted that plants fall into three natural groups, called sub-families, which evolved perhaps by 20 million years ago as a result of a gradual adaptive evolutionary process. By this time, Plate Tectonics had spread the Atlantic sea floor to such a width that these adaptations were absolutely confined to the Americas. Consequently, Cactaceae are native only to the Americas.

Sub-Family Pereskioideae
Of the two genera, Pereskia and Maihuena, forming this most primitive sub-family, the Pereskiae are a genus of about 20 species of jungle trees, vines and shrubs native to Central America and the West Indies. Plants are scarcely succulent, woody, usually shrubby or tree-like. All species have persistent leaves and shiny black seeds. Seedlings bear fleshy cotyledons. Maihuena, the second genus, is a mound forming, low plant. One species of pereskia has been naturalized on the west coast of Africa, Although no proof has been found, there is no doubt that it was introduced by ocean curr ents, birds, or even, perhaps, by ancient mariners.

Pereskia godsefiana

Sub-family Opuntioideae
Members of this sub-family range in form from low shrubs to large tree-like plants. There are 9 genera and approximately 300 species within this sub-family. Plant members are unique for having deciduous leaves that soon dry up, and for possessing a second type of very small spines called glochids, which are barbed and very easily detached. Seedlings possess fleshy cotyledons similar to those of the Pereskiae.

There are three sub-tribes of Opuntiae;

  1. the 'Cylindropuntias', Chollas with cylindrical, sausage-like, linked stems which are the most closely related to the Pereskiae through their early-deciduous, large and terete leaves;
  2. the 'Tephrocacti'with many globe-shaped linked stem segments; and
  3. the 'Platyopuntias', Prickly Pears with flat pads. These latter cacti comprise the Flat-stemmed Opuntiaand the Nopalea,and are the most widely distributed, of all cacti, having evolved selected traits allowing them to inhabit many otherwise inhospitable environments. They are the least primitive plants of the Opuntioideae.

The Opuntioideae sub-family is particularly interesting because its members occupy the greatest geographic range as compared to any other major group of cacti. The Opuntiae range in both North and South America, from mid Saskatchewan to Patagonia and have become naturalized in southern Africa and Australia where they are now considered noxious weeds. In some Mediterranian lands, they are cultivated for their fruit.

Opuntia engelmannii

Sub-family Cactoideae
This is the most highly differentiated sub-family of the Cactaceae, containing about 90% of all species diversity within the family. There are over a thousand species showing a wide range of morphological diversity. All plants are more or less fleshy and can be either terrestrial or epiphytic. They have no leaves and no glochids and the flowers are usually funnel shaped. Spines are usually present and vary in color, structure, desnity and arrangement. The cotyledons of the Cactoideae members are microscopic in the seed and unlike the Pereskiae and Opuntiae, they do not enlarge in proportion to the growing embryo.

Cactologists today recognize about 8 evolutionary independent lineages called tribes. The first six contain stem-succulent plants that have ribs, tubercles, areoles bearing spines and flowers having a long tube. The last two are epiphytic, tree or cliff-dwelling jungle cacti.

Within the sub-family Cactoideae can also be inferred a system of four lineage groups based on perceived relationships of morphology and adaptation which very roughly conform to four American regions, the Carribean, the Central-, the North- and the South- American regions.

    Group I contains certain Carribean genera descended from Pereskia which first developed a columnar
        morphology as thin stemmed, erect and creeping types. They are thought to be the ancestors of all Cactoideae, evolving differently through several sub-groups and dispersing as the next three groups.

    Group II are the Epiphytes, three recognizable sub-groups of so-called "Jungle cacti" (a) the tree-like

        or climbing Carribean So. American genus Harrisia, (b) the thin stemmed or flat stemmed climbers and trailers of Central America and (c) the So. American epiphytes familiar as the "Holiday-, Orchid-, and Mistletoe cacti" among others.

    Group III consists of the Mexican-No. American spherical cacti descended from Group I through a

        sub-group of Echinocereus, the "Hedgehog cacti" via Central America, the primary dispersal centre for Group III as as for the following, Group IV.

    Group IV comprises the spherical and columnar cacti of South America which are more or less distinct

        from their No. American counterparts because of the different evolutionary forces which acted on them.

