We’re starting a new experiment this year to test for a phylogenetic Janzen-Connell effect across seasons on seeds dispersed by lemurs.

A phylogenetic Janzen-Connell effect (Liu et al. 2012) refers to a high mortality of seeds / seedlings beneath a closely related adult-tree because some natural enemies such as herbivores and pathogens may specialize on closely related host-species (due to a phylogenetic conservatism in the plants’ defense and susceptibility traits).

Using seed dispersal by lemurs in Ranomafana National Park as a model system, this project will test for phylogenetic Janzen-Connell effects and determine whether such effects vary across seasons.

setting-up experiments in Valohoaka

In 2012-13, we have already conducted an experiment inside the forest in dry and wet season using seeds of four co-fruiting plant species per season. Each experimental plot was made of cages with 10 seeds of the same species, and set-up under trees along a gradient of phylogenetic relatedness (i.e. under trees that are conspecific, closely related and distantly related to the seed species).

hole dug by rodents to access seeds in experimental cages

Unfortunately, we found almost complete post-dispersal seed predation and removal by presumably rodents, which always found a way to access the caged seeds (a project examining rodent effect will also be started this year). Thus, this year, we will conduct our experiment in a nursery that we will set-up adjacent to the forest.

Updates from the field will be added soon …



Liu, X., et al., Experimental evidence for a phylogenetic Janzen–Connell effect in a subtropical forest. Ecology Letters, 2012. 15(2): p. 111-118.