University of Wisconsin-Madison | Botany Plant Growth Facilities
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Room # 7
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The succulents provide the most dramatic example of evolutionary convergence. The different deserts of the world have been isolated from one another since the origin of the flowering plants, with only limited opportunities for migration among different areas. Hence, succulents have evolved independently in many different families in different deserts. Desert regions are characterized by low precipitation and often by high day time temperatures during at least part of the year. The present deserts of the world are of relatively recent origin, and their plants and animals have been selected from those found in the bordering areas. Annual plants are better represented, both in number and kind, in the deserts and semiarid regions of the world than anywhere else. The relatively few perennial herbs that grow in the desert are often bulbous and dormant for much of the year. Most of the taller plants are either succulent or have small leaves that are either leathery or are shed during an unfavorable season. Many of the succulent species in this biome have adopted CAM (Crassulacean Acid Metabolism) photosynthesis and absorb carbon dioxide at night. Perhaps the most magnificent examples of convergent evolution are shown by the succulents of the deserts of the world. The one raised in the cactus deserts of Arizona, however, the convergance of leaf types in the many families of deciduous forest herbs and trees might seem just as bizarre and noteworthy! |
Agave,(Century Plant), Aloe (Medicinal Aloe), Cactaceae (Plants in Cactus Family)), Cissus (Veldt Grape), Crassulaceae (Plants in Stonecrop Family), Didierea (Didierea), Euphorbiaceae (Plants in Milkweed Family), Pachypodium (Bottle Tree), Phoenix (Date Palm), Puya (Puya), Senecio (Inchworm), Stapelia (Starfish Cactus) |
