Arecidae

Arecidae is the name of a plant taxon located in the taxonomic category of subclass, which according to the International Code of Botanical Nomenclature must necessarily be circumscribed by at least the order Arecales. This taxon was used by the popular Cronquist (1981) classification system. Its members share a series of superficial characters, such as the habit (which united the palms with the cyclantaceae and the pandanaceae), and the inflorescences in spadix with spathe (which included the araceae and lemnaceae in this subclass). Today this taxon is known to be polyphyletic, and its members are distributed in the monophyletic Commelinidae, Pandanales, and Alismatales.

Characters

In their habit they are herbs, shrubs, vines, or in some cases trees, with limited secondary growth and no formation of new vascular tissue.

They have alternate leaves, sometimes all are basal, or in a terminal crown.

The flowers are numerous and generally small, hermaphroditic or unisexual, hypogynous. Frequently its inflorescence is a spadix and is surrounded by a spathe.

The perianth can be well developed with two whorls of three tepals, or sometimes be very reduced and vestigial or even absent.

The androecium can have one or many stamens with binucleate or sometimes trinucleate pollen grains.

The gynoecium is generally formed by three carpels (or even one or many), united or free, with one to many seminal primordia in each loculus.

The fruit is usually indehiscent, usually a berry or drupe, the fruit can be multiple.

Ecology

Pollination is mediated by insects (entogamous) or by wind (anemogamous).

Phylogeny

Molecular DNA analyzes done since the 1990s have shown that this taxon as circumscribed here is polyphyletic.

The Arecaceae, Cyclanthaceae and Pandanaceae share a vine-like arborescent or herbaceous habit, tetracytic stomata, indehiscent and fleshy fruits, and similar embryo development. However, in Pandanaceae/Cyclanthaceae the characters present in the Commelinidae clade, to which Arecaceae belongs today, are absent. Palms today are Arecales, as in Cronquist, but are placed in subclass Commelinidae, Cyclantaceae and Pandanaceae today are located in Pandanales, and are not closely related to palms.

Finally, Araceae and Lemnaceae are now in Alismatales, having been resolved that inflorescences with spadix and spathe appeared many times in different unrelated clades of plants, so they are not useful for discerning phylogeny at these levels of the tree.

Taxonomy

It comprises 4 orders with 5 families and about 5,600 species; most belonging to the Arecales order.

Order Arecales:

Arecáceas or palmaceae, family Arecaceae, also called Palmae.

Order Cyclanthales:

Cyclantaceae, family Cyclanthaceae.

Pandanales Order:

Pandanaceae, family Pandanaceae.

Arales Order:

Araceae, Araceae family.

Lemnáceas, family Lemnaceae.