Evolutionary anachronism

Evolutionary anachronism in plants, refers to those fruit, flower, leaf and stem attributes that evolved as an interaction with animals that are now extinct.^[1]

The megafauna dispersal syndrome

Dispersal syndromes are complexes of fruit traits that enable plants to disperse seeds. The kind of fruits that birds are attracted to are usually small, with only a thin protective skin, and the colors are red or dark shades of blue or purple. Fruits categorized as mammal syndrome are bigger than bird fruits. They possess a tough rind or husk, emit a strong odor when ripe but retain a dull coloration of brown, burnished yellow, orange or remain green. The megafauna dispersal syndrome refers to those attributes of fruits that evolved in order to attract megafauna (animals that weigh or weighed more than 44 kilograms) as primary dispersal agents. Since the Holocene extinction, the large herbivores have become extinct outside Africa and to a lesser extent Australia, leaving these fruits without a suitable dispersal mechanism in the absence of agriculture.

Typical anachronism in Chorisia speciosa: stem protection from now extinct mammals

Ecological indicators of missing dispersal partners

• The fruit either rots where it falls or is ineffectually disseminated by current dispersal agents.
• The plant is more common where horses and cattle are present (proximegafauna).
• The seeds germinate and grow well in upland habitats where planted but the species almost exclusively inhabits floodplains in the wild.
• The geographic range is inexplicably patchy or restricted.^[1]

Examples

• Avocado ^[2][3]
• Devil's walking stick^[4]
• Guanacaste tree, Enterolobium cyclocarpum
• Honey locust^[4][5]
• Kentucky coffee tree^[4][5]
• Mesquite^[4]
• Osage orange^[4][5]
• Papaya^[4][5]
• Pawpaw^[4][5]
• Persimmon^[4][5]

References

1. Barlow, Connie C. (2000). The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms. New York: Basic Books. ISBN 9780465005512.
2. Cited in Barlow, Connie C. (2000). The ghosts of evolution: nonsensical fruit, missing partners, and other ecological anachronisms. New York: Basic Books. ISBN 0-465-00551-9.
3. B. N. Wolstenholme; A. W. Whiley (1999). "ECOPHYSIOLOGY OF THE AVOCADO (Persea americana Mill.) TREE AS A BASIS FOR PRE-HARVEST MANAGEMENT" (PDF). Revista Chapingo Serie Horticultura 5: 77–88.
4. Bronaugh, Whit (2010). "The Trees That Miss The Mammoths". American Forests 115 (Winter): 38–43.
5. Connie Barlow. Anachronistic Fruits and the Ghosts Who Haunt Them. Arnoldia, vol. 61, no. 2 (2001)