Implication of demographic data of rediscovering Eugenia fajardensis (Myrtaceae), a possibly endangered species

Background/Question/Methods

Biodiversity is being lost at unprecedented rates requiring more than ever the study of endangered species. Meaningful recovery programs for threatened and endangered species necessarily require gathering comprehensive information about their life cycle. The ecology chapter AKKA SEEDS began a project funded by ESA-SEEDS to generate baseline data on the ecology of the tree species, E. fajardensis.The species was re-discovered in 2005 and only three small populations are known to date.  State officials are preparing to list the species as endangered based on its abundance and restricted distribution but little is known about the ecology of this species, except that is has an extremely restricted distribution.. In December 2013, AKKA SEEDS tagged all individuals found in North Eastern Corridor (NEC) reserve, the largest population of this species in Fajardo Puerto Rico. The population was visited monthly to evaluate various demographic aspects including the distribution and growth rate of different stage categories (seedlings, juveniles and adults), the timing of fruiting and flowering phenology and factors that may relate to the variation in the incidence of seedling herbivory (i.e. seedling size, seasonality).

Results/Conclusions

The population at NEC has 229 individuals with a pyramidal demographic profile characterized by an overabundance of seedlings relative to juveniles and adults.  Using previously reported size categories for the genus, only 19 individuals were adult plants and 46 were juveniles.  Adults and juveniles exhibited 0% mortality but there was a 10% mortality rate for seedlings.  Fruit production did occur in 2013 based on incidental observations of fruits on the forest floor but not in 2014 where only three adult plants flowered in September 2014 with no fruit production.  Seedlings exhibit high rates of herbivory by a variety of pest types (leaf miner, white flies and undescribed macro herbivores) but white flies were the only herbivore type to exhibit seasonality in its incidence.  For leaf miners and macro herbivores the incidence of herbivory increased with time. Results suggest that the number of reproductive individuals is much less that previously reported for this population and that while the population size might be increasing, downward fluctuations are expected due to mortality factors at the seedling stage what seems to be an erratic reproductive cycle for this species.  Our results emphasize that while the population occurs in a highly protected area, there is a need to monitor how ecological factors may influence the demographic stages to determine if indeed this population is growing.