|Butter-and-eggs, or Linaria vulgaris, is a
close relative of the snapdragon, and
no longer in the Scrophulariaceae.
Sadly the snapdragon family has suffered a nasty divorce, and what we now call the Scrophulariaceae no longer contains the snapdragons. The old Scrophulariaceae has in fact been split into at least six smaller families (Olmstead, et. al 2001). The pieces, it was found, were not closely related to each other, some pieces were actually closer to other families, including the mint, gloxinia, and verbena families.
The family is a victim of the more precise analytic tools of the late 20th century and the new phylogenetic taxonomy. The similarities among the members of the old Scrophulariaceae were superficial, it turns out. The general flower shape and form of the seed capsule evolved many times from different ancestors (convergent evolution) because they were adapting to similar pollinators and seed dispersal strategies. In sum, the old family was polyphyletic.
The story involves all the drama and complications of modern plant taxonomy. For two centuries, botanists have worked to define more "natural" families. Natural families contain genera that share fundamental characteristics, including similar structural features of flowers and fruits. In the late 19th century the word natural took on the new meaning of evolutionary relationship. Following Darwin's lead, biologists interpreted fundamental similarities within families, genera, and other categories as due to common ancestry. For the next century or so interpretations of natural similarity and evolutionary history went hand in hand. More and more information from anatomy, chemistry and genetics became available, often confirming, but sometimes toppling earlier assumptions about relationship. The information available became so huge that putting it altogether into a master classification of plants relied on the experience and gut feelings of a handful of the leading taxonomists. But the classifications of these wise old men often differed markedly, as much of the information could be interpreted in different ways.
In the middle of the twentieth century, there were many attempts to decipher evolutionary history (or phylogeny) with rigorous and objective statistical tools. The most successful of these was cladistic analysis, a process in which similarity among a group of organisms was distilled into distinct and narrowly defined characters, and the organisms sorted out based on the number of shared characters. Organisms with the most shared characters came out close together on a tree-like cladogram. The branches of the cladogram were then grouped into taxonomic categories, and the cladogram was also interpreted as representing the evolutionary history of the group (i.e. as a phylogenetic tree). Cladistic analysis,now routinely applied to structural, chemical, and genetic data, remains the core of systematic biology.
|This lousewort, Pedicularis bracteosa,
is now in the Orobanchaceae.
|Nothing is more snapdragonish than a
monkeyflower, but this common western
American genus is now in a family
no one has heard of - the Phrymaceae.
|Plantago is a genus of weedy,
wind-pollinated herbs, that is
unfortunately atypical of the
new Snapdragon Family. Photo by Bernd Haynold
|Veronica was the basis for the proposed
family name Veronicaceae. This name was
preferred by many, because at least it was
more symbolic of the types of flowers found
in most members the family. Plantaganiceae,
however had priority.
The old Scrophulariaceae was polypheletic, and in order to create families that represented genuine evolutionary relationship, it had to be broken up. Other traditional families have suffered a similar fate, including the Lily Family, Liliaceae. Daylilies, for example, are no longer in the Lily Family - but that's another story.
Reference: Olmstead, et. al. 2001. The Disintegration of the Scrophulariaceae. American Journal of Botany 88:348-361.