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Eric J. Fuchs - One of the best experts on this subject based on the ideXlab platform.
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Spatial distribution of Guaiacum sanctum (Zygophyllaceae) seedlings and saplings relative to canopy cover
2016Co-Authors: Eric J. Fuchs, Tatiana Robles, James L. HamrickAbstract:Abstract: Distribución espacial de Guaiacum sanctum (Zygophyllaceae) en relación con la cobertura de dosel en el Parque Nacional Palo Verde, Costa Rica. The spatial distribution of individuals is a fundamental property of most species and constitutes essential information for the development of restoration and conserva-tion strategies, especially for endangered plant species. In this paper we describe the spatial distribution of dif-ferent size classes of the endangered tropical tree Guaiacum sanctum and the effect of canopy cover on spatial aggregation. Adult G. sanctum were located and mapped in a 50ha plot in Palo Verde National Park, Costa Rica. Seedlings, saplings and juveniles were mapped to the nearest centimetre and permanently marked in three 50x50m subplots. Within each subplot spatial aggregation was assessed using Ripley’s K statistic and canopy opening readings were performed every 5m using a densitometer. Kriging spatial interpolation and Monte Carlo simulations were used to determine if average canopy cover differed among size classes. Individuals of G. sanc-tum were spatially aggregated at all size classes with seedlings being the most frequent size class in all subplots. Seedlings were found predominantly in areas with significantly higher canopy cover. In contrast, juveniles were more likely found in areas with higher light availability. The high number of seedlings, saplings, and juveniles relative to adults suggests that populations of G. sanctum in PVNP are expanding. Light availability and canopy structure are important factors shaping the spatial distribution of this species. The contemporary demographi
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Mating system and pollen flow between remnant populations of the endangered tropical tree, Guaiacum sanctum (Zygophyllaceae)
Conservation Genetics, 2010Co-Authors: Eric J. Fuchs, James L. HamrickAbstract:Tropical trees are generally long-lived making it difficult to assess the long-term effects of habitat fragmentation on genetic diversity. Maintenance of genetic diversity in fragmented landscapes is largely dependent on the species’ mating system and the degree of genetic connectivity (seed and pollen flow) among fragments. Currently, these parameters are largely unknown for many endangered tropical tree species. Additionally, landscape fragmentation may isolate tropical tree populations from larger, more continuous populations. The role of isolated individuals in pollen transfer within and between remnant populations is not clear. In this study, we estimate the mating system and pollen flow patterns in continuous and remnant populations of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae). Fractional paternity analyses were used to estimate average gene flow distances between fragmented remnant populations and the siring success of an intermediately located, but isolated individual. In these populations, G. sanctum is a mixed-mating species (t m = 0.72 − 0.95) whose pollen is transported over large distances (>4 km). An isolated tree may have functioned as a stepping-stone between two clusters of individuals, assisting long-distance pollen movement. This individual also sired a disproportionately high number of seeds (13.9%), and is thus an important component of the reproductive success of these populations, thus rejecting Janzen’s “living-dead” hypothesis. The high levels of genetic diversity maintained as a consequence of long-distance pollen-flow suggest that this endangered species may have the potential for future adaptation and population expansion if suitable habitats become available.
