Genetic structure and diversity of the selfing model grassBrachypodium stacei(Poaceae) in Western Mediterranean: out of the Iberian Peninsula and into the islands

Abstract

Annual Mediterranean species of the genus Brachypodium are promising model plants for energy crops since their selfing nature and short-life cycles are an advantage in breeding programs. The false brome, B. distachyon, has already been sequenced and new genomic initiatives have triggered the de-novo genome sequencing of its close relatives such as B. stacei, a species that was until recently mistaken for B. distachyon. However, the success of these initiatives hinges on detailed knowledge about the distribution of genetic variation within and among populations for the effective use of germplasm in a breeding program. Understanding population genetic diversity and genetic structure is also an important prerequisite for designing effective experimental populations for genomic wide studies. However, population genetic data are still limited in B. stacei. We therefore selected and amplified 10 nuclear microsatellite markers to depict patterns of population structure and genetic variation among 181 individuals from 19 populations of B. stacei occurring in its predominant range, the western Mediterranean area: mainland Iberian Peninsula, continental Balearic Islands and oceanic Canary Islands. Our genetic results support the occurrence of a predominant selfing system with extremely high levels of homozygosity across the analyzed populations. Despite the low level of genetic variation found, two different genetic clusters were retrieved, one clustering all SE Iberian mainland populations and the island of Minorca and another one grouping all S Iberian mainland populations, the Canary Islands and all Majorcan populations except one that clustered with the former group. These results, together with a high sharing of alleles (89%) suggest different colonization routes from the mainland Iberian Peninsula into the islands. A recent colonization scenario could explain the relatively low levels of genetic diversity and low number of alleles found in the Canary Islands populations while older colonization events are hypothesized to explain the high genetic diversity values found in the Majorcan populations. Our study provides widely applicable information about geographical patterns of genetic variation in B. stacei. Among others, the genetic pattern and the existence of local alleles will need to be adequately reflected in the germplasm collection of B. stacei for efficient genome wide association studies.

Genetic analysis of invasive populations of Ventenata dubia (Poaceae): an assessment of propagule pressure and pattern of range expansion in the Western United States

“…Similar results are reported for gene diversity statistics (Nei and Chesser 1983) (Table 4), which indicates that 86.4% of the total diversity is partitioned among populations (GST = 0.864). This level of genetic differentiation among populations of V. dubia is greater than that reported for invasive populations of other selfing grass species such as B. tectorum (Novak and Mack 2016) and Brachypodium stacei (Shiposha et al 2016), but very similar to the level reported for T. caput-medusae (GST = 0.907) (S.J. Novak, unpublished data).…”

The impact of Pleistocene sea-level oscillations on plant genetic diversity: the case of the western Mediterranean endemic Carduncellus dianius (Asteraceae)

“…3). Previous studies with similar plant distributions in the eastern Iberian Peninsula and Balearic Islands also identify the mainland as the area of origin (Prentice et al, 2003;Juan et al, 2012;Garnatje et al, 2013;Shiposha et al, 2016).…”

“…The active history of multiple colonizations in C. dianius could have meant the erosion of part of its genetic diversity at each colonization step (due to founder effects) as other studies reported (e.g. Shiposha et al, 2016). In addition, the restricted seed dispersal and the reduced inter-population gene flow (Table S5) would have fostered the predominance of drift, which has been reported as one of the main evolutionary forces to explain the high plant diversity in the Mediterranean area (Rosselló, 2013 and references therein).…”

Cryptic species in an ancient flowering‐plant lineage (Hydatellaceae, Nymphaeales) revealed by molecular and micromorphological data

“…occurs in ephemeral aquatic ponds probably further reduces the probability of gene flow between them. The absence of genetic variation within populations observed in this study is not uncommon in highly autogamous plants (e.g., Shiposha & al., ; Marques & al., ).…”