Molecular systematics reveals multiple lineages and cryptic speciation in the freshwater crayfish Parastacus brasiliensis (von Martens, 1869) (Crustacea : Decapoda : Parastacidae)

Abstract

The characterisation of intraspecific genetic diversity in representatives of the South American crayfish genus Parastacus Huxley, 1879 is here carried out for the first time by comparing populations of Parastacus brasiliensis (von Martens, 1869) as currently defined. Phylogenetic reconstructions based on mitochondrial and nuclear markers indicate the existence of multiple lineages, of which only one can be considered as P. brasiliensis sensu stricto. In addition, there are seven other lineages, one of which is the subspecies Parastacus brasiliensis promatensis Fontoura & Conter, 2008, which is here elevated to species level. We thereby increase to 14 the number of recognised species within Parastacus in South America. Genetic distances among P. brasiliensis sensu stricto and the lineages ‘A’, ‘B’ and ‘C’ increase with geographical distances, suggesting isolation by distance as an important driver of diversification, and eventually speciation, in these burrowing crayfishes. Parastacus brasiliensis occurs mainly in the Guaíba Lake basin and studied populations show limited connectivity and gene flow, probably due to habitat fragmentation. On the basis of genetic and distribution data, the conservation status of P. brasiliensis sensu stricto is confirmed as Near Threatened (NT). These findings lead us to encourage the establishment of preservation areas for isolated populations. The importance of preserving the newly recognised distinct gene pools in order to maintain overall genetic diversity is emphasised.

Evolving in islands of mud: old and structured hidden diversity in an endemic freshwater crayfish from the Chilean hotspot

“…According to previous phylogeographic studies, aquatic continental organisms tend to have their genetic diversity more structured than other organisms e.g., 39 . This pattern of highly structured variation is consistent with those of other parastacids 40 – 42 , including P. pugnax . In general, we detect low genetic diversity and predominance of private haplotypes within each sampling locality, but high differentiation among them.…”

“…The little phenotypic variation displayed by some species of Parastacus is evident when comparing, for example, the species of Brazil and Chile, which would have diverged more than 40 Mya. A genealogical study suggested the existence of cryptic speciation in P. brasiliensis 42 . In agreement with this, six new Brazilian species of Parastacus have been described in the last five years supported largely by genetic distinction 55 – 58 , which suggests that the real species richness of the genus is far from being fully detected.…”

Ficha de Parastacus brasiliensis

“…Estados Rio Grande do Sul Biomas Mata Atlântica, Pampa Bacias Hidrográficas Sub-bacia Guaíba Distribuição Endêmica do Brasil: Sim Parastacus brasiliensis é endêmico do Brasil meridional e ocorre apenas na depressão central do Estado do Rio Grande do Sul, mais especificamente nos cursos d'água e áreas alagadas adjacentes que formam a bacia do rio Guaíba (Buckup & Rossi, 1980;Miranda et al, 2018). Sua extensão de ocorrência (EOO) foi estimada em cerca de 14.691 km².…”

Ficha de Parastacus promatensis

“…Areola mais estreita do que a base rostral. Quelípodos longos com palma achatada e margem interna com a área medial com tubérculos irregularmente distribuídos (Miranda et al, 2018).…”