Invasive shrub abundance predicts the abundance of common avian frugivores

Jason Gleditsch, Penn State

November 3, 2010 @ 01:20 pm to 02:10 pm

10 Tyson

Biological invasions pose one of the most severe threats to global biodiversity. Still, invasions can create positive ecological relationships and services, which can sometimes result in challenges for conservation efforts. A case in point is the invasion of alien plants that form mutualisms with native frugivorous birds. Here we examined the correlation between honeysuckles (Lonicera spp.) and the bird communities in a landscape of central Pennsylvania. We conducted point counts to quantify the abundance of birds and fleshy-fruited plant species within a 187.5 km2 landscape that included forested, urban, and agricultural lands. We also compared fruit-removal rates for a native fruiting plant under low and high Lonicera densities. The abundance of birds showed a strong positive association with Lonicera fruits, with the abundance of Turdus migratorius and Dumetella carolinensis showing the strongest correlations. We also found that fruit-removal rates increased by 30% for a native plant species in areas of high Lonicera density compared to a site with low density of Lonicera. Our results suggest that Lonicera may currently serve as a main axis for the organization of bird communities and the networks of frugivore-plant interactions in central Pennsylvania. Since populations of key bird frugivores may be currently depending on Lonicera resources, we argue that control measures should account for the negative effects that the loss of this fruit resource could have on populations of native consumers in highly invaded regions. To further understand Lonicera s role in local ecosystems, I propose that we continue to explore the effect that Lonicera invasions have on local bird populations. To do this we need to investigate how Lonicera invasions affect nesting behavior and to try to quantify the importance of Lonicera resources in the development of bird offspring.

Contact

Dan Grear
ecologyservice@psu.edu