Liliales is an order of monocotyledonous flowering plants. This order of necessity includes the family Liliaceae, but both the family and the order have had a widely disputed history, with the circumscription varying greatly from one taxonomist to another. Well known plants from the order include Lilium (lily), tulip, the North American wildflower Trillium, and greenbrier.
The APG II system (2003) places this order in the clade monocots and uses this circumscription:
Thus circumscribed, this order consists mostly of herbaceous plants, but lianas and shrubs occur. They are mostly perennial plants, with food storage organs such as corms or rhizomes. The family Corsiaceae is notable for being heterotrophs.
The order has worldwide distribution. The larger families (with more than 100 species) are roughly confined to the Northern Hemisphere, or are distributed worldwide, centering on the north. On the other hand, the smaller families (with up to 10 species) are confined to the Southern Hemisphere, or sometimes just to Australia or South America. The total number of species in the order is now about 1300.
As with any herbaceous group, the fossil record of the Liliales is rather scarce. There are several species from the Eocene, such as Petermanniopsis anglesaensis or Smilax, but their identification is not definite. Another known fossil is Ripogonum scandens from the Miocene. Due to the scarcity of data, it seems impossible to determine precisely the age and the initial distribution of the order. It is assumed that the Liliales originate from the Lower Cretaceous, over 100 million years ago. The initial diversification to the families took place between 82 and 48 million years ago (Vinnersten and Bremer, 2001).
The APG system (1998) also placed the order in the clade monocots, but with a slightly different circumscription (missing the family Corsiaceae):
- order Liliales
- family Alstroemeriaceae
- family Campynemataceae
- family Colchicaceae
- family Liliaceae
- family Luzuriagaceae
- family Melanthiaceae
- family Philesiaceae
- family Ripogonaceae [sic]
- family Smilacaceae
The Cronquist system (1981) placed the order in subclass Liliidae in the class Liliopsida [= monocotyledons] of division Magnoliophyta [= angiosperms]. It used a much wider circumscription (many of the plants here are assigned to Asparagales and Dioscoreales by APG II):
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