Photos from the Field: Peguero & Espelta 2014
Guille Pegueroand Josep M. Espelta. 2014. Endozoochory and Fire as Germination Triggers in Neotropical Dry Forests: an Experimental Test. Biotropica 46(1): 83-89.
Endozoochory and fire are crucial ecological factors determining germination success and recruitment in many plant species. Fire is a well-known germination trigger while endozoochory may allow seed dispersal along with an increase in germination. Their interaction has rarely been addressed, however, even though both factors are pervasive in human-transformed ecosystems like most Neotropical Dry Forests (NDF). For three common Mesoamerican tree species (Acacia pennatula, Enterolobium cyclocarpum, and Guazuma ulmifolia), we used feeding trials to assess the preference of cattle, which are their main seed dispersal agent. We also experimentally tested the interaction between gut passage and fire as triggers of germination. The fruits of the three species were eaten by cattle, but the small seeds of G. ulmifolia were ingested 10-fold more than those of the other species. While gut passage did not have any effect on germination, heat-shocks above 90 °C increased the number of germinating seeds by 15 percent. These results suggest that cattle may be a key dispersal vector in NDF, but that fire may be an important germination trigger. Physical dormancy in these species may have been selected for by extinct megaherbivores because it was a key trait ensuring seed survival after gut passage. However, in light of the recent expansion of cattle-ranching and fire occurrence in NDF, it has become a useful exaptation facilitating the colonization of disturbed areas.