Multi-scale landscape influences on genetic diversity and adaptive traits in a neotropical savanna tree
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2020-03
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Changes in landscape structure can affect essential population ecological features,
such as dispersal and recruitment, and thus genetic processes. Here, we analyze
the effects of landscape metrics on adaptive quantitative traits variation, evolutionary
potential, and on neutral genetic diversity in populations of the Neotropical savanna
tree Tabebuia aurea. Using a multi-scale approach, we sampled five landscapes with
two sites of savanna in each. To obtain neutral genetic variation, we genotyped 60
adult individuals from each site using 10 microsatellite loci. We measured seed size and
mass. Seeds were grown in nursery in completely randomized experimental design and
17 traits were measured in seedlings to obtain the average, additive genetic variance
(Va) and coefficient of variation (CVa%), which measures evolvability, for each trait. We
found that habitat loss increased genetic diversity (He) and allelic richness (AR), and
decreased genetic differentiation among populations (FST ), most likely due to longer
dispersal distance of pollen in landscapes with lower density of flowering individuals.
Habitat amount positively influenced seed size. Seeds of T. aurea are wind-dispersed
and larger seeds may be dispersed to short distance, increasing genetic differentiation
and decreasing genetic diversity and allelic richness. Evolvability (CVa%) in root length
decreased with habitat amount. Savanna trees have higher root than shoot growth rate
in the initial stages, allowing seedlings to obtain water from water tables. Landscapes
with lower habitat amount may be more stressful for plant species, due to the lower plant
density, edge effects and the negative impacts of agroecosystems. In these landscapes,
larger roots may provide higher ability to obtain water, increasing survival and avoiding
dying back because of fire. Despite the very recent agriculture expansion in Central
Brazil, landscape changes are affecting neutral and adaptive variation in T. aurea. Several
populations have low additive genetic variation for some traits and thus, may have limited
evolvability, which may jeopardize species long-term persistence. The effect of habitat
loss on highly variable neutral loci may only be detected after a certain threshold of
population size is attained, that could become dangerously small masking important
losses of heterozygosity endangering species conservation.
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Agroecosystem, Cerrado, Bignoniaceae, Fragmentation, Genetic diversity, Tabebuia aurea, Landscape genetics, Quantitative genetics
Citação
COLLEVATTI, Rosane Garcia; SANTOS, Juliana Silveira dos; ROSA, Fernanda Fraga; AMARAL, Tatiana S.; CHAVES, Lazaro José; RIBEIRO, Milton Cezar. Multi-scale landscape influences on genetic diversity and adaptive traits in a neotropical savanna tree. Frontiers in Genetics, Laussane, v. 11, p. 259, Mar. 2020. DOI: 10.3389/fgene.2020.00259. Disónível em: https://www.frontiersin.org/articles/10.3389/fgene.2020.00259/full. Acesso em: 23 mar. 2023.