BIOL 317 LECTURE NOTES – WEEK 4 SUMMARY

CARYOPHYLLIDS, SAXIFRAGALES, ROSIDS (MALVIDS PART I)

Caryophyllids – One of the 3 major groups of ‘core’ eudicots (along with Rosidae and Asteridae). Currently thought to be sister to the Asteridae. There is a well-defined clade recognized through much of the history of angiosperm classification, with several distinctive synapomorphies, including:

1) free-central placentation (hence the archaic name ‘Centrospermae’). Sometimes basal or parietal (e.g., Cactaceae): the loss of septa separating locules can result in basal, parietal, or free-central placentae. 2) betalain pigments, red pigments containing nitrogen. Most other flowering plants have a different type of red pigments, called anthocyanins. EXCEPTION: members of Caryophyllaceae have anthocyanins and NOT betalains, unlike other families in this clade. 3) perisperm nutritive tissue in seeds. Perisperm is derived from the ovule wall, rather than from endosperm = diploid (sporophyte) parent tissue. 4) curved embryo. 5) “P-type plastid”: unique sieve-tube plastid with a proteinaceous inclusion.

The families sharing these traits have been recognized as the order Caryophyllales in the past. However, this classification has changed over time, with current systems broadening the definition of the order Caryophyllales to include its sister clade, Polygonales. According to this broader circumscription (which is used in the textbook), Caryophyllales consists of 2 sub-orders: Caryophyllinae (= former Caryophyllales, share synapomorphies listed above) and Polygoninae (= former Polygonales, do not share synapomorphies listed above).

Caryophyllales (Polygoninae) - Polygonaceae (43 gen/1100 spp) – Buckwheat family. Includes buckwheat and rhubarb. (1) Herbaceous or woody (woody species mostly in the tropics). (2) Leaves simple, alternate; with sheathing stipules at the nodes (called an ocrea). Note: the large native genus Eriogonum contains species without evident ocrea. (3) Flowers 3-parted - tepals usually 6 (sometimes 5) - stamens 6-9 - 2-3 fused carpels, superior ovary, basal placentation - fruit achene or nutlet, often 3-angled or winged.

Some anatomists interpret the flowers in the Caryophyllinae to be without petals and consider all perianth parts to be tepals, modified bracts (sepals in Portulacaceae), or modified stamens (petals in Caryophyllaceae). Halophytes (e.g., Chenopodiaceae) and xerophytes (e.g., Cactaceae) are common in this group, hence a lot of plants are succulent, which is an adaptation for conserving water.

Caryophyllales (Caryophyllinae) - Caryophyllaceae (70 gen/2200 spp) – Carnation, or pink family. (1) Herbaceous. (2) Opposite leaves, swollen nodes. Leaves usually simple and entire. (3) Floral parts in 5s; petals often bilobed, or with well developed claw (forming tube) and blade - 10 stamens - ovary of 2-5 fused carpels, superior - fruit a capsule - placentation usually free-central. (4) NO BETALAINS.

Caryophyllales (Caryophyllinae) - “Portulacaceae” (19 gen/450 spp) – Purslane family. This family is paraphyletic with respect to the Cactaceae (i.e., Cactaceae are derived from within Portulacaceae). (1) Herbaceous, plants often somewhat succulent. (2) Leaves simple, alternate or opposite, often fleshy. (3) Flowers with characteristic paired bracts, usually called sepals, beneath each flower - petals (really tepals, because ‘sepals’ are really bracts) 5 or more - stamens 5 (or many). Lewisia is an important exception here in PNW with many (2-9) sepaloid bracts and many tepals. 2-3 fused carpels, ovary superior - free-central to basal placentation - fruit a capsule.

