Demographic history and spatial genetic structure in a remnant population of the subtropical tree Anadenanthera colubrina var. cebil (Griseb.) Altschul (Fabaceae)

Abstract

& Key message A remnant population of Anadenanthera colubrina var. cebil in Northern Argentina showed a mixed mating system, high genetic diversity, and moderate spatial genetic structure, which was stronger in saplings than in adults. Demographic history analyses revealed an ancient population expansion. Despite high genetic diversity, high inbreeding suggests caution in the use of this stand as seed source. & Context Information on fine-scale spatial genetic structure (FSGS) and demographic history is essential to determine which mechanisms are responsible for population persistence and evolution. This is particularly important in fragmented biomes, such as the seasonally dry tropical forests. & Aims To assess the level of genetic diversity and population genetic structure in a remnant population of A. colubrina var. cebil, and to evaluate the influence of historical and contemporary environmental change on the genetic constitution of this population. & Methods Eight microsatellites were typed in 60 adults and 59 saplings. The existence of (non-spatial) genetic clusters was evaluated using STRUCTURE and PCAs. FSGS was evaluated by kinship analyses and sPCA. MCMCglmm models were used to provide insights into factors underlying FSGS. Demographic history was studied using bottleneck statistics and approximate Bayesian computation. & Results We found high levels of genetic diversity and high inbreeding. Genetic structure was stronger in saplings than in adult trees, probably due to assortative mating, and was not explained by altitude or DBH. Demographic analyses suggested an ancient population expansion. & Conclusion Patterns of inbreeding and relatedness suggest a mixed mating system. High genetic diversity and moderate genetic structure suggest long-term population viability. High inbreeding suggests caution when using this stand as a source of material for reforestation.

Climate change will disproportionally affect the most genetically diverse lineages of a widespread African tree species

“…The high GD coupled with endemic gene pools in the Southern range may be due to barriers to gene flow, triggered by the heterogeneous complex mosaic of landscapes 38 among the surrounding populations. In addition to demographic history 49 , spatially heterogeneous landscapes in most cases support greater genetic and species diversity 50 – 52 . The presence of mountains (e.g., Spitzkoppe, Erongo region and Brandberg, Naukluft) and inhospitable landscapes (e.g., Khormas highlands that seperates populations Rehoboth and Solitaire) within the sampled range in Namibia, might be acting as a barrier, thus limiting gene flow and facilitating differentiation in local populations.…”

Spatial genetic structure and mating system in forest tree populations from seasonally dry tropical forests: a review

“…In this way, limited foraging distances of pollinating insects within the forest fragments, and overall short distances of seed dispersal, high tree densities, and mixed mating systems influence gene dispersal patterns of these species. Gene dispersal patterns within populations of A. colubrina were characterized by short gene dispersal distances ( g = 5-17 m) and a significant FSGS (Goncalves et al 2019).…”

Una nueva variedad de Anadenanthera colubrina (Leguminosae, Mimosoideae) de Argentina

“…Por otro lado, Altschul (1964) atribuye importancia taxonómica al fruto, carácter no considerado aquí en virtud de la deformación permanente encontrada en el material estudiado, probablemente debido a la acción de depredadores en estado larval o una fecundación incompleta (Sallabanks & Courtney, 1992;Goncalves et al, 2019).…”