Research: Shade coffee promotes genetic diversity of native trees

by JulieCraves on December 26, 2008

Shade coffee farms promote genetic diversity of native trees. 2008. Jha, S. and C. W. Dick. Current Biology 18:R1126-1128.

Chestnut-sided Warbler in winter plumage.

This study looked at genetic differences and gene flow in an understory shrub, Miconia affinis, in a 1200  ha matrix of forest and shade coffee farms in Nueva Alemania, Chiapas, Mexico. Birds are extremely important as agents of seed dispersal in tropical ecosystems. The authors wanted to explore how shade coffee farms — with their attendant suite of vertebrate seed dispersers such as birds, bats, and mammals — might act as corridors or reservoirs promoting healthy gene flow in trees. Other studies have indicated that limited seed dispersal in fragmented landscapes results in inbreeding and demographic declines in tree populations.

Clay-colored Thrush.

Genetic analyses showed that the Miconia in the coffee farms were genetically diverse, and came from multiple source populations. Clusters of Miconia in the forest were actually more closely related to each other than the clusters on coffee farms. The authors speculated that this may be due to the short foraging ranges of birds that specialize in forest habitats, versus the birds found in shade coffee, which are often wide-ranging generalists. [Note that the interpretation of this aspect in the Science Daily article is somewhat misleading. The paper stated that Miconia seeds are spread by birds such as the resident Clay-colored Robin (Turdus grayi) and the migrant Chestnut-sided Warbler (Dendroica pensylvanica), a North American breeder than winters in the tropics. The SD article said that the warbler is a short-ranging forest specialist responsible for limited seed dispersal in forests; this was not stated in the paper.]

The authors conclude that “[S]hade coffee farms support extensive dispersal processes crucial for the connectivity of remnant forest and agricultural habitats…[and they play a role] as potential foci of native forest regeneration.”

Chestnut-sided Warbler by Jerry Oldenettel. Clay-colored Robin by Arthur Chapman.

S. Jha, C. Dick. (2008). Shade coffee farms promote genetic diversity of native trees. Current Biology, 18 (24) DOI: 10.1016/j.cub.2008.11.017

Revised on November 14, 2019

Posted in Research on coffee growing

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