My main research interests are gene flow and dispersal in plants, population and conservation genetics of forest trees and fragmented population genetic processes. I have a good background in genetic data analysis, especially at the population level (parentage analysis and spatial statistics), and a good experience in SSR marker genotyping. My PhD thesis concerned the genetics of colonization of the treeline ecotone as investigated using parentage analysis and the study of genetic variability along an altitudinal transect (from the core of the forest to the treeline) in an alpine spruce population. At present, I’m working on the biogeography of Italian fragmented populations of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.), and on the estimation of long distance dispersal capability of Silver fir (Abies alba Mill.) analysing parentage relationship in a small relic Apennine population. I have also extensively worked on several aspects of beech biology, from quantitative genetics of early stage traits to phenology. As minor researches, I have studied ecological and evolutionary aspects related to gene flow in plankton species, and several aspects of ant evolutionary ecology.
Abstract: Twenty-one populations of Scots pine sampled over the entire Italian range of the species were analysed for genetic variation scored at 9 nuclear SSR markers. The main aim of the work was to find genetic features useful for conservation management, namely allelic composition, gene diversity and differentiation.
High levels of intra-population variability were scored. The only population sampled in the Apennines gave the lowest values, confirming the genetic erosion undergone in the Scots pine remnants in this area. A low level of genetic variability was also scored for populations from the Po valley and hills of Piedmont. Most genetic diversity was found within-populations, while only a small amount occurred among them (FST = 0.058). Both Bayesian clustering and sPCA analysis showed a East-West subdivision, notwithstanding the unclear position of populations from the Po valley. The population from the Apennines was always clearly separated from the others.
The results are discussed in terms of post-glacial recolonisation, as well as for defining the regions of provenance of Scots pine in Italy. The management of genetic resources could benefit from the identification of genetically homogeneous regions, thereby avoiding the use of non-local reproductive material for plantations, which is well known as one of the most important reason for failure of reforestation.
Abstract: Fragmentation can affect the demographic and genetic structure of populations near the boundary of their bio-geographic range. Higher genetic differentiation among populations coupled with lower level of within population variability is expected as a consequence of reduced population size and isolation. The effects of these two factors have been rarely disentangled. Given their high gene flow, anemophilous forest trees should be more affected, in terms of loss of genetic diversity, by small population size rather than geographic isolation alone. We studied the impact of distance from the main range (a measure of isolation) and reduced population size on the within and among population components of genetic variability. We assayed 11 isozyme loci in 27 marginal populations of European beech (Fagus sylvatica L.) in Central Italy. Populations were divided in three groups with an increasing level of fragmentation. In the most fragmented group the within population genetic variability was slightly smaller and the among population differentiation significantly larger than in the other two groups. Isolation-by-distance was lost when only pairs of populations involving at least one from the most fragmented group were considered and maintained in the other groups. These results support the role of random genetic drift having a larger impact on the most fragmented group, while gene flow seems to balance genetic drift in the two less fragmented ones. Given that average distance from the main range is not different between the intermediate and the most fragmented group, but average population size is smaller, we can conclude that gene flow is effective, even at relatively long distances, in balancing the effect of fragmentation if population size is not too small.
Abstract: The study of the dispersal capability of a species can provide essential information for the management and conservation of its genetic variability. Comparison of gene flow rates among populations characterized by different management and evolutionary histories allows one to decipher the role of factors such as isolation and tree density on gene movements. We used two paternity analysis approaches and different strategies to handle the possible presence of genotyping errors to obtain robust estimates of pollen flow in four European beech (Fagus sylvatica L.) populations from Austria and France. In each country one of the two plots is located in an unmanaged forest; the other plots are managed with a shelterwood system and inside a colonization area (in Austria and France, respectively). The two paternity analysis approaches provided almost identical estimates of gene flow. In general, we found high pollen immigration (~75% of pollen from outside), with the exception of the plot from a highly isolated forest remnant (~50%). In the two unmanaged plots, the average within-population pollen dispersal distances (from 80 to 184âm) were higher than previously estimated for beech. From the comparison between the Austrian managed and unmanaged plots, that are only 500âm apart, we found no evidence that either gene flow or reproductive success distributions were significantly altered by forest management. The investigated phenotypic traits (crown area, height, diameter and flowering phenology) were not significantly related with male reproductive success. Shelterwood seems to have an effect on the distribution of within-population pollen dispersal distances. In the managed plot, pollen dispersal distances were shorter, possibly because adult tree density is three-fold (163 versus 57 trees per hectare) with respect to the unmanaged one.