Cacti in groups III and IV have evolved deeply notched ribs and often tubercles, an advantage to coping with sporadic water supplies. When water is scarce the folds sink in between the ribs and when water is plentiful the folds swell out. In this way, the overall form remains more or less similar at either extreme. A ribbed body can change its volume while the area of the skin remains unchanged. This contrasts with the flat pads of Opuntiawhich wrinkle up in an uneven manner upon water loss. Cacti which bear notched ribs and large tubercles are believed to be those which have developed farthest from the basic cactus form.

Columnar cactus
Epiphytic cactus Notched ribs

Cactus evolution info


As in nearly all fields of science, it seems we DON'T know more
than we DO know, but if you will forgive the brevity of discussion
for each of these enormous topics, I'll try to give a summary of what
we do know about cactus evolution in general. Readers are advised
to examine pertinent references such as Gibson and Nobel's (1986)
^Cactus Primer^ and Benson's (1982) Cacti of the United States and
Canada, as well as other resources such as Cullmann, Goetz &
Groener, "The Encyclopedia of Cacti", all of which have some
discussion of cactus evolution. None of these sources are
complete with respect to a "total assessment" of current data, but
Gibson & Nobel do an admirable job of covering a very complicated
topic. Given the above caveat, I'll try to give some "highlights"
of cactus evolution, with respect to the systematic (phylogenetic)
study of the family, and relevant biology when appropriate.

FOSSIL CACTI - Since the major processes of fossilization
generally require sedimentation of mineral materials over
vegetative/floral materials, you can realize very quickly that with
even a hypothetical [xerophytic] ancestor to the cacti (perhaps
Pereskia-like in appearance), the environmental factors that favor
fossil preservation (save for amber entombment) would have been an
unlikely combination of cacti and ample water for sedimentation.
Thus the fossil record for cacti is poor, or in fact absent. In
1944, a presumed fossil cactus ^Eopuntia douglasii^ was described
from Eocene deposits in Utah. There was much controversy over
whether this compression fossil was indeed a cactus, and after
significant bantering about the literature, most people do not
believe this "fossil" is indeed a cactus. For literature citations
see Benson (1982), pages 76-79. Except for relatively recent
pack rat middens (containing a variety of cactus seed) our knowledge
of cacti from any fossil remains continues to be depauperate at
best. Scientists today must rely on the morphology of present day
cacti, or other sources of data (biochemical, chromosomal, or in my
case nucleic acids [DNA]). Through the study of these sources of
evolutionary information, we can make some general conclusions
about cactus evolution.


From some~ very recent studies of DNA variation and from
vascular anatomy, the closest angiosperm family to the cacti is the
Portulacaceae, with the genera Portulaca, Talinum, and Anacampseros
the likely "cousins" (among others). The long standing previous
assumptions that the Aizoaceae (including the mesembs) was the
sister family to the cacti (due to the floral hypanthium) was proved
fallacious in independent tests of phylogeny for the order
(Caryophyllales). We are ~continuing to amass various sorts of data
which continue to corroborate this hypothesis.


ASSUMING that from some common ancestor between the
Portulacaceae and the "proto-cacti", a xerophytic lineage arose
which was capable of radiating and speciating in the "New World",
most likely after the split up of Gondwanaland. The "exact" center
of origin for the cacti has been disputed for many years. two
prevailing "centers" of likely origin persist: The first is within
the Caribbean Islands (proposed by Buxbaum); and the other is in
north [western] South America; I tend to support the latter
hypothesis, and hopefully my studies of chloroplast DNA variation
will help provide data to answer this question. Regardless of the
geographic center of origin, the result we see today is a very
diverse and widespread New World family of angiosperms, having
approximately 1,500-2,200 species and about 100 genera
[conservatively]. It is the second largest family of angiosperms
restricted to the New World (the first being the Bromeliaceae), and
has geographic limits extending from central Canada to Patagonia,
and virtually every habitat in-between.

Divergence of the Major Groups

Students of of the cacti can generally recognize three major
lineages within the family, based upon gross morphology, flower
and fruit structures, as well as other characters. These three
groups, treated previously as tribes, are now considered to be
subfamilies, and have been shown to be monophyletic (of one common
ancestral lineage). The three subfamilies are briefly discussed


