DNA Science and Wildlife

Every living animal on Earth contains the most basic building blocks of life ? DNA, which provides them their biological identity either as an individual, a species or a population as well as their geographical origin and evolutionary history.  Using the understanding of DNA science, coupled with the presence of efficient molecular techniques to examine information in DNA markers (segments of DNA in the genome of organisms that reveal variations), biological information can be tapped, revealing otherwise unreachable information at all levels of life.  Furthermore, with the support of specific statistical tools and bioinformatics to analyse DNA data, inferences about the biology of organisms can be done, thus providing essential details for evolutionary, population and conservation biology.

Applications:

Molecular DNA Sex typing of  Birds

In a recently completed study in collaboration with Zoo Negara Malaysia, we applied a non-invasive DNA sexing method (through the use of feathers) on birds.   Knowing the sex of wildlife is crucial for the success of breeding efforts and this is more apparent in birds as both sexes do not show any distinct differences in their external morphology (sexual dimorphism) at their juvenile stage as well as at their adult stage.  DNA sexing has also provided a more reliable determination of the sex of birds which otherwise is done though invasive means such as surgical sexing or through morphological and behavioral features that can either be misleading and also not entirely accurate.  By utilizing the highly specific set of primers binding to the sex linked gene during PCR amplification followed by agarose gel electrophoresis; two fragments would be observed in females (CHD-Z and CHD-W) due to intron length differences which exist within the conserved regions whereas one fragment (CHD-Z) would be seen in males as shown in the figure below.  The complete study has been published in ?Ong, H.K.A., and Vellayan, S., (2007).  An Evaluation of CHD-Specific Primer Sets for Sex Typing of Birds from Feathers.  Zoo Biology. 27 (1): 62-69

In another related study, with molecular sex-typing as a reference, discriminant analysis was applied to develop a morphometric sexing method (discriminating male from female birds using body length measurements) of adult Milky Storks (Mycteria cinerea) and Painted Storks (Mycteria leucocephala).  The best one-variable discriminant function seen in both Milky and Painted stork is the bill length which predicted an accuracy of about 90% and 95% respectively.

Painted Stork        Milky Stork        Bill measurement                          Hybrid

(Painted x  Milky)

Conservation Genetics

Studies on genetic diversity involving wildlife and/or biological resources provide valuable information on the distribution of genetic variation within and between populations, either in captivity or in the wild.  Such information provide more holistic options for maintaining individual fitness, avoiding dilution of the natural population gene pool causing possible extinction of the affected species and strategies for sustainable development of our natural resources.

(i)       Hybrid detection of birds

An undergraduate project involving the development of Single Nucleotide Polymorphism (SNP) markers on a coding region of the nuclear DNA showed the potential of the gene region as a DNA marker for hybrid typing.  The initial study showed two diagnostic heterozygous base on the hybrid bird as compared to the pure species which were homozygous at the same site.   Hybridization can have both beneficial and deleterious effect on the conservation of biological diversity.

(ii)      Our current research is on the population structure of a highly endangered local freshwater crocodile (Tomistoma schlegelii) using nuclear and mitochondria markers to infer biogeographical distribution of the species range within Malaysia and South East Asia.  A similar approach is used in another study involving intraspecific variation and interspecific divergence for sergestid shrimps (the shrimp species used in local delicacies such as ?Belachan? and ?Chinchalok?), caught by trawlers along the west coast of Malaysia.

                                                          False gharial   (T.  schlegelii)                   

Contributor,                                                  

Dr. Alan Ong Han Kiat