It has long been recognized that climate can influence the diversity and dynamics of communities and regional assemblages. Within this thesis, I ask three questions: (1) which processes are most important in mediating climate-species richness relationships; (2) are predictions of spatial climate-richness models temporally consistent, and (3) is local community structure determined primarily by regional or local processes.
Metabolic theory proposes that climate-richness relationships arise due to the temperature dependence of metabolic rate. I tested the theory's predictions for six taxa in North America. Contrary to the theory's predictions, temperature-richness relationships were curvilinear and their slopes deviated from the predicted value. This suggests that the mechanism proposed by metabolic theory does not underlie climate-richness relationships.
If climate determines species richness, then climate should predict how species richness will change over time. To test this, I compared alternative methods (regression and niche modelling) of forecasting shifts in species richness given global climate change. Models were trained on butterfly richness data from the early 20th century and their predictions were compared to observed changes throughout the 20th century. Overall, regression-based approaches that incorporated spatial autocorrelation outperformed other methods.
Broad-scale richness gradients could arise from climatic niche conservatism. I tested this hypothesis for treefrogs (Hylidae) by combining data on species' distributions and phylogeny. I found that while niches were conserved with respect to cold tolerance, species richness was determined by precipitation, not temperature. This suggests that the processes determining regional species composition and richness are controlled by fundamentally different climatic components.
I evaluated the relative importance of regional and local processes and how there were affected by climatic gradients by examining patterns of body size dispersion at local and regional scales for hylid frogs. On average, communities were over-dispersed, but there was no increased signature of competition in the tropics. Dispersion of regional assemblages decreased in cold areas, but this was not due to an elevated tropical rate of body size evolution. Overall, regional processes explained twice as much variance in body size dispersion than did local processes.
This thesis rejected several hypotheses for the link between climate and macroevolutionary patterns. In doing so, it provided new insight to the role of ecological and evolutionary processes along broad-climatic gradients.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/29933 |
| Date | January 2009 |
| Creators | Algar, Adam C |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 152 p. |
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