Fri 03 May 2013: 3.00pm @ S1A SR: Tang Qian on “Origin and spread of the German cockroach, Blattella germanica”

Qualifying  Examination

“Origin and spread of the German cockroach, Blattella germanica (Blattodea: Blattellidae)“

TANG Qian
Graduate Student
Dept. of Biological Sciences, NUS

Fri, 3 May 2013: 3.00pm
@ S1A, #02-17
Supervisor: Assoc Prof Evans, Theodore Alfred

All are welcome

Abstract:

“The German cockroach (Blattella germanica) is likely to be the world’s most widespread domestic pest, from large cities to rural areas, on all continents (except Antarctica) and across most latitudes.

How this situation transpired is unknown, even the origin of this species is unknown; the name indicates where it was named, as an invasive species. Historical records and morphological phylogeny suggest that the German cockroach is of African or Asian origin.

Considering the evidence from both sources, I hypothesize that the German cockroach and its Asian relatives share a common ancestor out of Africa, and that the ancestors of the German cockroach was brought to Europe and domesticated there.

Adaptation to buildings allowed for transportation by humans, and thus spread to the rest of the world.

I will test my hypothesis using different genetic markers on cockroach samples collected from over 100 cities or regions.  I will use various genetic analyses to trace the history of the Genus Blattella (ribosomal DNA, mitochondrial DNA) and the species B. germanica (microsatellites). 

This study may also provide evidence for the expansion of B. germanica and suggest processes of domestication by pest species in the urban environment.”

Read Full Post »

Mon, 22 Apr 2013, 2pm @ S1A SR – Brandon Seah on “Investigating Microbial Symbiosis with Molecular Tools”

Read Full Post »

Tue, 23 Apr 2013: 1.00pm @ DBS CR II – Zhang Manping on “Population Structure and Gut Flora Diversity in Coptotermes gestroi in Southeast Asia”

Qualifying  Examination

“Population Structure and Gut Flora Diversity in Coptotermes gestroi in Southeast Asia”

Zhang Manping
Graduate Student
Dept. of Biological Sciences, NUS

Tues, 23 April 2013: 1.00pm
@ DBS Conference Room ii (S1 Level 3, Mezzanine)
Supervisor: Assoc Prof Evans, Theodore Alfred

All are welcome

Abstract:

“Coptotermes gestroi (Wasmann) (Insecta: Isoptera: Rhinotermitidae), commonly known as the house termite, is one of the most destructive urban pests in Southeast Asia.  This species has gut microorganisms (protists, bacteria and archea) to aid wood digestion and nutrient intake. 

It appears to be an urban adaptor or exploiter, as it rare in natural forests, but common in urban centres; it has been found to infest up to 80% of buildings in Malaysia.

The species is invasive as well, and had spread though human trade to other geographic regions, including east and south Asia, North and South America, Europe and several islands in the Pacific, Caribbean and India Oceans. 

Although C. gestroi is an important pest species, little is known about its origins, endemic distribution, geographic spread, and adaptation to urban life. Indeed it is only in the last decade its taxonomy was resolved.

My project aims at uncover some of this unknown information, by elucidating the population structure and genetic diversity of C. gestroi across Southeast Asia and invasive populations using microsatellite markers.  A better sampling strategy (sampling in cities, countrysides and forest) and comparative Copototermes species would be adopted. 

Pyrosequencing survey of the gut flora diversity will be used as a facilitated method to reveal the dispersal pattern, and help understand adaptation to urban life.

A laboratory experiment that tests the effect of food types on gut flora diversity of C. gestroi will complement the pyrosequencing. 

My project intends to shed some light on

1. The origin and dispersal pattern of C. gestroi.
2. The underlying mechanism for wide distribution of the species.
3. The adaptive strategy of C. gestroi to urbanization.”

