Investigation of the utilization of microsatellites for fingerprinting in three endangered southern African crane species.
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Date
2006
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Abstract
Cranes are large elegant birds that occur on all continents of the world except for
South America and Antarctica. Of the fifteen species of crane worldwide, three
predominantly occur in southern Africa; the Wattled crane (Bugeranus carunculatus),
the Blue crane (Anthropoides paradisea) and the Crowned crane (Balearica
regulorum). Crane numbers throughout the world are diminishing, mostly because of
the destruction of their habitat and illegal bird trading. Efforts are underway to
prevent species extinction, legally and through the compilation of a studbook that
contains descriptions of physical attributes, ownership, location and possible
kinships of birds in captivity . This investigation, first of its kind, WdS undertaken to
assess whether twelve published and unpublished microsatellite primers developed
for the related Whooping crane and Red-Crowned crane could be used to fingerprint
the southern African crane species using cost effective polyacrylamide gel
electrophoresis. The results obtained were then used to determine the extent of
genetic variation within species and distance between species.
All primer sets amplified heterologous microsatellite loci in the three crane species,
however, the unpublished primers produced poorly defined fingerprints even after
extensive optimization. Of the twelve microsatellite loci investigated, the Blue crane
and the Wattled crane revealed a high level of polymorphism. The Blue crane
displayed 76% polymorphism and the Wattled crane 92%. In contrast, for the
Crowned crane, that belongs to a different subfamily, Balearicinae, only 50% of the
loci were polymorphic. The alleles displayed sizes similar to that of the species for
which the primers were developed. Little variation in size, less than 10 bp, was noted
for the different alleles of the polymorphic loci. The number of alleles, on the other
hand, at each of the polymorphic loci was found to be low. The frequency of the
most prevalent allele at most of the loci was generally reasonably high. These
results therefore suggest that these primer sets are not suitable for individual
identification and differentiation using polyacrylamide gel electrophoresis.
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The observed heterozygosity of the three crane species was low; 12% in Blue crane;
7% in Crowned crane; and 13% in Wattled crane. Nei's identity further confirmed the
high similarity between individuals; 66-100% for Blue crane; 55-100% for Crowned
crane and 41-95% for Wattled crane. This low genetic variation is attributed to
possible relatedness between birds supplied by aviculturists whom have a limited
number of birds in captivity. A Hardy-Weinberg test for equilibrium revealed that
most of the microsatellite loci displayed a deficiency of heterozygotes, while a few
loci displayed an excess of heterozygotes. In general, the Hardy Weinberg test of
equilibrium supported the notion that the individuals within each of the species might
have been related.
Differentiation between the three crane species ranged from 3-5%, with Blue and
Wattled crane displaying a higher degree of genetic similarity when compared to the
Crowned crane, known to be the oldest extant crane species.
The limited allelic variation within the microsatellite loci tested, as well as the
extensive genetic similarity between individuals suggests that a wide-ranging search
for additional microsatellite loci that are more polymorphic and contain a larger
number of alleles should be undertaken for the southern African crane species.
Description
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
Keywords
Cranes (Birds)--Africa, Southern., Microsatellites (Genetics)., Birds, Protection of--Africa, Southern., DNA fingerprinting., Genetic markers., DNA fingerprinting--Technique., Genetic polymorphisms., Theses--Genetics.