Abstract: The ever-increasing use of paternity analysis to estimate the dispersal capability of forest trees suggests the need for a quantitative evaluation of potential errors due to sampling design. Previous work on sampling strategies for seed trapping experiments suggested a link between sampling effort and error rate in the reconstruction of the seed dispersal kernel. We considered 92 papers on paternity analysis to quantitatively assess the sampling strategy used to study the characteristics of pollen dispersal patterns (pollen immigration rate, distribution of male reproductive success and estimates of pollen dispersal kernel parameters). For each studied stand we report data on the sampling effort (the total number of sampled seeds, the number of mother trees and the number of seeds per mother tree) and additional information on the studied species and characteristics of the sampling areas. The reviewed papers used a median of 8 mother trees (that act as pollen traps in paternity analysis studies), a median of 29 seeds per mother tree and a median of 240 total sampled seeds. These are values (especially the number of mother trees) lower than usually found in classical seed trapping studies, for which accuracy and precision of seed dispersal estimates had already been assessed. These findings underline the need of evaluating the consequences of realistic sampling efforts on the estimation of parameters describing the pollen dispersal pattern to provide the basis for meaningful guidelines for paternity analysis.
Abstract: Small and isolated silver fir populations from Emilian Apennines (Northern Italy) were studied to assess their levels of genetic variation and their relation with Alpine populations. We investigated the variability of two chloroplast microsatellites to analyze the within-population genetic variability of four peripheral and fragmented Apennine populations, and to determine their phylogenetic relatedness with seven Alpine populations covering all the distribution of silver fir in the Alps. Haplotypic richness and haplotype diversity as well as the fraction of private haplotypes resulted lower in Apennine populations, indicating the genetic impoverishment of these stands. The among-population genetic variability analysis highlighted genetic peculiarity of Apennine populations. In fact, AMOVA analysis showed that most of the among-populations variation occurs between Alpine and Apennine regions, and the Neighbor-joining analysis revealed a well-distinct Apennine cluster, including the closest Alpine population. Our results represent the first genetic evidence of a common origin for Emilian Apennine populations, suggesting that these populations are relicts of past extensive silver fir stands in Northern Apennines. The results of this study indicate a relevant conservation value for these stands, suggesting that they are worth of preservation and that particular attention in management decisions is needed.
Abstract: Several hypotheses were proposed to account for geographic parthenogenesis that is the disjointed distribution of a speciesâ sexual and asexual forms. In the areas affected by glaciations the parthenogenetic forms would have had ecological success and hybridization and polyploidy would have been the driving forces in their success. Limnocythere inopinata is well-represented in Quaternary non-marine sequences and is useful for studying the evolution of geographic parthenogenesis. We analysed the genetic variability of twelve populations from sub alpine Italian lakes, Austrian lakes and a pond, in an area that was covered by ice during the Pleistocene. In all samples we only found parthenogenetic females. Using allozymes, we described at least 33 different clonal lineages in a total of 812 females. We found no evidence for polyploidy. Clonal diversity is relatively high and may reflect the genetic diversity of ancestral sexual metapopulations. In L. inopinata, geographical parthenogenesis seems the result of historical and ecological factors and is not linked to polyploidy and hybrid advantage.
