Mate Selection by Calopteryx haemorrhoidalis - PhDify.com
The topic of mate selection has always been an important one for researchers of animal behavior precisely because mate selection is vital to the species that those researchers are examining. No living organism can sustain life indefinitely and must eventually procreate to pass on their genetic information to the next generation. I have therefore chosen to study sexual selection and in particular the physiological traits that influence it by examining a species in which the factors of effective mate selection are relatively transparent to the observer. In particular this research examines mate selection in the damselfly Calopteryx haemorrhoidalis.
Following the work of Alex Cordoba-Aguilar, who performed a series of experiments in 2003 that supported the argument that female sexual behavior in Caleopteryx haemorrhoidalis is influenced by male wing pigmentation, this research tested the hypothesis that females do in fact choose their mates based on their preferences on wing color and thus on the indirect knowledge gathered by the females on the insects’ overall fitness since the sexually selected trait of wing pigmentation demonstrates to the female the degree of the male’s innate ability to protect itself from harm from an intestinal parasite. Cordoba-Aguilar (2002) demonstrated that males of Caleopteryx haemorrhoidalis with a higher proportion of wing pigmentation were more likely to mate, had fewer intestinal parasites and defended their territories more effectively.
In choosing Caleopteryx haemorrhoidalis as the focus of this research I was influenced by the fact that there was not a insubstantial amount of research on this topic that I could use to inform my own research. I also selected it at least in some measures for the same reason (I believe) that other researchers have chosen this species, which is that it provides the researcher with a relatively large number of matings to observe. The fact that the species is easy to see, native to where I live, relatively unafraid of humans and easy to approach for observation and exhibits relatively easily distinguished differences in pigmentation also helps to increase its attractiveness as a subject species.
While previous studies have not demonstrated conclusively that females are using wing color as a proxy for determining fitness, this is the most parsimonious explanation of the data yet recorded.
As was the case in previous research on this species (Cordoba-Aguilar, 2002; Cordoba-Aguilar, Salamanca-Ocana, Lopezaraiza, 2003) I determined that the most appropriate place initially in which to determine the behavior of the damselflies was in a native environment. There were two reasons for this. The most important was that if I were to capture damselflies and observe them in an artificial environment, either the capture or the artificiality of the environment might well influence the insects to act in a way that was at odds with their natural behavior. (It might also be that placing the damselflies in a holding device would prevent their mating). Secondly, there may well be some aspect of damselflies that allows some to be more easily captured than others that also has significant repercussions for mating selection. By looking at a native population I did not introduce any bias into it.
I observed damselfly mating behavior for four hours (during one-two hour session and two one-hour sessions) in a place near to my own residence where my own previous experience had led me to know that the standing water attracts damselflies because of the presence by the water of mosquitoes and other food species for the damselflies. I made two brief initial visits to the site to determine that there would be damselflies there and to determine an appropriate place for me to observe from. During the observations themselves I did not wear any insect repellent to avoid disturbing either mosquitoes or damselflies.
I focused on a “window” that other researchers (Cordoba-Aguilar, 2002; Cordoba-Aguilar, Salamanca-Ocana, Lopezaraiza, 2003; Fitzstephens, Getty; 2000) have not examined as carefully, looking at interactions between males and females prior to the beginning of courtship between the two individuals.
During the second part of the experiment I captured 10 light-winged and 10 dark-winged males and placed them in a glass tank with five females to determine how wing coloration affected mate selection in a controlled environment and so to demonstrate that it is less likely to be an extraneous environmental factor that influences female Caleopteryx haemorrhoidalis sexual behavior than it is likely to be physiological factors. I observed the captive damselflies for an hour before releasing them.
From the results of the observations that I conducted in the natural setting I determined that males with dark-colored had on average four times as many “contacts” with females (in which a female flew up to a male, hovered briefly and then flew off without mating behavior being initiated) than was the case for light-winged males. Dark-winged males were also much more likely to mate by a ratio of 2.5-to-one.
The study of captive damselflies produced no such conclusive results because there was only one mating during the hour – no doubt at least in part because of the factors discussed earlier.
The next step for this research would be to investigate the importance of wing pigmentation on mate selection in uninfected populations. This has 5 not yet been done, in no small part because the infection is very widespread and may even be endemic among damselfly populations.
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