High levels of genetic structuring as a result of population fragmentation in the tropical tree species Caesalpinia echinata Lam.

Abstract

We have investigated levels of genetic diversity within and among seven remnant populations of Caesalpinia echinata Lam., an endangered species found as fragmented populations in three major areas around the coastal regions of Brazil. Using amplified fragment length polymorphism (AFLP) genetic markers, we detected levels of within-population genetic diversity ranging from 0.092 to 0.163, with the lowest values generally being found in the smallest populations. Estimates of between-population genetic differentiation were strongly correlated with geographical distance ( r = 0.884, p <0.001), which, along with a neighbour-joining phylogenetic analysis, strongly suggested high levels of genetic isolation by distance. Over half (62%) of the total genetic diversity was partitioned between populations, further highlighting the genetic distinctness of individual populations. Taken together, these results suggest that fragmentation has led to an increase in population differentiation between fragments of C. echinata. These formations will be of great value in the development of conservation plans for species exhibiting high levels of genetic differentiation due to fragmentation, such as indication of conservation unit size, which populations should be chosen as priority in conservation plans and which samples should be introduced in areas with a low number of individuals of brazilwood.Peer reviewe

Population structure and one-year dynamics of the endangered tropical tree species Caesalpinia echinata Lam. (Brazilian red-wood): the potential importance of small fragments for conservation

“…The fact that this emergent, long-lived tree is involving the same set of sub-populations investigated here (Cardoso et al 1998;Cardoso et al 2005) pointed to a considerable within-population genetic diversity in the Cabo Frio region and that the sub-populations studied are actually one genetic population with gene flow between them. Therefore, conservation initiatives for this threatened species, and possibly of the coastal plain forests of Brazil as a whole, should consider the relevance of small-sized fragments.…”

“…All sampled subpopulations were treated here as a unique population, which was a legitimate approach as demonstrated by molecular biology studies (Cardoso et al 2005). The matrix is of the form: n t+1 = A x n t .…”

“…Some of the last natural remnant populations of the Brazilian southeast are found in the Cabo Frio region in Rio de Janeiro state. This is a very fragmented Centre of Plant Diversity (Araujo 1997) and pointed out as the habitat of the most genetically diverse and preserved C. echinata population in southeastern Brazil (Cardoso et al 2005). Therefore, longterm studies on population dynamics of this species would be essential for conservation planning.…”

Vegetative responses to temperature and photoperiod in saplings of brazilwood (Caesalpinia echinata Lam., Leguminosae)

“…(brazilwood) is a tree species native to the Atlantic Forest. The species was abundant along the seacoast of the northeastern and southeastern regions of Brazil (Rocha, 2004), mainly in three major areas of dry seasonal forests separated by regions of humid vegetation (Lewis, 1998;Cardoso et al, 2005 and references therein). The species was overexploited at the beginning of the colonization period (16 th to 18 th centuries) due to the interest in the red dye produced by the trees.…”

“…Studies on the genetic variability of brazilwood indicated a high level of differentiation in five natural populations in Southeast Brazil (Cardoso et al, 1998). More recently, Cardoso et al (2005) suggested that fragmentation of populations of C. echinata has led to an increase in genetic differentiation between fragments, emphasizing the relevance of investigating the performance of the species in different environments.…”