Abstract: Understanding the genetic structure and diversity of edge populations can shed light on the role of peripheral populations and their relevance for conservation strategies. In this study, three fragmented and isolated Apennine populations of Scots pine (Pinus sylvestris L.) belonging to the rear edge of the speciesâ distribution were analyzed using both nuclear (nSSR) and chloroplast (cpSSR) microsatellites and were compared with an Alpine population belonging to the speciesâ main range. Although small population size and considerable isolation have probably reduced the genetic variability of Apennine populations, these fragmented populations maintain a high level of within-population genetic diversity. A significant among-population differentiation was found using both nSSR (Fst = 0.08) and cpSSR markers (Ï = 0.14). Analysis of molecular variance (AMOVA) on the nSSRs attributed all variabilities to the among Apennine populations component supporting the theoretical predictions regarding fragmentation effects on genetic structure. On the other hand, AMOVA on the cpSSRs attributed all variances to the between-region component and no differentiation was found within region, among the Apennine populations. This result suggests the importance of pollen gene flow in homogenizing populations on this geographical scale. Our results confirm the genetic distinctiveness of Apennine populations and their possible derivation from different glacial refugia than those of the Alps. Considering their peculiarity and the high level of intrapopulation genetic diversity that they still retain, fragmented Apennine populations should be considered of high priority for conservation
Abstract: At treeline, selection by harsh environmental conditions sets an upward limit to arboreal vegetation. Increasing temperatures and the decline of traditional animal raising have favoured an upward shift of treeline in the last decades. These circumstances create a unique opportunity to study the balance of the main forces (selection and gene flow) that drive tree migration. We conducted a parentage analysis sampling and genotyping with five microsatellite markers in all Norway spruce individuals (342 juveniles and 23 adults) found in a recently colonized treeline area (Paneveggio forest, Eastern Alps, Italy). Our goal was to evaluate local reproductive success versus gene flow from the outside. We were able to identify both parents among local adults for only 11.1% of the juveniles. In the gamete pool we sampled, two-thirds were not produced locally. Effective seed dispersal distance distribution was characterized by a peak far from the seed source (mean 344.66 mplusminus191.02 s.d.). Reproductive success was skewed, with six local adults that generated almost two-thirds (62.4%) of juveniles with local parents. Our findings indicate that, although a few local adults seem to play an important role in the colonization process at treeline, large levels of gene flow from outside were maintained, suggesting that the potential advantages of local adults (such as local adaptation, proximity to the colonization area, phenological synchrony) did not prevent a large gamete immigration.
Abstract: Habitat fragmentation is one of the most serious threats to plant biodiversity at the within-population level. Growing attention on the genetic effects of habitat fragmentation is reflected in the 2008 publication of several review papers. In general, fragmentation showed a negative effect on the genetic variability of plant populations. However, for forest trees the genetic signal of fragmentation seems less clear. Here I discuss the development of less explored issues that can help to clarify some unresolved questions about tree responses to fragmentation. In particular, the understudied effect of delay in sexual maturity and the need for accurate estimates of gene flow are taken into account. I finally underline the potential role of the Italian peninsula as an open-sky laboratory for forest fragmentation studies.
Abstract: The presence of silver fir (Abies alba Miller) in the Apuan Alps was first described in 1667. Nowadays it is restricted to a small and relict population on the northern slope of Mt. Contrario (Minucciano, LU) constituted only by 14 individuals. The stand is highly isolated with respect to silver fir Apennine distribution. A few kilometres away, there is another small population of unknown origin (near the Donegani refuge). The aim of this work is to assess the level of genetic variability of the Apuan population using microsatellite markers. In addition, its genetic connection with surrounding populations was evaluated by means of paternity analysis. This can help to understand the degree of genetic isolation affecting the autochthonous stand. Twenty-eight seedlings sampled in an artificial regeneration area close to the Apuan population were analyzed. These individuals came from local seeds sampled by Alpi Apuane Natural Park during a conservation project. Gene flow from external populations was assessed estimating the percentage of foreign pollen contributing to artificial regeneration. The results were discussed focusing on future conservation strategies to enhance regeneration and to maintain the genetic variability of the highly endangered silver fir Apuan populations.
Abstract: We report data on the coexistence of apomictic and amphimictic lineages of Eucypris virens within the same pond and discuss the role of intraspecific hybridation as a source of genetic variability. We describe the genetic structure of 36 populations of E. virens from Europe. Most (28) populations were made up of putative parthenogenetic females, in 8 populations from Spain and Sicily we found males. Using three polymorphic allozyme markers (MPI, PGM and GPI) we described at least 214 different multilocus genotypes (clones) in a total of 1151 analysed specimens and confirmed that parthenogenetic reproduction is apomictic. Most multilocus genotypes, 74 %, were limited to a single population indicating the absence of a single widespread 'clone'. In E. virens, genetic diversity was not affected by latitudinal cline or reproductive mode and was probably the result of several processes. Apomictic lineages were the likely result of at least two independent transitions from different sexual ancestors located in Southern Europe, in Central Spain and in Sicily. Transitions probably happened after the last glaciation. We found sympatric amphimictic and apomictic females in Extremadura (Western Spain) and reported evidence of gene flow between different lineages (intraspecific hybridation). Further genetic differentiation within and among populations reflects time of divergence and mutation accumulation. We found putative polyploid multilocus genotypes in all populations with males, further support for the coexistence of lineages with different reproductive modes. The presence of polyploid genotypes (14 %) is probably underestimated and this limits our ability to assess the role of hybridisation as a major route to parthenogenesis.
