Fri 21 Apr 2017: 10.30am (*time change*) @ S1-03-02 CR2 – Zhang Yuchen on “Modelling of cropland expansion and its effects on biodiversity in Myanmar”

Department of Biological Sciences
National University of Singapore
Qualifying Exam

“Modelling of cropland expansion and its effects on biodiversity”

By Zhang Yuchen
Graduate Student, Dept. of Biological Sciences, NUS
Friday 21 April 2017: 10.30am | S1-03-02 – Conference Room-II (S1, Level 3, mezzanine)(*note the time change*) 
Supervisor: Asst Prof Carrasco T, L Roman

Abstract – While the world population is expected to exceed 9 billion by 2050, global crop demand is projected to increase by 100-110%. Demand for food is rising in tandem with a growing population, and accelerated by contaminant diet changes. Agricultural expansion is one of the common ways to meet this increasing food demand but it is also a major global driver of deforestation. With increasing world market integration, demand for new land is likely to be concentrated in tropical developing nations that have large areas of land suitable for agriculture. However, these are also areas in the early stages of forest transition and that have high conservation importance. In the face of these rising pressures, spatially explicit predictions of future demand for agricultural land could play a critical role in guiding conservation efforts to conserve key biodiversity areas.

Many forests have so far been spared due to inaccessibility, possibly due to lack of infrastructure and political and economic constraints on investment. For instance, recent political and economic liberalization in Myanmar is expected to remove some of these constraints and lead to increased investment into agriculture and thus increased risk of deforestation. In order to protect Myanmar’s rich biodiversity, we urgently need to predict areas at highest risk of deforestation with a view to designing a robust network of protected areas. Therefore, Myanmar could be used as a case study to model cropland expansion and its effects on biodiversity before modelling global cropland expansion and its environmental impacts.

I thus aim to 1) investigate how cropland in Myanmar would expand after political and economic reforms and its influence on the Key Biodiversity Areas; 2) project how global cropland would expand temporally and spatially and examine its biodiversity consequences; 3) map spatially-explicit global conservation economic cost based on forgone agricultural rent; 4) prioritize human-centered global conservation resource allocation facing increasing food demand and projected cropland expansion.

Thu 13 April 2017: 10am @ DBS CR1 (S3-05) – “Past, Present and Future of Southeast Asian Peatlands” by Lahiru Suranga Wijedasa

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Department of Biological Sciences
National University of Singapore
Qualifying Exam

“Past, Present and Future of Southeast Asian Peatlands”

Lahiru Suranga Wijedasa
Graduate Student, Dept. of Biological Sciences, NUS
Thu 13 April 2017: 10am | DBS Conference Room (S3, Level 5)
Supervisor: Asst. Prof Ryan Chisholm

Abstract – Southeast Asian peatswamp forests are wetland ecosystems created and maintained by the interaction of vegetation and hydrology. Extreme habitat conditions such as high acidity, low nutrients and fluctuating water tables have resulted in special adaptations and high levels of endemism in peatswamp biodiversity. The conditions that led to adaptations (i.e. high acidity and low oxygen levels) have also resulted in peatswamps accumulating and storing vast quantities of carbon. While understanding peatswamp biodiversity and carbon storage is still in its early stages, vast areas of peatswamp forests have already been converted or have been designated for conversion to agriculture with the loss of biodiversity and release of vast quantities of carbon into the atmosphere.

I aim to reduce uncertainties in our understanding of Southeast Asian peatswamp biodiversity distribution, management and conservation through the following three chapters: 1) quantify drivers of land use change and estimate resultant CO2 emissions, 2) quantify and estimate above ground biomass distribution, 3) prioritize peatswamp areas for conservation and 4) understand the drivers of forest structure in peatswamps.

Thu 19 Jan 2017: 10.00am @ DBS CR1– Nesibe Özsu on “The genetic basis of eyespot color pattern development in Bicyclus anynana butterflies”

Image004PhD Defense Seminar cum Oral Examination

The genetic basis of eyespot color pattern development in Bicyclus anynana butterflies

Speaker: Nesibe Özsu (Graduate Student Dept.of Biological Sciences, NUS)
Date: 19 January 2017, Thursday
Time: 10 am
Venue DBS Conference Room (S3 Level 5)
Supervisor: Assoc Prof Antonia Monteiro

All are welcome

Abstract – The origin of novel traits remains an outstanding question in evolutionary biology. In particular, it is largely unknown how these novel traits originate via modifications in development. Butterfly eyespots are complex novel traits that originated once, from simpler coloured spots, within the family Nymphalidae. Although several genes associated with eyespot development have been identified, the underlying gene regulatory network and function of eyespot genes still remains largely unknown.

Using a transcriptome analysis, I first identified 186 genes that were differentially expressed in wing tissues that develop eyespots in Bicyclus anynana compared to wing tissues that don’t. Many of these genes were involved in wound healing, suggesting that butterfly eyespots may have originated with the co-option of the wound healing gene regulatory network. Second, I investigated the genetic basis of eyespot number variation using an eyespot number mutant, Spotty, with two additional eyespots. Only a handful of the 461 genes that were differentially expressed between Spotty and wild-type butterflies overlapped with genes from the eyespot gene regulatory network, indicating possible targets for Spotty. Finally, I tested the function of wingless, a gene previously implicated in eyespot development, by down-regulating it in transgenic B. anynana butterflies via RNAi. Transgenic butterflies showed significant reductions in the size of eyespots and wings, compared to wild-type controls, indicating that wingless is a positive regulator of eyespot and wing development in B. anynana butterflies.

Fri 13 Jan 2017: 10.00am @ DBS CR1 – Mindy Tuan on “Comparative and experimental approaches to understanding sexual selection in Sepsidae (Diptera)”

Image004PhD 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.