Variabilidade espacial em caracteres morfológicos e diversidade genética de Dendropsophus walfordi (Anura: Hylidae) em bancos de macrófitas na Amazônia

Abstract

The Amazon is home to a high biological diversity, which has attracted researchers since the 19th century. Although, the actual number of species occurring in the Amazon, and the processes responsible for the origin and maintenance of this great diversity, are still widely debated. Much of what is known of the Amazon herpetofauna is related to non-floodable forest areas; little is known about diversity in seasonally flooded environments. For amphibians a mode of dispersion in flooded forests can occur through macrophyte banks. These aquatic plant communities are considered to be the most densely populated habitats in the várzea water bodies. Generally, in amphibians, the dispersion movements are of short distances. Longdistance dispersions are not common, but important for population expansion, colonization of new habitats, and gene flow. Dendropsophus walfordi occurs in the central region and further north of the Amazon Basin in Brazil, in flooded environments associated with macrophytes. In this work we used morphometric data to evaluate if there are significant morphological differences between the sampled populations, as well as gene mtDNA 16S sequence data, to evaluate the distribution pattern of the genetic variability of the species. Considering that Dendropsophus walfordi occurs in macrophytic banks our null hypothesis is that populations are panmíticas throughout their distribution, since the dislocations of the macrophyte banks would facilitate the gene flow. To verify patterns of morphological divergence a PCA was performed. The mtDNA 16S gene was sequenced from 64 individuals distributed in 10 locations. Bayesian inferences were used to investigate the number of real populations. Population structure was obtained through the AMOVA and demographic events were investigated via Tajima D and Fu Fs. The index of genetic diversity was also calculated. In addition, considering the lack of phylogenetic relationships for the species of the group Dendropsophus microcephalus of which D. walfordi is a part, we incorporated this approach in the present work using as strategy the obtaining of all mtDNA 16S sequences deposited in GenBank for the species of the group, taking species of the group Dendropsophus leucophyllatus as an external group. The analysis of the main components showed that there are no apparent phenotypic differences among the populations of D. walfordi. Neutrality tests showed population expansion, and AMOVA revealed high levels of population structure. Although there is no relationship between genetic distance and geographic distance, some other factor such as river barriers may be contributing to these levels of structuring. Considering the database obtained, we also explore the phylogenetic relationships of D. walfordi with the other species of the group D. microcephalus. The results of the maximum likelihood analysis indicated little resolution (low support) for the confirmation of the monophyletic group D. microcephalus and, interestingly, the species D. walfordi and D. nanus showed to be paraphyletic and the brother group of D. coffea, the which suggests that D. walfordi is synonymous with D. nanus.