The effects of distance to range edge on bird responses to habitat change in tropical forests
File(s)
Author(s)
Bellotto Trigo, Flavia
Type
Thesis
Abstract
Habitat change is arguably the most important environmental driver of species decline. In spite of this, there is still uncertainty surrounding the mechanisms that mediate species sensitivity when disturbances occur in their habitat. One source of variation in species responses to habitat change is location within their distribution range. In this thesis I attempt to answer some of the questions related to variation in species sensitivity to habitat change across ranges. First I investigate the relative effects of habitat fragmentation on species sensitivity. I reveal that populations within a species can show positive, negative or neutral responses to fragmentation depending on location within the geographic range and the amount of local forest cover. Then I try to detect the more sensitive populations based on phenotype asymmetry due to physiological stress caused by environmental change. The results are inconclusive, which suggest that either these populations are able to implement mechanisms that compensate for asymmetry during development under stress; or that they are not under physiological stress near range edges. Finally, I investigate if variation in trait size across the range change systematically and provide a mechanism to explain sensitivity. I find no consistent pattern of decrease in trait size or increase in variance of trait size near the range edge, with only forest cover amount potentially showing a decreasing trend in trait size with increase of forest cover. Overall my work demonstrates how complex the study of species sensitivity to habitat change across species distribution ranges are, and that species responses cannot always be generalised. In general, future studies should consider including distance to range edge as a predictor variable in analyses, as it might help explain some of the variation in intraspecific responses to environmental change.
Version
Open Access
Date Issued
2023-11-07
Date Awarded
2024-05-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Banks-Leite, Cristina
Orme, David
Publisher Department
Life Sciences
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)