Revealing an Endemic Herbivore-Palm Interaction in Remote Desert Oases of Baja California

Elisabet V Wehncke,Xavier López-Medellín,Exequiel Ezcurra,Michael Wall

doi:10.4236/ajps.2013.42a060

Abstract

In the Central Desert of northern Baja California, blue fan palm populations (Brahea armata) are found as isolated oases on mountaintops and along canyons with ephemeral flow conditions. Here, the effect of the interaction between the larva of an endemic moth, Litoprosopus bajaensis, and this endemic blue fan palm was documented for the first time. We registered the phenology of palms by counting the number of shoots with flowers or fruits, assessing their damage and calculating the reproductive success per individual palm within three populations: San Pedro Martir, Catavi?a, and La Libertad. Palm populations were severely impacted by this larva, causing high damage to the inflorescences. No differences were found in the number of inflorescence stems produced and damaged among study sites; but the reproductive success of palms was significantly higher in Catavi?a than in the other sites during the entire sampling period, and consequently an important proportion of stems escaped from the herbivore predation. We suggest that differences among sites may be explained by the fact that Catavi?a is the only alluvial canyon and can be considered an area of high nutrient uptake, resource availability, and rooting depths. In contrast the other two are bedrock canyons, where water runs intensely, sweeping away great portions of the nearby vegetation. Catavi?a received the highest precipitation during the winter season of 2010 allowing a continuous production of inflorescence stems and fruits. This preliminary study reveals a new endemic interaction, it occurrence at population and regional levels, and highlights the role of desert oases as resource patches and connectivity pathways for mobile insects. Finally, it also highlights the effects of different water flow dynamics and water pulses in providing an opportunity window of escape from predation for host plant species living in desert environments.

Highlights

A fundamental goal in the study of herbivore-plant interactions is to understand how and under what circumstances insect herbivory affects the fitness and dynamics of plant populations
Brown and Faulkner described in 1997 six adults of Lepidoptera collected in the Cataviña area, and named it Litoprosopus bajaensis an endemic species of the Central Desert Region, no information existed about the natural history of this species
The occurrence of this water pulse might help explain the continuous stem and fruit production in the Cataviña site. This preliminary study reveals and evaluates the impact of a new blue fan palm-insect herbivory interaction at the population and ecosystem level and shows the role of desert oases as resource patches and corridors for insects. It represents the first record of a damage produced by an insect that strongly affects the fitness of the blue fan palm populations

Summary

Introduction

A fundamental goal in the study of herbivore-plant interactions is to understand how and under what circumstances insect herbivory affects the fitness and dynamics of plant populations. The distributions of insect species can be influenced by individual traits such as dispersal ability, sexual attraction, or aggregation [6,7], by habitat factors such as resource density and heterogeneity [8], and by temporal climatic variations [9], such as peaks or pulses of water. Habitat fragmentation or how resources are distributed in space and time has important effects on insect population dynamics [10]. When habitat is fragmented the dispersal behavior of insects explains much of the variation of population densities throughout the resource patches [11]. The link between ecological processes and spatial patterns is of the outmost importance in the conservation of endangered species as well as in pests and invasions control by relating the spatial distribution of both, insect populations and resources to damage [12,13,14]

Methods

Results

Conclusion