Lentibulariaceae

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Lentibulariaceae

Description

A small family of annual or perennial herbs, all of which are variously adapted for the capture and digestion of small animals (insects, Crustacea, etc.).

Distribution

Africa: present Asia: present Asia-Tropical: Australasia: New World: present Patagonia: present Polynesia: present South America: present Tropical Africa: present the Mediterranean: present
Only one genus (Utricularia) occurs in Malesia.
The family is cosmopolitan, including arctic regions, but is more or less absent from Polynesia. It includes 4 genera with c. 250 spp.
The largest and most widely spread is the cosmopolitan genus Utricularia L. with c. 180 spp., almost half of which occur in the New World, the rest being more or less equally distributed between tropical Africa, Asia, and Australia, with a few in the north temperate zone, 22 spp. occurring in Malesia.
Pinguicula L., with some 50 spp., has a curious distribution, with a few circum-boreal species and concentrations in the Mediterranean region and in North, but especially in Central and in South America, as far south as Patagonia.
Genlisea ST.HIL., with c. 16 spp., is confined to the tropics of South America and Africa.
Polypompholyx LEHM., with 2 spp., occurs only in Australia.

Taxonomy

The affinities of the family have been the subject of considerable discussion and opinions are divided between a relationship with Scrophulariaceae and Primulaceae. The combination of free basal (or free central) placentation, a spurred personate corolla (the spur is always present but occasionally reduced), two stamens and the carnivorous habit is diagnostic for the family. In favour of affinity with Scrophulariaceae are the morphology of the corolla, the structure and number of the stamens, the bilobed stigma, and such cytological evidence as is available. The pollen of Lentibulariaceae is similar to that of both of the families in question. The placentation (and no doubt the mode of dehiscence of the probably most derived aquatic European species, i.e. those most usually studied) is certainly the reason for a suggested alliance with Primulaceae but the two families have little else in common. The transition from axile to free central (or basal) placentation by the loss of the septum is quite feasible and the mode of dehiscence of at least what are presumably the most primitive Utricularia species could support such a hypothesis.
Within the family the combination of two-lobed calyx and trap structure is diagnostic for the genus Utricularia. Polypompholyx is very close to Utricularia but with 4 calyx lobes in two whorls. Genlisea and Pinguicula both have true leaves and a 5-lobed calyx, the traps of the former genus being extremely complex but quite different from those of Utricularia. Genlisea has also a unique type of fruit dehiscence — likening the fruit to a globe it splits at the equator and at least partially at both tropics. Pinguicula has an apparently much less complex trapping mechanism consisting of two types of superficial glands on the leaves while the dehiscence is constantly valvate. Theories have been advanced as to how the various trapping mechanisms could be derived one from the other but they are on the whole unconvincing.