Lack of Genetic Structuring among Tropical Brazilian Wood Stork Populations and Low Genetic Differentiation from North American Populations

Abstract

The Wood Stork (Mycteria americana) is a wading bird inhabiting subtropical and tropical regions of the American continent. This species is considered endangered in the United States. We compared variability and genetic structuring of nine Brazilian Pantanal subpopulations with an North American population using eight allozyme loci data (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, and PEP‐A) and four microsatellite loci data (WS1, WS2, WS4, and WS6). Average expected heterozygosity of Pantanal population was similar (0.198 ± 0.065) to that expected for the North American population (0.231 ± 0.066). No significant genetic differentiation was found among Pantanal subpopulations (Fst= 0.012) and low differentiation was detected between Pantanal and North American populations (Fst= 0.023). Lack of differentiation among Pantanal subpopulations may have been due to high gene flow level among birds of neighbor breeding colonies and low natal philopatry. We propose that low differentiation between North and South American populations has arisen either because these populations occupied neighboring regions during late glaciation or because there is a continuous gene flow between them, via Central American or northern South American populations. RESUMO O Cabeça‐seca (Mycteria americana) é uma ave aquática habitante das regiões tropicais e subtropicais do continente americano. Essa espécie está ameaçada de extinção nos Estados Unidos. Nós comparamos a variabilidade e a estruturação genética de nove subpopulações brasileiras do Pantanal com as da população norte americana, baseando‐se em dados de oito locos alozímicos (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, e PEP‐A) e em dados de quatro locos de microssatélites (WS1, WS2, WS4, e WS6). A heterozigosidade média esperada para a população do Pantanal (0.198 ± 0.065) foi semelhante á esperada para a população norte americana (0.231 ± 0.066). Não foi encontrada diferenciação genética significativa entre as subpopulaçóes do Pantanal (Fst= 0.012) e baixa diferenciação genética foi detectada entre as populações do Pantanal e a norte americana (.Fst= 0.023). A não diferenciação entre subpopulações do Pantanal pode ser resultante de um alto nível do fluxo génico entre aves de colónias reprodutivas vizinhas e da baixa filopatria natal. Nós propomos que a baixa diferenciação entre as populações norte e sul americanas seja decorrente da ocupaçaTo de regiões vizinhas por essas populações durante a última glaciação ou devido á existéncia de fluxo contínue entre elas, via populações da América Central ou do norte da América do Sul.

Genetic diversity and evidence of recent demographic expansion in waterbird populations from the Brazilian Pantanal

“…Similarly, Wood Stork population analyses revealed no statistical differences in genetic diversity between the threatened southeastern US breeding populations and those of the Pantanal (Tomasulo-Seccomandi, 2004). The lack of difference in genetic variability levels between Wood Stork samples collected in these two areas was also reported in previous studies based on allozymes and four different microsatellite loci (Del Lama et al, 2002;Rocha et al, 2004). Expansions of Jabiru Stork variability analyses indicated that the Pantanal samples exhibited no significant differences when compared to both northern South American population (Venezuela and Guyana) or to the endangered Central American (Belize) population (Lopes et al, unpublished data).…”

Demographic history of wood stork (Mycteria americana) Brazilian Pantanal colonies revealed by mitochondrial DNA analysis

“…Previous studies of the genetic structure of the wood stork Pantanal breeding colonies using nuclear genetic markers showed no genetic differentiation and a high level of gene flow among breeding colonies (Del Lama et al, 2002;Rocha et al, 2004) which led investigators to conclude that all the wood stork Pantanal colonies belong to a single panmictic population and that distance did not represent a significant barrier to gene flow among colonies in the same region. Our AMOVA showed no differentiation among wood stork colonies in the Pantanal.…”

“…Previous studies investigated the spatial patterns of variation and genetic differentiation among wood stork colonies using nuclear DNA markers (Stangel et al, 1990;Van Den Bussche et al, 1999;Del Lama et al, 2002;Rocha et al, 2004). Allozyme (Stangel et al, 1990), microsatellite, and DNA fingerprint-ing analyses (Van Den Bussche et al, 1999) have indicated low levels of genetic differentiation among wood stork colonies in the US, and the authors speculated that these patterns were the result of recent colonization and high gene flow.…”

“…The genetic structure of wood stork colonies in the Brazilian Pantanal has been assessed using the same allozyme and microsatellite loci described in the US population. No differentiation was detected and the survey indicated high gene flow among members of neighboring colonies (Del Lama et al, 2002;Rocha et al, 2004).…”

Genetic status of the wood stork (Mycteria americana) from the southeastern United States and the Brazilian Pantanal as revealed by mitochondrial DNA analysis

“…Previous comparisons of genetic variability and differentiation among wood stork colonies sampled in the US and Brazil have used nuclear DNA markers (Del Lama et al, 2002;Rocha et al, 2004). Analyses of these markers showed similar levels of genetic variability between the two regions using allozymes (Del Lama et al, 2002) and/or microsatellites (Rocha et al, 2004).…”