How has convergent evolution helped the North American Cacti of the Cactaceae Family and the African Euphorbias of the Euphorbiaceae Family to adapt to desert environments?
Convergent Evolution
Adaptations of North American Cacti and African Euphorbias
The North American Cactus and African Euphorbia species originated from two different, but similar plants. These plants were the typical herbaceous species of the early Earth, characterised by their slim stems and large, wide leaves. However, their evolutionary paths began to change with the separation of the early supercontinents, Pangaea and Gondwana. As variations in the climate caused the development of harsh, arid, desert environments, both plant families experienced convergent evolution in order to adapt and survive. Cacti and Euphorbias both converged on similar forms and metabolisms after prolonged exposure to corresponding environments, due to the fact that similar biomes can require the same adaptations.
Adaptations
- Branching Stems Covered In Longitudinal Ribs
- Smaller leaves And Short Spines
- Spreading, Shallow, Fibrous Root System
- Water Storage System - Succulent Stems
- Crassulacean Acid Metabolism
Branching Stems Covered In Longitudinal Ribs
A common characteristic which has developed for both plant species, as a result of convergent evolution, is the adaptation of branching stems and longitudinal ribs. In order to contend with the harsh desert environments, the African Euphorbias and North American Cacti had to somehow adjust to the climate. One of the adjustments that were induced was the evolution of branching stems covered in longitudinal ribs. This is especially evident in the Peniocereus Striatus (also known as 'Cordoncillo, the 'Gearstem cactus' or 'Dahlia-rooted cactus') Cactaceae species of Arizona and the Sonora Desert, and the Euphorbia Cryptospinosa, a Euphorbiaceae species of East Africa. Both species, although unrelated, have developed slender, succulent, branching stems covered in longitudinal ribs. These ribs are able to contract in periods of very hot weather or climate, acting as shield in order to protect the stomata (pores in the plant leaf – serves as the site for gas exchange) hidden deep within the cactus or euphorbia furrows. This is especially efficient in desert environments because the plant is able to protect its pores, conserve water and regulate gas exchange.
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© 2014 Natasha Nguyen