Effect of fragmentation on the natural genetic diversity of Theobroma speciosum Willd. ex Spreng. populations

Abstract

ABSTRACT. Forest fragmentation reduces the effective size of natural populations, isolates individuals in the landscape, and, consequently, changes species' mating systems by increasing the degree of relatedness between individuals and inbreeding. Investigating the impact of habitat degradation on forest fragments helps to assess the genetic and ecological consequences of these changes, and allows the development of effective and sustainable conservation strategies to manage the genetic resources of species living in degraded landscapes. The aim of the present study was to assess the genetic diversity of fragmented Theobroma speciosum populations using microsatellite markers. Three urban forest fragments were selected in the municipality of Alta Floresta, Mato Grosso State, Brazil, namely C/E park, J park, and Zoo Botanical park. Seventy-five individuals (25 in each fragment) were sampled by collecting their leaves for genomic DNA extraction. Polymerase chain reaction amplifications were performed using nine polymorphic simple sequence repeat primers, which amplified 84 alleles. The mean expected heterozygosity was 0.970, and it was always higher than the observed heterozygosity. Analysis of molecular variance revealed that most variability occurred within populations (64%) rather than between them (36%). The Structure software and an unweighted pair group method with arithmetic mean dendrogram revealed three distinct groups, showing that individuals were allocated to their correct populations. Genotype number 3 from C/E park, number 45 from J park, and number 51 from Zoo Botanical park could be used as stock plants in breeding programs, because they were the most dissimilar within the populations studied. The high genetic diversity levels detected in all three populations studied emphasize the importance of protecting this species in its natural habitat.

Research Article The genetic diversity and population structure of <i>Genipa Americana</i> (Rubiaceae) in Northern Mato Grosso, Brazil

“…The observed heterozygosity in the three G. americana populations was lower than the expected heterozygosity. Similar results have been found in several studies conducted with tropical species (Silvaet al, 2017;Dardengoet al, 2016;Varella et al 2016). According to Alves et al (2007), the number of alleles is correlated with the expected heterozygosity value.…”

“…It showed that the three original populations share genetic material and that the genetic diversity is not geographically structured in the individuals belonging to these populations. Studies about Amazon species such as Maurita flexuosa, Theobroma speciosum and Spondias mombin showed that the genetic diversity was geographically structured (Silva et al, 2017;Varella et al, 2016;Rossi et al, 2014), unlike what we observed.…”

“…Polymorphism in these genes allows us to make inferences about the relation between an individuals' genotype and phenotype; this type of information can help increase the efficiency of breeding programs and species conservation strategies. These markers have been widely used to estimate the genetic diversity of native Amazon species such as Bertholletia excelsa (Lecythidaceae) (Ramalho et al, 2016), Theobroma grandiflorum (Malvaceae) , Theobroma Speciosum (Malvaceae) (Varella, 2016) and Spondias mombin (Anacardiaceae) (Silva, 2017). According to Costa et al (2011), genetic diversity studies are fundamental, especially for native species whose diversity is yet to be fully understood.…”

Diversidade genética de duas espécies de Theobroma L. em um fragmento florestal no Portal da Amazônia, MT, Brasil

“…De acordo com Varella et al (2016), com base em observações de campo, a dispersão das sementes T. speciosum é realizada principalmente por macacos, que ao se alimentarem dos frutos deixam cair as sementes próximas da árvore mãe. Esse padrão de dispersão, aliado ao sistema reprodutivo da espécie que é autoincompatível (SOUZA & VENTURIERI, 2010), gera um agrupamento maior de indivíduos aparentados e aumenta a possibilidade de cruzamentos entre indivíduos da mesma família.…”

BIOLOGIA FLORAL DE Theobroma speciosum Willd ex Spreng., UMA MALVACEAE NATIVA DA AMAZÔNIA BRASILEIRA

“…Além disso, com as sementes (amêndoas) pode-se preparar chocolate (ROSSI et al, 2017). Diante disso, a espécie pode atuar como fonte de renda para as comunidades nativas, promover o desenvolvimento regional e incentivar o uso racional e conservação dos recursos genéticos existentes (VARELLA et al, 2016).…”