Read Full Post »

Fri, 19 Apr 2013, 10.30am @ DBS CF: Ng Ting Hui on “Investigating the introduction and impacts of gastropods in Singapore’s fresh waters”

Qualifying  Examination

“Investigating the introduction and impacts of gastropods in Singapore’s fresh waters”

Ng Ting Hui
Graduate Student
Dept. of Biological Sciences, NUS

Friday, 19 April 2013: 10.30am
@ DBS Conference Room (S3 L5)
Supervisor: Asst. Prof. Darren Yeo, Dr. Tan Heok Hui

All are welcome

Abstract:

“Introduction of freshwater gastropods are a concern globally owing to negative impacts like habitat-modification, competition with native species, and the spread of zoonotic parasites. In contrast to other native aquatic fauna in Singapore, which are usually found in unmodified habitats, freshwater molluscs here are almost exclusively found in human-impacted habitats, e.g., reservoirs and canals. Hence, it is suspected that many species may have been introduced. The lack of comprehensive information regarding native freshwater molluscs has made it difficult to determine the true status of many species found here. My inspection of museum collections and unpublished data found that only six species of gastropods were found here half a century ago, while the current malacofauna consists of 33 species, including freshwater bivalves. Preliminary data from a review of freshwater mollusc introductions to Southeast Asia shows that the aquarium trade has been most often proposed as a source for introductions, including in Singapore. A survey of the aquarium trade here revealed 58 species. While the results indicate that the trade is a likely introduction pathway, it is also implied that there are other potential pathways.

I also aim to investigate if the genetic diversity of local freshwater molluscs can resolve the status of cryptogenic species, and to examine the factors facilitating the spread of freshwater molluscs by investigating physico-chemical parameters and life history traits that may influence their distribution in canals. Finally, preliminary data indicates that the decline in distributions of native apple snail Pila scutata coincides with the introduction and spread of the confamilial golden apple snail Pomacea canaliculata. Potential ecological overlap between these two species will thus be investigated. The results of the genetic and ecological studies will be used to determine the management measures necessary to control introduced freshwater gastropods in Singapore.”

Read Full Post »

Tue 23 Apr 2013: 10.00am @ DBS CF – Pitta de Araujo, Diego on “Morphological and Chemical Evolution in Sepsidae”

Qualifying  Examination

“Morphological and Chemical Evolution in Sepsidae: An Evolutionary Approach to Phenomics and Shape Analysis”

Pitta de Araujo, Diego
Graduate Student
Dept. of Biological Sciences, NUS

Tues, 23 April 2013: 10.00am
@ DBS Conference Room (S3 Level 5)

Supervisor: Prof. Rudolf Meier
Co-Supervisor: Dr. Joanne Yew

All are welcome

Abstract:

“New advancements in morphological and chemical analysis are promoting a renaissance of the studies of phenotypes in the era of genomics. Here I propose to use a “phenomics” approach to fully explore the morphology and chemistry of Sepsidae flies. These flies have very complex and variable morphological structures most of which are used in sexual behaviour and serve as a model clade to study phenotypic evolution. I am combining several morphological imaging techniques (Visionary Digital, Light Microscopy, Confocal Microscopy and Scanning Electron Microscopy) and chemical imaging (Ultra-Violet Laser Desorption Ionization Mass Spectrometry) to understand key changes during sepsid evolution. The three main questions that be addressed in this research are: How much morphological and chemical change happened in the evolution of Sepsidae? Is there a phylogenetic pattern and correlation among different phenotypes? How to quantify morphological change in an evolutionary context?

I carried out a detailed morphological and chemical study of the mysterious osmeterium, a gland that is located on the hind tibia of males. I use UV-LDI Mass Spectrometry to solve the identity of its secretion, the time of secretion, and the secretion’s fate when it is transferred to the female’s body during mating. My preliminary morphological results pertain to the morphology of the head capsule and mouthparts and indicate variation among species, mainly with regard to the structure of the head capsule. For this part of the flies’ body there is little evidence for sexual dimorphism. The thorax morphology of sepsids varies among species with regard to the shape of thoracic plates and patches of micropilosity. I am also the first entomologist studying the male intromittent organ in sepsids and document its variation across the species.

Lastly, I propose to explore new tools in 3D design to create representations of morphological structures. I propose to use new techniques in shape analysis for advanced 3D visualization and shape measurement: evolutionary morphing, shape similarity and shape complexity. With these tools I hope to quantify and visualize how sepsid morphology changed over evolutionary time.”

Read Full Post »

Tue 16 Apr 2013: 3.00pm – William Eckman on “Ecology and Restocking of Giant Clams”

Qualifying  Examination

“Ecology and Restocking of Giant Clams”

William Eckman
Graduate Student,
Dept. Biological Sciences, NUS

Tue 16 April 2013: 3.00pm
@ DBS Meeting Room
(S3 Level 5,General Office #05-010)

Supervisor: Asst Prof Peter Alan, Todd

All are welcome

Abstract:

“As giant clams inhabit shallow waters, primarily in developing nations, many of their species are in danger of becoming directly extirpated by human activity, or of being unable to reproduce due to falling population densities. Over their long lifespans, giant clams produce large numbers of offspring, which have low survival rates at the larval and juvenile level. This is a successful reproductive strategy in the absence of human intervention.

