Research: Pollination and fruit set in India

by on June 19, 2012

ResearchBlogging.orgStatus of pollinators and their efficiency in coffee fruit set in a fragmented landscape mosiac in South India. Krishnan, Kushalappa, Shaanker, and Ghazoul. 2012. Basic and Applied Ecology 13:277-285.

The role of various types of pollination — self, wind, and insect — on robusta coffee (Coffea canephora) was studied in the Kodagu (Coorg) region in Karnataka state in south India. Robusta coffee is generally thought to be wind-pollinated, with fruit set being enhanced if cross-pollinated by insects.

Many insects (as well as other arthropods and birds) can act as pollinators, but in this study bees made up nearly 97% of the floral visitors to the coffee. The main pollinator was the giant Asian honeybee (Apis dorsata, a relative of the familiar European honeybee).  Apis cerana and Tetragonula iridipennis were the other two bee species that most frequently visited coffee flowers, and together with the giant Asian honeybee comprised 98.3% of all visits to coffee flowers. While pollination can occur from wind, bee pollination increased fruit set by 50% over wind.

Amegilla bee on lantana. This genus of bees were once common in coffee plots, but now feed on non-native lantana flowers. Photo from Wikimedia Commons.

The authors noted that in other countries studied, the suite of pollinators usually comprised of many more species, rather than being dominated by so few as in the present study. They looked at a similar, though limited, study of pollinators of coffee done in the same area in 1915.  In that study, Apis cerana was the most common; this species has recently (early 1990s) declined due to a virus. The older study listed the second most abundant bees pollinating coffee as those in the genus Amegilla; in the present study these made up a mere 0.1% of visits.  The authors observed Amegilla bees foraging instead on a non-native invasive plant, Lantana camara. This indicates that invasive species may change the behavior of coffee pollinators — and this role of invasive species deserves more study.

The giant Asian honeybees nest in nearby forests in large trees. The authors concluded that, given the high dependence on pollination by this species, preservation of these trees in remnant forests within the foraging range of the bee is crucial to the successful production of coffee in this area.

This post is in recognition of Pollinator Week, an international celebration of the valuable ecosystem services provided by bees, birds, butterflies, bats and beetles.

Smitha Krishnan, Cheppudira. G. Kushalappa, R. Uma Shaanker, & Jaboury Ghazoul (2012). Status of pollinators and their efficiency in coffee fruit set in a fragmented landscape mosiac in South India. Basic and Applied Ecology: dx.doi.org/10.1016/j.baae.2012.03.00

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Revised on June 15, 2013

Posted in Research on coffee growing

{ 2 comments… read them below or add one }

T R Shankar Raman July 19, 2012 at 12:51 am

Hi,
This is an important piece of research emerging from India. The DOI link provided in your article seems incomplete, the correct link is here: http://dx.doi.org/10.1016/j.baae.2012.03.007

The influence of remnant forests on bee abundance, visitation, and pollination is another noteworthy aspect in this research, taken along with another recent study by the team from the same landscape:
Impact of forest fragments on bee visits and fruit set in rain-fed and irrigated coffee agro-forests
Virginie Boreuxa, Smitha Krishnan, Kushalappa G. Cheppudira, and Jaboury Ghazoul
Agriculture, Ecosystems & Environment
http://dx.doi.org/10.1016/j.agee.2012.05.003

Retaining remnant forest patches is shown to be useful in promoting pollination and pollinator abundance is linked to fruit set. Still, the direct relationship between forest patches (size and distance) and fruit-set is complex and influenced (or confounded) by irrigation and other factors, as established in the latter study.

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JACraves July 19, 2012 at 6:27 am

Thanks for bringing attention to the second paper — it is on my desk but I have not gone over it yet. I find so much of the research coming out of India extremely interesting and worthwhile!

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