July 28, 2019

Asteraceae - Tribes and subfamilies

Some flora break the Asteraceae into subfamilies or "tribes". I thought that a first step towards finding my way with the Asteraceae might be understanding these "tribes", but this hasn't worked out as I hoped. There are two problems. One is that there doesn't seem to be any unanimous agreement about how to do this. The other (and much more important) is that some flora ignore the tribes entirely and provide an "artificial" key. This is in particular true of "Arizona Flora", which is the book I expect to use more than any other. This is also true of the Jepson Guide for California, although a tribal key has been published separately.

This makes mastering a division of the Asteraceae into tribes of less utility than I had originally hoped. In particular, I cannot simply turn to "Arizona Flora" for a plant I have identified and have an interest in and find out what tribe it belongs to. There is probably a good reason why a modern book like the Jepson Guide makes no effort to utilize a tribal division of the Asteraceae. Perhaps the required characteristics are not easily observed.

Some publications

The 2009 PDF is chapter 11 from a book, "Systematics, Evolution, and Biogeography of Compositae". Entire books are being written about this group, which isn't terribly surprising.

The tribes circa 1960

I have an old text, "Plant Classification" by Lyman Benson which describes a division of the Asteraceae into 15 tribes. These same tribes are used by two flora I have on my shelf, namely "Manual of the Plants of Colorado" by H.D. Harrington, 1964 and "Vegetation and Flora of the Sonoran Desert" by Shreve and Wiggins, 1964. Shreve and Wiggins have representatives from all 13 tribes. Colorado omits Madieae and Mutisieae, so has 11 tribes represented.

Treatment in "Botany in a Day"

This is an odd little book with a ridiculous title. First published in 1996. It devotes several pages to an organization of the Asteraceae. It first uses a four-way division into the following major subfamilies. The Asteroideae then get divided into 11 tribes: We can take the 3 subfamilies and the 11 tribes from the Asteroideae to get 14 entities to try to corollate with Benson's division. It looks like Gnaphalieae and Inulaeae could be lumped. What happened to Madieae?

The view from Wikipedia

This may offer the most up to date view of the subject. If so, the one thing that can be said is that things have been reworked drastically since the above division was in use. Other than that, I am hard pressed to find any connection to the above except for the first 4 big divisions.

According to the Wikipedia article, there are now 13 recognized subfamilies.

The earliest division of the Asteraceae was into two subfamilies:

The first subfamily (Asteroideae) still stands today, but the second has been divided into 12 subfamilies. As things stand, four subfamilies dominate and contain 99 percent of the species:

Here is the full list of subfamilies:

In case you are curious about Hecastocleis shockleyi, it is found in California and Nevada deserts, and has the popular name "prickle leaf"

Treatment in Arizona Flora

This book does not give names to the subfamilies, but a preliminary key leads you to one of 8 major divisions. It simply assigns the letters shown, I have attempted to corrolate these with named subfamilies from other sources. It is not clear to me that the divisions in Arizona Flora are according to recognized subfamilies, though they may be in part. The fact that the same genus appears in multiple places in different divisions suggests that the divisions in the keys are synthetic and not according to actual subfamilies.

Treatment in the Jepson Manual, second edition, 2012

Here we have 15 "groups" and I am tempted to say that it looks unwise to attempt correlation with subfamilies. Rather, these groups are by readily recognized physical characteristics. This makes sense in a key, as the point is to identify plants, not classify them.
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