The smallest subfamily of the Cactaceae has 18 species; all
having persistent leaves and large shiny black seeds. The two
genera, ^Pereskia^ (16 spp) and ^Maihuenia^ (2 spp.) are found
predominantly in South America. Pereskia plants are usually
shrubby, tree-like, or in one species (P. aculeata) form vines. The
flowers can be very showy (i.e P. grandifolia, P. bleo) or can be
diminutive (i.e. P. humboldtii, P. weberiana, P. diaz-romeroana).
The genus Maihuenia is found only in relatively high elevation
habitats of Andean Argentina and Chile; these are low growing mat or
cushion-forming plants, and are strikingly different than their
sister genus Pereskia in vegetative form. Maihuenia was originally
placed next to (or in some cases within) the genus Opuntia. Both of
these genera of the subfamily Pereskioideae are on an independent
evolutionary lineage from the other cacti, and have not been as
"successful" as the other two subfamilies in terms of speciation and
geographic range. They are likely a relictual group, PERHAPS
similar (but not the same) as the "proto-Cactaceae" ancestor, and
have differentiated into at least four or five geographically
isolated groups within South America and the Caribbean.


The monophyly of this subfamily can be clearly (and painfully)
demonstrated with the uniquely derived feature of the opuntioid
areole... the presence of small bristles called glochids are unique
derived feature of the opuntioids, obvious to anyone~who~has~touched
one of these plants. Additionally, the seeds of members of this
family (originally described somewhat inaccurately as arillate) have
a funicular envelope and accessory tissues (which become stone-like
in many taxa) which are shared by virtually all members of the
subfamily. There are about 300 species or so (more or less) within
this subfamily. Conservatively, there are five genera [Opuntia with
>200 species; Pereskiopsis with ca. 9 spp; Quiabentia with 2-4 spp.;
and Tacinga with ca. 2 spp.] The taxonomy of this subfamily is
perhaps the worst in the family, and is in desperate need of study.
"Splitters" will fragment the genus Opuntia into as many as 20
genera, while "lumpers" will take a broader concept of the genus and
transfer the splitting to an infrageneric level. Regardless of its~
generic level classification, this subfamily is clearly the winner
when it comes to occupying the most geographic range for may major
group of cacti----> coast to coast (E-W) in both N. America and S.
America, and from central Canada to Patagonia... It's also
successfully invaded (with the help of.....???) southern Africa and
Australia where it's become a noxious plant pest, and it's been
cultivated in the Mediterranean region for perhaps nearly 500 years
(probably brought back by good ol' Chris Columbus). Except for
horticultural interest in the other cacti, this subfamily represents
a major economic use for the cacti, especially the "prickly pear"
group of Opuntia, which provides Nopales and Tunas for human
consumption. The major growth forms are the cholla-type,
cylindrical stemmed forms (chollas with short-lived ephemeral
leaves; Pereskiopsis and Quiabentia with cylindrical stems and
persistent succulent leaves; Tacinga with cylindrical stems and
hummingbird flowers (!), and Pterocactus (9 spp) from Argentina with
unusually winged seeds and a geophyte growth habit. Some very
interesting research on Opuntioid evolution is being done by
Wolfgang Stuppy (University of Kaiserslautern, Germany) a Ph.D.
student (who's actually writing his thesis on Euphorbiaceae!) nearly
completed, using the seed internal anatomy as a useful source of
phylogenetic morphological information. We need as much information
as we can get about this group......Any prospective students want to
go to grad school???


Wow! About 86% of the species diversity of the family is found
in this subfamily..Probably 99% or more of the cactus cultivated in
hobbyists collections are from this subfamily as well. With over
1,000 species, showing extremes of morphological diversity where do
I start? Basically, this group shows many of the really confusing
problems of parallel evolution within the cacti. Witness, for
example, the morphological similarities of the north American "ball"
cacti (Mammillaria, Coryphantha, etc. of Tribe Cacteae) and the
similarly structured members of the Notocacteae (Parodia, Notocactus
s.str., Frailea) or the Tall, columnar members of the Tribe
Pachycereeae (saguaro, Lophocereus, Stenocereus, Pachycereus,
Myrtillocactus, Polaskia) from Mexico/Central America/USA and the
Andean members of Tribes Browngieae and Trichocereeae which have
virtually the same vegetative structures. It is no wonder that
Britton and Rose, using a purely "pigeon-hole" concept of taxonomy
grouped evolutionarily unrelated cacti based upon superficial
resemblance. Today most cactologists recognize about eight to ten
(presumably) evolutionarily independent lineages within this
subfamily which are called TRIBES. It would take many many pages of
text to explain the presumed hypotheses of relationships between the
tribes of this subfamily, and for many of these the relationships
are nothing more than educated speculation. I am attempting to
clarify some of these relationships using DNA techniques, but we are
several months (years?) away from resolving the problems
conclusively. There also is the question of which of certain
controversial genera should be placed within what tribe. There are
countless unanswered questions still remaining about this subfamily
as well. Many of these would warrant their own discussions!!!
Basically there are about 4 tribes which we feel evolved in
North America (Tribes Cacteae [largest], Pachycereeae, Echinocereeae
[incl. Leptocereeae], and Hylocereeae). These have morphological
"counterparts" in South America: Tribes Notocacteae, Trichocereeae,
Browningieae, Cereeae, and Rhipsalideae. There~are~parallel
evolution scenarios hypothesized for barrel cacti, columnar cacti,
and epiphytic cacti, each occurring in North and South America.
This creates many more phylogenetic and biogeographic hypotheses
which are in need of study. The degrees of specialization,
biogeographic affinities, and changes in floral/pollinator
syndromes preclude further elaboration here; it would take at least
a seminar or two to get through the basics of cactus evolution, let
alone discuss adequately, how recent data is answering many of these


