RESUMO
A major problem in conservation biology is the extent to which the loss of genetic variability in isolated populations reduces their chance of survival. We present data in which the loss of genetic diversity in small and isolated populations can be directly related to population dynamics. Genetic similarity in red squirrels is inversely correlated with population size. The loss of genetic variation and the lower population densities in isolated populations are both the result of reduced immigration. Our data suggest that population processes rather than genetic problems are the real threat to small squirrel populations.
Assuntos
Ecologia , Variação Genética , Sciuridae/genética , Animais , Bélgica , Conservação dos Recursos Naturais , Impressões Digitais de DNA , Demografia , Feminino , Masculino , Dinâmica PopulacionalRESUMO
A polymorphism at the adenosine deaminase locus of the house sparrow, Passer domesticus, has been investigated by starch gel electrophoresis. Five alleles have been identified, and most populations seem to be close to the Hardy-Weinberg equilibrium. The allele frequencies differ strikingly across Europe, and in Britian there are significant differences between urban and rural populations. Samples from introduced populations in Australia and New Zealand lack some of the rarer alleles, as predicted from the Founder Effect.
Assuntos
Adenosina Desaminase/genética , Aves/genética , Nucleosídeo Desaminases/genética , Polimorfismo Genético , Adenosina Desaminase/metabolismo , Animais , Animais Domésticos , Cruzamentos Genéticos , Feminino , Genótipo , Isoenzimas/genética , Masculino , Modelos Genéticos , Fenótipo , Distribuição TecidualRESUMO
Nine falcon single-locus minisatellite probes have been cloned, characterized and shown to provide a powerful alternative to multilocus f1p4fingerprinting for determining the parentage of broods of young. Eight clones derived from size-selected peregrine Falco peregrinus and merlin F. columbarius charomid libraries were found to detect single minisatellite loci in all tested members of the genus Falco. A further clone (cFti1) randomly selected from a kestrel F. tinnunculus library identified a single locus in other members of the genus and certain species of the Accipitridae. The nine loci display a mean heterozygosity of 88% and considerable allelic diversity in the peregrine and merlin. Pedigree analysis provides evidence consistent with the clustering of minisatellites in linkage groups that are conserved between species. Mutations were observed at five loci among families of peregrines and kestrels. Composite profiles produced with this suite of probes provide an excellent means of confirming identity and parentage. The use of profiling for investigating familial relationships, population dynamics and combating the illegal trade in wild falcons is discussed.
Assuntos
Aves/genética , Repetições Minissatélites , Técnicas de Sonda Molecular , Animais , Clonagem Molecular , Impressões Digitais de DNA , Sondas de DNA , Pai , Ligação Genética , Heterozigoto , MutaçãoRESUMO
Over the past twenty years, several techniques from biochemical and molecular genetics, such as enzyme electrophoresis and isoelectric focusing, have been widely and successfully applied to the study of population differentiation and evolution. However, they have been less applicable to demographic problems such as assigning parentage to individuals within a population. This stems from a general weakness of data derived from enzyme loci: allele frequencies at polymorphic loci are sufficiently skewed that the majority of individuals are of one or two genotypes. Many enzyme systems can only be examined post mortem, so that the loci are of little use if the animals are to be studied in the wild. The search for new and more sensitive techniques for detecting genetic variation has continued, and recently a major discovery has come from molecular biology. Jeffreys et al. have reported the detection of a type of hypervariable 'minisatellite' DNA that is extraordinarily polymorphic in human populations. We have applied their technique to several bird species and particularly to a population of house sparrows (Passer domesticus) near Nottingham. We report here that one of the human minisatellite clones is a suitable probe for sparrow DNA and that it reveals variation as extensive as that found in man. These results suggest that analysis of minisatellite DNA will be a powerful tool in the study of demographic population genetics.
Assuntos
Aves/genética , DNA/genética , Genética Populacional , Mapeamento de Nucleotídeos , Animais , DNA Recombinante , DNA Satélite/genética , Feminino , Variação Genética , Humanos , Masculino , Hibridização de Ácido Nucleico , Polimorfismo GenéticoRESUMO
Populations of seaweed fly Coelopa frigida are polymorphic at three loci determining the enzymes peptidase-1 (Pep-1), alcohol dehydrogenase (Adh) and larval esterase-2 (Es-2). Alleles at these loci have been shown by others to be non-randomly associated with each other. In the present paper we report non-random associations between the Adh and Es-2 loci and inversions on chromosome I. The two common alleles Adh-B and D are in strong linkage disequilibrium with the alpha and beta inversions, but the Adh-A and C alleles are not so. The X and Y alleles at the Es-2 locus show weak, but still significant, associations with the inversions. We consider possible linkage relationships of the loci on the chromosomal arrangements, and discuss the hypothesis that they constitute part of a coadapted gene complex whose members code for functionally related enzymes.
Assuntos
Oxirredutases do Álcool/genética , Inversão Cromossômica , Dípteros/genética , Esterases/genética , Peptídeo Hidrolases/genética , Polimorfismo Genético , Animais , Cromossomos/ultraestrutura , Genes , Ligação GenéticaRESUMO
The establishment of cormorant breeding colonies inland within south-east Britain since 1981 is a matter of major conservation and pest management concern. This study was initiated to investigate the subspecific origin of two recently established breeding colonies. The analysis examined sequence variation of the control (D-loop) region of the mitochondrial genome. Samples of tissue were obtained from 334 individuals from across the species range in western Europe from both subspecies (Phalacrocorax carbo carbo and P. c. sinensis) and 84 birds from two inland breeding colonies in Britain. Single-strand conformation polymorphism (SSCP) was used to assess mitochondrial variation among samples, revealing four haplotypes. The samples from the traditional breeding colonies clustered into three distinct phylogeographic groupings: Norway-Scotland, Wales-England-Iles des Chausey and the rest of Continental Europe. These results only partly agree with the traditional subspecific taxonomic groupings and are slightly at variance with results using microsatellite DNA frequencies, and a hypothesis using results from both studies is advanced. The subspecific origin of the inland colonies was investigated using maximum likelihood and Bayesian models.
Assuntos
Aves/genética , Animais , Teorema de Bayes , Aves/classificação , Cruzamento , Funções Verossimilhança , Filogenia , Polimorfismo Conformacional de Fita Simples , Reino UnidoRESUMO
Broods of young merlins were compared with the adults in attendance at their nest by DNA fingerprinting. No offspring were found that mismatched genetically suggesting that intraspecific brood parasitism and extrapair fertilization are very rare in this population. The results are discussed in the light of the Paternity Assurance Hypothesis.