Federico Vessella

Multiple genome relationships and a complex biogeographic history in the eastern range of Quercus suber L. (Fagaceae) implied by nuclear and chloroplast DNA variation.

Abstract The complex evolutionary history of Quercus suber has been throughly investigated in many recent works, but the details of its differentiation processes are still largely unknown. In addition, the geographical and evolutionary roles of the eastern parts of the species range have gained much less attention compared to other southern European areas. In order to fill this gap, new insights to infer the species diversification and range establishment of the cork oak in the east-central Mediterranean are here provided by means of inter- and intra-specific plastid DNA and nuclear ribosomal ITS phylogeographic studies. We analyzed 95 natural cork oak populations; 6 closely related, sympatric oaks were included in the study and used for comparisons. Evidence for a clear phylogeographical structure was detected with PCR-RFLP at 5 chloroplast loci, while ITS sequence variation is apparently unrelated with the geographical distribution. Five chloroplast haplotypes and three ITS main lineages were identified. Three haplotypes and all ITS lineages occur in the Italian Peninsula, stressing the importance of these territories for the evolutionary history of the species. Two divergent “Italian” haplotypes are highly shared, and one ITS variant is basal to the ingroup, revealing sister relationships within Cerris taxonomic group. Hypotheses of hybridization, lineage sorting of ancient DNA polymorphisms and of reticulate evolution of the whole species group are presented and discussed.

Plastome data reveal multiple geographic origins of Quercus Group Ilex

Nucleotide sequences from the plastome are currently the main source for assessing taxonomic and phylogenetic relationships in flowering plants and their historical biogeography at all hierarchical levels. One major exception is the large and economically important genus Quercus (oaks). Whereas differentiation patterns of the nuclear genome are in agreement with morphology and the fossil record, diversity patterns in the plastome are at odds with established taxonomic and phylogenetic relationships. However, the extent and evolutionary implications of this incongruence has yet to be fully uncovered. The DNA sequence divergence of four Euro-Mediterranean Group Ilex oak species (Quercus ilex L., Q. coccifera L., Q. aucheri Jaub. & Spach., Q. alnifolia Poech.) was explored at three chloroplast markers (rbcL, trnK/matK, trnH-psbA). Phylogenetic relationships were reconstructed including worldwide members of additional 55 species representing all Quercus subgeneric groups. Family and order sequence data were harvested from gene banks to better frame the observed divergence in larger taxonomic contexts. We found a strong geographic sorting in the focal group and the genus in general that is entirely decoupled from species boundaries. High plastid divergence in members of Quercus Group Ilex, including haplotypes shared with related, but long isolated oak lineages, point towards multiple geographic origins of this group of oaks. The results suggest that incomplete lineage sorting and repeated phases of asymmetrical introgression among ancestral lineages of Group Ilex and two other main Groups of Eurasian oaks (Cyclobalanopsis and Cerris) caused this complex pattern. Comparison with the current phylogenetic synthesis also suggests an initial high- versus mid-latitude biogeographic split within Quercus. High plastome plasticity of Group Ilex reflects geographic area disruptions, possibly linked with high tectonic activity of past and modern distribution ranges, that did not leave imprints in the nuclear genome of modern species and infrageneric lineages.

Ecological behavior of Quercus suber and Quercus ilex inferred by topographic wetness index (TWI)

The ecological behaviors of a network of pure evergreen oak stands (Quercus suber L. and Quercus ilex L.) in the Central-Western Mediterranean Basin were investigated toward climatic and edaphic factors implemented with the application of topographic wetness index (TWI). A Categorical Principal Component Analysis (Catpca) using climatic and soil physico-chemical parameters was performed on 23 cork oak and holm oak pure stands with the aim to understand better the effectiveness of TWI for characterizing soil ecology of the two species. Catpca pointed out that, although cork oak and holm oak are able to growth in similar Mediterranean conditions, they show different behaviors in terms of needs and tolerance to soil water content. TWI confirmed such results at local scale, allowing highlighting some interesting features of the species differential ecology. Although both species confirmed to be drought-tolerant, the heliophilous cork oak revealed to dominate the landscape on wettest soils with high TWI values—indicating the capacity to tolerate stresses due to periods of waterlogging—, while the shade-tolerant holm oak prevails for low-medium TWI values—drier and mesophilous sites. Despite the application of TWI to vegetation science and ecology is relatively recent, results are encouraging and suggest considering this user-friendly and synthetic index in ecological investigations and modeling.

