A fundamental goal in herbivore-plant interactions is to understand how and under what circumstances insect herbivory affects the fitness and dynamics of plant populations. Understanding connections between plant defenses, herbivory and environmental conditions in boundary areas have recently raised special attention for the preservation of biodiversity. Although occasional large effects of insect herbivore are documented, evidence of the direct effects of herbivory on desert or semi-arid plants, particularly the long-lived dominant species, is limited. In 1997, Brown and Faulkner described six adults of an endemic Lepidoptera, Litoprosopus bajaensis of the Central Desert Region. Between July 2009 and September 2010 we documented the impact produced by the larva of this moth on blue fan palm inflorescences of three desert oases areas of northern Baja California, San Pedro Martir, Cataviña, and La Libertad. During four sampling periods we registered the phenology of palms and the total number of shoots with flowers, fruits, and with damage, and calculated the total shoots produced by each palm. Four hectares were censed in SPM and LL, and two in Cat.
Results/Conclusions
The damage caused by the caterpillars to the inflorescences was very high in all three areas at the peak of palm flowering (89%, 62% and 95% palms with inflorescences damaged in SPM, Cat, and LL, respectively). As the number of palms showing shoot damage increased, the number of palms with fruits decreased drastically with time in SPM and LL, but not in Cat where the proportion of palms with fruits remained more or less constant during the entire sampling period. Similar results were observed when the mean number of shoots with flowers, fruits, damaged, and produced were analyzed. Even though damage was present in Cat, palms did not stop to produce shoots along the sampling period. Cataviña is the only alluvial canyon and it can be considered as an area of high availability of resources. Since changes in blue fan palm distributions may produce cascading effects on the entire ecosystem, revealing and evaluating the impact of a new blue fan palm-insect herbivory interaction at the population and ecosystem level, will help to understand the level of species responses to fluctuating environments. This represents the first record of palm-insect interaction occurring that strongly affects the fitness of blue fan palm populations. Our study stresses the importance of supporting long-term studies that would help in detecting and predicting the impacts of environmental changes on desert ecosystems.