DNA sequence variation in the fruit tree Inga inicuil (Leguminosae: Mimosoideae) from contrasting altitude distinguishes two different species

Abstract

Background: Inga inicuil is a leguminous tree in Veracruz, Mexico whose fruits are locally commercialized. One taxonomic hypothesis suggests that I. inicuil is a species with a wide altitudinal range, while another segregates I. paterno from I. inicuil by altitude and morphology. The aim of this study was to explore variation in non-coding regions from the chloroplast and nuclear genomes within individuals of I. inicuil from contrasting altitude.
 Hypothesis: Phylogenetic analyses with sequence data would separate exemplars of I. inicuil in two different species and as the case with other metabolites, the sugar content in the sarcotesta would vary with altitude.
 Studied species: Inga inicuil 
 Study site: The mountainous region of Coatepec and the coastal region of Tolome and San Pancho in Veracruz, Mexico.
 Methods: Representative individuals of I. inicuil were selected from localities with contrasting altitude. Maximum Likelihood and Bayesian Phylogenetic Inference approaches were used for phylogenetic analyses with sequence data from the ITS1-5.8S-ITS2 and trn L-F. Sugar content in ripe fruit was measured using a refractometer.
 Results: Sugar content was not related to altitude or with sequence variation. However, sequences from the trn L-F revealed an insertion/deletion of approximately 309 nucleotides present only in trees growing at the coastal plain. Phylogenetic analyses with sequence data support the hypothesis that I. inicuil and I. paterno are two different species.
 Conclusions: The remarkable differences of sequence data from the trn L-F within the species make necessary further research increasing taxon sampling along with its distribution range for clarifying its taxonomy.