Thu 25 Jan 2018: 10.00am [Phd Defense] – Seshadri Kadaba Shamanna on “Discovery, parental care and conservation of frogs in the Western Ghats of India”

PhD Defense Seminar cum Oral Examination
Department of Biological Sciences, NUS

“Discovery, parental care and conservation of frogs in the Western Ghats of India”

Speaker:            Seshadri Kadaba Shamanna  (Graduate Student, Dept. of Biological Sciences, NUS)
Date:                  25 Jan 2018, Thursday
Time:                  10am
Venue:               DBS Conference room  (S3 Level 5, #05-02)
Supervisor:        Asst. Prof. Frank E. Rheindt

Abstract –  Amphibians are a diverse group of vertebrates that are relatively understudied with nearly 30% of them being discovered only in the last decade. Globally, a third of all amphibians are already threatened with extinction and the need to rigorously document their natural history and ecology is imperative. Thus, my thesis is focused on bridging our knowledge gaps about frogs. It was undertaken in the Western Ghats of India, a renowned biodiversity hotspot where amphibians are underrepresented in research.

Specifically, I report the discovery of two hitherto undescribed species belonging to two families and reappraise the descriptions of three other extant frogs. I then document a novel behaviour in two species wherein the adult frogs of Raorchestes ochlandrae and Raorchestes aff. chalazodes (Rhachophoridae) enter bamboo stalks via narrow openings and lay direct developing eggs and provide parental care to developing embryos inside the bamboo internodes. This behaviour is unique among all extant anurans and is described as a novel reproductive mode.

Subsequently, I focused on the behaviour of R. aff. chalazodes and to do so, required an effective tool for which, I undertook a mini-review of methods used to study animals dwelling in cavities. This enabled me to choose endoscopes to study the behaviour of R. aff chalazodes.

I then established the evolutionary significance of parental care behaviour in R. aff chalazodes using insitu adult removal experiments and found that conspecific males cannibalized unattended eggs. Unattended eggs were also eaten by ants, parasitized by flies, and died from fungal infections or drowned. Thus, male parental care behaviour in form of egg attendance, egg guarding and, oviposition site defence increases offspring survivorship.

With an ultimate goal of conserving R. aff chalazodes, I predicted the potential geographic distribution using species distribution modelling. Finally, my contributions are summarized in the context of existing knowledge about diversity and reproductive ecology of amphibians to identify avenues for further research.

All are welcome

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Wed 17 Jan 2018: 4.00pm [PhD defence] – Bilgenur Baloglu on “Biological assessment and monitoring of Singapore’s aquatic environments using NGS tools”

PhD Defense Seminar cum Oral Examination
Department of Biological Sciences, NUS

Biological assessment and monitoring of Singapore’s aquatic environments using NGS tools

Speaker:       Bilgenur Baloglu (Graduate Student, Dept. of Biological Sciences, NUS)
Date:             17 Jan 2018, Wednesday  
Time:             4pm
Venue:           DBS Conference Room
Supervisor:    Prof Meier Rudolf

Abstract –  “Non-biting midges (Chironomidae: Diptera) are an important component of freshwater ecosystems. However, most freshwater quality assessment or conservation biology studies rarely incorporate species-level information on midges. This is because traditional methods for sorting and identifying midges are too expensive. Here, I optimize, test, and use a new DNA barcoding technique that is based on Next Generation Sequencing (NGS). I use “NGS barcodes” for >30,000 individual specimens to demonstrate how NGS barcodes can improve analyzing the community structure of specimen- and species-rich invertebrate taxa.

I first demonstrate that the midge fauna of a reservoir can be characterized by barcoding 500–1000 specimens. I recommend that biomonitoring programs could cheaply gather data with only a small number of NGS-barcoded specimens or metabarcoded bulk samples. Next, I show how a new sequencing technique (MinION™) can be used for obtaining NGS barcodes within 24 hours. I estimate that a single run of MinION^TM can generate >100 barcodes and conclude that an estimate of species composition can be obtained 10 hours since sample handling. Lastly, I reveal that Singapore’s biggest swamp forest remnant (Nee Soon Swamp Forest) maintains a rich and largely unique fauna (>400 chironomid species) that is resistant against the invasion of species from surrounding artificial reservoirs. I show that the chironomid occurrence in the swamp forest is associated with several physicochemical variables, such as pH, stream depth, and conductivity rather than the presence of or distance to the reservoirs.

This study suggests that even fragmented or small swamp forests, like the Nee Soon Swamp Forest, can be suitable habitats for a rich and likely native chironomid community. I expect that the results of this study will promote further studies on the use of NGS barcoding of chironomid communities for characterizing and conserving the threatened Southeast Asian swamp forests. Overall, these studies expose the enormous power of NGS barcoding in ecological research, to study ecosystem health, biological diversity, and habitat conservation.”

All are welcome

Tue 16 Jan 2018: 10.00am [PhD Defense] – Nathaniel Ng on “The influence of Pleistocene climate change on patterns of gene flow in the avifauna of Wallacea”

PhD Defense Seminar cum Oral Examination
Department of Biological Sciences, NUS

The influence of Pleistocene climate change on patterns of gene flow in the avifauna of Wallacea

Speaker:     Ng Shengrong, Nathaniel (Graduate Student, Dept. of Biological Sciences, NUS)
Date:          16 Jan 2018, Tuesday
Time:          10am
Venue:       DBS Conference Room
Supervisor: Asst Prof Rheindt Frank Erwin

 

Abstract –  “Wallacea is both highly biodiverse and poorly explored, with many undiscovered taxa as yet unknown to science. A main driver of the region’s biodiversity is thought to be repeated fluctuations in sea level, the result of cyclical glaciation events (“ice ages”) that have occurred throughout the Pleistocene.

In my thesis, I examine species limits and patterns of diversification in Wallacean birds using a range of different methodologies including genome-wide analyses, morphological examination, and bioacoustic techniques. In particular, I investigate how Pleistocene sea level changes may have driven divergence and speciation in these birds. I identify several evolutionarily-distinct bird taxa unknown to science, two of which I describe. Investigations into the effect of Pleistocene land bridges show that their relative significance varies depending on the life histories and habits of each bird taxon, and emphasize the importance of dispersal over vicariance in driving recent diversification in Wallacean birds.”

All are welcome