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spatial genetic structure within size classes of the endangered tropical tree Guaiacum sanctum zygophyllaceae
American Journal of Botany, 2010Co-Authors: Eric J. Fuchs, J L HamrickAbstract: Premise of the study : Patterns of spatial genetic structure (SGS) were analyzed within a population of the endangered tropical tree Guaiacum sanctum located in northwestern Costa Rica. Documentation of these patterns provides insights into the gene dispersal mechanisms that play a central role in the maintenance and structure of genetic diversity within plant populations. Methods : Allozyme analyses were used to examine SGS in Palo Verde National Park, Costa Rica. The SGS was compared among three plots and different age classes. Key results : High levels of genetic diversity were found overall with a pooled genetic diversity of H e = 0.302 ( ± 0.02). Selfi ng was proposed as the proximate cause for signifi cant levels of heterozygote defi ciency observed across size classes and plots. An unexpected lack of SGS ( r j < 0.02) was observed for all size classes, suggesting the mixing of seeds from several adults. A parent-pair parentage analysis indicated that at least 48% of the smaller individuals within a plot were produced by parents located at distances of at least 150 m. Conclusions : Populations of G. sanctum are established and maintained by bird-mediated, moderate- to long-distance seed dispersal, which results in a mixture of seeds from unrelated maternal individuals, effectively eliminating SGS. Proximity between individuals is, therefore, a poor predictor of family structure in this species. Long-distance seed dispersal, coupled with estimates of high genetic diversity, suggests that this endangered species has the potential for natural regeneration and restoration given the availability of suitable habitats.
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genetic diversity in the endangered tropical tree Guaiacum sanctum zygophyllaceae
Journal of Heredity, 2010Co-Authors: Eric J. Fuchs, J L HamrickAbstract:Fragmentation of tropical forests has changed continuous tropical landscapes into a network of poorly connected fragments, reducing population sizes and potentially increasing genetic isolation. This study quantifies genetic diversity within and among the 7 extant populations of the endangered tropical tree Guaiacum sanctum in Costa Rica. We describe how genetic diversity differs between populations representing continuous and fragmented habitats. Allozyme analyses were conducted on adult samples from populations representing 2 geographic regions in northwestern Costa Rica. We found high levels of genetic diversity within the species (H(es) = 0.329) and significant but relatively small differences in allele frequencies among populations (G(ST) = 0.101) and between regions (G(ST) = 0.053). We found no differences in genetic diversity between fragmented and continuous populations. Evidence for significant isolation-by-distance (IBD) was seen only when all populations were analyzed. If populations within the 2 regions were analyzed separately, IBD ceased to be significant. Our results suggest that the patterns of genetic diversity observed for G. sanctum may be caused by the ancient separation of populations into 2 disjunct geographic regions with extensive historical rates of gene flow among populations within each region. Recent forest fragmentation has not yet affected patterns of genetic diversity in this species.
J L Hamrick - One of the best experts on this subject based on the ideXlab platform.
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spatial genetic structure within size classes of the endangered tropical tree Guaiacum sanctum zygophyllaceae
American Journal of Botany, 2010Co-Authors: Eric J. Fuchs, J L HamrickAbstract: Premise of the study : Patterns of spatial genetic structure (SGS) were analyzed within a population of the endangered tropical tree Guaiacum sanctum located in northwestern Costa Rica. Documentation of these patterns provides insights into the gene dispersal mechanisms that play a central role in the maintenance and structure of genetic diversity within plant populations. Methods : Allozyme analyses were used to examine SGS in Palo Verde National Park, Costa Rica. The SGS was compared among three plots and different age classes. Key results : High levels of genetic diversity were found overall with a pooled genetic diversity of H e = 0.302 ( ± 0.02). Selfi ng was proposed as the proximate cause for signifi cant levels of heterozygote defi ciency observed across size classes and plots. An unexpected lack of SGS ( r j < 0.02) was observed for all size classes, suggesting the mixing of seeds from several adults. A parent-pair parentage analysis indicated that at least 48% of the smaller individuals within a plot were produced by parents located at distances of at least 150 m. Conclusions : Populations of G. sanctum are established and maintained by bird-mediated, moderate- to long-distance seed dispersal, which results in a mixture of seeds from unrelated maternal individuals, effectively eliminating SGS. Proximity between individuals is, therefore, a poor predictor of family structure in this species. Long-distance seed dispersal, coupled with estimates of high genetic diversity, suggests that this endangered species has the potential for natural regeneration and restoration given the availability of suitable habitats.
