Spatial Autocorrelation of Tree Phenological Timing in a Neotropical Perhumid Forest

Abstract

Whether the timing of tropical tree phenophases is spatially structured at the within-stand scale and whether such structure depends on the sexual system is essentially unknown. Using ten years of weekly records from 377 trees of 32 species across 20 transects in a perhumid forest at Los Tuxtlas, Mexico, we removed each species’ seasonal signal and quantified the correlation of the resulting timing anomalies between conspecific trees as a function of inter-tree distance, within hermaphroditic, polygamous and dioecious species separately. Conspecific similarity decayed with distance for every phenophase, confirming short-range spatial autocorrelation of timing. The signal was strongest and most consistent for young-leaf flush, whose within- versus between-transect gradient was positive in 28 of 29 species across all three sexual systems. Across the reproductive sequence, the imprint was about half as strong and did not vanish toward ripening: in hermaphrodites, flowers, unripe and ripe fruits all retained a significant gradient. A model of the gradient found a significant phenophase effect but no effect of sexual system. We interpret the leaf-flush signal as a microsite imprint on environmentally cued initiation that is diluted, but not erased, by developmental pacing and that is independent of how reproductive function is partitioned among individuals.