Plants and Society 7th Edition by Estelle Levetin ,Karen McMahon

Exercise 2

Many large herbivores in North America became extinct around 13,000 years ago. Plants that had coevolved with native animals to distribute their fruits and seeds were left without animal assistance. The Osage orange tree ( Maclura pomifera ) produces a grapefruit-sized fruit with a fibrous texture (see fig. 8.5a). After the presumed loss of its animal distributor, the range of Osage orange, which originally was widespread throughout the eastern half of North America, had shrunk to a few valleys in east Texas. Introduced from Europe, horses (but not cattle) can bite through the tough pericarp and eat the Osage oranges (also known as horse apples) after they fall to the ground.
What features would you look for to discover if animals distributed a fruit What may the information about European horses reveal about the extinct North American distributor of Osage oranges What alternatives do plants have for reproduction and survival if they lose their animal dispersal agents to extinction
Figure 8.5 Mock orange is a common name shared by (a) the tree Maclura pomifera , with its fruit resembling a grapefruit, and (b) the shrub Philadelphus lewisii , with its flowers resembling orange blossoms.