Patterns of intraspecific genetic variation of Andoa berthelotiana (Myuriaceae, Bryophyta) in the Azores (Macaronesia)

Abstract

Macaronesia is home to several endemic bryophytes, such as Andoa berthelotiana. Recent genetic studies revealed the existence of two intraspecific lineages within this species, one in Madeira and the Canary Islands and another in the Azores. However, patterns of intraspecific variation within archipelagos, remain a relatively unexplored area of research. In this study we investigate patterns of intraspecific variation of Andoa berthelotiana within the Azorean archipelago and potential associations with elevation. Our investigation is based on the analysis of chloroplast DNA sequences and AFLP data. The dataset includes trnL-trnF sequences from 23 samples and AFLP data from 34 samples collected in seven of the nine Azorean islands, encompassing elevations of up to 1200 m. For the DNA sequence data haplotype diversity, nucleotide diversity and a statistical parsimony haplotype network were calculated. The AFLP data were analyzed by AMOVA (Analysis of Molecular Variance) and PCoA (Principal Coordinates Analysis). A Chi-Square test was carried out to assess the significance of the relationship between elevation and AFLP groups or trnL-trnF haplotypes, respectively. The observed intraspecific genetic variation clustered into three trnL-trnF haplotypes and two AFLP groups, without a clear geographical structure across the Azorean archipelago. Group AFLP1 and haplotypes trnL_F1 and trnL_F3 only appeared below 600 m elevation, where low-elevation vegetation (coastal woodlands, lowland forests and montane Laurus azorica forests) prevails, while group AFLP2 and haplotype trnL_F2 occurring along the whole elevational range, but with most samples above 600 m. Associations between elevation and molecular groups were significant according to the Chi-Square test. Our study reveals the presence of genetic variation within Andoa berthelotiana in the Azorean archipelago. The two main genetic groups do not seem to be related to geographical location of islands nor groups of islands, but rather to elevation. One group exhibits a broader ecological amplitude, whereas the other may be genetically adapted to environmental conditions at lower elevations (below 600 m), which includes the area where the native laurel forests dominate and where anthropogenic activities have altered the majority of natural vegetation. Conservation efforts should therefore not only consider the species Andoa berthelotiana itself, which is associated with natural forest, but also intraspecific genetic diversity of Andoa populations, in particular genotypes restricted to lower elevations.