USING HERBARIUM DATA TO INCREASE THE LIKELIHOOD OF FINDING FERTILE PLANTS IN THE FIELD

The Phenological Predictability Index (PPI) is an algorithm incorporated into Brahms, one of the most widely used herbarium database management systems. PPI uses herbarium specimen data to calculate the probability of the occurrence of various phenological events in the field. Our hypothesis was that use of PPI to quantify the likelihood that a given species will be found in flower bud, flower or fruit in a particular area in a specific period makes field expeditions more successful in terms of finding fertile plants. PPI was applied to herbarium data for various angiosperm species locally abundant in Central Brazil to determine the month in which they were most likely to be found, in each of five areas of the Distrito Federal, with flower buds, flowers or fruits (i.e. the ‘maximum probability month’ for each of these phenophases). Plants of the selected species growing along randomised transects were tagged and their phenology was monitored over 12 months (method 1), and two one-day field excursions to each area were undertaken, by botanists with no prior knowledge of whether the species had previously been recorded at these sites, to record their phenological state (method 2). The results showed that field excursions in the PPI-determined maximum probability month for flower buds, flowers or fruits would be expected to result in a > 90% likelihood of finding individual plants of a given species in each of these phenophases. PPI may fail to predict phenophase for species with supra-annual reproductive events or with high event contingency. For bimodal species, the PPI-determined maximum probability month is that in which a specific phenophase is likely to be most intense. In planning an all-purpose collecting trip to an area with seasonal plant fertility, PPI scores are useful when selecting the best month for travel.