Phenology and flowering periodicity of Neotropical dry forest species: Evidence from herbarium collections

To examine the potential contribution of herbarium material to the description and analysis of tropical tree phenology, flowering times and geographical distribution were graphed for 1673 flowering collections from 18 species native to Neotropical dry forests and phenological differences between species were analysed. These include the timing and duration of flowering as well as morphological differences such as flowering on leafless twigs vs flowering on shoots bearing old or new foliage. Species-specific flowering periods of herbarium collections are similar to those observed in phenological field studies, but are often longer because of the larger geographical and temporal sampling range. Conspecific collections of different geographical origin show distinct differences in flowering periodicity, which are correlated with differences in the timing and intensity of the dry season. Interspecific differences in the timing of phenology relative to the dry season indicate differences in the control of phenology by seasonal drought. Herbaria thus represent a large potential source of phenological information which can either supplement and extend phenological field studies or provide phenological information for dry forest species not studied in the field but well represented in herbarium collections.