Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Do plant species really exist? Why, yes, scientists say

23.03.2006


Are plant species real or imaginary? Many botanists have argued grouping plants into species is merely an exercise of convenience.Credit: Robert Czarny


Notoriously "promiscuous" plants like oaks and dandelions have led some biologists to conclude plants cannot be divided into species the same way animals are.

That perception is wrong, say Indiana University Bloomington scientists in this week’s Nature. Their analysis of 882 plant and animal species and 1,347 inter-species crossings -- the first large-scale comparison of species barriers in plants and animals -- showed that plant species are just as easily categorized as animal species.

The study also yielded a surprise. The hybrid offspring of different animal species are more likely to be fertile than the hybrid offspring of plant species.



"Not only are plants just as easily subdivided into species as animals when analyzed statistically, plants are more likely to be reproductively isolated due to hybrid sterility," said evolutionary biologist Loren Rieseberg, who led the study. "Most plant species are indeed ’real.’ The problem has been that botanists have been way over-attracted to the plant species that readily hybridize and where the hybrids perpetuate themselves asexually. While it’s true that dandelions and blackberries pose problems, these horror stories only make up 1 percent of the whole."

The scientists did find categorization problems with nearly half of the plant and animal species they surveyed.

Rieseberg and his co-authors, doctoral student Troy Wood and postdoctoral research associate Eric Baack, examined hundreds of peer-reviewed papers reporting the measurement of various plant and animal characteristics, or reporting on the success or failure of hybridization of plant and animal species with similar species. The scientists culled the papers for information, grouped and combined data for each given species, and then looked at how often characteristics clustered in accordance with named species.

The scientists found that while real, quantifiable clusters did exist in most groups of plants and animals, the one-to-one correspondence of species names and character clusters was quite low -- about 54 percent. One explanation for this, Rieseberg said, is that too many taxonomists are "splitters" -- they give too many species names to a single group of related organisms.

After analyzing the hybridization data, the scientists found that only 30 percent of the approximately 500 plant species they surveyed are able to produce fertile hybrids when mated with other species. By stark contrast, 61 percent of animal species surveyed are able to reproduce successfully with other species.

The hybridization of animal species is often portrayed as rare and strange, or else the result of human-forced matings, as is the case with ligers (lion-tiger hybrids) and mules (horse-ass hybrids). It is not common knowledge that many bird and fish species successfully hybridize in the wild. The scientists found that birds were most likely to produce fertile hybrids when crossed with other bird species. Ferns, of all things, were least likely to generate fertile hybrids.

Many of the hybridization papers that Rieseberg, Wood and Baack looked at reported crossings under laboratory conditions, and therefore the crossings may not accurately represent what happens in nature. For example, two species that can hybridize may not actually do so, perhaps because they exist on different continents or because they prefer to mate with members of their own species. For that reason, the percentages of plant and animal species that hybridize in the wild are likely to be lower than those reported by the scientists.

The Nature study is meant to address gaps in scientists’ knowledge in two areas: the fundamental nature of species and the divisibility of plant and animal species using commonly accepted definitions of species. Debates in both areas began with the 1859 edition of Darwin’s Origin of Species, and they have not yet been settled.

"These discussions should have been settled earlier, but no one bothered to summarize the relevant literature, perhaps because it is so vast," Rieseberg said.

Over the past 50 years, numerous scientific papers have been published in which species are categorized by statistical analysis of observable traits (i.e., numerical taxonomy) and/or by the ease with which species can be hybridized (i.e., breeding studies). "After going through all this literature, we realized someone just needed to compile and analyze it all," Rieseberg said.

The scientists decided to use the mass of data to see whether taxonomists were doing a good job, and whether cross-species mating in the plant kingdom is especially likely to be successful.

"The species concept debate has devolved from an empirical discussion into a philosophical one," Rieseberg said. "But this is fundamentally an empirical question. These data support the notion that species can be both units of evolution and products of evolution."

Rieseberg holds the Class of ’54 Chair and is a distinguished professor of biology at IU Bloomington. Troy Wood and Eric Baack also contributed to the report. It was funded primarily by a Guggenheim Fellowship grant. Supplementary support came from the MacArthur Foundation, the National Institutes of Health and the National Science Foundation.

Troy Wood | EurekAlert!
Further information:
http://www.indiana.edu

More articles from Life Sciences:

nachricht Climate Impact Research in Hannover: Small Plants against Large Waves
17.08.2018 | Leibniz Universität Hannover

nachricht First transcription atlas of all wheat genes expands prospects for research and cultivation
17.08.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>