RESUMO
PREMISE: The mechanisms generating the geographical distributions of genetic diversity are a central theme in evolutionary biology. The amount of genetic diversity and its distribution are controlled by several factors, including dispersal abilities, physical barriers, and environmental and climatic changes. We investigated the patterns of genetic diversity and differentiation among populations of the widespread species Brosimum alicastrum in Mexico. METHODS: Using nuclear DNA microsatellite data, we tested whether the genetic structure of B. alicastrum was associated with the roles of the Trans-Mexican Volcanic Belt and the Isthmus of Tehuantepec as geographical barriers to gene flow and to infer the role of past events in the genetic diversity patterns. We further used a maximum-likelihood population-effects mixed model (MLPE) to identify the main factor affecting population differentiation in B. alicastrum. RESULTS: Our results suggested that Mexican B. alicastrum is well differentiated into three main lineages. Patterns of the genetic structure at a finer scale did not fully correspond to the current geographical barriers to gene flow. According to the MLPE mixed model, isolation by distance is the best model for explaining the genetic differentiation of B. alicastrum in Mexico. CONCLUSIONS: We propose that the differentiation patterns might reflect (1) an ancient differentiation that occurred in Central and South America, (2) the effects of past climatic changes, and (3) the functions of some physical barriers to gene flow. This study provides insights into the possible mechanisms underlying the geographic genetic variation of B. alicastrum along a moisture gradient in tropical lowland forests.
Assuntos
Variação Genética , Moraceae , Fluxo Gênico , México , Repetições de Microssatélites/genéticaRESUMO
Palms are important components of tropical and subtropical ecosystems and have even been considered keystone plant resources that can support a large array of pollinators and frugivores. Palms are also economically important. Chamaedorea tepejilote Liebm. is a widely distributed palm with important bioeconomic potential for food, traditional medicine and ornamental purposes. Eighteen microsatellite primers were developed for C. tepejilote. Polymorphism and genetic diversity were evaluated in 71 individuals from four populations in Costa Rica. Thirteen loci were polymorphic and the number of alleles in the pooled sample ranged between 5 and 20, the average number of alleles was 10.61. Average observed heterozygosity was Ho = 0.607 ± 0.04 (SD) and the average expected heterozygosity was He = 0.600 ± 0.03. The exclusion probability of the combined 13 loci, was PE = 0.998. We tested transferability of the markers in the congeneric C. costaricana, C. pinnantifrons and C. macrospadix. Dioecious species are common in tropical forests; however, few studies have analyzed gene flow patterns in these species. The markers developed for C. tepejilote are an important tool to quantify gene flow patterns and the distribution of genetic diversity within populations. This information will be useful for the development of conservation and management practices of this dioecious tropical palm species.
Assuntos
Arecaceae/genética , Repetições de Microssatélites , Costa Rica , Ecossistema , Fluxo Gênico , Genes de Plantas , Variação Genética , Heterozigoto , Polimorfismo GenéticoRESUMO
Microsatellite markers are a useful genetic tool to answer ecological and conservation genetics questions. Microsatellite primers were developed and characterized to evaluate forest fragmentation effects on genetic structure, diversity and gene flow patterns in the dioecious tropical tree Astroniumgraveolens (Anacardiaceae). Using genomic library enrichment, sixteen microsatellite loci were developed for A.graveolens. Polymorphism was evaluated in 80 individuals from four localities in Mexico. The overall number of alleles detected was 63, average alleles per locus 3.9 with a range from one to 11 per locus. Cross amplification trails on related species in the Anacardiaceae family: Spondiaspurpurea and Amphipterygiumadstringens, achieved successful amplification for all primers. Microsatellite markers described here are the first to be characterized for A.graveolens. These genetic markers will be a useful tool to assess the genetic consequences of habitat fragmentation and selective logging on A.graveolens populations. Cross amplification success on S.purpureaandA.adstringens suggest that they may be used for population genetic studies in other species within the family.
Assuntos
Anacardiaceae/genética , Repetições de Microssatélites/genética , Alelos , Anacardiaceae/metabolismo , Primers do DNA/genética , DNA de Plantas/genética , Fluxo Gênico/genética , Frequência do Gene/genética , Loci Gênicos/genética , Marcadores Genéticos/genética , Biblioteca Genômica , Genótipo , Heterozigoto , Desequilíbrio de Ligação/genética , México , Polimorfismo Genético/genética , Especificidade da Espécie , Árvores/genética , Árvores/metabolismoRESUMO
Microsatellite markers provide high polymorphism levels, useful to study genetic diversity and gene flow patterns in plant populations. Here we develop and characterize microsatellite primers to evaluate patterns of genetic structure and diversity, and gene flow levels in the dioecious tropical tree Spondias purpurea (Anacardiaceae). Twenty-four microsatellite primers were developed for Spondias purpurea. Polymorphism was evaluated in 139 individuals from three localities in Mexico. Ten loci were polymorphic. The number of alleles ranged between two and 21, the average number of alleles was 5.88. Cross-amplification trials on S. mombin, S. radlkoferi, Astronium graveolens and Amphipterygium adstringens achieved successful amplification for only six microsatellites in S. mombin and S. radlkoferi. Microsatellites developed for S. purpurea will be a useful tool to estimate genetic diversity within and among populations, as well as to assess the consequences of habitat fragmentation on gene flow patterns of this species.
Assuntos
Anacardiaceae/genética , Repetições de Microssatélites/genética , Alelos , Animais , Primers do DNA/genética , DNA de Plantas/genética , Fluxo Gênico/genética , Loci Gênicos/genética , Heterozigoto , Desequilíbrio de Ligação/genética , México , Polimorfismo Genético/genética , Especificidade da Espécie , Árvores/genéticaRESUMO
PREMISE OF THE STUDY: Microsatellite primers were developed for the parasitic Psittacanthus schiedeanus, a common mistletoe species on cloud forest-adapted tree hosts in Mesoamerica, to investigate intraspecific genetic patterns of diversity and genetic structure. ⢠METHODS AND RESULTS: Using an enriched library, 10 polymorphic microsatellite loci were developed in P. schiedeanus. All loci consisted of dinucleotide repeats. Average alleles per locus were 12 (4-17), and a total of 120 alleles were recorded across 39 individuals from four populations in Mexico. Primers were tested in 11 additional species, but only amplified successfully in P. calyculatus and P. angustifolius. ⢠CONCLUSIONS: The polymorphic loci described will be useful in studies of genetic diversity and genetic population differentiation in natural populations of these parasitic plants, and will provide valuable information to understand the importance of host distribution.