Fine-scale genetic structuring, divergent selection, and conservation prospects for the overexploited crab (Cardisoma guanhumi) in tropical mangroves from North-eastern Brazil

Abstract

Popularly known as blue land crab,Cardisoma guanhumiis heavily exploited as food and considered as an important economic resource in Brazil. In recent decades, the species has experienced a sharp population decline by the loss and/or degradation of its natural habitat and overfishing. The present study aimed to investigate the genetic variation and connectivity among 154 specimens ofC. guanhumisampled along the coast of Pernambuco in five different levels of tropical mangroves conservation. Nine ISSR primers were used for assessing the genetic variation of the species. The genetic diversity observed inC. guanhumiwas high reinforcing the condition of a resilient species, indicating a good conservation status of this resource in Pernambuco. The hypothesis of panmixia was rejected in favour of a heterogeneous distribution of the genotypes ofC. guanhumi(ФST= 0.19) despite the high gene flow observed in the study region. Such difference could be attributed to the candidate loci being under positive selection and differentially distributed between the geographic regions assessed. The genetic structure showed a pattern of fine-scale genetic structuring better fitted to a model of selection-mediated geographic cline. Cluster analysis and candidate loci under positive selection suggested that the populations ofC. guanhumiin the North-central and South coasts of Pernambuco might be different management units and must be managed independently. In conclusion, exhaustion of natural stocks upon which fishing is totally dependent will lead to serious ecological and sociocultural impacts.

Population Structure of the Rockpool Blenny Entomacrodus vomerinus Shows Source-Sink Dynamics among Ecoregions in the Tropical Southwestern Atlantic

“…Finer genetic subdivision may also occur if the marine ecoregions inhabited by this species coincide with important geographic or ecological barriers. This has been shown in some marine organisms from Tropical Southwestern Atlantic inhabiting coastal [ 18 , 19 ], island environments [ 20 ], or both [ 21 ]. Nonetheless, the patterns and processes underlying the genetic distribution of marine lineages in South America are largely unknown, and could be important to understand macroecology, impacts of geological features in species diversification and to detect areas of high conservation priority [ 22 ].…”

Variación genética de Balmea stormiae (Rubiaceae) en el centro-occidente de México

“…En el caso de los ISSR se realizaron pruebas preliminares con 28 cebadores de los desarrollados por el Laboratorio de Biotecnología de Universidad de Columbia Británica, en Vancouver, British Columbia, Canadá. De estos se eligieron con base en la obtención de bandas claras y su reproducibilidad en todos los ensayos, a los oligonucleótidos denominados UBC807, UBC811, UBC814, UBC825, UBC841, UBC842 y UBC844 (Cuadro 2), anteriormente utilizados en varios estu- dios (Lau et al, 2005;Li y Jin, 2008;Muthusamy et al, 2008;Datta et al, 2010;Gama-Maia y Torres, 2016;George et al, 2017). Las condiciones de amplificación siguieron el procedimiento realizado por Santillán-Mendoza et al (2018).…”