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genetic diversity in the endangered tropical tree Guaiacum sanctum zygophyllaceae
Journal of Heredity, 2010Co-Authors: Eric J. Fuchs, J L HamrickAbstract:Fragmentation of tropical forests has changed continuous tropical landscapes into a network of poorly connected fragments, reducing population sizes and potentially increasing genetic isolation. This study quantifies genetic diversity within and among the 7 extant populations of the endangered tropical tree Guaiacum sanctum in Costa Rica. We describe how genetic diversity differs between populations representing continuous and fragmented habitats. Allozyme analyses were conducted on adult samples from populations representing 2 geographic regions in northwestern Costa Rica. We found high levels of genetic diversity within the species (H(es) = 0.329) and significant but relatively small differences in allele frequencies among populations (G(ST) = 0.101) and between regions (G(ST) = 0.053). We found no differences in genetic diversity between fragmented and continuous populations. Evidence for significant isolation-by-distance (IBD) was seen only when all populations were analyzed. If populations within the 2 regions were analyzed separately, IBD ceased to be significant. Our results suggest that the patterns of genetic diversity observed for G. sanctum may be caused by the ancient separation of populations into 2 disjunct geographic regions with extensive historical rates of gene flow among populations within each region. Recent forest fragmentation has not yet affected patterns of genetic diversity in this species.
James L. Hamrick - One of the best experts on this subject based on the ideXlab platform.
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Spatial distribution of Guaiacum sanctum (Zygophyllaceae) seedlings and saplings relative to canopy cover
2016Co-Authors: Eric J. Fuchs, Tatiana Robles, James L. HamrickAbstract:Abstract: Distribución espacial de Guaiacum sanctum (Zygophyllaceae) en relación con la cobertura de dosel en el Parque Nacional Palo Verde, Costa Rica. The spatial distribution of individuals is a fundamental property of most species and constitutes essential information for the development of restoration and conserva-tion strategies, especially for endangered plant species. In this paper we describe the spatial distribution of dif-ferent size classes of the endangered tropical tree Guaiacum sanctum and the effect of canopy cover on spatial aggregation. Adult G. sanctum were located and mapped in a 50ha plot in Palo Verde National Park, Costa Rica. Seedlings, saplings and juveniles were mapped to the nearest centimetre and permanently marked in three 50x50m subplots. Within each subplot spatial aggregation was assessed using Ripley’s K statistic and canopy opening readings were performed every 5m using a densitometer. Kriging spatial interpolation and Monte Carlo simulations were used to determine if average canopy cover differed among size classes. Individuals of G. sanc-tum were spatially aggregated at all size classes with seedlings being the most frequent size class in all subplots. Seedlings were found predominantly in areas with significantly higher canopy cover. In contrast, juveniles were more likely found in areas with higher light availability. The high number of seedlings, saplings, and juveniles relative to adults suggests that populations of G. sanctum in PVNP are expanding. Light availability and canopy structure are important factors shaping the spatial distribution of this species. The contemporary demographi
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Mating system and pollen flow between remnant populations of the endangered tropical tree, Guaiacum sanctum (Zygophyllaceae)
Conservation Genetics, 2010Co-Authors: Eric J. Fuchs, James L. HamrickAbstract:Tropical trees are generally long-lived making it difficult to assess the long-term effects of habitat fragmentation on genetic diversity. Maintenance of genetic diversity in fragmented landscapes is largely dependent on the species’ mating system and the degree of genetic connectivity (seed and pollen flow) among fragments. Currently, these parameters are largely unknown for many endangered tropical tree species. Additionally, landscape fragmentation may isolate tropical tree populations from larger, more continuous populations. The role of isolated individuals in pollen transfer within and between remnant populations is not clear. In this study, we estimate the mating system and pollen flow patterns in continuous and remnant populations of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae). Fractional paternity analyses were used to estimate average gene flow distances between fragmented remnant populations and the siring success of an intermediately located, but isolated individual. In these populations, G. sanctum is a mixed-mating species (t m = 0.72 − 0.95) whose pollen is transported over large distances (>4 km). An isolated tree may have functioned as a stepping-stone between two clusters of individuals, assisting long-distance pollen movement. This individual also sired a disproportionately high number of seeds (13.9%), and is thus an important component of the reproductive success of these populations, thus rejecting Janzen’s “living-dead” hypothesis. The high levels of genetic diversity maintained as a consequence of long-distance pollen-flow suggest that this endangered species may have the potential for future adaptation and population expansion if suitable habitats become available.
