Conservation strategies for Arapaima gigas (Schinz, 1822) and the Amazonian várzea ecosystem

Abstract

In the present study we report a spatial autocorrelation analysis of molecular data obtained for Arapaima gigas, and the implication of this study for conservation and management. Arapaima is an important, but critically over-exploited giant food fish of the Amazonian várzea. Analysis of 14 variable microsatellite loci and 2,347 bp of mtDNA from 126 individuals sampled in seven localities within the Amazon basin suggests that Arapaima forms a continuous population with extensive genetic exchange among localities. Weak effect of isolation-by-distance is observed in microsatellite data, but not in mtDNA data. Spatial autocorrelation analysis of genetic and geographic data suggests that genetic exchange is significantly restricted at distances greater than 2,500 km. We recommend implementing a source-sink metapopulation management and conservation model by proposing replicate high quality várzea reserves in the upper, central, and lower Amazon basin. This conservation strategy would: 1) preserve all of the current genetic diversity of Arapaima; 2) create a set of reserves to supply immigrants for locally depleted populations; 3) preserve core várzea areas in the Amazon basin on which many other species depend. We stress that conservation strategies should not only preserve current genetic diversity, but also the evolutionary processes which have generated the observed patterns.Keywords: pirarucu, gene flow, reserves, várzea, autocorrelation, microsatellites. Estratégias de conservação para Arapaima gigas (Schinz, 1822) e para o ecossistema Amazônico de várzea ResumoNo presente estudo, é descrita uma análise de autocorrelação espacial de dados moleculares obtidos para Arapaima gigas e a implicação deste estudo para sua conservação e manejo. Arapaima é uma espécie de peixe gigante da várzea Amazônica de grande importância econômica, e criticamente sobre-explorada. A análise de 14 locos microssatélites e de 2.347 pb do DNAmt de 126 indivíduos amostrados em sete localidades na bacia Amazônica sugere que Arapaima forma uma população contínua com grande fluxo genético entre localidades. Um pequeno efeito de isolamento por distância é observado através dos dados de microssatélites, mas não através dos dados de DNAmt. A análise de autocorrelação espacial de dados genéticos e geográficos sugere que o fluxo gênico é significativamente restrito em distâncias maiores que 2.500 km. É recomendada a implementação de um modelo de manejo e conservação de metapopulação no padrão doador-receptor, replicando as reservas de várzea na bacia Amazônica superior, central e inferior. Esta estratégia de conservação iria: 1) preservar toda a atual diversidade genética da Arapaima; 2) criar um conjunto de reservas para fornecer imigrantes para populações locais reduzidas; 3) preservar áreas centrais de várzea na bacia Amazônica das quais diversas outras espécies dependem. Estratégias de conservação não deveriam somente preservar a atual diversidade genética, mas também os processos evolutivos que têm gerado os padrões observados.

Genetic diversity of Arapaima gigas (Schinz, 1822) (Osteoglossiformes: Arapaimidae) in the Araguaia-Tocantins basin estimated by ISSR marker

“…The floodplain inundation areas remain at very high rates for an extended period, allowing for the movement of "pirarucus" for a longer period (called the process lateral migration) (Castello, 2008a), since the lakes remain connected for a relatively long time. Thus, Hrbek et al (2005Hrbek et al ( , 2007 and Araripe et al (2013) results demonstrated that the levels of genetic diversity among stocks from different localities of the Amazon basin, although reflecting a consistent population structure, show that there is an effective gene flow. On the other hand, the results for the middle rio Araguaia region are interesting as they show little genetic variability and low gene flow, indicating that some of the stocks studied apparently represent consistent family groups.…”

“…There was also no significant association between geographic distance and genetic differentiation (determined with mitochondrial markers) among "pirarucus" in the Amazon basin (Hrbek et al, 2005); however, in these cases, the analysis suggested the presence of an intense gene flow between the populations sampled. Moreover, the effects of the geographic distance that structured the "pirarucus" populations can be observed between location distances to at least 2,500 km (Hrbek et al, 2007).…”

Conserved Cytogenetic Features in the Amazonian Arapaima, Arapaima gigas (Schinz 1822) from Jamari River, Rondônia–Brazil

“…Moreover, microsatellite and mtDNA studies in specimens collected at seven distinct sites in the Amazon basin revealed a high gene flow among localities, indicating that A. gigas composes a single connected population, where the gene flow becomes restricted only over long distances, higher than 2500 km [7].…”

“…Despite the large number of studies on conservation and management [5][6][7], cytogenetic data are scarce in A. gigas. Marques et al [8] carried out cytogenetic studies in a population of this species collected in Middle Araguaya River, municipality of Araguaiana (MT, Brazil).…”

Evidence of polygamy in the socially monogamous Amazonian fish Arapaima gigas (Schinz, 1822) (Osteoglossiformes, Arapaimidae)

“…Even though it has been exploited commercially for many years, much basic life history data are still lacking. However, several recent publications have made significant advances of our understanding of growth and reproductive behavior (Arantes et al, 2010), population dynamics (Coutinho et al, 2010;Castello et al, 2011), spatial and temporal distribution and trophic ecology (Watson et al, 2013) as well as population structuring (Hrbek et al, 2005;Hrbek et al, 2007;Araripe et al, 2013).…”