I hope I've given a digestible synopsis of major trends in
cactus evolution, -- if you're still awake, I'll refer you the
previously mentioned references for more reading. Please feel free
to discuss various issues - I'll TRY to jump in when I can. The
preceding summary was done as part of my displacement behavior which
is keeping me from grading ca. 60 term papers, each about 20 pages.
(Arrrgh!) Cactus evolution is fascinating, and its result is the
manifestation of natural selection and speciation processes which
has given us a marvelous array of xerophytes which we cherish and
admire in our collections. Please respect the evolutionary process
and practice conservation whenever possible; don't buy field
collected plants, and propagate as much as possible.

I'd appreciate knowing if this was digestible and/or useful (I don't
want to babble-on incessantly if no one can use the information!).

All Best Regards,

(Dr.) Robert S . Wallace Internet:
Associate Professor of Botany
Department of Botany
Iowa State University
Ames, Iowa 50011 USA

Baja cactus info

Cardón cactus, Pachycereus pringlei
by Bob Chamlee

Cardón Cactus (Pachycereus pringlei) The cardón cactus (Pachycereus pringlei) is the world's largest cactus. There are about 1200 species of cactus, all of them native to the Americas. The cardón is nearly endemic to the deserts of the Baja California peninsula. Some of the largest cardones have been measured at nearly 21 meters (70 feet) high and weigh up to 25 tons. These very slow growing plants are also extremely long-lived, and many specimens live well over 300 years. ''Cardo'' means ''thistle'' in Spanish. It is said that when Hernando Cortes attempted to establish a settlement in Baja in 1535, the many spiny cacti earned it the name ''Isla de Cardón'', because at the time, they believed the peninsula was an island. In Latin, ''pachy'' means thick and ''cereus'' means waxy. One has only to see the thick arms of this pale gray-green, waxy skinned cactus to understand what the traveling American botanist, Cyrus Pringle, meant when he named the species.

Many first time visitors to Baja mistake this giant cactus for the ecologically similar saguaro cactus (Carnegiea gigantea), another inhabitant of the Sonoran Desert. However, the saguaro does not live in Baja and while there are a few stands of cardón found across the Gulf of California on the Mexican mainland, they seldom occur near the saguaro. The Sonoran Desert in Baja California can be divided into distinct sub-regions: the San Felipe, Vizcaino, Magdalena, and Gulf Coast Deserts. The cardón has adapted to all of these sub-regions and is also found in the tropical dry forests of the Cape. In many of these areas, the cardón is the predominant plant, and may be found growing in large tracts of forest. These large stands of the tall columnar cacti are called ''cardonales''.

The cardón grows best in the deeper soil of the alluvial fans of arroyos and other waterways. The cardón can be found between sea level and about 950 meters (3200 feet) in elevation from near El Rosario in the north, to the tropical Cape region at the southern tip. The cardón occupies only the relatively frost free regions of the Baja deserts, being confined by the freezing temperatures to the areas of Baja south of 31.2 degrees N. The seeds of the cardón will sprout only in the warm wet conditions following the tropical late summer rains or ''chubascos'', which bring most of the seasonal precipitation to many of these desert regions. Another factor limiting geographical distribution is that germination of seeds is best when air temperature exceeds 40 C, but soil surface temperatures remain under 70 C.

