Population genetics of the westernmost distribution of the glaciations-surviving black truffle Tuber melanosporum

Abstract

The black truffle (Tuber melanosporum Vittad.) is an important natural resource due to its relevance as a delicacy in gastronomy. Different aspects of this hypogeous fungus species have been studied, including population genetics of French and Italian distribution ranges. Although those studies include some Spanish populations, this is the first time that the genetic diversity and genetic structure of the wide geographical range of the natural Spanish populations have been analysed. To achieve this goal, 23 natural populations were sampled across the Spanish geographical distribution. ISSR technique demonstrated its reliability and capability to detect high levels of polymorphism in the species. Studied populations showed high levels of genetic diversity (h N = 0.393, h S = 0.678, Hs = 0.418), indicating a non threatened genetic conservation status. These high levels may be a consequence of the wide distribution range of the species, of its spore dispersion by animals, and by its evolutionary history. AMOVA analysis showed a high degree of genetic structure among populations (47.89%) and other partitions as geographical ranges. Bayesian genetic structure analyses differentiated two main Spanish groups separated by the Iberian Mountain System, and showed the genetic uniqueness of some populations. Our results suggest the survival of some of these populations during the last glaciation, the Spanish southern distribution range perhaps surviving as had occurred in France and Italy, but it is also likely that specific northern areas may have acted as a refugia for the later dispersion to other calcareous areas in the Iberian Peninsula and probably France.

SSR-based identification of genetic groups within European populations of Tuber aestivum Vittad

“…The absence of a recent bottleneck suggested that T. aestivum is not yet an endangered species, not even in Mediterranean regions since genetic group 3 is limited to southern populations (see above). A similar result was found for T. melanosporum in the Iberian Peninsula indicating a nonthreatened genetic conservation status (García-Cunchillos et al 2014). However, even under conservative scenarios, future climate changes are likely to cause further increases in mean temperature (about 2-4°C globally) with significant drought in some regions (Seager et al 2007) as well as increases in frequency and severity of extreme droughts, extreme heat levels and heat waves (IPCC 2013;Sterl et al 2008).…”

“…Among Tuber spp. these analyses have mainly been carried out in T. melanosporum, T. magnatum and T. brumale (Murat et al 2004(Murat et al , 2011(Murat et al , 2013Rubini et al 2004;Riccioni et al 2008;Merényi et al 2014;García-Cunchillos et al 2014). For example, a strong genetic structure with significant fixation indices was observed among T. melanosporum populations at a European scale (F st =0.20 and F st =0.177; Murat et al 2004;Riccioni et al 2008).…”

“…ectomycorrhizal species such as Laccaria amethystina (Hortal et al 2012), Rhizopogon roseolus (Okuda et al 2013), Tuber brumale (Merényi et al 2014), Tuber magnatum (Rubini et al 2005) and Tuber melanosporum (Murat et al 2004;Riccioni et al 2008;García-Cunchillos et al 2014). On the other hand, the absence of any genetic differentiation among populations was shown in Pisolithus microcarpus (Hitchcock et al 2011) and Suillus spraguei (Rivera et al 2014).…”

Diversity, population genetics, and evolution of macrofungi associated with animals

“…These similar population genetic characteristics were explained by the “glaciation hypothesis.” In the hypothesis, the truffle populations in southern areas in Italy and Spanish acted as epibiotic species during glaciation and they spread northward along with their host trees as the ice receded (Bertault et al 1998). The research results of García-Cunchillos et al (2014) also supported this hypothesis. In this study, the Spanish populations of T. melanosporum were found to have higher genetic diversity than the Italian and French populations, with the species separated into two groups by the Iberian Mountain System (Table 1).…”

Tuber 2013: scientific advances in sustainable truffle culture

“…Understanding and conserving the natural diversity within truffle populations is important to future truffle culture. García-Cunchillos et al (2014) observe a high level of genetic diversity between two main groups separated by the Iberian mountain system when examining natural Spanish populations of T. melanosporum. They discuss the possibility that Spanish populations of T. melanosporum acted as a refuge during glaciation periods and later migrated to southwest France during post glaciation.…”