Abstract: Intercastes of the slave-making ant Polyergus rufescens (Hymenoptera, Formicidae) were morphometrically analyzed and compared with queens and workers castes. Clear cut differences among these three ëmorphologicalà castes were recognized. Results of multivariate analysis showed significant differences in mean size for most morphological characters. On the basis of 15 external features we measured, intercastes were more similar to workers but distinguishable from them by a larger head and a queen-like abdomen (petiole and gaster). Canonical discriminant analysis also indicated this morphological differentiation. Mahalanobisà distances were 21.65 between queens and workers, 20.26 between queens and intercastes, and 6.02 between intercastes and workers.
Abstract: In the Alps global warming and change in land use, in particular the drastic reduction in cattle grazing, are causing a progressive treeline ecotone upwards shift. The colonization dynamics of woody species are modulated by high selective pressure on seedlings due to the extreme ecological conditions of this habitat. We studied the colonization dynamics of Norway spruce in a treeline plot, at the upper limit of the Paneveggio forest (Trentino, Italy). We have exhaustively sampled the study stand, collecting needle tissue from all the adults and the juveniles detected, and we have genotyped all the samples (376) with 4 SSR markers. Parentage relationships between the few adults presents in the stand (23) and the juveniles were established. Our results indicate that, in spite of extreme ecological condition of the treeline environment, local adaptations do not seem to favour local parents: only 4% of juveniles have both parents among local adult trees, while 96% of juveniles are completely or partially sired outside the sampling area. Assessing parentage relationship also allowed the estimation of relative reproductive success of local adult trees. Out of a total of 23 adult trees, 5 trees were involved in the 59% of successful reproductive events detected inside the sampling area.
Abstract: We report the genetic structure of 47 all-female populations of Heterocypris incongruens from Italy. Most populations (34) were collected from ricefields in the Po Plain (Northern Italy). Using three polymorphic allozyme markers (MPI, PGM and GPI) we found 125 different multilocus genotypes (clones) in a total of 3235 studied females. One clone was present almost everywhere (66 % localities) and in about a third (35 %) of all analysed females. Only a few clones (9 or 7 %) were found in more than ten localities while the majority (77 or 62 %) were found in only one population (private clones). Almost half (48 %) of all private clones were from the eight ricefields with the highest clonal richness while 16 % were from isolated temporary pools sampled for comparison. Clonal diversity seems to be the result of the presence of at least two different clonal lineages. One of the two, made up of the largest number of clones, probably had an autochthonous origin, a condition that probably favoured adaptation to local conditions. The other lineage was possibly introduced with imported rice seeds and its descendants carry adaptations to warm ricefield conditions. The weak relationship between genetic and geographic distance and the lack of spatial patterns in genetic variability might be due to the species' long-distance dispersal ability and to the persistence of founder effects sustained by large resting egg banks, conditions that blur isolation by distance. The lack of phylogeography in genetic variation may also be due to the spatially stochastic process of initiation and cessation of local ricefield cultivation known to have happened since the 15th Century in this area of Northern Italy
Abstract: A method in population genetics (Dutech et al., Am. J. Bot. 92 (2), 252-261, February 2005) is described and discussed as an interesting tool for investigating the effects of fragmentation in forest ecosystems.
Abstract: This chapter describes the many applications for neutral genetic markers from the perspectives of population and conservation genetics, phylogeography and gene flow studies of conifers and includes a comprehensive review of the studies performed in these research fields. The chapter starts with a review of the different kinds of neutral genetic markers most frequently used in conifers in the recent literature. In a second part, it describes how variation is organized within and among natural populations at the three conifer genomes (chloroplast, mitochondrial and nuclear). In a third part, it highlights how stochastic processes have shaped this organization focusing on two large areas of investigation in population genetics: phylogeography and gene flow. Finally, it demonstrates that neutral genetic markers and the information they generate are fundamental for the conservation and management of genetic resources. This chapter is addressed to plant molecular geneticists as well as plant breeders in the public and private sectors.
Notes: the authors have contributed equally to this paper and are listed in alphabetical order