Phylogeographic structuring of plastome diversity in Mediterranean oaks (Quercus Group Ilex, Fagaceae)

Oaks of Quercus Group Ilex are emblematic components of the Mediterranean landscapes and the full extent of their diversity in a geographic context is still poorly assessed. In order to detail differentiation patterns within Group Ilex and to illuminate causes and circumstances that underlie the distribution of its lineages, we examined plastome differentiation in the four species currently representing this oak group across the Mediterranean Basin (Quercus ilex, Quercus coccifera, Quercus aucheri, Quercus alnifolia). Plastid DNA variation was explored with three markers on 124 individuals and spatial analyses were performed with phylogenetic and landscape genetics approaches. A strong geographic sorting, entirely decoupled from species boundaries, was found. Spatial coincidences with phylogenetic splits highlights the presence of four geographic regions (the Middle East, the Aegean region, the central and the western Mediterranean) characterised by different degrees of isolation. Distinct sub-regional structures were identified. Inter- and intra-lineage divergence patterns appear to reflect the complex orogeny of the Mediterranean region and Pleistocene climatic oscillations, while a few widespread haplotypes might represent the remnants of the ancestral Group Ilex range. Regional differentiation in this group is recognised to be triggered by a number of factors, including disruption of the original range, incomplete lineage sorting, repeated phases of asymmetrical introgression and isolation. The key role played by some Mediterranean regions on the range establishment and dynamics of this oak group is discussed.

Wood anatomy and technological properties of an endangered species: Picconia Azorica (Oleaceae)

Picconia azorica (Tutin) Knobl. is an Azorean endemic species of the Oleaceae, exploited over centuries and recently classified as endangered. It suffers from reduction and fragmentation of its habitat, and from competition with exotic species. Wood anatomy was examined and compared with Picconia excelsa, enhancing our knowledge about the genus Picconia which contains only these two species. Macroscopic and technological characterizations by colour, pH, wood density, compression and bending strengths, shrinkages, static quality factor, ash content and Higher Heating Value were investigated and compared with other Oleaceae and other hardwoods. At the anatomical level, P. azorica does not differ from P. excelsa, except for the number of vessels and rays per mm2 and the ray type. The technological features support the profitable use of P. azorica for the furniture industry instead of biomass production. Because of its valuable wood, P. azorica might be reconsidered and its properties emphasized to combat the species’ decline and to encourage the restoration of its habitat.

Combined dendroecological and normalized difference vegetation index analysis to detect regions of provenance in forest species.

Abstract In the past 15 years several European countries have defined regions of provenance for forest species, to achieve better management of genetic resources and to detect and certificate plant material origin. The main methods involved the use of ecological parameters (e.g. pedological, phytoclimatic), presumed to be homogeneous within each area, thus identifying ecoprovenances for a species as a consequence of evolutionary differentiation according to the effects of natural selection. In this study a dendroecological approach in defining regions of provenance was tested in Latium (Italy) and combined with the phenological responses of forests. Previous dendroclimatic research demonstrated the relationship between plant growth and climatic parameters; in Latium, similar bioclimatic responses from different forest stands growing at similar elevations were statistically grouped into three homogeneous altitudinal belts using principal component analysis and hierarchical cluster analysis. Phenological patterns of forest species were quantified using the photosynthetic activity signals expressed in the normalized difference vegetation index (NDVI). Through a beech tree-ring network, NDVI was compared with dendroecological results using Geographical Information System analysis, obtaining high correspondence in overlapping, and underlying the relevance of altitude as a main factor defining homogeneous spatial vegetation dynamics, thus delimiting ecological regions of provenance based on tree responses to climate.

