Genetic diversity and stand structure of neighboring white willow (Salix alba L.) populations along fragmented riparian corridors: a case study

Abstract

Remnant riparian woodlands have an important landscape function, due to their ability to act as ecological corridors. In this study we used molecular markers to assess the genetic variation occurring within and between spontaneous white willow (Salix alba L.) riparian woodlands. Our main goal was to evaluate the extent to which the fragmentation of a woodland corridor along a heavily impacted river in northeastern Italy and stand structural conditions may have affected the population genetics. Although having different structures, the three examined white willow stands showed high estimates of genetic similarity, as well as low genetic differentiation between them, indicating that they shared a similar gene pool and that the stands could result from a common set of individual genotypes, and should be regarded as metapopulations. The magnitude of genetic diversity within each of the stands and genetic differentiation between them, despite their high sexual reproductive capacity associated with a highly marked gene flow, suggest that these stands are dynamic and capable of adaptive responses to possible changes in their fluvial environment. However, the factors influencing genetic diversity should be interpreted from a long-term perspective. Fluvial geomorphic patterns in regulated rivers may be modified to a degree that could lead to changes in dispersal processes, sexu­al reproduction vs. asexual propagation, and hence genetic diversity.

Exploring Correlation between Stand Structural Indices and Parameters across Three Forest Types of the Southeastern Italian Alps

“…Most of these planted stands have been changing their structure, but, in some cases, the results from the R aggregation index reveal the original reforestation design with a grid pattern and uniform distances among trees (Figure 5c). On the other hand, despite the presence of a high variability, in chestnut stands, a low average value of the R aggregation index reveals the presence of clumped pattern typical of coppice management, as already suggested by some research works [15,48,49]. The distribution of the R aggregation index in beech forest reveals the presence of near-to random spatial distributions.…”

The Ovule Number Variation Provides New Insights into Taxa Delimitation in Willows (Salix subgen. Salix; Salicaceae)

“…“The problem of the identification of pure and hybrid S. alba and S. fragilis entities is one of the critical matters of systematics of this genus” [ 16 ]. Many molecular studies were conducted to clarify definitions of these species [ 10 , 11 , 12 , 13 , 16 , 17 , 18 , 19 , 20 , 21 ]. Some of them showed high genetic similarity and suggested a shared ancestry for S. alba and S. fragilis [ 12 , 16 , 22 ].…”

Notes on the Taxonomy of Salix vitellina (Salicaceae)

“…Salix alba and S. fragilis , which are closely related species characterized by the lanceolate, acuminate, and serrulate leaves, represent one of the most difficult taxonomic groups in the genus [ 2 ]. Many molecular studies have been conducted to clarify the definitions of these species, and some of them have shown high genetic similarity and a shared ancestry for S. alba and S. fragilis [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Yet, the boundaries between these species are defined by relatively few diagnostic characters, resulting in various taxonomic interpretations of their taxa, including the taxonomic affiliation of S. vitellina L.…”