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Museum DNA reveals the demographic history of the endangered Seychelles warbler.

Spurgin LG, Wright DJ, van der Velde M, Collar NJ, Komdeur J, Burke T, Richardson DS - Evol Appl (2014)

Bottom Line: We found a 25% reduction in genetic diversity between museum and contemporary populations, and strong genetic structure.Such a rapid decline, due to anthropogenic factors, has important implications for extinction risk in the Seychelles warbler, and our results will inform conservation practices.Reconstructing the population history of this species also allows us to better understand patterns of genetic diversity, inbreeding and promiscuity in the contemporary populations.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of East Anglia Norwich, Norfolk, UK ; Behavioural Ecology and Self-organization Group, Centre for Ecological and Evolutionary Studies, University of Groningen Groningen, The Netherlands.

ABSTRACT
The importance of evolutionary conservation - how understanding evolutionary forces can help guide conservation decisions - is widely recognized. However, the historical demography of many endangered species is unknown, despite the fact that this can have important implications for contemporary ecological processes and for extinction risk. Here, we reconstruct the population history of the Seychelles warbler (Acrocephalus sechellensis) - an ecological model species. By the 1960s, this species was on the brink of extinction, but its previous history is unknown. We used DNA samples from contemporary and museum specimens spanning 140 years to reconstruct bottleneck history. We found a 25% reduction in genetic diversity between museum and contemporary populations, and strong genetic structure. Simulations indicate that the Seychelles warbler was bottlenecked from a large population, with an ancestral N e of several thousands falling to <50 within the last century. Such a rapid decline, due to anthropogenic factors, has important implications for extinction risk in the Seychelles warbler, and our results will inform conservation practices. Reconstructing the population history of this species also allows us to better understand patterns of genetic diversity, inbreeding and promiscuity in the contemporary populations. Our approaches can be applied across species to test ecological hypotheses and inform conservation.

No MeSH data available.


Related in: MedlinePlus

Population history of the Seychelles warbler (pictured inset). Dates represent first dates that Seychelles warblers were present on individual islands, and the last known date on Marianne, where the warbler was known to exist but is now extinct. Note that populations on Cousine, Aride, Denis and Frégate were established by translocations.
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fig01: Population history of the Seychelles warbler (pictured inset). Dates represent first dates that Seychelles warblers were present on individual islands, and the last known date on Marianne, where the warbler was known to exist but is now extinct. Note that populations on Cousine, Aride, Denis and Frégate were established by translocations.

Mentions: Here, we examine how genetic diversity has changed over a period of 140 years in the Seychelles warbler (Acrocephalus sechellensis), a small passerine endemic to the Seychelles archipelago in the Indian Ocean (Fig.1). In the 1960s, this species was reduced to a single population of reportedly fewer than 30 individuals on the tiny island of Cousin (4°20′S, 55°40′E, 0.29 km²; Penny 1967; Loustau-Lalanne 1968), and its recovery has been the focus of great conservation attention and scientific interest (Komdeur 1994; Komdeur and Pels 2005; Wright et al. 2014). In the process, the Seychelles warbler has become a long-term ecological and evolutionary model system (Komdeur 1992; Richardson et al. 2003; Barrett et al. 2013), making it an excellent candidate for studying population history. The species was confined to a restricted range (two predator-free islands) in the late 19th century (see Materials and methods), and it is unknown whether it was ever more widespread across the Seychelles, although it is assumed to have been so before the introduction of predators such as rats (Rattus spp.) and cats (Felis catus) (Collar and Stuart 1985). Relatively low levels of genetic diversity have been observed in the warbler at neutral and functional loci, and this has been linked to fitness (Richardson and Westerdahl 2003; Richardson et al. 2005; Brouwer et al. 2007, 2010). Despite this, the roles of natural and anthropogenic factors in shaping the patterns of genetic diversity in this species remain unknown. We first use DNA extracted from museum specimens to compare microsatellite diversity in the historical population with the contemporary population, allowing us to calculate how much genetic diversity has been lost over time. We then use a Bayesian approach, informed by available knowledge of the warbler's demographic history, to estimate ancestral population size and determine the timing and severity of the bottleneck. We then discuss how natural and anthropogenic factors have shaped patterns of genetic diversity in the Seychelles warbler, as well as the broader implications of using our methods and results for evolutionary and conservation biology.


