Influence of Male Mating Behavior on Wing Morphology in Brassolini Butterflies
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University of New Orleans ScholarWorks@UNO Senior Honors Theses Undergraduate Showcase 5-2012 Influence of Male Mating Behavior on Wing Morphology in Brassolini Butterflies Susan E. Frichter University of New Orleans Follow this and additional works at: https://scholarworks.uno.edu/honors_theses Recommended Citation Frichter, Susan E., "Influence of Male Mating Behavior on Wing Morphology in Brassolini Butterflies" (2012). Senior Honors Theses. 11. https://scholarworks.uno.edu/honors_theses/11 This Honors Thesis-Unrestricted is protected by copyright and/or related rights. It has been brought to you by ScholarWorks@UNO with permission from the rights-holder(s). You are free to use this Honors Thesis-Unrestricted in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/or on the work itself. This Honors Thesis-Unrestricted has been accepted for inclusion in Senior Honors Theses by an authorized administrator of ScholarWorks@UNO. For more information, please contact [email protected]. Influence of Male Mating Behavior on Wing Morphology in Brassolini Butterflies An Honors Thesis presented to The Department of Biological Sciences of the University of New Orleans In Partial Fulfillment of the Requirements for the Degree of Bachelor of Science, with University Honors and Honors in Biology by Susan E. Frichter May 2012 ACKNOWLEDGEMENTS I would like to thank my thesis advisor Dr. Carla M. Penz for her exemplary support and dedication to aiding me in completing this research as well as Dr. Phil DeVries for being a constant support. In addition, I would like to thank my father, Carl Frichter, for encouraging me to pursue my dreams, and my mother, Thresea Frichter, for listening to my complaints for all these years. This work is dedicated to the memory of my brother, Sean Frichter. I hope that I’m making you proud of me. ii LIST OF TABLES Table 1. Species sampled for statistical comparisons between males and females of Caligo and Opsiphanes . Table 2. Statistical comparisons between males and females of Caligo and Opsiphanes. Table 3. Species sampled for estimated flight speeds of male and female Caligo and Opsiphanes. Table 4. Estimated flight speeds of male Caligo and Opsiphanes. iii LIST OF FIGURES Fig. 1. The phylogeny of the tribe Brassolini, illustrating that the Brassolini tribe contains seventeen genera separated into three subtribes (Penz 2007). Fig. 2. Caligo illioneus male. Fig. 3. Opsiphanes cassina male. Fig. 4. Photograph of transparent flight tunnel marked at 20 centimeter intervals that was used to estimate flight speed at the Tirimbina Biological Reserve in Sarapaqui, Costa Rica. Fig. 5. Using Photoshop and Illustrator (Adobe Systems), the wings of each butterfly were overlapped and divided into fifteen arches. iv TABLE OF CONTENTS Section Page Title Page i Acknowledgments ii List of Tables iii List of Figures iv Table of Contents v Abstract vi Introduction 1 Methods and Materials 6 Results 13 Discussion 16 References 19 v ABSTRACT The influence of male mating behavior on wing morphology in two genera of the tribe Brassolini, Caligo and Opsiphanes , was examined. This study consisted of fieldwork and laboratory components. During fieldwork, male and female butterflies from each genus were flown through a flight tunnel and recorded with a video camera for further analysis of flight speed in the laboratory. In addition, male and female butterflies were observed in their natural environment, and the differences in their mating and flight behavior were noted. In the laboratory, photographs of previously captured Brassolini butterflies were taken and edited. Each image was adjusted to life size, the wings were overlapped in a standardized way for all specimens, and the forewing length and total wing area for each butterfly were determined subsequently. The image of each butterfly was cut into fifteen arches, weighed, and documented in order to calculate the aspect ratio and wing centroid. After pooling the data for Caligo and Opsiphanes species, the calculated aspect ratio and wing centroid data were used to perform a t- test in accordance with the determined variance for each of the comparisons. A total of eight comparisons were made as follows: male Caligo aspect ratio versus female Caligo aspect ratio, male Caligo wing centroid versus female Caligo wing centroid, male Opsiphanes aspect ratio versus female Opsiphanes aspect ratio, male Opsiphanes wing centroid versus female Opsiphanes wing centroid, male Caligo aspect ratio versus male Opsiphanes aspect ratio, male Caligo wing centroid versus male Opsiphanes centroid, female