Archaeologists know that humans have been harvesting clams for thousands of years, but modern technologies such as commercial fishing boats and SCUBA gear are depriving clams of refugia from which to repopulate other reefs. Increasing water turbidity due to coastal development, eutrophication, and dredging can make deeper water uninhabitable to giant clams, forcing their populations to reestablish in areas where they are more vulnerable to harvesting, tropical storms, and increasing water temperatures.

There is a significant amount of scientific literature regarding giant clams, particularly regarding their anatomy, physiology, and their symbiotic relationship with zooxanthellae. However, there are major gaps in the areas of their general ecology, reproductive behavior, and larval stages.

I will present the results of my experiments to determine giant clam larval tolerances to elevated water temperature, reduced light penetration, and reduced salinity.

I will also outline a proposed general ecology paper which will highlight and attempt to quantify the role that giant clams play in maintaining healthy reef ecosystems. There have been attempts in many countries to restock reefs with giant clams, although success rates have been low. Those efforts have not documented their strategy for placing clams in order to achieve high rates of survival and reproductive success.

I have carried out some preliminary investigations into giant clam reproductive behavior, and will continue and expand that work into a model resulting in guidelines for optimal clam placement. Clams in restocking efforts are initially placed in anti-predator cages, but their design is haphazard. I will experimentally compare several designs, including intertidal, benthic, and floating models, to determine which is most suitable for clam protection and growth in Singapore’s waters.

Finally, I plan to investigate the impacts of sediments on giant clams, using machinery which is capable of varying the timing and intensity of sediments to simulate various environmental or anthropogenic events.”

Read Full Post »

Fri 19 Apr 2013: 4.00pm – Dr Benito Tan on “Nomenclature and Plant Taxonomy: a challenging and interesting experience”

Read Full Post »

Wed, 17 Apr 2013,10am @ S1A SR: Mindy Tuan on “Comparative and experimental approaches to understanding sexual selection of sepsid flies”

Qualifying  Examination

“Comparative and experiment approaches to understanding  sexual selection of sepsid flies”

Speaker: Mindy Tuan 
Graduate Student,
Dept. of Biological Sciences, NUS
Wednesday, 17th April 2013: 10.00am
At the S1A Seminar Room, S1A- 02-17
(Next to the S1A Car Park/CBIS)
Supervisor: Prof Rudolf Meier

All are welcome

Abstract:

“Males often differ from females by having exaggerated ornaments and/or performing complex behaviours. Such sexually dimorphic traits are usually the product of sexual selection and can be morphological, behavioural, chemical or tactile in nature.

Here I use sepsid flies to study the evolution of such sexual dimorphisms to test whether they evolve faster and make a more significant contribution to speciation when compared with non-sexual traits.

Sepsid flies occur worldwide and comprise over 300 species. They possess a fascinating array of sexually dimorphic morphological and behavioural traits that are used during mating. In my research, I use sepsid flies to quantify the amount of correlated evolution between morphology and behaviour, study the evolution of copulation duration, and compare character change in pairs of closely related species and distantly related, allopatric populations.

My comparative work on 30 species already shows that sepsid fly mating behaviour varies tremendously, with flies assuming static positions and performing dynamic actions that are largely sex-specific. Furthermore, my data clarifies the relationship between morphology and behaviour by indicating instances in which morphological change is linked to behavioural change, and instances in which there is no such correlation.

I also studied the evolution of copulation duration across the 29 taxa and demonstrate that it evolves quickly although there is a significant phylogenetic effect with “basal” species having longer copulation times. I am currently testing whether this pattern correlates with the complexity of behaviour and morphology.

Moreover, I will look for traits that are influential in speciation, by studying morphological, behavioural and chemical traits in groups of closely related sister species (genetic distance for COI: 0-3%), as well as distantly related populations of a species (genetic distance for COI: 1.5% to 3%). Preliminary data suggest that behavior and morphology may evolve the fastest while the chemicals in a sexually dimorphic male gland evolve slowly.”