Museum DNA reveals the demographic history of the endangered Seychelles warbler.

Spurgin LG, Wright DJ, van der Velde M, Collar NJ, Komdeur J, Burke T, Richardson DS - Evol Appl (2014)

Population history of the Seychelles warbler (pictured inset). Dates represent first dates that Seychelles warblers were present on individual islands, and the last known date on Marianne, where the warbler was known to exist but is now extinct. Note that populations on Cousine, Aride, Denis and Frégate were established by translocations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231601&req=5

fig01: Population history of the Seychelles warbler (pictured inset). Dates represent first dates that Seychelles warblers were present on individual islands, and the last known date on Marianne, where the warbler was known to exist but is now extinct. Note that populations on Cousine, Aride, Denis and Frégate were established by translocations.
Mentions: Here, we examine how genetic diversity has changed over a period of 140 years in the Seychelles warbler (Acrocephalus sechellensis), a small passerine endemic to the Seychelles archipelago in the Indian Ocean (Fig.1). In the 1960s, this species was reduced to a single population of reportedly fewer than 30 individuals on the tiny island of Cousin (4°20′S, 55°40′E, 0.29 km²; Penny 1967; Loustau-Lalanne 1968), and its recovery has been the focus of great conservation attention and scientific interest (Komdeur 1994; Komdeur and Pels 2005; Wright et al. 2014). In the process, the Seychelles warbler has become a long-term ecological and evolutionary model system (Komdeur 1992; Richardson et al. 2003; Barrett et al. 2013), making it an excellent candidate for studying population history. The species was confined to a restricted range (two predator-free islands) in the late 19th century (see Materials and methods), and it is unknown whether it was ever more widespread across the Seychelles, although it is assumed to have been so before the introduction of predators such as rats (Rattus spp.) and cats (Felis catus) (Collar and Stuart 1985). Relatively low levels of genetic diversity have been observed in the warbler at neutral and functional loci, and this has been linked to fitness (Richardson and Westerdahl 2003; Richardson et al. 2005; Brouwer et al. 2007, 2010). Despite this, the roles of natural and anthropogenic factors in shaping the patterns of genetic diversity in this species remain unknown. We first use DNA extracted from museum specimens to compare microsatellite diversity in the historical population with the contemporary population, allowing us to calculate how much genetic diversity has been lost over time. We then use a Bayesian approach, informed by available knowledge of the warbler's demographic history, to estimate ancestral population size and determine the timing and severity of the bottleneck. We then discuss how natural and anthropogenic factors have shaped patterns of genetic diversity in the Seychelles warbler, as well as the broader implications of using our methods and results for evolutionary and conservation biology.

Bottom Line: We found a 25% reduction in genetic diversity between museum and contemporary populations, and strong genetic structure.Such a rapid decline, due to anthropogenic factors, has important implications for extinction risk in the Seychelles warbler, and our results will inform conservation practices.Reconstructing the population history of this species also allows us to better understand patterns of genetic diversity, inbreeding and promiscuity in the contemporary populations.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of East Anglia Norwich, Norfolk, UK ; Behavioural Ecology and Self-organization Group, Centre for Ecological and Evolutionary Studies, University of Groningen Groningen, The Netherlands.

ABSTRACT
The importance of evolutionary conservation - how understanding evolutionary forces can help guide conservation decisions - is widely recognized. However, the historical demography of many endangered species is unknown, despite the fact that this can have important implications for contemporary ecological processes and for extinction risk. Here, we reconstruct the population history of the Seychelles warbler (Acrocephalus sechellensis) - an ecological model species. By the 1960s, this species was on the brink of extinction, but its previous history is unknown. We used DNA samples from contemporary and museum specimens spanning 140 years to reconstruct bottleneck history. We found a 25% reduction in genetic diversity between museum and contemporary populations, and strong genetic structure. Simulations indicate that the Seychelles warbler was bottlenecked from a large population, with an ancestral N e of several thousands falling to <50 within the last century. Such a rapid decline, due to anthropogenic factors, has important implications for extinction risk in the Seychelles warbler, and our results will inform conservation practices. Reconstructing the population history of this species also allows us to better understand patterns of genetic diversity, inbreeding and promiscuity in the contemporary populations. Our approaches can be applied across species to test ecological hypotheses and inform conservation.

No MeSH data available.


Related in: MedlinePlus