Morphological and molecular data from Madeira support the persistence of an ancient lineage of Taxus baccata L. in Macaronesia and call for immediate conservation actions

Macaronesia is an important biodiversity hotspot in the Mediterranean bioclimatic region, hosting a number of endemics, and encompassing outstanding refugia for ancient Tertiary plant lineages. We investig past occurrence and present distribution of yew (Taxus baccata L.) in the Madeiran archipelago, providing preliminary morphological and genetic descriptions and addressing conservation issues. Fifty-eight individuals presently occur in 19 micro-populations, as probable survivors of the continued yew exploitation across the centuries. Plants were characterized and compared with Euro-Mediterranean provenances by leaf morphology, anatomy, nuclear ITS (Internal Trascribed Spacer) and plastid trnS–trnQ DNA markers. The Madeiran provenance showed peculiar leaf size and morpho-anatomical characters. DNA sequences revealed a basal position of Madeiran yew in the Baccata phylogenetic clades along with the Azorean provenance. Gathered data suggest the survival of a lineage of T. baccata different from those on the continent, and with a possible closer derivation from the species’ ancestors. Such evidences provide a base for identifying a great phylo- and phytogeographical interest of the Macaronesian provenance, and confirm the role of the archipelagos to preserve relict flora and lineages. The risk of extinction of Madeiran yew also calls for conservation strategies and restoration programs for a prompt species rescue.

Irrigation regime as a key factor to improve growth performance of Quercus suber L.

Abstract Cork oak (Quercus suber L.) is a Mediterranean evergreen tree species which plays a key economic role due to its precious bark. Cork oak stands start to become productive 30–40 years after planting, i.e. when commercial cork can be removed every 10 years after the first bark stripping, according to the laws in force. Forcing plant growth with appropriate irrigation, fertilization, top-dressing and stand density minimizes the time between cork oak planting and first bark stripping and makes commercial cork available earlier. In this study, the objective was to determine the influence of different irrigation regimes on cork oak growth. An experimental field was established near Tarquinia (Tuscia District, North Latium, Italy), within the natural cork oak range, to test the effects of irrigation regime on growth performance of cork oak. Three treatments were applied that differed in the amount and timing of water supplied. Treatments were replicated three times. Dendrometric and biomass parameters were measured at three different times for 2 years after planting and statistical descriptive analysis, as well as anova, were used to evaluate the benefits of irrigation. Irrigation with 4 l m−2 three times per week for 2 years improved diameter growth by 33% and shortened the time to first bark stripping by 6–10 years, thus producing substantial economic benefits.

A tree species range in the face of climate change: cork oak as a study case for the Mediterranean biome

Species distribution models are feasible methods for projecting theoretical responses of living organisms’ occurrence under several future climate change scenarios. The major interest is focused on trees, which regulate the equilibrium within ecosystems and guarantee the survival of many life forms on the Earth. The repercussions of climatic drivers are expected to pose the strongest threats for the Mediterranean biome, an acknowledged hotspot of biodiversity. Here, we focused on cork oak (Quercus suber L.), a keystone species of many landscapes, sustaining a rich biodiversity, ecological processes and economic incomes. Results of 8 combined ecological modelling techniques and two Global Circulation Models highlight a broad contraction of the species potential range over the twenty-first century, both under intermediate and high emissions scenarios. Coupled northward and upward shifts are predicted, mostly pertaining Iberia and North Africa. The potential areas detected at Levantine will likely undergo disappearance. To exacerbate the impacts of climate change, the future of the ecosystems linked to cork oak remains uncertain, because of the expected implications on the phenotypic plasticity or evolutionary responses. A synergy among niche-based, physiological and eco-genetic investigations is strongly needed in the field of applied research, to improve the assessment of conservation and reforestation actions.

Quercus suber Distribution Revisited

The complex evolutionary history of Quercus suber is still under debate. Also, data and evidence at the eastern end of the species range are largely incomplete. In this study, historic floras, fossil data, and local toponyms were surveyed and genetic analyses and linguistic research used in order to point towards a previously neglected occurrence of Q. suber east of Italy. Such a multidisciplinary approach depicts a scenario in which cork oak survived in the Balkan Peninsula until recently and suggests how Q. suber might have been evicted and relegated westward, due to climate changes, ecologic competition and human impact. Our findings also suggest that the differentiation core of Q. suber was in a yet unidentified area corresponding to present-day central Europe to southwestern Asia. Radiation occurred during the Middle Miocene, with a later extension into southern Europe, Iberia and North Africa, as documented by samples collected from the late Miocene-early Pliocene. The causes of extinction in the east, however, should be investigated further and may lead to investigations about other species that might have experienced range shifts similar to that of cork oak.