Download Plant Geography Botany 422, 2011 Greenhouse/Outdoor/Fossil

Plant Geography
Botany 422, 2011
Greenhouse/Outdoor/Fossil Tour No. 3
This tour has both indoor and outdoor components. For the greenhouse portion, remember that the greenhouse is
open weekdays from 8:00am to 4:00pm, and is located on the B-2 basement level of Birge hall. The greenhouses
are numbered 1 to 8. (See the map on the last page of this handout). Please leave any backpacks and bags in the
lockers in the hallway so as to avoid knocking plants off tables. To find these plants, look for the number labels
with Plant Biogeography. The outdoor portion of the tour begins on the hill south of the Botany greenhouses (10),
continues through the Botany garden (11-13), makes a stop in front of Chadbourne Hall (14) and ends on Bascom
Hill (15). All fossils for Part 3 of the tour are located in Birge Hall, Room 245 on the benchtop.
Part 1: Indoors
Greenhouse 2
1. Psilotum nudum — whisk fern (Phylum Pteridiophyta)
This genus is one of only two genera in the once-recognized phylum Psilotophyta. It best represents what some of
the first vascular land plants in the Devonian would have look like, with green, dichotomously branching stems, no
leaves, and naked sporangia (spore producing structures). Recent molecular evidence suggests, however, that
Psilotum is not as primitive as most people believed and is simply a reduced fern.
2. Pisonia umbellifera — “para-para”, lettuce trees (Nyctaginaceae)
Found on many old world islands including Mauritius, New Zealand, and Bonin Islands. Most species in the genus
become quite tree-like with cabbage or lettuce like leaves. The fruits are glandular and represent a LDD mechanism
(bird-viscid) to remote islands. Fruits often used to snare or entrap birds.
Greenhouse 3
3. Wollemi nobilis — Wollemi pine (Araucariaceae)
This monotypic genus (it is not a pine, nor in the pine family) was discovered in 1994 in the rugged Blue Mountains
NW of Sydney, Australia. Only 39 adult plants are known from the wild. Pollen analysis shows this species is more
closely related to a widespread fossil in Australia than it is to the two other extant genera in the family (Araucaria
and Agathis). Since its discovery, unauthorized visits to the secret wild population have introduced a non-native root
rot fungus that threatens the survival of this relict and "living fossil" species.
4. Cocos nucifera — coconut (Arecaceae)
The coconut palm is the only species in the genus Cocos, and is a large palm, growing to 30 m tall. The coconut has
spread across much of the tropics, probably aided in many cases by seafaring people. In the Hawaiian Islands, the
coconut is regarded as a Polynesian introduction.
Greenhouse 4
5. Dioon, Zamia, Cycas — cycads (Phylum Pinophyta or Cycadophyta)
Cycads are a relictual group of gymnosperms once much more prominent in the Earth's flora (Triassic & Jurassic)
where they co-existed with dinosaurs. Many species today are very local endemics and critically endangered. The
flat leaves of cycads have given rise to false accounts of angiosperm fossils well before the Cretaceous.
6. Polypodium sp. — ferns (Phylum Pteridiophyta)
Ferns are notoriously great dispersers to islands due to their small, air-borne spores. Some of the first colonists of
Krakatau were ferns. Ferns represent a larger than expected proportion of the Hawaiian flora, although they show
considerably less endemism.
Greenhouse 5
7. Navia sp. — a bromeliad (Bromeliaceae)
A closely related genus to Brocchinia and also found on tepui summits of the Guayana Highlands. This genus is
more species rich than Brocchinia, but it has apparently speciated not via “adaptive radiation” but rather through its
lack of dispersality (i.e., different populations on tepui summits become isolated and diverge).
Greenhouse 6
8. Marchantia polymorpha — liverwort (Phylum Hepaticophyta)
An example of what the earliest land plants might have looked like. Fossils from the Ordovician and early Silurian
indicate that non-vascular liverworts are the first recognizable land plants. Liverworts are now in their own phylum
as DNA indicates that liverworts are the first diverging lineage of extant land plants.
Greenhouse 7 (Desert House)
9. Aeonium tabuliforme — (Crassulaceae)
This spectacular genus of species primarily from the Canary Islands (Macaronesia) is a good example of island
plants that become woody. It is also succulent and possesses crassulacean acid metabolism (CAM), a type of
photosynthetic adaptation to high light and low moisture environments.
