|Ranunculaceae||Few or many pistils
The Ranunculaceae is a large family, both locally and globally. Shaw shows 50 species as occurring in northern Utah, of which only 7 are introduced. Globally, it consists of around 1,800 species in about 50 genera.
Distribution: The Ranunculaceae occurs throughout the world, but is most abundant in temperate and cool regions of the northern and southern hemispheres.
Importance: The Ranunculaceae includes several attractive species, but is not an economically important family. The commercially available species are almost all ornamentals. A few of the more common ornamentals in this part of the world are Anemone, Aquilegia, Cimifuga, Clematis, Delphinium, Helleborus, Nigella, Ranunuculus, Thalictrum, and Trollius.
Some genera are important as poisonous plants. The poisonous properties of Aconitum and Delphinium are well known, particularly to those in involved with cattle. Many, possibly most, other genera contain poisonous species. The compounds involved vary but include alkaloids (in Aconitum and Delphinium), protoanemonin (in Anemone, Clematis, and Ranunculus), and cardiac glycosides (in Helleborus). A drink of Aconitum tea was the lethal drug used for giving the death penalty in ancient times and infirm old men on the island of Ceos were also forced to commit suicide with Aconitum. It is not a nice way to go.
In our part of the world, the Ranunculaceae is useful for demonstrating the concept that families, and other taxonomic categories, are constructed on the basis of many characters; there is no single character that HAS to be present. Or, to put it slightly differently, by "overall similarity". This phrase should immediately make you think "phenetic or natural classification". In other words, a genus may differ from other genera in its family by one or two characters without being kicked out of the family, so long as it resembles the other genera in other respects.
The Ranunculaceae is also an example of a family whose circumscription is supported by cladistic analysis of morphology and various kinds of nucleotide sequence data.
An interesting question that arises when considering a deviant genus is whether it acquired its deviant characteristics after the family as a whole diversified (making it a recent genus), or retained it from the ancestors of the family (making it one or the more primitive members of the family, at least in that respect). Answering such questions is the goal of one part of taxonomy, phylogenetics. Answering them is beyond the scope of this class, but we can look at a few well-known examples in the Ranunculaceae that occur in northern Utah.
Morphological characteristics: Almost all members of the Ranunculaceae are herbaceous, but most species of Clematis are woody vines. The leaves are usually basal or alternate, but are opposite in Clematis. The leaves are usually without stipules, but stipules are present in Thalictrum, Caltha, and Ranunculus. Because the structure of the wood in Clematis is rather unusual, it is thought that Clematis is derived from a herbaceous ancestor. I am not sure what the situation is with respect to the opposite leaves and stipules. I think that they are considered to be derived.
The flowers are usually radially symmetric and bisexual, but Delphinium and Aconitum are bilaterally symmetric and Thalictrum has unisexual flowers (and is dioecious). The calyx and corolla are often poorly differentiated, but by no means always. The number of perianth parts varies from 3 to many, even within a species, but is often a multiple of five. They are separate from each other. The androecium usually consists of many stamens on an elongated receptacle, but is may be less than 10 in Ceratocephalus. The gynoecium consists of few (3-7) to many ( > 10) simple carpels. If there are few carpels, the fruit consists of follicles, but if there are many, the fruit consists of numerous achenes. And yes, there are exceptions here, too. Actaea has a gynoecium of 2 united carpels, with parietal placentation; its fruit is a berry. Nigella, a cultivated species has a gynoecium of 5 united carpels, and forms a capsule at maturity. The ovary is always superior (so far as I know).
Most genera are insect-pollinated, but Thalictrum (which lacks a corolla) is wind-pollinated. Some genera provide only pollen for their insect visitors; others also provide nectar.
Similar families: There are two structures that it is important to remember are not present in the Ranunculaceae, a hypanthium and stipules. Why should you remember this? Because members of the Rosaceae can look very like the Ranunculaceae, but they always have a hypanthium and almost always have stipules.
Origin: The Ranunculaceae is thought to have evolved from one of the older groups of angiosperms, the same group that includes magnolias and tulip-trees. Among the features that suggest this are its spirally arranged stamens, its tendency to have an indefinite number of perianth parts, and its reliance on alkaloids as a means of deterring herbivores (including humans).