Sympatry and evolution: relationships between the endemic Myrcia guarujana and the widely distributed M. spectabilis

Myrcia spectabilis DC. has a wide distribution in the south and southeast Brazilian regions. M. guarujana Sobral, Magenta & Caliari is known from the few collections in submontane ombrophilous forest and a transitional site between restinga and ombrophilous forest in São Paulo state. These species are morphologically similar and occur in sympatry, which prompted us to investigate the morphological aspects, sequence the genomes and consider the effects of such sympatry. In a fragment of Brasilian Atlantic rainforest, we collected leaves from individuals of M. guarujana and M. spectabilis. Morphological analysis and DNA extraction were performed for sequencing and construction of the GBS library. A total of 3,429 loci containing neutral SNP markers were identified, and 446 represented outlier loci. The fixation index (FST) had a high value (0.735; p < 0.05). By AMOVA, the highest variance percentage found was 73.54% (P = 0.0079) between the species. Principal component analysis presented two clusters referring to the species, with the MS1 (M. spectabilis- 1) sample isolated from both. On the neighbour-joining dendrogram, both species presented strongly sustained branches (100 and 99, respectively), and MS1 emerged as an intermediate. Among the outlier loci, we have LNG1, which promotes foliar elongation, and MYB82, a transcription activator functionally equivalent to GL1, in which high levels of expression result in decreased trichome abundance. Studies with more representative samples, together with the discovery of the SNPs found here, will constitute a powerful tool to understand the evolution, diversification, and conservation of these two species.