Part 2: Outdoors
University Ave. side of Birge Hall and outdoor Botany Garden
10. Metasequoia glyptostroboides — dawn redwood (Taxodiaceae)
This tree is a bona fide living fossil in the sense that fossils of the genus had been collected (though misinterpreted
as Sequoia or Taxodium) long before the living plant was discovered in China in 1941. Though presently narrowly
endemic to a small area of central China, fossils are known from the Tertiary of Europe, Greenland and the United
States as well as Asia. Compare this plant to Sequoia, which has a similar paleo-distribution but is now confined to
the Pacific Northwest. Although its leaves resemble those of an evergreen tree (like Sequoia) it is actually
deciduous, dropping whole "twigs" of leaves in the fall.
11. Liriodendron tulipifera -- tulip tree (Magnoliaceae)
This species and L. chinense, the only other species in the genus, form one of the most famous Eastern Asia Eastern North American disjunctions. Unmistakable Tertiary fossils of the genus are known from the western U.S.,
Greenland, Iceland, and continental Europe. Although these species must have been out of genetic contact for well
over 10 million years, artificial hybrids between the two species have been made. The tulip tree is characteristic of
the mixed mesophytic forest to the south and east of Wisconsin (SW Michigan for example), but our winter low
temperatures are too extreme to allow the tulip tree (as well as redbud and flowering dogwood) to survive in the
wild in the state.
12. Ginkgo biloba — ginkgo (Ginkgoaceae)
Ginkgo has an extensive fossil record first known from the Jurassic (180mya) and still extant in the western United
States into the Miocene and in Europe as late as the Pliocene. Long thought to be extinct in the wild, apparently
natural populations of this tree have recently been discovered in eastern China. A recent phylogeographic study
suggests two areas of Pleistocene refuge in China. The Botany Garden has a pair of Ginkgo trees, male and female.
13. Magnolia sp. — magnolia (Magnoliaceae)
Long thought to be the most primitive of flowering plants (angiosperms), recent molecular studies have identified
other, more ancient groups of angiosperms. However, the fossil record for the genus Magnolia still stretches back
almost 100 million years. During the middle of the tertiary (30-40 mya), when the large epicontinental sea covered
large portions of what is now Midwest North America, magnolia fossils are found as far north as Wyoming.
Magnolias are classic examples of the Arcto-Tertiary disjunct pattern, being currently found in eastern North
America and eastern Asia, but with a fossil record demonstrating a continuous north temperate distribution during
the Tertiary. Magnolias are characteristic of the southeastern U.S. deciduous and semi-evergreen forests, but do not
occur natively in Wisconsin.
14. Cercidiphyllum japonicum — Katsura tree (Cercidiphyllaceae)
Although this plant would appear to have female floral parts composed of several free carpels (apocarpous),
anatomical studies have shown that each female flower consists of a single ovary, the inflorescences being so
contracted that they resemble a single flower. Though now endemic to China and Japan, Cercidiphyllum is known
from Tertiary deposits of the western United States, Greenland, Spitsbergen and elsewhere.
15. Ulmus americana — American Elm (Ulmaceae)
The genus Ulmus (elms) currently occurs in north temperate regions (Asia, Europe, and North America). As are
most deciduous trees, elms are wind pollinated. Elm seeds are also wind dispersed, as is evidenced by the wings
surrounding the seed (there should be some on the ground beneath the tree). The distinctive leaves and fruit of this
genus are well represented in the fossil record and were an important part of the Arcto-Tertiary flora. The
architecture of this tree has made it a very popular tree for lining streets and long promenades (see Bascom Hill).
Unfortunately, dutch elm disease, a fungus which attacks and ultimately kills the tree was introduced into North
America during the mid-1900’s from eastern Asia. Elms were a very significant element of the eastern deciduous
forest (ranking in the top 5 most important species) prior to the introduction of the disease. Since that time, the
majority of American Elms have been affected by the invasion of this fungus.
Part 3: Fossils
Room 256, Birge Hall
16. Lepidodendron — a giant lycopod (related to extant “clubmosses” of Lycopodiophyta) of the equatorial coal
swamps. [Carboniferous]
17. Calamites — a tree-like horsetail (or “sphenopsid” of the once recognized Equisetophyta, and now in
Pteridiophyta or ferns) of the equatorial coal swamps. [Carboniferous]
18. Delnortea (seed fern) — An example of the once diverse and now extinct lineage of woody plants with fern-like
leaves but producing seeds like gymnosperms and angiosperms. This fossil genus is restricted to the north-central
shales of Texas. [Permian]
19. Metasequoia (dawn redwood) — see #10 above. Compare this to the adjacent Sequoia fossil.
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