Popolazioni frammentate nelle aree rifugio: la connessione anfiadriatica

Responsabili di progetto

Giovannigiuseppe Vendramin, Jelena Lazarevic

Accordo

MONTENEGRO - MoS-not in force - Ministero della Scienza del Montenegro

Bando

CNR/MoS 2015-2016

Dipartimento

Scienze bio-agroalimentari

Area tematica

Scienze bio-agroalimentari

Stato del progetto

Nuovo

Proposta di ricerca

The loss of biodiversity by genetic erosion is a major threat for the survival of forest ecosystems all over the world. Genetic erosion can be caused by habitat fragmentation and marginality in species' range (Bacles & Jump 2011). Fragmentation reduces population size and increases isolation, potentially leading to genetic bottlenecks. Remnant populations are expected to experience increased genetic drift, elevated inbreeding and limited gene flow. This can lead to a decrease of within-population genetic variation and an increase in differentiation among populations (Ouborg et al. 2006). The role of peripheral populations in biodiversity conservation depends on their genetic characteristics. Peripheral populations often experience different selective pressures than central ones, and genetic peculiarities can also develop as a consequence of their post-glacial recolonization history or local persistence during climatic changes (Hampe & Petit 2005). Climate warming is expected to strengthen the loss of genetic variability as well as the decline in growth and survival of fragmented populations at the rear edge of temperate tree species' distribution (Jump & Penuelas 2005), as shown for conifers in Southern Europe (e.g. Reich & Oleksyn 2008).
Coupling genetic and palaeobotanical data is considered the most promising approach for inferring past retraction-colonization dynamics in plants. For some tree species, large genetic and palaeobotanical records are available, from both the distribution core and edges, leading to well-grounded hypotheses on the topography of glacial refugia and recolonization routes (e.g. Cheddadi et al., 2006; Magri, 2008). On the other hand, such inference has been inevitably carried out also on species for which the coverage of the distribution area is scarcer. From the analysis of biogeographic literature it is particularly evident how circum-Mediterranean refugial areas such as the Apennines and the Balkans have been scarcely represented in genetic and palaeobotanical large-scale surveys carried out on several species.
It is therefore urgent the genetic characterization of tree populations at the rear edge of their distribution for their historical relevance and because they can represent the source of potentially adaptive genetic variation to cope with ongoing climate change (Hampe & Petit, 2005). This is particularly true for species with geographically limited distribution, for which migration can be further impeded due to lack of suitable sites and competition with other species.
The Apennines and the Balkans are considered as major refugial areas during past glacial cycles, and for several circum-Mediterranean species it has been demonstrated how most genetic variation and adaptive potential is concentrated in the southern part of their distributions. The number of tree species for which glacial refugia are thought to have been located in the Italy/Apennines and in Montenegro is impressive. Only considering conifers, these areas host the southernmost Norway spruce (Picea abies), silver fir (Abies alba) and Bosnian pine (Pinus heldreichii) populations, besides other interesting species with locally highly fragmented distribution (e.g. Black pine, Pinus nigra) or extremely limited distribution (e.g. Macedonian pine, Pinus peuce). Since the low-latitude limit of species ranges remains understudied, and rear edge populations are of critical importance as long-term stores of species genetic diversity, the abovementioned peculiarities of Apennine and Montenegro forest genetic resources calls for a joined effort towards comparative phylogeographic and population genetics studies focused on the most interesting species.
Therefore, this research proposal primarily aims at establishing a collaboration between CNR and MoS to genetically characterized forest tree populations in close proximity with refugial area with nuclear and chloroplast microsatellite markers (hereafter nSSRs and cpSSRs). The survey will be focused on most relevant species such as Abies alba, Picea abies, Pinus heldrichii, Pinus nigra and Pinus peuce (hereafter Aa, Pa, Ph, Pn and Pp, respectively). Apart from the highly fragmented and isolated species Pinus peuce, the other species have been the subject of several projects in which the CNR has been involved. This guarantee a number of already sampled populations and optimized lab protocols that can provide a solid starting point to efficiently add rear edge populations to existing datasets.
The primary aim of the research proposal is to understand the genetic relationship between populations in the Apennines and the Balkans. More specifically, the estimation of divergence time and historical rates of gene flow between these refugial areas, carried out through Bayesian and ABC approaches on nSSR and cpSSR dataset, can provide valuable hints about future conservation strategies to be applied on sources of biodiversity from glacial refugia.
Bibliography
Bacles & Jump (2011) Trends Plant Sci 16:13
Cheddadi et al. (2006) Global Ecol and Biogeogr 15:271
Hampe & Petit (2005) Ecol Lett 8:461
Magri (2008) J Biogeogr 35:450
Ouborg et al. (2006) J Ecol 94:1233
Reich & Oleksyn (2008) Ecol Lett 11:588

Obiettivi della ricerca

The specific objectives of the research proposal are:
1) The genetic characterization with already available molecular markers (nSSRs and cpSSRs) of at least 6 populations (3 from the Apennines and 3 from Montenegro, 50 geo-referenced individuals per populations) of Aa, Pa, Pn and Ph;
2) The genetic characterization with nSSRs and cpSSRs of at least 3 populations (2 continuous and 1 peripheral and fragmented, 50 geo-referenced individuals per populations) of Pp, with test for transferability of markers from other Pinaceae; at least 12 markers, combining nSSRs and cpSSRs will be tested;
3) After having added the newly genotyped Aa, Pa, Pn and Ph populations to already existing datasets, estimating the existing spatial and non-spatial genetic structure at the biogeographical level;
4) Estimating divergence time through ABC-based approaches (e.g. DIYABC or popABC software, depending on the level of differentiation found);
5) Estimating migration rates through Bayesian approaches (e.g. Migrate software);
6) Comparing parameters describing genetic variation, divergence and inbreeding between continuous and fragmented Pp populations;
7) Propose actions for the conservation of the genetic resources of the selected species in Italy and in Montenegro;
8) Strengthen the scientific collaboration between the two countries and favour the exchange of scientists and students.

Ultimo aggiornamento: 13/12/2024