PhD Defense Seminar cum Oral Examination
“Comparative and experimental approaches to understanding sexual selection in Sepsidae (Diptera)”
Speaker: Tuan Jia Min Mindy
(Graduate Student, Dept. of Biological Sciences ,NUS)
Date: 13 January 2017, Friday
Time: 10 am
Venue: DBS Conference Room (S3 Level 5)
Supervisor: Professor Meier, Rudolf
All are welcome
Abstract – Natural history and discovery science has taken a back-seat as hypothesis-testing using model species has become a standard approach in biology. This is one reason why the vast majority of described species are severely data-deficient and very little is known is known about their behaviour, interactions with other species, and ecosystem functions. In my thesis, I explore the behavioural diversity within black scavenger flies (Diptera: Sepsidae) which have ca. 350 described species. Sepsidae include a few “model species” (e.g., Sepsis cynipsea, Sepsis punctum, and a few species of Themira, Archisepsis and Microsepsis), but little is known about the remaining taxa. In my thesis, I use a comparative approach to explore the behavioural diversity space of Sepsidae by studying the mating behaviour of 49 species and use comparative and experimental approaches to document and understand the behaviour.
I find that sepsids are one of the few insects that perform “sensory kissing”, which is significantly different from the nuptial kissing observed in other dipterans or the kissing performed by drosophilids to assess females’ receptivity before mating. Sepsids also evolved a variety of ways to terminate copulations. For example, some species use a novel “twisting” motion that allows the male to “pivot” clock- or anti-clockwise in order to separate from the female. Data analysis suggests that this new behaviour is adaptive because it allows for faster and more predictable separation times. Similarly variable is copulation time. The copulation time of sepsids varies 5 minutes to 5 hours and I show through ancestral state reconstruction and sensitivity analyses that copulation time undergoes considerable amounts of evolution. Furthermore, I used experimental reciprocal crosses between separated conspecific populations to determine which sex controls copulation duration. Experimental perfuming of females using osmeterium secretions from males were also performed to test whether the secretion possessed an anti-aphrodisiac function. Finally, I detailed the repertoire, action patterns and phases for 24 species of sepsids.
This work revealed interesting and rare behaviours, as well as widespread polymorphism within species, which would have remained hidden if only model species had been studied. This illustrates the importance of comparative research on the natural history of many species. It both broadens and deepens our knowledge of animal diversity.