Caryophyllales (Caryophyllinae) - Cactaceae (93 gen/1400 spp) – Cactus family. (1) Succulent stems, usually photosynthetic, variously shaped, sometimes flattened or fluted - ‘primitive’ cacti are vines or shrubs, have ‘normal’ leaves, not succulent. (2) Leaves ephemeral or reduced - axillary buds, called areoles, with leaves in the form of spines (glochids). (3) Flowers exhibit a secondary increase in the number of parts - many tepals usually united at the base into a hypanthium - many stamens arising from the hypanthium - inferior ovary of 3-many fused carpels - placentation parietal - fruit a berry.

Saxifragales, unlike Caryophyllineae, has historically not been straightforward to define. It is currently recognized as a clade of 15 families, sister to the Rosidae.

Saxifragales - Saxifragaceae (30 gen/550 spp) – Saxifrage family. This family contains herbaceous plants centered in the western USA. (1) Herbaceous. (2) Leaves simple, alt., often palmate; often forming basal rosette. (3) Flowers actinomorphic (rarely zygomorphic, e.g., Tolmeia) - sepals and petals in 5s, often attached to a cup-shaped or flared hypanthium - stamens 5 or 10 - carpels 2-3 partially fused at base - ovary may be superior, half inferior, or inferior (depending on degree of fusion of hypanthium to ovary wall) - fruit usually a capsule.

Rosidae. Together with Asteridae, this clade contains most of the species of eudicots. We have already covered two families of rosids: Fagaceae and Betulaceae (both in the order Fagales).

Geraniales - Geraniaceae (7 genera; 750 spp) – Geranium family. (1) Herbs to subshrubs. (2) Leaves alternate or opposite; often palmate; simple, lobed, or compound. (3) Flowers bisexual, actinomorphic or zygomorphic - sepals 5, petals 5 - stamens (5-) 10 or 15 - carpels 5, fused - ovary superior with persistent, sterile column in center that elongates after the flower is pollinated - axile placentation - fruit a schizocarp splitting into 5 one-seeded segments (achenes) that separate from the central column.

Myrtales - Onagraceae (16 gen/650 spp) – Evening primrose family. This small family is particularly prominent in the western USA and includes evening primroses, Clarkia, fireweed, etc. (1) Herbaceous. (2) Leaf arrangement variable (alternate, opposite or whorled); leaves simple, usually entire. (3) Flowers bisexual, actinomorphic or zygomorphic - parts in 4’s (except Circaea, WA native with 2-parted fls) - anthers versatile - which means attached by a thin connective allowing them to dangle loosely - pollen usually in tetrads (four grains that don’t separate); attached by viscin threads - ovary inferior - axile placentation - fruit a capsule. A good monophyletic family not threatened with extinction due to inclusion in another group!

In Oenothera, SC/SI are highly variable, so it is a good system to study breeding system evolution. Shifts are usually from SI -> SC; self-incompatibility has been lost multiple times independently. Extreme environments and small populations select for SC, as does limited pollinator availability. Where the chance of reproductive failure is increased, reproductive assurance (selfing) confers higher fitness than outcrossing. “It is better to have reproduced by selfing than never to have reproduced at all” – Holsinger 1992.

Sapindales - Aceraceae (2 gen/113 spp) – Maple family. (1) Woody trees or shrubs. (2) Leaves opposite - typically palmate venation; usually simple to palmately lobed, sometimes palmately compound (ancestral leaves in Sapindaceae are pinnately compound). (3) Flowers actinomorphic, bisexual or unisexual; unisexual flowers usually male - may be insect or wind pollinated - sepals and petals 4-5 - stamens 4-10 - 2 fused carpels each with pronounced wing - fruit a samaroid schizocarp: splitting into 2 one-seeded segments, each segment winged and dispersed by wind.

In most systems (incl. in the textbook), the family Aceraceae is included in a larger family, Sapindaceae, which is a paraphyletic ancestral group. Sapindaceae are largely tropical, and include more variation in floral morphology. The Hippocastanaceae (Horse Chestnut or Buckeye family) is another north- temperate family derived from within Sapindaceae. Aceraceae and Hippocastanaceae both are monophyletic, but by recognizing those families as distinct from the traditional Sapindaceae, the Sapindaceae are paraphyletic.