LIFE HISTORY
Joshua trees need to undergo a dormant period of cold weather before flowering, but once they flower, they are dependent upon one tiny insect for pollination. Yucca moths (genus Tegeticula) transfer pollen between flowers to ensure seeds will form, and then they lay their eggs inside the pollinated flower. When the larvae hatch, they feed on some of the seeds and the rest are able to disperse and grow into new Joshua trees. This type of interaction, where two organisms are dependent upon each other for mutual benefits, is called a mutualistic symbiotic relationship. A number of other animals are also served by Joshua trees. For example, 25 bird species nest in Joshua trees. Lizards and invertebrates use various parts of the tree for cover, and a number of mammals rely on Joshua trees for food. Humans have used the trees for food and to make baskets and sandals.
Joshua trees are slow-growing, but because of this, they live for a long time. Joshua trees don’t have annual growth rings like actual trees, so accurately determining their age is quite difficult. Instead scientists measure the height of a Joshua tree and divide it by an estimate of growth per year. One Joshua tree in California is thought to be over 1,000 years old. A more common lifespan is about 150 years.
CONSERVATION
Because they require a cold period to flower, Joshua trees are vulnerable to climate change. The U.S. Fish & Wildlife Service is currently reviewing the Joshua tree for listing under the Endangered Species Act.
FUN FACT
SOURCES
Defenders of Wildlife
National Park Service
NatureServe Explorer
U.S. Fish & Wildlife Service
U.S. Forest Service
For more details follow this link.