Hamrick, James L. - One of the best experts on this subject based on the ideXlab platform.
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Spatial distribution of Guaiacum sanctum (Zygophyllaceae) seedlings and saplings relative to canopy cover in Palo Verde National Park, Costa Rica
'Universidad de Costa Rica', 2016Co-Authors: Fuchs Castillo, Eric J., Robles Tatiana, Hamrick, James L.Abstract:La distribución espacial es una característica fundamental de las especies y es importante para el desarrollo de estrategias de conservación y manejo. Aquí presentamos la distribución espacial de varias etapas de desarrollo del árbol tropical Guaiacum sanctum, una especie en vías de extinción. Todos los adultos de G. sanctum se geo-referenciaron en una parcela de 50ha en el Parque Nacional Palo Verde. Las plántulas, los briznales y juveniles se mapearon en tres sub-parcelas de 50x50m. En cada sub-parcela se estimó la agregación espacial de los individuos mediante la K de Ripley. Observamos que los individuos de G. sanctum se encuentran siempre agregados, sin importar en que etapa de desarrollo se encuentren. Registramos la apertura del dosel cada 5m con un densiómetro y mediante una extrapolación espacial (Krigin) determinamos que las plántulas se agregan con mayor frecuencia en áreas con abundante cobertura de dosel, mientras que es más probable encontrar juveniles agregados en áreas con una mayor incidencia de luz. Las plántulas son los individuos más abundantes, esta distribución de edades nos sugiere que esta población probablemente está en expansión. Concluimos que el régimen lumínico y la cobertura de dosel son factores que afectan significativamente la distribución espacial del Guayacán Real.The spatial distribution of individuals is a fundamental property of most species and constitutes essential information for the development of restoration and conservation strategies, especially for endangered plant species. In this paper we describe the spatial distribution of different size classes of the endangered tropical tree Guaiacum sanctum and the effect of canopy cover on spatial aggregation. Adult G. sanctum were located and mapped in a 50ha plot in Palo Verde National Park, Costa Rica. Seedlings, saplings and juveniles were mapped to the nearest centimetre and permanently marked in three 50x50m subplots. Within each subplot spatial aggregation was assessed using Ripley’s K statistic and canopy opening readings were performed every 5m using a densitometer. Kriging spatial interpolation and Monte Carlo simulations were used to determine if average canopy cover differed among size classes. Individuals of G. sanctum were spatially aggregated at all size classes with seedlings being the most frequent size class in all subplots. Seedlings were found predominantly in areas with significantly higher canopy cover. In contrast, juveniles were more likely found in areas with higher light availability. The high number of seedlings, saplings, and juveniles relative to adults suggests that populations of G. sanctum in PVNP are expanding. Light availability and canopy structure are important factors shaping the spatial distribution of this species. The contemporary demographic structure of G. sanctum is dependent on forest gap dynamics and changes in human disturbance during the past 25 years
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Mating system and pollen flow between remnant populations of the endangered tropical tree, Guaiacum sanctum (Zygophyllaceae)
'Springer Science and Business Media LLC', 2011Co-Authors: Fuchs Castillo, Eric J., Hamrick, James L.Abstract:Tropical trees are generally long-lived making it difficult to assess the long-term effects of habitat fragmentation on genetic diversity. Maintenance of genetic diversity in fragmented landscapes is largely dependent on the species’ mating system and the degree of genetic connectivity (seed and pollen flow) among fragments. Currently, these parameters are largely unknown for many endangered tropical tree species. Additionally, landscape fragmentation may isolate tropical tree populations from larger, more continuous populations. The role of isolated individuals in pollen transfer within and between remnant populations is not clear. In this study, we estimate the mating system and pollen flow patterns in continuous and remnant populations of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae). Fractional paternity analyses were used to estimate average gene flow distances between fragmented remnant populations and the siring success of an intermediately located, but isolated individual. In these populations, G. sanctum is a mixed-mating species (t m = 0.72 − 0.95) whose pollen is