Read Full Post »

Fri, 19 Apr 2013, 4.00pm @ DBS Conf Rm: Chong Kwek Yan on “The Effects of Urban Greenery on Biodiversity”

PhD Defense Seminar cum Oral Examination

“The Effects of Urban Greenery on Biodiversity”

Chong Kwek Yan
Graduate Student
Dept. of Biological Sciences, NUS
19 April 2013, Friday
4:00PM
DBS Conference Room (S3, Level 5)
Supervisor: Assoc Prof Hugh Tan T W

All are welcome

Abstract – “The world’s growing urban population and urbanized areas have occurred in areas with high biodiversity value. Frontiers of urbanization are also approaching protected areas and encroaching upon habitats of threatened or endemic species. Urbanization usually involves the destruction of habitat when natural vegetation is cleared to make way for buildings and roads, but cultivated greenery and open green spaces such as parks are also created. Such greenery and green spaces have been used as urban planning tools to improve the quality of life for human residents in cities, but have also been thought to be able to improve habitat quality for urban wildlife.

Using data from surveys of birds and butterflies, and satellite imagery in Singapore, my analyses show that cultivated tree cover and natural vegetation both promoted alpha diversity, while traffic density reduced alpha diversity. However, after controlling for the confounding effects of alpha diversity on community dissimilarity, cultivated vegetation was found to produce homogeneous bird and butterfly communities compared to natural vegetation. In addition, there was evidence of interactions between traffic density and tree cover.

In addition, I explored how abundances of 20 most common bird species in a subset of transects that were surveyed a decade ago (from 2000 to 2001) have changed, and if changes in abundance were related to changes in the urban landscape, or attributable to species interactions. The brood parasitic Asian koel (Eudynamys scolopaceus), which is known to prefer house crow (Corvus splendens) as hosts, has increased in abundance even though the house crow has declined from culling. There was also no evidence that the decline in house crow abundances through culling had resulted in release from competition for its co-invading alien, the Javan myna (Acridotheres javanicus). Instead, increased urbanization was correlated with the increase in abundance of the Javan myna.

In conclusion, cultivated greenery has not been a good substitute for natural greenery in terms of providing for biodiversity. This poses problems for maintaining truly urban biodiversity in compact cities such as Singapore, where future urbanization will necessarily involve the loss of remnant or regenerating natural vegetation within the built-up areas.”

 

Read Full Post »

Thu 04 Apr 2013: 2.00pm @ DBS Conf Rm: Lynette Loke on “Enhancing biodiversity on tropical seawalls”

Qualifying Examination

“Enhancing biodiversity on tropical seawalls: the role of habitat complexity in regulating the diversity and composition of intertidal communities”

Loke Hui Ling, Lynette
Graduate Student,
Dept. of Biological Sciences, NUS
Supervisor: Asst Prof. Peter A. Todd

Thu 04 Apr 2013: 2.00pm
DBS Conference Room (S3, Level 5)

All are welcome

Abstract – “Increasing coastal urbanisation has resulted in widespread replacement of natural habitats with large-scale artificial structures, such as seawalls, which tend to support less diverse biological communities. With the realization that such infrastructure cannot be removed, there is now a call for more research into ways seawalls can be built to increase their value as a habitat while meeting engineering criteria.

To understand how seawalls can be better designed, I first focused on improving their structural complexity. Habitat complexity has been hypothesized to be one of the primary drivers of biodiversity, however, the mechanism(s) by which it does this remains unclear. One of the greatest impediments to advancing this critical area is the ambiguity regarding the definition of ‘complexity’.

In addition to making comparisons of ‘complexity studies’ highly problematic, this lack of terminological clarity and precision has undermined attempts to standardise the measurement of habitat complexity or to develop indices that can be used to create artificial habitats with different levels of complexity—an essential first step for both systematically studying the relationship between habitat complexity and biodiversity and for creating artificial habitats for restoration efforts.

I address these issues by describing a new framework for conceptualising ecological complexity and then introduce a novel software program that enables users to visualize static, physical complexity. My program also provides output files that can be used to create artificial substrates at any scale and level of complexity for experimental and/or restoration and reconciliation studies. With it, I built concrete tiles to test for the effects of complexity and different component types (while controlling for area) and subsequently, the effects of scale and water-retention.

With the knowledge gained from these experimental studies, I plan to design and fabricate a composite tile (BioBoss). Using this new tile, I will investigate the effects of other processes, including hydrodynamics, fragmentation and population dynamics.

Read Full Post »