Navigation Links
Herbivores select on floral architecture in a South African bird-pollinated plant

Floral displays, such as the color, shape, size, and arrangement of flowers, are typically thought to have evolved primarily in response to selection by pollinatorsfor animal-pollinated species, being able to attract animal vectors is vital to an individual plant's reproductive success. But can herbivores also exert similarly strong selective forces on floral characters? New research on two sister species in South Africa suggests that this may indeed be the case for inflorescence architecture in the rat's tail plant, Babiana ringens. By modifying the primary location of its floral display in response to pressure from mammalian herbivores, B. ringens may have not only reduced floral herbivory, but may also have enhanced pollination by providing a specialized perch for its principal pollinator.

Endemic to the Cape region of South Africa, Babiana ringens produces bright red flowers that are situated close to the ground on an unusual inflorescence axis that protrudes above the floral display. Its primary pollinator, the malachite sunbird, is attracted to the flower's red color and abundant nectarthe color, shape (tubular), and size of the flowers indicates that these characters likely evolved in response to sunbirds. In previous research, Bruce Anderson (University of Stellenbosch, South Africa) and colleagues discovered that the protruding modified inflorescence axis serves as a perch for sunbirds, allowing them to turn upside down in a perfect position to access nectar and facilitate pollination.

In Babiana ringens, the inflorescence axis is modified such that growth of the apical side branches is suppressed and flowers are only produced on a single branch at the ground level. A close sister species, B. hirsuta, exhibits similar inflorescence morphology, except that flowers are produced on side branches all along the stalk and not just at the base.

Caroli de Waal, a graduate student at the University of Toronto, was intrigued by how the bird perch in B. ringens may have originated. This required determining the potential selective forces responsible for influencing the inflorescence architecture in the two Babiana species. Based on field observations, De Waal and colleagues investigated whether herbivory might have played a role in the evolution of this unique bird perch. Their findings were recently published in the American Journal of Botany (

"It is hard not to be curious about the origin of the curious rat's tail of Babiana ringens, which is unique in the flowering plants," commented Anderson.

"We noticed that in populations of the sister species, B. hirsuta, many plants had suffered damage from herbivores, with the upper portions of the stems completely eaten off," De Waal noted. "We then started to wonder: what if herbivory could contribute to selection for the floral display in B. ringens?"

Given the close phylogenetic relatedness of these species and their similar floral morphologies and pollinators, De Waal and colleagues hypothesized that the specialized bird perch in B. ringens may have originated from a B. hirsuta-like ancestor through reduction in the production of the side branches. This could happen if mammalian herbivores preferentially eat apical flowers and left the basal flowers alone.

Indeed, when De Waal and co-authors compared herbivory rates in three B. hirsuta and three B. ringens populations, they found much higher levels of herbivore damage to B. hirsuta---as much as 53% of the inflorescences were eaten. Moreover, they found that Cape grysbok (the primary herbivore) mostly grazed the top parts of inflorescences, leaving the basal parts to continue flowering. In comparison, herbivory in B. ringens was much lower and the ground-level flowers were never eaten.

To further test their idea, De Waal and colleagues conducted a field experiment with B. hirsuta in which they manipulated flower position along the stalk they removed side branches in plants so that they displayed either flowers only at the top or only at the bottom of the stems (the latter resembling the display of B. ringens). Using cages, they then excluded herbivores from half of the treatments.

"Our most important result," De Waal stated, "is that flowers at the tips of stems were eaten by browsing antelope, whereas flowers at ground-level were consistently ignored." Notably, this was even the case for plants that were not protected from herbivores by cages, yet were manipulated to have only ground-level flowers.

"Significantly, plants with only ground-level flowers produced more seeds," she said. "This means that plants that manage to escape damage by herbivores also have higher reproductive success, and this may be the reason why B. ringens evolved its unusual ground-level flowers."

Moreover, Anderson adds, "The overwhelming herbivore preference for plants with only apical flowers indicates why plants like B. ringens, with basal flowers, could have evolved while plants with only apical flowers would be maladapted."

"Our results indicate that in addition to pollinators, herbivores can also be important selective agents on inflorescence architecture," concluded Anderson. "This is significant because most scientists have attributed variation in floral display to selection by pollinators and the importance of herbivores is often forgotten."

Contact: Richard Hund
American Journal of Botany

Related biology news :

1. Minneapolis Heart Institute selected to participate in Cardiovascular Cell Therapy Research Network
2. Elsevier selected as new publisher of the American Journal of Geriatric Psychiatry
3. Financial tool considered climate change uncertainty to select land for conservation
4. Mesquite trees displacing Southwestern grasslands
5. FirstMark Announces New Hire Jay Houtman as Southeast Regional Sales Manager
6. Southampton researchers lead 2 international projects to help people out of poverty
7. Bark beetle management and ecology in southern pine forests
8. Beetle-fungus disease threatens crops and landscape trees in Southern California
9. Latest Southern Ocean research shows continuing deep ocean change
10. UNH researchers find African farmers need better climate change data to improve farming practices
11. Treatment to benefit African infants at risk of endemic fever
Post Your Comments:
Related Image:
Herbivores select on floral architecture in a South African bird-pollinated plant
(Date:11/4/2015)... --> --> ... Transparency Market Research "Home Security Solutions Market - Global Industry ... 2022", the global home security solutions market is expected to reach ... market is estimated to expand at a CAGR of ... Rising security needs among customers at homes, the emergence ...
(Date:10/29/2015)...  The J. Craig Venter Institute (JCVI) policy group ... Biosecurity: Lessons Learned and Options for the Future," which ... Services guidance for synthetic biology providers has worked since ... --> --> Synthetic biology promises great ... pose unique biosecurity threats. It now is easier than ...
(Date:10/29/2015)... , Oct. 29, 2015  Connected health pioneer, ... driving the explosion of technology-enabled health and wellness, and ... new book, The Internet of Healthy Things ... sensors or smartphones even existed, Dr. Kvedar, vice president, ... of health care delivery, moving care from the hospital ...
Breaking Biology News(10 mins):
(Date:11/25/2015)... Md. , Nov. 25, 2015  PharmAthene, Inc. ... Directors has adopted a stockholder rights plan (Rights Plan) ... net operating loss carryforwards (NOLs) under Section 382 of ... --> PharmAthene,s use of its NOLs ... "ownership change" as defined in Section 382 of the ...
(Date:11/25/2015)... 25, 2015 Studies reveal the ... plaque and pave the way for more effective treatment for ...     --> --> ... health problems in cats, yet relatively little was understood about ... studies have been conducted by researchers from the WALTHAM Centre ...
(Date:11/25/2015)... 25, 2015  Neurocrine Biosciences, Inc. (Nasdaq: NBIX ... and CEO of Neurocrine Biosciences, will be presenting at ... New York . .   ... approximately 5 minutes prior to the presentation to download ... presentation will be available on the website approximately one ...
(Date:11/25/2015)... ... November 25, 2015 , ... A long-standing partnership between ... (OPBAP) has been formalized with the signing of a Memorandum of Understanding. , ... leaders Capt. Karl Minter and Capt. Albert Glenn Tuesday, November 24, 2015, at ...
Breaking Biology Technology: