A new computational method to estimate adaptation time in Avicennia by using divergence time.

Evolutionary studies of plant groups which are distributed in vast geographical regions and face different ecological and environmental conditions are important as they through light on different mechanisms of local adaptation and species divergence through time. The genus Avicennia is one of these plant groups which inspire of few species show interesting geographical distribution with some degree of species-specific geographical isolations. In general, very limited molecular phylogenetic investigations have been carried out in the genus Avicennia, and therefore we conducted the present study with the following aims: 1. To estimate the species divergence time based on different nuclear and chloroplast DNA regions, separately. This will illustrate how different genetic regions evolved in this genus, 2. To identify the sequences with potential adaptive value against geographical variable by latent factor mixed models (LFMM) analysis, 3. To illustrate the phylogenetic signal of these DNA regions and their role in speciation within the genus and, 4. To introducing a new computational strategy for estimating adaptive time for the sequences. The results showed that different genetic regions may produce different species divergent time, both the nuclear ribosomal internal transcribed spacer (ITS) region and chloroplast DNA sequences, contained potentially adaptive single nucleotide polymorphisms (SNPs).We could present a suggestive time for these adaptive sequences for the first time. In conclusion both local adaptation and independent mutations seem to have played role in Avicennia speciation and evolution.