Doctoral Dissertations

Date of Award

5-1996

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Life Sciences

Major Professor

John L. Gittleman

Committee Members

Gordon Burghardt, Gary McCracken, David White

Abstract

Anal sacs of felids are relatively large and secrete chemicals for communication. These chemicals vary intraspecifically and are used in recognition of status, such as individual, species, sexual, reproductive, and dominance. In addition, chemical signals are used in species recognition, and therefore, may potentially be used for phylogenetic study. Chemical secretions that are explicitly tied to species recognition attributes may be more informative characters for phylogenetic reconstruction when morphological or molecular characters lack resolution. Furthermore, these chemicals vary considerably in size and structure among species, suggesting their functional significance in interspecific communication.

Anal sac secretions from species within the Felidae were chemically analyzed to assess intraspecific variation and to determine whether these chemical signals were potentially useful for recognition of individual, species, sexual, reproductive, and dominance status (Chapter 3). This study further investigates the utility of chemical signals as systematic characters. I apply phylogenetic analyses of scent secretions among species within the Family Felidae (Order Carnivora) to test four competing hypotheses about phylogenetic relationships within this family (Chapter 4). Phylogenies currently based on molecular and morphological data are posed as hypotheses for testing species relationships using biochemical analyses of anal sac secretions. This study, therefore, examines phylogenetic relationships within the Felidae using an independent character set to evaluate current phylogenies for this group. Finally, the volatility of chemical signals in relation to their functional significance is evaluated by assessing the correlations between relative volatility and several ecological, morphological, and life history traits (Chapter 5).

Results of this study show a large number of chemical compounds in the anal sacs of species within the Felidae. Minor compounds comprise the majority of the chemical compounds, with fewer major components. The compounds vary quantitatively among individuals within a species, but each species possess a unique set of compounds that are identical among individuals. Chemical signals among individuals within a single species are quantitatively found to be used in recognition of individual, species, sex, and reproductive status. There are no apparent differences in chemical composition between right and left anal sacs of Panthera pardus (leopard), P. leo (lion), and P. tigris (tiger), suggesting no functional difference between the two. Additionally, the chemical profile of leopards and tigers remains stable over a one year time interval, suggesting their potential for individual recognition. The lion and P. uncia (snow leopard) have a unique set of compounds that differ quantitatively between reproductive and non-reproductive individuals, suggesting their potential for recognition of reproductive status. Similarly, reproductive male lions, snow leopards, tigers, and Acinonyx jubatus (cheetah) have a unique set of chemicals that differ quantitatively from reproductive females of those species, and suggests their potential for recognition of sexual status. Dominant lion males and females and dominant snow leopard females have a unique chemical profile that is quite different from that of subordinate individuals, suggesting the ability for individuals to discriminate among dominant and subordinate individuals.

The phylogenetic analysis reveals consistent relationships among felid species with that proposed by other authors based on morphological and molecular data, and resolves some of the relationships that are unclear with these other data sets. For example, the cheetah is placed as the most primitive branch on the phylogenetic tree, a position that is not resolved in phylogenies based on morphological and molecular data sets. Furthermore, this analysis resolves the relationships among the Panthera species, placing the leopard and lion as most closely related taxa and placing Panthera onca (jaguar), tiger, and snow leopard as sister taxa to this group. However, the position of Felis concolor (puma) remains unresolved as its relationship with other felid species switches depending upon the type of chemical data used (i.e., glycolipids, neutral lipids, phospholipids, or the combined data set). The topology of the trees from this study agrees most closely with that presented by Collier and O'Brien (1985) based on molecular data. This study illustrates the species-specific nature of chemical signals, and their usefulness as phylogenetic characters.

Cross-taxa correlations between relative volatility of chemical compounds in a scent mark and various ecological (population density, home range size), morphological (body weight, olfactory bulb size, body length, orbit area), and life history (litter size, inter-birth interval) characters are investigated. Litter size is larger in felid species that produce scent of higher volatility, and smaller in those species that produce less volatile scent marks. Additionally, there is a trend for felid species with large olfactory bulbs to possess low volatile compounds and those with small olfactory bulbs to have highly volatile compounds. Overall, the functional significance of the volatility of the chemical compounds in relation to various ecological, morphological, and life history traits remains unclear. For example, felid home range size is not directly correlated with volatility, suggesting that there are other strategies used to communicate spatial patterns among conspecifics. Similarly, population density, inter- birth interval, and orbit area are not significantly correlated with relative volatility. A significant correlation is found between both head and body length and body weight with medium volatility, suggesting that there is no cost associated with sequestering compounds. Results of this study also reveal that species who live in open grassland areas have more highly volatile scents than those that live in forests, suggesting that the scent deposited by forest species needs to remain for a longer period of time to ensure that the intended receivers perceive the signals.

In summary, this study demonstrates that the chemical compounds present in the anal sacs of felid species do not vary qualitiatively among individuals within the same species, suggesting their importance as species specific attributes and useful phylogenetic characters. However, the chemicals do vary quantitatively among individuals within a single species and are used in recognition of individual, reproductive, and sexual status.

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