Diversity and genetic connectivity among populations of a threatened tree (Dalbergia nigra) in a recently fragmented landscape of the Brazilian Atlantic Forest

Abstract

In this study we evaluated the influence of recent landscape fragmentation on the dynamics of remnant fragments from the Brazilian Atlantic Forest. This biome is one of the richest in the world and has been extensively deforested and fragmented. We sampled five populations of the threatened Dalbergia nigra, a tree endemic to the Brazilian Atlantic Forest, two located in a large reserve of continuous forest and three in fragments of different sizes and levels of disturbance. In order to assess historical changes, considering the longevity of the analyzed species, 119 adults and 116 saplings were genotyped for six microsatellite loci. Lower levels of genetic diversity were found in the most impacted fragments when compared to the most preserved population located inside the reserve, and there was significant genetic structure among the populations studied (pairwise F(ST) = 0.031-0.152; pairwise D(EST) = 0.039-0.301). However, genetic structure among saplings (F ST) = 0.056; D(EST) = 0.231) was significantly lower than among adults (F(ST) = 0.088; D(EST) = 0.275). Estimates of contemporary gene flow based on assignment tests corroborated this result, suggesting that fragmentation led to an increase in gene flow. This connectivity among remnant fragments could mitigate the loss of genetic diversity through a metapopulation dynamic, but the high rate of habitat loss and the unknown long-term genetic effects add uncertainty. These results, taken together with the presence of private alleles in disturbed populations, highlight the importance of preserving the extant fragments.

Fine-scale spatial genetic structure of Dalbergia nigra (Fabaceae), a threatened and endemic tree of the Brazilian Atlantic Forest

“…Earlier studies also found high diversity in the Campolina population of D. nigra in comparison to small fragments when using allozymes ( H E = 0.296; Ribeiro et al , 2005), sequences of chloroplast DNA (haplotypic diversity = 0.733; Ribeiro et al , 2011) and microsatellites markers ( H E = 0.798; Resende et al , 2011). All of these studies had a sampling strategy that was only directed towards evaluating the genetic diversity of the population through the analysis of a smaller number of trees (≤ 23) and in a larger area compared to the present study.…”

“…Bees probably perform pollination, and seeds are dispersed by the wind (Carvalho, 1994). Although much effort is required to protect this species, few genetic studies have been performed to date (Ribeiro et al , 2005, 2011; Juchum et al , 2007; Resende et al , 2011) and we are not aware of any study about fine-scale spatial genetic structure of D. nigra .…”

Allozyme variation of the endemic and vulnerable Dyera lowii Hook.f. in Central Kalimantan: Implications for genetic resources conservation

“…In wind-pollinated, long-lived woods, the average F ST values tend to be low (Duminil et al, 2009), F ST =0.028 in Cryptomeria Japonica (Takahashi et al, 2005), the average G ST =0.073 in Gymnosperms (Hamrick et al, 1992). The moderately level was similar to seedling population of Vochysia Ferruginea (F ST =0.069) at Ladrillera (Davies et al, 2010) and a threatened tree Dalbergia nigra (F ST =0.088) in the Brazilian Atlantic Forest (Resende et al, 2011). These values are within the range of differentiation found in other tropical tree populations, where low differentiation was found for Dinizia excelsa (F ST =0.00167) (Dick et al, 2003a) and high levels of differentiation have been found for Caryocar brasiliense (F ST =0.29) (Collevatti et al, 2001), Taxodium distichum shown strong genetic differentiation between populations F ST =0.208 (Tanaka et al, 2012), and Gonystylus bancanus (G ST = 0.9956) (Kusumadewi et al, 2010).…”

“…(H E =0,247) using RAPD (Hartati et al, 2007), and Shorea leprosula (H E =0.406) using isozyme (Lee et al, 2000;Finkeldey, 2007). The H E value of D. lowii was lower than Hevea brasiliensis (H E =0.742) (Le Guen et al, 2010) and a threatened tree Dalbergia nigra (H E =0.735) using microsatellite (Resende et al, 2011).…”

Diversidade genética, estrutura genética espacial e fluxo gênico da erva-mate (Ilex paraguariensis A. St. Hil.) em dois fragmentos florestais na área de entorno do Parque Nacional do Iguaçu

“…A análise da estrutura genética espacial foi realizada para os adultos das duas (RATHMACHER et al, 2010;RESENDE et al, 2011;SEBBENN et al, 2011 (LLORENS et al, 2012;MANOEL et al, 2012;ROSAS et al, 2011;SEBBENN et al, 2011).…”