Images of dry tropical habitat: the Cactus Family (Cactaceae)

The Cactus Family is almost entirely restricted to the Americas. Though often associated with deserts, cacti are actually most diverse and abundant in dry parts of the tropics. The strange forms of cacti are among the most striking elements of dry tropical habitats in the Americas. So far, all of the photos here are from Mexico, but cacti are also very important in the rest of the American tropics. Click on a thumbnail for a larger image.


Cephalocereus columna-trajani in the Tehuacan Valley in southern Puebla, Mexico. This strange white cactus usually has only one stem for its whole life. Legions of C. columna-trajani covering hillsides is one of the strangest sights I've ever seen. The grayish swatch on one side of the stem near the tip is a mass of hairs from which the flowers emerge . The genus Astrophytum is largely found in the tropical parts of the Chihuahuan Desert complex of drylands. This species A. myriostigma, varies greatly in color. This individual comes from a population of mostly green individuals.
It's easy to mistake this Ariocarpus trigonus in Tamaulipas, Mexico, for a member of the Agave or Pineapple family. Most of the plant body of this plant is hiding underground.
In contrast, this population of A. myriostigma is made up mostly of brilliant white individuals.
A large Coryphantha elephantidens in tropical dry forest of Guerrero, Mexico.
Astrophytum ornatum is the barrel cactus of the genus. This species is often more than a meter tall. It is a lovely plant, with golden spines and white splotches on the dark green stem. These individuals were photographed growing in a tropical dry forest with many other cacti, such as the columnar species visible in the background Stenocereus dumortieri and S. queretaroensis, in the state of Guanajuato.
The columnar Neobuxbaumia tetetzo of Puebla and Oaxaca, Mexico, can form extremely dense stands that are hard to squeeze through. The forest floor is a harsh place for a small, globular cactus. However, Mammillaria sphaerica manages to grow in dense colonies in the understory of tropical dry forest on the Gulf Coast of Mexico. These cacti have remarkable mechanisms for coping with the rapid accumulation of leaf litter in these forests, which would bury most small cacti. Note the exposed roots of the individual in the foreground.
Echinocactus platyacanthus growing with small palms (Brahea) in northern Oaxaca, Mexico.
A typical Mexican highland pair:  Stenocereus dumortieri (foreground) and Myrtillocactus geometrizans (behind) are common large cacti of the central Mexican dry tropical highlands.
The wild architecture of Escontria chiotilla in Puebla, Mexico.
A September rainbow over the massive columns of Pachycereus weberi in Puebla state.
Another unbranched columnar cactus, Neobuxbaumia mezcalensis, in Guerrero, Mexico.

The massive candelabras of Pachycereus weberi are one of the most memorable images of Mexico's dry forests. Echinocactus

Wavy-ribbed Stenocactus are often hidden in clumps of grass. This individual in San Luis Potosí is remarkably tall.

Some cacti grow in the extremely fine soil of muddy desert flats. These flats are remarkable because the very top of the soil is consolidated by lichens, bacteria, bryophytes and other tiny organisms into what is known as a cryptogamic crust. This Stenocactus pokes through the cryptogamic crust of such a flat in Tamaulipas.

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Instituto de Biología, Universidad Nacional Autónoma de México
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all material © 2006 Mark E Olson