transported over large distances (>4 km). An isolated tree may have functioned as a stepping-stone between two clusters of individuals, assisting long-distance pollen movement. This individual also sired a disproportionately high number of seeds (13.9%), and is thus an important component of the reproductive success of these populations, thus rejecting Janzen’s “living-dead” hypothesis. The high levels of genetic diversity maintained as a consequence of long-distance pollen-flow suggest that this endangered species may have the potential for future adaptation and population expansion if suitable habitats become available.Universidad de Costa RicaOrganization for Tropical StudiesNational Science FoundationUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
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Genetic diversity in the endangered tropical tree, Guaiacum sanctum (Zygophyllaceae)
'Oxford University Press (OUP)', 2010Co-Authors: Fuchs Castillo, Eric J., Hamrick, James L.Abstract:Fragmentation of tropical forests has changed continuous tropical landscapes into a network of poorly connected fragments, reducing population sizes and potentially increasing genetic isolation. This study quantifies genetic diversity within and among the 7 extant populations of the endangered tropical tree Guaiacum sanctum in Costa Rica. We describe how genetic diversity differs between populations representing continuous and fragmented habitats. Allozyme analyses were conducted on adult samples from populations representing 2 geographic regions in northwestern Costa Rica. We found high levels of genetic diversity within the species (Hes = 0.329) and significant but relatively small differences in allele frequencies among populations (GST = 0.101) and between regions (GST = 0.053). We found no differences in genetic diversity between fragmented and continuous populations. Evidence for significant isolation-by-distance (IBD) was seen only when all populations were analyzed. If populations within the 2 regions were analyzed separately, IBD ceased to be significant. Our results suggest that the patterns of genetic diversity observed for G. sanctum may be caused by the ancient separation of populations into 2 disjunct geographic regions with extensive historical rates of gene flow among populations within each region. Recent forest fragmentation has not yet affected patterns of genetic diversity in this species.Idea WildUniversidad de Costa RicaOrganization for Tropical StudiesNational Science FoundationUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
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Spatial genetic structure within size classes of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae)
'Botanical Society of America', 2010Co-Authors: Fuchs Castillo, Eric J., Hamrick, James L.Abstract:Premise of the study: Patterns of spatial genetic structure (SGS) were analyzed within a population of the endangered tropical tree Guaiacum sanctum located in northwestern Costa Rica. Documentation of these patterns provides insights into the gene dispersal mechanisms that play a central role in the maintenance and structure of genetic diversity within plant populations. • Methods: Allozyme analyses were used to examine SGS in Palo Verde National Park, Costa Rica. The SGS was compared among three plots and different age classes. • Key results: High levels of genetic diversity were found overall with a pooled genetic diversity of He = 0.302 ( ± 0.02). Selfi ng was proposed as the proximate cause for signifi cant levels of heterozygote defi ciency observed across size classes and plots. An unexpected lack of SGS ( rj < 0.02) was observed for all size classes, suggesting the mixing of seeds from several adults. A parent-pair parentage analysis indicated that at least 48% of the smaller individuals within a plot were produced by parents located at distances of at least 150 m. • Conclusions: Populations of G. sanctum are established and maintained by bird-mediated, moderate- to long-distance seed dispersal, which results in a mixture of seeds from unrelated maternal individuals, effectively eliminating SGS. Proximity between individuals is, therefore, a poor predictor of family structure in this species. Long-distance seed dispersal, coupled with estimates of high genetic diversity, suggests that this endangered species has the potential for natural regeneration and restoration given the availability of suitable habitats.Idea WildUniversidad de Costa RicaOrganization for Tropical StudiesNational Science FoundationUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
Fuchs Castillo, Eric J. - One of the best experts on this subject based on the ideXlab platform.
