Recent demographic histories of temperate deciduous trees inferred from microsatellite markers

Background Accurate inference of demographic histories for temperate tree species can aid our understanding of current climate change as a driver of evolution. Microsatellites are more suitable for inferring recent historical events due to their high mutation rates. However, most programs analyzing microsatellite data assume a strict stepwise mutation model (SMM), which could cause false detection of population shrinkage when microsatellite mutation does not follow SMM. Results This study aims to reconstruct the recent demographic histories of five cool-temperate tree species in Eastern Asia, Quercus mongolica, Q. liaotungensis, Juglans cathayensis, J. mandshurica and J. ailantifolia, by using 19 microsatellite markers with two methods considering generalized stepwise mutation model (GSM) (MIGRAINE and VarEff). Both programs revealed that all the five species experienced expansions after the Last Glacial Maximum (LGM). Within butternuts, J. cathayensis experienced a more serious bottleneck than the other species, and within oaks, Q. mongolica showed a moderate increase in population size and remained stable after the expansion. In addition, the point estimates of the multistep mutation proportion in the GSM model (pGSM) for all five species were between 0.50 and 0.65, indicating that when inferring population demographic history of the cool-temperate forest species using microsatellite markers, it is better to assume a GSM rather than a SMM. Conclusions This study provides the first direct evidence that five cool-temperate tree species in East Asia have experienced expansions after the LGM with microsatellite data. Considering the mutation model of microsatellite has a vital influence on demographic inference, combining multiple programs such as MIGRAINE and VarEff can effectively reduce errors caused by inappropriate model selection and prior setting.

Recent demographic histories of temperate deciduous trees inferred from microsatellite markers

Background Accurate inference of demographic histories of temperate tree species can aid our understanding of current climate change as a driver of evolution. Microsatellites are more suitable for reflecting recent historical events due to their high mutation rates. However, most programs analyze microsatellite data following a strict stepwise mutation model (SMM), which could cause false detection of population shrinkage when microsatellite mutation is not according with SMM. Results This study aims to reconstruct the recent demographic histories of five cool-temperate tree species, Quercus mongolica, Q. liaotungensis, Juglans cathayensis, J. mandshurica and J. ailantifolia, in eastern Asia by using 19 microsatellite markers and two methods considering generalized stepwise mutation model (GSM) (MIGRAINE and VarEff). Both types of software revealed that all populations experienced expansions after the Last Glacial Maximum (LGM). In particular, J. cathayensis experienced a more serious bottleneck in its history than the other species, leading to a smaller effective population of ancestors, while Q. mongolica showed only a moderate increase in population size and remained stable after the expansion. In addition, the point estimates of the multistep mutation proportion in the generalized stepwise mutation model (pGSM) in all populations were between 0.50 and 0.65, which indicates that when inferring population demographic history of the above forest species using microsatellite molecular markers, it is better to assume a GSM rather than a SMM. Conclusions This study provides the first direct evidence that five cool-temperate tree species in East Asia have experienced expansions after the LGM using microsatellites data. Moreover, since the mutation model of microsatellite have a vital influence on demographic inference, combining multiple software programs such as MIGRAINE and VarEff can effectively reduce unnecessary errors caused by inappropriate model selection and prior setting.

Variabilidade genética de larvas e alevinos de piracanjuba (Brycon orbignyanus)

RESUMO O objetivo do presente trabalho foi avaliar a variabilidade genética de larvas e alevinos de piracanjuba em programa de repovoamento. Foram coletadas 180 larvas de piracanjuba de três dias e 90 alevinos de três meses de idade. Foram avaliados cinco loci microssatélites, os quais produziram 19 alelos. Não houve presença de alelos raros nem perdas de alelos ao longo do período. A heterozigosidade observada foi superior nas larvas em relação aos alevinos. Houve desvio no equilíbrio de Hardy-Weinberg na maioria dos loci em ambos os grupos. O coeficiente de endogamia foi positivo em ambos os grupos, sendo a média dos alevinos superior em relação às larvas. O excesso de heterozigotos foi significativo no modelo Stepwise Mutation Model para os alevinos, indicando a possibilidade de efeito gargalo recente. Conclui-se que, apesar da adequada variabilidade genética encontrada, os valores do coeficiente de endogamia e a possibilidade de efeito gargalo nos alevinos atentam para a necessidade de constante monitoramento genético desses estoques antes da liberação no ambiente.