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.
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).
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.