What Is The Fate Of a Forest Without Vertebrate Frugivores? Merging Case Studies With Theory
Wednesday, August 7, 2013: 8:00 AM-11:30 AM
101F, Minneapolis Convention Center
Haldre S. Rogers, Rice University
Clare E. Aslan, Arizona-Sonora Desert Museum
Joshua J. Tewksbury, Future Earth
Frugivorous vertebrates are disproportionately prone to extinction due to wide range requirements and high hunting pressures (Peres 2001). In a range of habitats, researchers have examined “empty forests” (Redford 1992) resulting from such losses and have detected impacts (McConkey et al 2012). While a growing number of case studies have examined loss of vertebrate seed dispersers (e.g., Meehan et al. 2002, Cordeiro and Howe 2003), the studies have focused primarily on the species-specific effects of their loss. We lack a comprehensive understanding of the importance of vertebrates to forest communities, which is critically important for predicting the impact of vertebrate loss on ecosystems. Several species coexistence theories rely on dispersal to maintain species diversity, but there has been little application of this theory to predict the effects of disperser loss on species diversity.
Fundamental community changes may result from seed disperser loss including: a) an increase in wind-dispersed or invasive species (Brodie and Aslan 2011); b) broad failure of gap colonization, accelerating forest fragmentation; c) extinction of large-seeded plants (McConkey and Drake 2002); d) stalled regeneration of degraded habitat (Kettle 2012); and e) extinction of species with strong negative density-dependent mortality. These changes would result from altered abundance and/or spatial pattern of tree species, a pattern that has appeared in many case studies (McConkey et al 2012). Yet, in practice, it is often assumed that plant restoration in degraded habitats will generate vertebrate return, and that deliberate restoration of vertebrate populations is unnecessary (Brodie and Aslan 2011).
To explore the community-level implications of disperser loss, it is necessary to move beyond case study to synthesis, and to unite theoreticians with empiricists. Can we identify overarching patterns in forest communities following seed disperser loss? Do communities universally change character or enter alternative stable states (Brodie and Aslan 2011), or do they largely retain their original characteristics?
We propose to gather speakers that have explored seed dispersal disruption through case study and theoreticians that have considered the effects of seed dispersal beyond individual communities. All presentations will describe results of current seed dispersal disruption research, and authors will be encouraged to present their results in the context of community-level impacts. It is our belief that the time is ripe for a community-scale theory of seed disperser loss and its impact on forests. Therefore, the final talk of the session will focus on that challenge and will invite ideas for a synthesis paper.