Footprint of the eastern euroasian past in Italian populations of Cryptotaenia thomasii (Ten.) DC
The mountains of Mediterranean basin, which were subject in the past to refuge area isolation processes as well as multiple biogeographical influences, constitute major centers of plant endemism and speciation (Thompson 2005). The populations of rare and endemic plant species deserve attention, especially when they are small and isolated, and then exposed to environmental events, demographic and genetic consequences developmentally harmful (Leimu et al. 2006; Gargano et al. 2009). Indeed, small populations can undergo genetic drift and biparental inbreeding with consequent loss of genetic diversity and fitness (Keller and Waller 2002; Reed and Frankham 2003; Gargano et al. 2015). Since some studies have estimated the size that allow a population to preserve much of their reproductive success and genetic diversity (Reed 2005), strategies for conservation of endangered species should be based on maintaining or increasing the size of their populations. Low or absent levels of gene flow increase the genetic difference between populations and the divergence of lineages could be favored by local adaptation (Morjan and Rieseberg 2004; Pickup et al. 2012). For this reason, biologists involved in conservation biology have used combined ecological and genetic data in order to identify those populations that represent significant evolutionary units and therefore require a conservation priority (Crandall et al. 2000; Stinchcombe and Hoekstra 2008).
The knowledge of the genetic architecture of closely related species and/or populations of a single species can be very useful to shed light on the processes that led to their current distributions. The variability and genetic structure of natural populations of plant species have been extensively evaluated by means of molecular markers. Molecular data, integrated with data from morphological, demographic, biological and climate, have allowed to correlate the genetic variability of plant species to historical and/or biological causes, often providing interesting insights for the understanding of the distribution of species (Petit et al. 1998; Thompson 1999).
The present study aims to provide a preliminary evaluation of the conservation status of the populations of the rare endemic Cryptotaenia thomasii (Ten.) DC. based on genetic data.
Cryptotaenia thomasii belongs to the Apiaceae, a family of dicotyledonous plants including 3700 species divided into 434 genera found in all temperate zones of the world. It is a family relatively homogeneous, characterized by a typical inflorescence: a simple or compound umbel. Cryptotaenia sensu lato is a small polyphyletic genus belonging to the subfamily Apioideae, tribe Oenantheae. It consists of eight species exhibiting a highly scattered distribution across continents (Spalik and Downie 2007). Cryptotaenia africana, C. japonica and C. canadensis, are widespread and occur in central and western Africa, eastern Asia, and eastern North America, respectively. The remaining species are narrow endemics and two of these species have Western Eurasian distribution: C. thomasii is a very narrow endemic species occurring in Calabria and Basilicata regions, southern Italy (Pignatti 1982); while C. flahaultii grows in the Caucasus (Tamamschian 1967). Both species were originally described in Lereschia (Boissier 1844) and then attributed to Cryptotaenia (Tutin 1968).
Cryptotaenia flahaultii has a very restricted range, grows on moist rocks in shaded forests up to 800 m asl. in only three populations located in Georgia, close the border with Turkey (Davis et al. 1972; Ketskhoveli et al. 1984). The total area of occupancy of this species is estimated to be approximately 12 km2, and the taxon is listed as Vulnerable under the D2 IUCN criterion (IUCN, 2012; Gagnidze 2014).
Mainly, C. thomasii occurs along mountain streams in forest areas, but in some cases it can colonize nitrogen-rich muddy habitats within mountain forests. The number of populations is low (ca. 20) and most of them account for a very low amount of individuals. The species is threatened by intrinsic factors, such as its restricted range and limited dispersal, by natural disasters such as drought, and by man-related pressures like forest exploitation, trampling and grazing. Based on the IUCN protocol of risk assessment (IUCN, 2012) it is precautionary assessed as Near Threatened (close to meet B2 requirements to fall into higher risk categories) (Ali 2010). Genetic data (Pellegrino et al. unpublished) showed that C. thomasii and C. flahaultii were phylogenetically closed related species.
This endangered species occurs in a few small populations, which are exposed to multiple pressures that threaten the species’ persistence. Genetic data for C. thomasii will allow informed conservation decisions involving satellite population establishment, population augmentation, and prioritization of conservation efforts. It was therefore conducted a molecular analysis on individuals belonging to 10 populations in order to assess levels and distribution of genetic variation within and between populations. For this purpose, were sequenced the Internal Transcribed Spacers (ITSs) of nuclear ribosomal DNA and analyzed the SNPs using appropriate restriction endonucleases.