Spatial relationship between conspecifics
Even though dispersal limitation is common in tropical forests (Hubbell,
2005) and habitat filtering is expected to influence species
distribution in harsh environments (Baraloto et al. , 2007), these
processes only drove the spatial associations between small/medium and
large trees of M. multiflora. Dispersal limitation drives the
spatial relationship between small and large trees and, as trees grow,
habitat filtering also becomes important for this species, which agrees
with the stronger associations (i.e. higher Z values) of medium
and large trees to environmental variables. Note that we estimated for
this species the smallest width of the kernel function (σ = 9 mvs . 15 m and 20 m for the other two congeners) of the dispersal
limitation model. Although it is consistent with species height
(occupation in different canopy strata), we cannot exclude the
possibility that the size of our plot is too small to allow for the
detection of the effects of dispersal limitation for M.
brasiliensis and M. racemosa .
Spatial independence between small and large trees was also found by
Getzin, Wiegand, and Hubbell (2014) in Barro Colorado Island, Panama.
The authors suggested that this pattern could be habitat-association
masked by unpredictable dispersal events created by disperser movement
behaviour or uncoupling the positive association of trees expected from
dispersal limitation due to high mortality of seeds and early
development stages. Negative density dependence caused by the attack of
species-specific natural enemies (Janzen, 1970; Connell, 1971) or by
intraspecific competition among seedlings (Wright, 2002) poses high
offspring mortality close to parent plants. Additionally, the spread of
natural enemies and competition from parents are major mortality causes
of seeds and seedlings in tropical forests (Fricke et al. , 2014).
A future venue is to assess seed distribution around large trees and
mortality through size classes in order to better understand
intraspecific spatial patterns.