Cardón Cactus in Baja's Vizcaíno Desert The cardón has adapted to the arid conditions of the Sonoran Desert as many cacti have. It has a columnar form to present greater surface area to the morning and evening sunlight, and less to the harsh sun of midday. The branching pattern of the arms maximizes the efficient capture of solar radiation. The cardón needs no leaves -- it is a true ''cladophyll'' -- a plant that performs photosynthesis through its skin, rather than through leaves. Modified epidermal cells in the skin of the stems, called ''chlorenchyma'' do the work of converting sunlight to energy. Water loss during photosynthesis is reduced through crassulacean acid metabolism (CAM), a method of photosynthesis that the cardón shares with many of the cacti and succulents that inhabit the dry areas of the world. The stomata on these plants open only after dark, allowing the cactus to absorb carbon dioxide during the cooler night hours, making these plants very water efficient.

Cardón Cactus (Pachycereus pringlei)The main trunk of the cardón may have as many as 25 vertical branches, up to 1.5 meters (5 feet) in diameter. In older plants the branches are usually taller than the trunk. The cardón are especially spiny when they are smaller, to protect them from predators. As they grow older, many of the spines fall off and are not replaced. The lower trunks of older plants turn gray, and a cracked, woody bark makes them look like the thick legs of an elephant. Woody vertical ribs allow the columnar cactus to expand and contract like an accordion, storing the water it needs to survive in the arid conditions. These cacti have developed extensive, shallow root systems which quickly capture the brief, but torrential rains of the region. A large cardón may store over a ton of water in the fleshy, pulp-like tissues of its trunk. In order to support this great weight, the large cactus has an interior framework of hardwood vertical rods, lightweight, yet extremely strong, which act to stiffen the ribs. This amazingly tough hardwood skeleton has allowed the cardón to become the largest cactus species, able to thrive in the very harsh climate of the Baja California's Sonoran Desert.

Cactus flowers From March through June, flowers appear on the upper tips of stems, especially stems with warm, southern exposure. Flowers open in the afternoon, stay open all night, then close about mid-morning the next day. The reason for this, is that the cardón, like most of the other columnar cacti of the southwestern corner of North America, depends on nightly visits from nectar feeding bats for pollination. Several studies have shown the importance of the nectar feeding bats to the reproductive processes of the columnar cacti stands of the Southwest. For most of these cacti, including the cardón, bats are the primary pollinator, with almost no viable seed production occurring from birds, insects, or any daytime visitor.

Cacti that depend upon these bats for pollination usually produce light, or white colored flowers, with a deep-throated, bell shape. Flowers are located on the upper portion of the plant and remain open only one night. They also produce copious amounts of nectar, a distinctive odor to attract bats, and a thick layer of pollen that coats the rim of the flower. The lesser long nosed bat (Leptonycteris curasoae) spends its winters in southern Mexico. Its annual migration northward is timed to coincide with the flowering Bat feeding on cactus flowerof the columnar cacti and agaves of the Sonoran Desert. Peak nectar production times for cardones are between 8:00 and 10:00 p.m. Later in the night, bats visit the cardón, circling a cactus several times in wide loops, then hovering in front of an individual open blossom. The bat thrusts its head down into the bell shaped tube of the flower, lapping the nectar from the tube with its long tongue. The large amount of pollen on the rim and sides of the tube sticks readily to the fur of the bat's face and head. The actual feeding visit lasts less than a second. When the bat visits the flower on another plant, cross pollination occurs.

The return migration of the lesser long nosed bat south from the deserts of Arizona in the late summer is during the cardón's fruiting period. The bats feast on the ripe cactus fruit, helping to spread the seeds. Many types of birds also feed on the fruit of the cardón, which is about 5 cm. in diameter (around the size of a golf ball) and has Lesser long nosed bats (Leptonycteris curasoae)short, golden, fuzzy spines all over the outside. The ripe fruit often splits, revealing the sweet, red flesh. Each fruit contains about 800 black seeds which are consumed along with the flesh by the bats and birds. This is also crucial to the successful growth of the cardón. For best germination, the seeds need several conditions, which the birds and bats help to bring about. Cardón seeds need to be ''scarified'', or have their skins roughed up before they will crack and sprout. The digestive juices in the stomach of the consumer does this job perfectly. Another requirement for the successful growth of a juvenile cardón is a ''nurse'' plant. To grow successfully, the seed must become established under another plant or shrub, which protects the young cactus from the full brunt of the sun, as well as predation. Birds and bats eat the seeds, then fly off to roost in a tree, depositing the scarified seeds with their droppings into the nurse plants below, to await the warm rains of wet summer. In the best of conditions, thousands of seeds must germinate to produce one cactus, as conditions are extreme and foragers are eager to eat the tiny plant. Growth of these seedlings is extremely slow, less than 2.5 cm. per year, and it may take decades for them to grow large enough to emerge from beneath the nurse shrub.