Caligo aspect ratio versus female Opsiphanes aspect ratio, and female Caligo wing centroid versus female Opsiphanes centroid. As expected, the results of the statistical analyses showed that although the wing morphology in male and female Caligo did not differ, the wing morphology in male and female Opsiphanes was significantly different due to the difference in activities. In addition, wing vi morphology of male Caligo and Opsiphanes also differed significantly from one another, while only the aspect ratio in female Caligo and Opsiphanes were significantly different from one another. Thus, these statistical analyses suggested that due to the differences in mating behavior between males of both genera, selection has caused the wing morphology of males in each genus to differ from the other in order to maximize their fitness. vii 1 INTRODUCTION Insects, including butterflies, compose more than half of the described living species and thus dominate terrestrial ecosystems. Furthermore, 99% of the described insect species are capable of flight, which is testimony to the importance of this characteristic for insect diversification. Natural selection has shaped butterfly wing architecture to perform a wide range of activities such as flapping, gliding, and hovering, which are various mechanisms for controlled flight. Flight is integral to butterflies survival and reproduction, since it is utilized to forage, evade predators, seek mates, and perform courtship. Thus, the reproductive success and survival of a butterfly is determined by its ability to fly in particular ways for specific purposes. For butterflies in wide ranges of habitats and conditions, each species will have wing architecture best suited to perform their different behaviors. For example, it has been noted that the diversity of Neotropical butterflies is stratified vertically into forest canopy and understory strata with each containing a similar proportion of the total species in the community (DeVries et al. 1997). Recent research by DeVries et al. (2010) has shown that wing shape in Morpho butterflies has evolved in the different species in order to maximize performance in their microhabitats, the canopy and the understory. Morpho species inhabiting the canopy have longer wings, which are efficient for gliding. In contrast, Morpho species inhabiting the understory have shorter wings used for flapping flight. It has been found that the morphology of insect wings has been selected for maximum performance and energy efficiency (Dudley 2000). Thus, the present study 2 aims to determine the effect of mating behavior on wing morphology in Caligo and Opsiphanes butterflies. Butterflies also use their wings to communicate with individuals of the same species, as well as with those of different species. For example, some Hamadryas butterflies of the Neotropics communicate with competing males of the same species by allowing their wings to collide during flight to produce a sound, which could be a part of a display as a component of species level recognition. In general, butterfly courtship begins with identification of species followed by a phase during which the decision to mate is determined (Wiklund 2003). Males initiate the courtship process, while females primarily decide the success or failure of the males’ visual displays. Since females only need to mate once in their lives, males searching for a virgin female are likely to be rebuffed by an already mated female. Because males need wings to find and perform courtship flight, the wings of butterflies are integral components of both flight and mating behavior. By undertaking research to discern whether mating behavior in Brassolini butterflies affects wing morphology, this work will have broad implications for the study of evolution of insect wing morphology as correlated with behavioral characteristics. The butterflies of the tribe Brassolini belong to the family Nymphalidae that is included under the superfamily Papilionoidea and order Lepidoptera. The Brassolini tribe contains seventeen genera separated into three subtribes, Biina, Naropina, and Brassolina as can be seen in Figure 1 below. 3 Figure 1. Phylogeny of the tribe Brassolini (source: Brower & Wahlberg 2010, after Penz 2007). These Neotropical butterflies consist of 102 species, including the memorable owl butterflies ( Caligo ), which have a large wing span. Generally, brassolines have a stout body with normally well-formed eyespots on the ventral hindwing (Penz 2007). These ventral hindwing eyespots are especially noticeable in Caligo as can be seen below in Figure 2. QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Figure 2. Caligo illioneus male. 4 Opsiphanes butterflies are dark brown