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Spatial distribution of Guaiacum sanctum (Zygophyllaceae) seedlings and saplings relative to canopy cover in Palo Verde National Park, Costa Rica
'Universidad de Costa Rica', 2016Co-Authors: Fuchs Castillo, Eric J., Robles Tatiana, Hamrick, James L.Abstract:La distribución espacial es una característica fundamental de las especies y es importante para el desarrollo de estrategias de conservación y manejo. Aquí presentamos la distribución espacial de varias etapas de desarrollo del árbol tropical Guaiacum sanctum, una especie en vías de extinción. Todos los adultos de G. sanctum se geo-referenciaron en una parcela de 50ha en el Parque Nacional Palo Verde. Las plántulas, los briznales y juveniles se mapearon en tres sub-parcelas de 50x50m. En cada sub-parcela se estimó la agregación espacial de los individuos mediante la K de Ripley. Observamos que los individuos de G. sanctum se encuentran siempre agregados, sin importar en que etapa de desarrollo se encuentren. Registramos la apertura del dosel cada 5m con un densiómetro y mediante una extrapolación espacial (Krigin) determinamos que las plántulas se agregan con mayor frecuencia en áreas con abundante cobertura de dosel, mientras que es más probable encontrar juveniles agregados en áreas con una mayor incidencia de luz. Las plántulas son los individuos más abundantes, esta distribución de edades nos sugiere que esta población probablemente está en expansión. Concluimos que el régimen lumínico y la cobertura de dosel son factores que afectan significativamente la distribución espacial del Guayacán Real.The spatial distribution of individuals is a fundamental property of most species and constitutes essential information for the development of restoration and conservation strategies, especially for endangered plant species. In this paper we describe the spatial distribution of different size classes of the endangered tropical tree Guaiacum sanctum and the effect of canopy cover on spatial aggregation. Adult G. sanctum were located and mapped in a 50ha plot in Palo Verde National Park, Costa Rica. Seedlings, saplings and juveniles were mapped to the nearest centimetre and permanently marked in three 50x50m subplots. Within each subplot spatial aggregation was assessed using Ripley’s K statistic and canopy opening readings were performed every 5m using a densitometer. Kriging spatial interpolation and Monte Carlo simulations were used to determine if average canopy cover differed among size classes. Individuals of G. sanctum were spatially aggregated at all size classes with seedlings being the most frequent size class in all subplots. Seedlings were found predominantly in areas with significantly higher canopy cover. In contrast, juveniles were more likely found in areas with higher light availability. The high number of seedlings, saplings, and juveniles relative to adults suggests that populations of G. sanctum in PVNP are expanding. Light availability and canopy structure are important factors shaping the spatial distribution of this species. The contemporary demographic structure of G. sanctum is dependent on forest gap dynamics and changes in human disturbance during the past 25 years
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Mating system and pollen flow between remnant populations of the endangered tropical tree, Guaiacum sanctum (Zygophyllaceae)
'Springer Science and Business Media LLC', 2011Co-Authors: Fuchs Castillo, Eric J., Hamrick, James L.Abstract:Tropical trees are generally long-lived making it difficult to assess the long-term effects of habitat fragmentation on genetic diversity. Maintenance of genetic diversity in fragmented landscapes is largely dependent on the species’ mating system and the degree of genetic connectivity (seed and pollen flow) among fragments. Currently, these parameters are largely unknown for many endangered tropical tree species. Additionally, landscape fragmentation may isolate tropical tree populations from larger, more continuous populations. The role of isolated individuals in pollen transfer within and between remnant populations is not clear. In this study, we estimate the mating system and pollen flow patterns in continuous and remnant populations of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae). Fractional paternity analyses were used to estimate average gene flow distances between fragmented remnant populations and the siring success of an intermediately located, but isolated individual. In these populations, G. sanctum is a mixed-mating species (t m = 0.72 − 0.95) whose pollen is