The main threats to the mature cardón are overgrazing by cattle, clear cutting by humans, and a little understood disease, called ''flat top decay'' which causes the withering of the top of the cactus. The disease is not widespread, and does not currently appear to threaten the cactus population. The cardón, like the other columnar cacti of the Sonoran Desert, has survived the harsh, arid conditions for thousands of years by its ability to adapt. Future studies may use genetic markers to further study the pollination and breeding structure of this cactus, and its ecological interdependence with the lesser long nosed bat. These studies may be crucial to the successful survival of many species of desert cacti, and even the Sonoran Desert ecosystem itself.

If you enjoyed this, check out the rest of our Los Cabos Information pages:
  • Sonoran Desert of Baja California
  • The Tropical Dry Forest of the Sierra de la Laguna
  • San Jose Estuary
  • Golf in Los Cabos
  • Los Cabos Shopping Guide


    CIBNOR. 2001. Conservation of exceptional stands of the giant cardon cactus in Baja California Sur, Mexico.

    Fleming, Theodore H. 1989. Climb Every Cactus. BATS. Vol 7, No 3:3-6.

    Fleming, Theodore H. 1991. Following the Nectar Trail. BATS. Vol 9, No 4:4-7.

    Fleming, Theodore H. 2000. Pollination of Cacti in the Sonoran Desert (Abstract). American Scientist. September-October 2000.

    Hamrick, James L. 2001. James L. Hamrick, Research Professor. Ph.D., University of California, Berkeley, 1970.

    Larson, Peggy. 1970. Deserts of America. Englewood Cliffs, NJ. Prentice-Hall, Inc.

    Minch, John A., Edwin S. Minch, and Jason I. Minch. 1998. Roadside Geology and Biology of Baja California. Mission Viejo, CA. John Minch and Associates, Inc.

    Ricklefs, R. E. 2001. The Economy of Nature, fifth edition. New York. W.H. Freeman and Company.

    Roberts, Norman C. 1989. Baja California Plant Field Guide. La Jolla, CA. Natural History Publishing Company.

    Tinoco-Ojanguren, Clara, and Francisco Molina-Freaner. 2000. Flower orientation in Pachycereus pringlei (Abstract). Canadian Journal of Botany. 78: 1489-1494.

    Turner, Raymond M., Janice E. Bowers, and Tony L. Burgess. 1995. Sonoran Desert Plants: An Ecological Atlas. Tucson. The University of Arizona Press.

    Valiente-Banuet, Alfonso, Maria Del Coro Arizmendi, and Alberto Rojas-Martinez. 1996. Nectar-Feeding Bats in the Columnar Cacti Forests of Central Mexico. BATS. Vol 14, No 2:10-11.

    Zwinger, Ann. 1983. A Desert Country Near the Sea. New York. Harper & Row, Publishers.
  • Wednesday, June 21, 2006

    Cultured Cacti

    Conservation adopts a new dimension as scientists strive to save endangered species.

    Within sausage-sized glass tubes on metal racks in a small, temperature-controlled room, 18 tiny sprouts of the cactus Ariocarpus agavoides bulge from hard, black seeds no larger than an oval pinhead. The transparent, jelly-like substance on which they grow glistens under the fluorescent lights overhead.

    This is Guadalupe Malda’s "growth chamber." There may be more of these tiny plants here than anywhere else in the world.

    "Many people think this species is extinct," says Malda, a doctoral student in botany at Arizona State University. The cactus is only known to grow in one location in Mexico, and Malda says no one has seen any there for a number of years.

    Ariocarpus agavoides is listed as one of the world’s 12 most endangered plant species by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). It belongs to a whole group of cacti highly prized for their unusual appearance and rarity. Most Ariocarpus have been devastated by overzealous collection. Some species have been known to fetch up to $1,400 per plant in places like Germany and Japan, where trade in exotic cacti is almost a fetish. Some European cactophiles even organize “adventure” trips, advertised in collectors’ magazines, to hunt for cacti protected by law in Mexico and the American Southwest. Cacti are also threatened by overgrazing and habitat destruction.

