Natural Resources, School of


Date of this Version

Summer 7-22-2011


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Natural Resource Sciences (Applied Ecology), Under the Supervision of Professor Craig R. Allen. Lincoln, Nebraska: August, 2011

Copyright 2011 Aaron Lotz


In this dissertation, I explore multiple tenets of the textural discontinuity hypothesis, which states that hierarchical landscape structures with scale-specific pattern entrain attributes of animals inhabiting the landscape. Landscapes form hierarchies that are structured by vegetative, geomorphological and contagious disturbance processes. The spatial and temporal patterns inherent in landscapes reflect numerous processes, interacting on distinct scales, which shape the assembly of animal communities. Analysis of body mass patterns and functional group distributions has been suggested as methods to provide insight about these underlying hierarchical processes. Scientists have posited that species at the edges of body mass aggregations may be exposed to highly variable resources. This dissertation focuses on the distribution of biological diversity in space and time and socio-ecological factors that are contributing to the worldwide increase in invasive and endangered species.

I analyzed invasions and extinctions of birds and mammals across five Mediterranean-climate ecosystems and in 100 countries using an information-theoretic approach. All body mass distribution data analyzed were discontinuous. This work provided further support for Holling’s textural discontinuity hypothesis. Alpha diversity of function increased in 9 out of the 10 Mediterranean-climate ecosystems analyzed when NIS were introduced into the community. After the introduction of NIS, I observed a decrease in cross-scale redundancy of functional groups in mammals and when both taxonomic groups were combined. In Eocene Epoch mammal data, speciation events were not detected near body mass aggregation edges. Only 64% of the biomes in mammals had ecoregions with similar structure and only 50% of the biomes in birds had ecoregions with similar structure, which may be a result of coarse landscape classification schemes. GDP per capita was positively correlated with the proportion of NIS bird and mammal species within a country. Resilience of a country was correlated to life expectancy. As life expectancy increased, resilience of a country decreased. Results may help us make proper management decisions in monitoring particular non-indigenous species and focus conservation efforts on those native species.