Tag Archives: ecology

Dragon’s Blood Tree

Posted on by
Reply

Dracaena cinnabara tree, image from Wikipedia, click on the image to see the original (large) image at Wikipedia

Dracaena cinnabari is not a cactus, but it is an amazing plant. D. cinnabari is endemic to Socotra Island in Yemen. Its common name, dragon blood tree, derives from the reddish sap obtained from the tree that is used as a dye or a medicine. Wikipedia reports that the red resin was used in dying wool, gluing pottery, as a breath freshener and as a lipstick. Purportedly, the red sap has been employed in magic rituals.

Some sources suggest that D. cinnabari was widely distributed over Socotra Island in the past, but while it is still widespread, it is in scattered populations. It is not clear why overall numbers of the tree have declined because Socotra Island is not yet subject to typical ecological pressures (eg, urbanization, ranching). The trees typicall grow “areas affected by the mists, low cloud and, in particular, the constant drizzle of the monsoon.” Perhaps such areas are not as common as in the past? One source reports that there is circumstantial evidence of drying in the region over the past few hundred years.

You can find out more about D. cinabari at the Arkive. 

Posted by: Joe Shaw shawjoej@gmail.com

One in Seven Million Seeds

Posted on by
Reply

Opuntia stricta seedlings, photo by Danny Green

Cactus seedlings generally can’t endure the conditions that mature plants can take in stride. Seedlings are sensitive to too much heat, sun, wind, and cold, as well as lack of water. Additionally, seedlings are more susceptible to grazing by insects and animals. Most cactus seeds never produce a cactus plant; they may germinate but very few live to produce a mature plant.

Many factors affect seed germination including temperature, moisture, and mechanical scraping of the seed. But, germination is just one aspect in plant reproduction. Seedlings must be able to survive and reproduce. Likely, many cactus seedlings only survive when special years occur, years with extra water or mild temperatures. Probably two or tree such years in a row are necessary.

One study showed that one in 20,000 Opuntia rastrera seeds survives to produce a plant in a grassland setting. The success rate is even worse in scrublands where one in 7,000,000 seeds produces a plant.

Posted by: Joe Shaw shawjoej@gmail.com

Chihuahuan Desert Cacti and Conservation

Posted on by
Reply

The World Wildlife Fund has prepared an interesting article that you can read here. It is concerned with “Trade and Conservation of Chihuahuan Desert Cacti.” The article describes plants in Texas, New Mexico, Arizona, and Mexico that are vulnerable to over-harvesting. Even Opuntia are vulnerable because they are harvested unsustainably for use in cosmetics (their mucilage is added to products as an emollient).

Most of us, as cactus hobbyists, only grow seed- or cutting-grown plants from reliable dealers, but a blackmarket trade continues across international and state borders.

World Wildlife Fund (WWF) considers the Chihuahuan Desert Ecoregion (CDE) of Mexico and the United States an important ecoregion for conservation because of its outstanding biological diversity, ecological fragility, and environmental concerns. The ecoregion, rich in natural resources, faces a range of visible threats stemming from human activities such as mining, fossil fuel exploration, livestock grazing, industrial agriculture, and development.

Posted by: Joe Shaw shawjoej@gmail.com

Rare Plants: Opuntia spinosissima

Posted on by
Reply
Opuntia spinosissima

Opuntia spinosissima, photo from plantsystematics.org

Some of the rarest plants in the world are opuntiads. One paper from about 10 years ago reported one of the stumbling blocks that Opuntia spinosissima (= Consolea spinosissima)  faces.

“Opuntia spinosissima (Martyn) Mill. (Cactaceae) is an extremely rare taxon with a single remaining wild population of 13 plants located on Little Torch Key, Florida. The plants rarely set viable seeds…I hypothesize that O. spinosissima is a sterile polyploid and that the 13 extant plants are asexually derived from a single lineage.”

This is terrible news. Essentially, in reporting her studies and findings, the author (Dr. Negron-Ortiz) concluded that all of the plants in the wild are really the same plant (ie, they are all derived from rooted pieces). All of the plants are self-incompatible (they don’t accept each other’s pollen). If any seeds are produced they are identical to the parent plant, and thus, identical to all of the plants. Lack of genetic diversity is a real problem that seems to cause sterility in this case.

Posted by: Joe Shaw shawjoej@gmail.com