    The damage has been so great that CITES, which has global guardianship of endangered species, has placed all but one of nearly 100 cacti genera under its protection. Of at least 850 species endemic to the United States and Mexico, more than 60 are considered so threatened that international trade of plants collected from the wild is illegal. Permits are required to trade the rest.

    Botanical gardens worldwide have long been trying to conserve endangered plants by sprouting new generations from permanent seed collections. But for some species, like A. agavoides, conventional planting doesn’t work so well.

    With a growing technique called tissue culture, scientists like Malda are trying to save these cacti, which otherwise wouldn’t have much hope for survival.

    Many species of cacti are very easy to grow. Some sprout readily from seed while others can be cultivated from cuttings rooted in soil. This kind of "artificial propagation" has become the mainstay of the horticultural nursery industry. Although threats to habitat still exist, many specialists say cultivation has dramatically reduced pressures on wild cactus populations once scoured for rare and tantalizing specimens. Most cacti now sold to collectors, landscapers, and household hobbyists are commercially grown.

    But some cacti are more recalcitrant. They either produce few seeds, are difficult to grow in soil, or grow so slowly that commercial production is not profitable. Cacti belonging to the genus Ariocarpus, for instance, are so lethargic scientists have dubbed them "living rocks." Some take as many as 20 years to reach a diameter of just 2.5 inches. Many seed-grown species never come to resemble wild plants.

    For these reasons, there is still a demand for wild-collected species on the international market. Those uprooted from their natural habitats are usually larger and much more unique than their cultivated counterparts. They display strange outgrowths and spectacular forms, are highly coveted by collectors with unquenchable appetites for the bizarre, and often sell for prices four times higher than plainer nursery-grown plants. Slow-growing and fragile species command the biggest bucks, from hundreds to thousands of dollars.

    In 1986, six of the nine most commonly-traded cacti in Japan were slow-growing species severely threatened by overcollection. Conservationists contended that many of the plants were wild imports smuggled in to meet demand. Malda and other scientists hope tissue culture will help reduce pressure on the native populations.

    Many cacti produced through tissue culture grow faster and larger than those raised by conventional techniques. The plants are nursed in a highly controlled environment on a substance called agar, a sugar-water mixture that resembles firm jelly. Nutrients and vitamins are added to the concoction to aid in growth. But the key ingredients are hormones.

    Hormones are chemical signals. Two major groups exist in plants: cytokinins, which stimulate cells to divide, and auxins, which induce cell growth. When hormones are present in the right proportions, combinations of cell growth and division lead plants to produce roots, stems, or flowers.

    In tissue culture, different concentrations of cytokinins, auxins, and other hormones are added to the medium to mimic stages of plant growth. The cultured plants absorb the hormones and respond accordingly.

    "You’re making the plant believe it is internally ready to produce shoots or roots or flowers, because chemically it’s the same," Malda says.

    Malda’s Ariocarpus seedlings are in a medium containing cytokinins that stimulate shoot production. Once the tiny plantlets are established, she can take cuttings or transfer them to auxin-rich cultures to induce root development. She predicts she will end up with about three new plants for every seed, and each seedling will probably support about three cuttings. At that rate, reproduction could continue indefinitely.

    "After one year you could in theory get one million copies of the same plant," says Ralph Backhaus, Malda’s advisor and an ASU professor of botany. "As long as there is someone there to take the cuttings, you can get continuous growth."

    That’s quite a feat in a species that takes at least five years to produce seeds in the wild, and whose natural cuttings don’t transplant well. Instead of yielding a new generation every five years, Malda’s Ariocarpus would reproduce with every cutting.

    And Ariocarpus is just the beginning. In the species Coryphantha minima, Malda teased up to 30 new growths from each seed. Her collection of Pediocactus simpsonii grew from 10 seeds to 85 tiny plants in less than a year.

    Some of her species have even displayed unusual characteristics. Obrecocius obregonia, for example, produced embryos—a seed-like growth that can be planted to begin a next generation.

    “This is not common for cacti,” Malda says. The embryos mean the cacti have by-passed maturation, the growth phase leading to flowers and seeds. Most cacti take at least five years to mature. Malda’s O. obregonia were less than a year old when she spotted the embryos. “This is a real potential for propagation,” she says.

    But the sailing isn’t all smooth. Before Malda can culture her plants in hormones, she must first figure out what amounts to use. The trouble is, what works with one species won’t necessarily work with another.