transported over large distances (>4 km). An isolated tree may have functioned as a stepping-stone between two clusters of individuals, assisting long-distance pollen movement. This individual also sired a disproportionately high number of seeds (13.9%), and is thus an important component of the reproductive success of these populations, thus rejecting Janzen’s “living-dead” hypothesis. The high levels of genetic diversity maintained as a consequence of long-distance pollen-flow suggest that this endangered species may have the potential for future adaptation and population expansion if suitable habitats become available.Universidad de Costa RicaOrganization for Tropical StudiesNational Science FoundationUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
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Genetic diversity in the endangered tropical tree, Guaiacum sanctum (Zygophyllaceae)
'Oxford University Press (OUP)', 2010Co-Authors: Fuchs Castillo, Eric J., Hamrick, James L.Abstract:Fragmentation of tropical forests has changed continuous tropical landscapes into a network of poorly connected fragments, reducing population sizes and potentially increasing genetic isolation. This study quantifies genetic diversity within and among the 7 extant populations of the endangered tropical tree Guaiacum sanctum in Costa Rica. We describe how genetic diversity differs between populations representing continuous and fragmented habitats. Allozyme analyses were conducted on adult samples from populations representing 2 geographic regions in northwestern Costa Rica. We found high levels of genetic diversity within the species (Hes = 0.329) and significant but relatively small differences in allele frequencies among populations (GST = 0.101) and between regions (GST = 0.053). We found no differences in genetic diversity between fragmented and continuous populations. Evidence for significant isolation-by-distance (IBD) was seen only when all populations were analyzed. If populations within the 2 regions were analyzed separately, IBD ceased to be significant. Our results suggest that the patterns of genetic diversity observed for G. sanctum may be caused by the ancient separation of populations into 2 disjunct geographic regions with extensive historical rates of gene flow among populations within each region. Recent forest fragmentation has not yet affected patterns of genetic diversity in this species.Idea WildUniversidad de Costa RicaOrganization for Tropical StudiesNational Science FoundationUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
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Spatial genetic structure within size classes of the endangered tropical tree Guaiacum sanctum (Zygophyllaceae)
'Botanical Society of America', 2010Co-Authors: Fuchs Castillo, Eric J., Hamrick, James L.Abstract:Premise of the study: Patterns of spatial genetic structure (SGS) were analyzed within a population of the endangered tropical tree Guaiacum sanctum located in northwestern Costa Rica. Documentation of these patterns provides insights into the gene dispersal mechanisms that play a central role in the maintenance and structure of genetic diversity within plant populations. • Methods: Allozyme analyses were used to examine SGS in Palo Verde National Park, Costa Rica. The SGS was compared among three plots and different age classes. • Key results: High levels of genetic diversity were found overall with a pooled genetic diversity of He = 0.302 ( ± 0.02). Selfi ng was proposed as the proximate cause for signifi cant levels of heterozygote defi ciency observed across size classes and plots. An unexpected lack of SGS ( rj < 0.02) was observed for all size classes, suggesting the mixing of seeds from several adults. A parent-pair parentage analysis indicated that at least 48% of the smaller individuals within a plot were produced by parents located at distances of at least 150 m. • Conclusions: Populations of G. sanctum are established and maintained by bird-mediated, moderate- to long-distance seed dispersal, which results in a mixture of seeds from unrelated maternal individuals, effectively eliminating SGS. Proximity between individuals is, therefore, a poor predictor of family structure in this species. Long-distance seed dispersal, coupled with estimates of high genetic diversity, suggests that this endangered species has the potential for natural regeneration and restoration given the availability of suitable habitats.Idea WildUniversidad de Costa RicaOrganization for Tropical StudiesNational Science FoundationUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí
