Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Family tree for orchids explains their astonishing variability

04.09.2015

Orchids, a fantastically complicated and diverse group of flowering plants, have long blended the exotic with the beautiful. Most species live on trees, often in remote, tropical mountains. Their flowers can be strange -- one even flowers underground, and many species deceive their pollinators into thinking they are good to eat.

Some are florist's staples, like phalaenopsis, the hot-pink and white flower that is easy to grow and easier to sell. Beyond the "job" of looking beautiful, only the vanilla orchids have any commercial role.


The genus Mormolyca is native to Central America and nearby regions.

Credit: David Tenenbaum/University of Wisconsin-Madison

The estimated 25,000 orchid species outnumber mammals, reptiles and birds combined.

Previously, botanists have proposed more than a half dozen explanations for this diversity. Now, research from the University of Wisconsin-Madison, published last week in Proceedings of the Royal Society B, corroborates many of these explanations, but finds no evidence for other logical suggestions, such as that deceitful pollination.

"It was surprising that many classic characteristics of orchids -- the tiny, dust-like seeds, the role of fungi in triggering germination, the fused male-female flower parts that define the orchid flower -- did not trigger the acceleration in species formation," says Thomas Givnish, a professor of botany and first author of the new study.

To build a family tree for the orchids, the scientists sequenced genes in the green structures, called chloroplasts, in which plants transform solar energy into sugar. The researchers looked at chloroplasts from 39 species, strategically placed throughout the orchid family, then added genetic data on 150 more species. By tying their molecular family to fossils of known ages, Givnish and his colleagues created a branching structure that indicated how many million years ago each major group of orchids appeared.

Then, based on the numbers of species known in each of these groups today, the researchers were able to calculate the rate of species diversification in each and test the many putative causes of the explosion in orchid species. They found that the factors that most greatly accelerated the formation of new species were life in extensive mountain ranges (like the Andes and New Guinea Highlands); the evolution of epiphytism (life in the trees); pollination by orchid bees, moths, or butterflies; and origin of pollinia (packages of hundreds to thousands of pollen grains dispersed as a unit).

Givnish and his colleagues found that initially, orchids speciated no more rapidly than their closest relatives, and at a slow rate relative to flowering plants as a whole. Then there were three waves of accelerated speciation beginning 60, 40 and 33 million years ago. Pollinia apparently sparked the first acceleration in speciation, Givnish says. The origin of epiphytism -- and the invasion in tropical mountains with a constant swirl of clouds and rain -- sparked the second, greater acceleration. The invasion of the Andes as they were being uplifted triggered the third and greatest acceleration.

Interestingly, a surprising number of proposed explanations for orchid diversity failed the new test. Not even deceitful pollination (present in about one-third of all orchid species) was linked to accelerated speciation, Givnish says. "Orchids, almost alone among flowering plants, have a large number of species that lure pollinators by mimicking a mate, or a nesting site or food resources -- 'lies all for the sake of love' -- but such deceit seems to have played no role in accelerating the formation of new orchid species."

Chloroplasts were a useful source of DNA for the study, Givnish says. "There are thousands of chloroplasts per cell, and many loops of DNA per chloroplast, and the genome structure is quite stable." Mercedes Ames of the UW-Madison Department of Botany sequenced most of the chloroplast genomes.

Other UW-Madison collaborators included Daniel Spalink, Alejandro Zuluaga, and orchid specialist Kenneth Cameron, director of the Wisconsin State Herbarium. Collaborators in Australia and Chile provided DNA for the study, and W. Mark Whitten and Norris Williams of the University of Florida provided genetic data.

Looking at the orchids as a family, Givnish finds "not one spark for their extraordinary diversification, but many. Many hypotheses advanced by previous investigators proved to be correct, but some of the defining characteristics of orchids -- their tiny seeds, their requirement for fungi to germinate, and their fused pistils and anthers -- were not themselves responsible for the high rate of orchid speciation. Only later, when the orchids acquired pollinia, started to grow in trees, and then colonized the cloud forests along extensive mountain ranges in the tropics, did the orchids' unrivalled diversification begin."

###

DOWNLOAD PHOTOS: https://uwmadison.box.com/orchids

Media Contact

Thomas Givnish
givnish@wisc.edu
608-265-5473

 @UWMadScience

http://www.wisc.edu 

Thomas Givnish | EurekAlert!

More articles from Life Sciences:

nachricht A novel socio-ecological approach helps identifying suitable wolf habitats
17.02.2017 | Universität Zürich

nachricht New, ultra-flexible probes form reliable, scar-free integration with the brain
16.02.2017 | University of Texas at Austin

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>