    For instance, while her O. obregonia produced embryos, they failed to generate either roots or shoots. Part of Malda’s project is to figure out which chemical combinations work, and which work best.

    Ultimately, Malda wishes to perfect her propagation techniques and use the plants she cultures for conservation. She could plant them in their original habitat and attempt to reestablish the species, but reintroduction is usually a last resort.

    "You don’t want to put them back into the wild only to have the cows eat them," Backhaus says.

    Malda’s ultimate goal is to sell the tissue-cultured plants commercially. She wants to return to her native Mexico, where her research in cactus conservation began.

    Once she has perfected her techniques, Malda wants to train others to grow the cacti and sell them in Mexican nurseries. If her methods produce good enough cacti, the move could not only deter people from collecting plants from the wild, it could be an economic boon to people who were once paid pennies a plant to rip cacti from their backyards for export, Backhaus says.

    One problem, however, is expense. Tissue culture requires specialized equipment to prevent contamination by bacteria and fungi that can steal nutrients from the plants and cause disease. Sterile labs cost at least $20,000 to start. Even in America, such money is hard to come by for research on very rare species, says Malda. And no one is sure what effect Mexico’s poor economic situation will have on funding.

    Still, Malda is hopeful her research will eventually lead to improvements in conservation of cacti from both sides of the border. If her techniques are successful, industries might become as interested in tissue culture as they are in horticultural development. Then, she says, she will have made a difference.—Alana Mikkelsen

    Cactus conservation


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    Cuban Explorers Observe Almost-Extinct Cactus

    Cuban Explorers Observe Almost-Extinct Cactus
    By Hugo Garcia Fernandez Photos: Adognis Sanchez

    • This unique specimen of the Cuban flora can be saved from extinction thanks to the efforts of members of an extreme sports team. They managed to get to the natural habitat of the plant to collect its seeds in order to sow them at the National Botanical Garden.

    Matanzas, Cuba — Melocactus antinacacthus is close to becoming a notation in botanical history. It has won notoriety for being in danger of extinction. Specialists assure that there is only one adult species living in a natural environment – in Cuba. The other two that exist in the world are part of collections in botanical gardens in England and France.

    In pursuit of the island’s sole plant, members of the “Extreme Club” traveled to a remote region in the central Cuban province of Villa Clara, where they climbed a steep and rocky mountain. The participation of the young sportspeople in the “Conservation of the Melocactus Antinacacthus Project” distinguished the team for their collaboration with the National Botanical Garden in a study that this institution is conducting to protect the curious cactus.

    “As it was very difficult to get to the plant’s natural habitat; we were asked for help to take photographs of the plant and collect its seeds,” said engineer Adognis Sanchez.

    In the Escambray Mountain Range —at a height of 468 meters, in the central region of the island— the youths climbed a nearly 160-meter-high mountainside. They then went down a gorge for another 100 meters until reaching the Melocactus antinacacthus’s natural home.

    The expertise of the Extreme Club was needed to get a close look at the world’s only adult specimen of Melocactus Antinacacthus living in a natural environment.

    After having spent several hours overcoming obstacles, Maykel and Adognis were dumbstruck when they eyed the much-sought cactus. They only observed it in silence, as they did not want to disturb the precious vegetal specimen.

    “You’re the king of this mountain!” exclaimed Adognis, praising the prickly cactus that clung fast to a huge stone, as if it were battling not to be crossed off the botanical list of living species. “I thought it would be bigger,” said Maykel at last, in a low voice, so as not frighten the plant, which had hardly been visited by a bird, insect, rain, or wind. The adventurers insatiably snapped pictures of the plant from different angles. Then, after several minutes, they decided to gently touch its smooth and beautifully green sides.

    Although they caressed it timidly, the curved and sharp thorns pricked both men’s fingers. Therefore, they took the tiny seeds very carefully and painstakingly wrapped them, as they knew their significance for the preservation of the species. Some children, who were members of an environmentalist club in a nearby school, looked up curiously from time to time while played in stream, waiting to see the pictures from the digital camera. At about 3:30 p.m., Maykel and Adognis were running out of time. Remembering that they had to leave the Melocactus antinacacthus they left it in its quite solitude – feeling lumps in their throats.

    They would have liked to tell it so many things, as if it were a beloved relative. Nevertheless, two imperceptible voices were barely heard as they fastened the ropes firmly onto their bodies for the return climb; “take care, friend,” they said.

    Tuesday, June 13, 2006

    Amazing rare plants for sale.

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