Caryophyllales
Comments on your first lecture exam and grade breakdown are now available on the General Course Announcements page.
Your third lecture assignment will be distributed on Friday, February 27th and is due in lecture on Monday, March 9th. This assignment will help you prepare for the upcoming lab exam (March 10 and 11). While the answers to these assignment questions should be obvious, think about your responses for this will help you study for the exam.
Lecture Assignment 2 has now being graded and will be returned to you next week in lab. The average grade on this assignment was quite low, about 70%, representative of a C-letter grade. If you are unclear how to construct a cladogram from a simple data set using the principle of maximum parsimony, please talk with us! You will see the same type of questions as the semester progresses.
Readings:
Judd et al., 2008, Plant Systematics: A Phylogenetic Approach (Third Ed.). Read the discussion on the order Caryophyllales, pages 318-320.
Important Note: When studying for upcoming exams, it will be important to study these web notes as well as read the assigned pages in your text so that concepts and family characteristics are reinforced. Also, if you are not coming to lecture regularly, you are missing valuable information that might help you do better on exams. Plus, I miss you when you aren't here.
General Objectives:
After studying this material you should be able to:
Eudicots: Order Caryophyllales
In Arthur Cronquist's (1981) treatment, "An integrated system of classification of flowering plants," this group was classified as subclass Caryophyllidae (of class Magnoliopsida) and comprised three orders (Caryophyllales, Polygonales, and Plumbaginales). In total, 14 families and some 11,000 species were treated in this subclass. Until recently, this was the system used by many authors and presented in many textbooks. The group Caryophyllales was formerly known as the Centrospermae, in reference to the free-central placentation found in many of its members.
Fig. 9.3 in your text shows the major clades within the Eudicots. The Caryophyllales are placed in the Core Eudicots (Core Tricolpates) clade within the major Eudicots lineage. In this system of classification, the older Polygonales and Plumbaginales, as well as some other novel groups, are all placed within the single order Caryophyllales (the Caryophyllales sensu lato).
The Caryophyllales sensu lato contain about 30 families, of which we will only treat four:
Notable among the families not covered are the Droseraceae (Venus fly-traps and sundews), Nepenthaceae (pitcher plants), Nyctaginaceae (four-o'clock family, incl. Bougainvillea), Phytolaccaceae (pokeweed family), Plumbaginaceae (Plumbago), Amaranthaceae (Amaranthus, pigweeds, plus the family Chenopodiaceae which incl. beets, spinach, goosefoot, swiss chard, and saltbush), and Simmondsiaceae (jojoba, used in cosmetics and skin/hair products).
Relationships within the Caryophyllales
The cladogram below shows the hypothesized relationships within the order Caryophyllales (Fig. 9.45 in Judd et al. 2007, p. 318). The order includes two large clades, recogized in your text as suborders Polygonineae and Caryophyllineae. Note the synapomorphies for each of these clades.
The Caryophyllineae (or Core Caryophyllales) are clearly monophyletic, as evidenced by numerous distinctive synapomorphies (chemical, anatomical, morphological, and molecular). Reversals are also common, such as the loss of betalain pigments, as are parallelisms (succulent habit).
General Features of the Core Caryophyllales (suborder Caryophyllineae)
Primarily herbaceous; succulents
Petals usually distinct
Carpels usually 2 or more, syncarpous, often with free-central (or basal) placentation
Embryo usually curved inside the seed around central PERISPERM. This seed storage tissue is similar to endosperm but is derived from the nucellus (sporangium wall), not from the fusion of a sperm nucleus with the polar nuclei. These ovules are described as campylotropous, which is an ovule where the micropyle (opening where the pollen tube enters) is positioned near the funiculus (stalk of the ovule).
Sieve tube plastids with protein crystalloid inclusions surrounded by proteinaceous filaments ("P-type plastids"). Figure from Sanderson (2006), Plant Systematics.
Another illustration of sieve tube plastids with crystalloid inclusions
Most other members of the Eudicots clade have sieve tube plastids with starch grains.
Pigments are BETALAINS instead of anthocyanins (however, they are NOT present in two of the families we will study: Caryophyllaceae and Polygonaceae). Both are water soluble pigments that give plants their blue, red, yellow, and orange colors. Betalains, however, possess N and differ in chemical structure.
NOTE! Of the four families that we will cover this semester:
Anthocyanins = Caryophyllaceae and Polygonaceae
Betalains = Cactaceae and Portulacaceae
Molecular Systematics:
Loss of the intron in chloroplast gene rpl2 serves a molecular synapomorphy for the suborder Caryophyllineae (or Core Caryophyllales). Click here to see the results and how this experiment was done.
An early chloroplast DNA phylogeny of the Caryophyllales based on structural rearrangements of the chloroplast genome (intron losses, ORF deletions, inversions) and restriction site variation from the evolutionary conserved inverted repeat region. Click here to see the results of this study. Several families are not monophyletic, and the anthocyanin-possessing taxa have evolved from betalain-containing ancestors.
Phylogenetic analysis of chloroplast DNA gene sequences reveals that Amaranthus (Amaranthaceae; many weeds and cultivated ornamentals) occurs within a paraphyletic Chenopodiaceae, Sarcobatus (Chenopodiaceae; greasewood) allies with Nyctaginaceae (four o'clock) and Phytolaccaceae (pokeweed) families, and Nepenthes is closely related to Caryophyllales.
In the Judd et al. text, the Amaranthaceae (Amaranth family) are broadly defined and include the Chenopodiaceae (Goosefoot family), which are usually maintained as a distinct, separate family. This broadly circumscribed Amaranthaceae is supported by cladistic analyses of both molecular and morphological data. The separation of Chenopodiaceae from Amaranthaceae is arbitrary and results in a paraphyletic Chenopodiaceae. See page 327 in the Judd et al. text for more information.
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