PRIMER NOTE
CHAPTER 6 CONCLUSION & FUTURE DIRECTIONS
6.2 FUTURE DIRECTIONS
2006). Of the 28 loci tested, 27 were polymorphic in both species and one locus did not amplify. The 27 polymorphic loci can provide a selection of loci with which to compliment an existing suite of microsatellite markers in the wattled crane, a species for which a few whooping crane loci have previously been used for a population study (Jones et al. 2006). In addition, these 27 loci can provide a source of loci with which to undertake genetic studies in the grey-crowned crane, a species for which no genetic studies currently exist.
This study has characterised 27 markers available to the blue, wattled and grey-crowned crane. However, there is an additional source of loci that can be used in these species from the blue-crane species-specific microsatellite library. Due to time limitations, these were not tested for polymorphism in this study. Only 19 of the 57 blue crane species-specific loci developed for this study were tested for amplification and polymorphism in the blue crane.
Of these, only 14 were tested for polymorphism in the wattled and grey-crowned crane.
Cross-species amplification of blue cane loci in these species was shown to have a high level of success, suggesting that more polymorphic loci for wattled and grey-crowned crane can be sourced by testing the remaining blue crane loci not tested in this study.
Validation procedures arose when shortfalls in scientific techniques were recognised during the initial cases involving DNA evidence (Giannelli 2006). Consequently, extensive standardisation procedures have been developed by organisations such as the International Society for Forensic Genetics (ISFG) and the Scientific Working Group on DNA analysis (SWGDAM) for molecular techniques used in forensic cases. In South Africa, the organisation that sets the standards required for validation is the South African National Accreditation System (SANAS). Understandably, most validation protocols were designed for human forensic casework such as the validation of STR markers for human identification, with the subsequent publication of detailed validation reports (see Collinset al. 2004; Morettiet al. 2001).
Two types of validation, developmental and internal, are required before the genetic markers can be implemented for forensic use (SWGDAM 2004). Developmental validation is the demonstration of the accuracy,precision, and reproducibility of a procedure by the manufacturer, technical organization, academic institution, government lab, or other party (SWGDAM 2004). Recommended procedures to be carried out during developmental validation of microsatellite markers include: the determination of general locus characteristics (Chapter 5), species specificity, population studies, examining PCR-based procedures, stability, mixture studies, sensitivity of amplification, precision and accuracy studies,reproducibility and the analysis of case-type samples. The latter five procedures are also carried out for internal validation. This type of validation is conducted by each forensic DNA testing laboratory and provides an in house demonstration of the reliability and limitations of the procedure (SWGDAM 2004). Additional procedures to be carried out for internal validation include: contamination assessments and qualifying tests. Once the markers have been validated using the above procedures, they will be able to be used by forensic-accredited laboratories to provide robust DNA evidence for cases involving the illegal trade in the blue crane.
6.2.2 Research on population structure of the blue crane
Population studies of endangered species often aim to identify genetically distinct populations that may require management as separate entities (Frankham et al. 2002). The
main reason for this is the potential that each population has to evolve adaptations to local environmental pressures (Frankham et al. 2002). For example, a population supplementation program that translocated individuals unknowingly across geographically defined breeding barriers could result in outbreeding depression (Storfer 1999), resulting in the 'contamination' of the gene pool with genes adapted to different environmental conditions. Population analyses performed for the wattled crane (Grus carunculatus) using 12 microsatellite loci identified the South African population as being genetically distinct from the south-central African population (Jones et al.2006). This has direct management implication for this species. Should translocation or re-introductions be required, plans should consider the geographic origin and the genetic diversity of translocated individuals and their impact on the target population. With a set of molecular markers, such as the ones developed in this study, the population structure of blue cranes could be analysed. This could determine whether there are different populations that should be managed as separate entities, thereby providing the genetic information should population supplementation or reintroduction be required in the future.
6.2.3 Studbook management
Very little data on the status of the illegal removal of chicks from the wild exists (Morrison 2002). However, this could be improved by requiring owners of captive blue cranes to have their birds 'fingerprinted', for incorporation into studbook records (McCann et al. 2002), since these data could be called upon when the relationship between individuals needs to be determined to verify or refute claimed parentage of the bird in question. Microsatellite markers used for maintaining studbooks have been shown to be valuable for the conservation of the endangered whooping crane (G. americana) (lones et al. 2002). The motivation for incorporating DNA data into the studbook was not trade-related, but to provide a tool for maintaining genetic diversity within captive populations. Comprehensive pedigrees were constructed for captive populations of whooping cranes using genotypic data obtained from 11 microsatellite markers originally developed in this species (lones et al. 2002). The maintenance of genetic diversity in captive populations is difficult due to potential for inbreeding and genetic drift. An understanding of the relationship between individuals can allow for selective mating of genetically different individuals to produce
offspring with levels of heterozygosity greater than those of the founder population. This will boost the populations gene diversity (Jones et al. 2002). Increased gene diversity is especially advantageous as it allows for the selection of genes to assist adaptation to novel environmental conditions (such as the presence of new diseases) in future generations (Frankhamet al. 2002).Ultimately,it can assist in reducing the captive population's risk of extinction. Blue crane captive populations could benefit in a similar manner by including genetic data into studbooks to assess the most advantageous breeding strategies.