Background:

Meristotheca cylindrica is a red alga distributed in the Campeche coast, usually misidentified by the morphological variation spectrum exhibited in its populations.

Objectives:

We proposed to evaluate the genetic variation and its relationship with morphological variation in M. cylindrica populations, to describe the possible genetic structure and its haplotypic distribution and to determine possible speciation events.

Methods:

We measured genetic variation, distances and structure of 45 individuals of M. cylindrica from five populations of Campeche, using DNA sequences of the spacer regions of RuBisCo and cox2-3. Additionally, phylogenetic analyses were performed considering sequences of Solieriaceae species available in the GenBank. A statistical analysis covering 30 morphological characters was performed on 10 herbarium specimens.

Results:

The RuBisCo spacer region revealed four interconnected haplotypes (R1-R4), as well as moderated genetic diversity parameters (Hd= 0.46458, π= 0.00785). Phylogenetic analysis showed a single monophyletic group that included all haplotypes. The cox2-3 spacer region revealed nine haplotypes (C1-C9) structured in the GI and GII groups, as well as elevated parameters of genetic diversity, distances and differentiation (Hd = 0.81, π = 0.06476; >10% of differences; ΦPT and FST> 0.35). Phylogenetic analysis showed two monophyletic groups congruent with GI and GII. Analysis of variance showed morphological homogeneity among populations.

Conclusions:

Findings suggest a speciation event is currently occurring in M. cylindrica.