natural history of the strangest plants in the world august 2003 hydnora africana, karasburg...
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Natural History of the Strangest Plants in the
World
Natural History of the Strangest Plants in the
World
August 2003Hydnora africana, Karasburg District, Namibia
Lytton John Musselman
Old Dominion University
Lytton John Musselman
Old Dominion University
Features of the family
Phylogeny of the family
Taxonomy
Floral biology
Diaspore
Features of the family
Phylogeny of the family
Taxonomy
Floral biology
Diaspore
Introducing the Hydnoraceae
Features of the Hydnoraceae
• No leaves or scales (unique among angiosperms)
• Subterranean holoparasites of semi-arid regions
• Relatively host specific
• Monocolpate pollen
Habit of Hydnoraceae
Succulent herbsAchlorophyllousObligate parasites
Systematic position of the Hydnoraceae has long
been debated due to extrememorphologial reduction.
Molecular data place Hydnoraceae with Aristolochiaceae
“Palaeoherbs”
Taxonomy
Only two genera comprisethe Hydnoraceae:
Hydnora and Prosopanche.
Hydnora-African
• H. johannis (=H. abyssinica)-widespread across Africa.
• H. africana-Restricted to southern Africa.
• H. triceps-found only in a small area along the Orange River in South Africa/Namibia.
• H. esculenta-Madagascar, a poorly known species.
• H. sinandevu-Kenya and Tanzania, described in 2002.
Hydnora-African
Prosopanche-New World
• P. americana -widespread on species of Prosopis (Fabaceae).
• P. bonacinae-Diversity of hosts.
Prosopanche-New World
Hydnora-Old World
Predicted distribution ofGondwanaland paleoherbs
Prosopanche
Prosopanche americana, Cordoba Province, Argentina
Hydnoraceae flowers are chamber flowers
A chamber is present abovethe stigma.
Chamber
Prosopanche americana
What is the function ofthe chamber?
Chamber
Prosopanche americana
For the insect--It provides a place for theinsect visitor to spend thenight. Mating often takes
place. Chamber
Prosopanche americana
For the plant--It provides a “holding room”
while the flower changessex.
Chamber
Prosopanche americana
Androecium
Gland
Stigma
Flower structure of Prosopancheamericana
Prosopanche americana
Prosopanche americana
Prosopanche americana
Pistillate phaseDay one
Prosopanche americana
Staminate phaseDay two
Prosopanche flowers aredichogamous, that is, have
distinctly staminate (male) andpistillate (female) phases.
Prosopanche americana
Pollinated by a nitulid (Neopocadius nitiduloides)
Oxycorynus spp. (weevils) lay eggs in flowers but are not pollinators
Life history of Prosopanche americana
Male phase
Female phase
Fruit
Host: Prosopis alba
Hydnora
Hydnora johannisAcacia spp. (Fabaceae)Beetles
Hydnora africanaEuphorbia spp.Beetles Hydnora
esculenta??????Hydnora triceps
Euphorbia dregeana???
Floral Syndromes and Hosts
OsmophoresHydnora africana-osmophores are elongate
Hydnora abyssinca-osmophores are tips of perianth
Hydnora triceps-osmophores arein folds of perianth
Oldest flowers on left
Is the osmophore in H. johannisunique?
Mature flower
Immature flower
Recent research on Hydnora triceps
Namaqualand
Namaqualand
Center of diamond dredging,
Port Nolloth
diamond smuggling….andHydnora diversity.
Succulent Karoo
• This biome is characterized by low but reliable rainfall (20-290 mm year), chiefly in the winter. It has the highest species richness for any semiarid vegetation and a high rate of endemism, exceeding 50% (Milton et al., 1997). The dominant plants in the sandy soil of these low hills are shrubby species of Euphorbia.
Rainy season, September 2001
Succulent Karoo near Port Nolloth, South Africa
Euphorbia dregeana,host of H. triceps
Dry Season, December 2002Dry Season, December 2002
Distribution of Hydnora africana is related to that of its common host, Euphorbia gregariaAssumption: true for other species as well.
History of Discovery
• Hydnora triceps first described by Drège in 1833 from material collected near Okiep in Namaqualand. Only ten specimens extant, all from the Okiep region.
• Last seen in 1888.
History of Discovery
• Johann Visser rediscovered H. triceps in 1988. Died shortly thereafter
• Eight populations located 1999-2001 in South Africa, near Port Nolloth.
• Discovered in Namibia in September 2001.
Namibia
South Africa
Previously known collections of H. triceps at red arrow
Rosh Pinnah--First Namibian collection
Orange River
Is the distribution of the parasite dependent uponthe host?
Hydnora triceps found only on E. dregeana
The sole evidence of Hydnora triceps
??
Hydnora triceps flowers underground!!
Hydnora triceps is the only known dicot with underground flowers!
Hypogeous floweringknown in only two genera
Rhizanthella gardneri Rogers, endemic to
Southwest Australia.
Hydnora triceps.
Hydnora triceps is dichogamous, that is, flowers are functionally pistillate the first day and functionally staminate
the second.
Stages in Development
Arrows indicate anthesis. Flowers to right are pistillate.
Stages in Development
Opening to chamber is openon day one
Day one
Stages in Development
Opening to chamber closes on day two
Opening to chamber is openon day one
Day two
Day one
Fruits previously unknown.
Fruits ofHydnoratriceps
Fruits hollowed out by unknown animal.
Hypogeous
floweringand fruiting known
only in H. triceps
Day one
Hydnora africana
Day oneDay two
Day one-PistillateDay two-Staminate
Day one
Day twoDay two plus
Closedantheral
ring.
Floral visitors can be trappedin flowers when ring closes.
Hydnora africana is dichogamous, that is, flowers are functionally pistillate the
first day and functionally staminate the second.
Fruit of Hydnora africana
Antheral ring does not closein H. johannis
Is H. johannis dichogamous?
Continuing research
--Determine pollinators and dispersers
--Study population structure
--Determine relationship among species
Meanwhile, back at home. . .
Can similar pollination syndromes befound in the Aristolochiaceae?
Aristolochia macrophylla
Hexastylis virginica
Aristolochia clematis
Note fused androecium
With Thanks to. . .
Piet Vorster, Department of BotanyStellenbosch University, Stellenbosch
Outstanding Hydnora hunter,Libby Musselman
Erika Maass, Department of Biology,University of Namibia,
Windhoek