Independent effects of habitat loss and fragmentation on pollination : tropical forest fragmentation alters hummingbird movements and pollination dynamics Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rf55zb19g

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  • A growing body of work reveals that animal-mediated pollination is negatively affected by anthropogenic disturbance. Landscape-scale disturbance results in two often inter-related processes: (1) habitat loss, and (2) disruptions of habitat configuration (i.e. fragmentation). Understanding the relative effects of such processes is critical in designing effective management strategies to limit pollination and pollinator decline. I reviewed existing published work from 1989 to 2009 and found that only six of 303 studies separated the effects of habitat loss from fragmentation. I provide a synthesis of the current landscape, behavioral, and pollination ecology literature in order to present preliminary multiple working hypotheses to explain how these two landscape processes might independently influence pollination dynamics (Chapter 2). Despite the potential importance of independent effects of habitat fragmentation, effects on pollination remain largely untested. Studies designed to disentangle the independent effects of habitat loss and fragmentation are essential for gaining insight into landscape-mediated pollination declines. I also found that the field of landscape pollination ecology could benefit from quantification of the matrix, landscape functional connectivity, and pollinator movement behavior. To test the hypothesis that pollinator movement can be influenced by landscape configuration, I translocated radio-tagged hummingbirds across agricultural and forested landscapes near Las Cruces, Costa Rica (Chapter 3). I found return paths were on average more direct in forested than in agricultural landscapes. In addition, movement paths chosen in agricultural landscapes were more forested than the most direct route suggesting that hummingbirds avoided crossing open areas when possible. To determine if differences in pollinator movement translated to differences in plant reproduction, I tested the relative importance of landscape composition versus configuration on the reproductive success of Heliconia tortuosa, a hummingbird-pollinated forest herb (Chapter 4). I used a stratified random sampling design to select sites across orthogonal gradients in patch size, amount of forest, and elevation. I tested four landscape change hypotheses (i.e., local, landscape composition, landscape fragmentation, and fragmentation threshold). I found that Heliconia reproduction supported both the local site and landscape fragmentation hypotheses. Seed set increased with increasing forest patch size independent of amount of forest in the surrounding landscape. I also found that increasing patch size positively influenced the relative abundance of pollinators. The observed differences in seed set likely resulted from differences in hummingbird movements (Chapter 3) and/or abundance under different landscape configurations.
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  • description.provenance : Submitted by Adam Hadley (hadleya@onid.orst.edu) on 2012-09-19T20:01:57Z No. of bitstreams: 1 HadleyAdamS2012.pdf: 10792706 bytes, checksum: d1028d82f4d027969f4aba8d4d03e118 (MD5)
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2012-09-21T21:05:35Z (GMT) No. of bitstreams: 1 HadleyAdamS2012.pdf: 10792706 bytes, checksum: d1028d82f4d027969f4aba8d4d03e118 (MD5)
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2012-09-20T16:14:54Z (GMT) No. of bitstreams: 1 HadleyAdamS2012.pdf: 10792706 bytes, checksum: d1028d82f4d027969f4aba8d4d03e118 (MD5)
  • description.provenance : Made available in DSpace on 2012-09-21T21:05:35Z (GMT). No. of bitstreams: 1 HadleyAdamS2012.pdf: 10792706 bytes, checksum: d1028d82f4d027969f4aba8d4d03e118 (MD5) Previous issue date: 2012-08-27

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