Introduction history of the invasive swimming crab Charybdis hellerii (A. Milne-Edwards, 1867) (Decapoda, Portunidae) on the American coast: molecular tools and comparative morphology

Author(s)

Mariana Negri Pereira

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
• Defense date: 2016-05-30

Examining board members

Fernando Luis Medina Mantelatto; Célio Ubirajara Magalhães Filho; Maura Helena Manfrin; Mateus Henrique Santos; Marcos Domingos Siqueira Tavares

• Advisor: Fernando Luis Medina Mantelatto

Abstract

Charybdis hellerii (A. Milne-Edwards, 1867), an invasive swimming crab species native to the Indo-West Pacific, dispersed to the Mediterranean Sea via Suez Canal. In 1987, it was first reported to the western Atlantic, where self-maintaining populations are currently found from the USA to southern Brazil. It is suggested that animals were transported to America in their larval stages through ballast water from ships probably loaded at Mediterranean ports. An integrative approach of morphological and molecular analyses using three molecular markers (one nuclear, H3 and two mitochondrial, COI and 16S rDNA) was performed in order to check the taxonomic status of C. hellerii and investigate its introduction history. For the latter purpose, this study aimed: (1) to track potential sources, routes of introduction, (2) assess the occurrence or not of multiple introductions and (3) of genetic bottlenecks. C. hellerii was confirmed as a single entity according to the following results: 100% of similarity for the nuclear marker; monophyly of C. hellerii clade in the phylograms including several species of the subfamily Thalamitinae; intraspecific genetic diversity (COI - 0 to 4.2% and 16S rDNA - 0 to 0.9%) inferior to interspecific value expected for the studied loci (COI - 6.2 to 21.5% and 16S rDNA - 3.9 a 15.2%) and total genetic similarity of individuals with different morphological traits. Genetic and morphometric structure was detected in C. hellerii native range (and the Mediterranean Sea), showing two groups: Western Indian Ocean + Mediterranean Sea and Eastern Indian + Pacific Oceans. The AMOVA results for COI revealed that 38.739% of variation was between both groups (ct = 0.38, p = 0.00). This genetic break between the Pacific and Indian Oceans is constantly associated with sea level fluctuations in the connection between both Oceans during the Pleistocene glaciation events. This genetic structure allowed the detection of independent introduction events along the American coast. As most animals from this exotic range were clustered with the Western Indian Ocean + Mediterranean Sea group, the Mediterranean populations were supported as the main source of the American ones. However, the cluster of animals from the southern Brazil with the Eastern Indian + Pacific Oceans group indicated that introductions from these native regions might also have occurred. A third group found solely in the American range and genetically related to Eastern Indian + Pacific also suggested introductions from an unsampled locality of native range. The haplotype diversities of American localities were comparable to those of source ones, whereas the nucleotide diversities were predominantly higher in the non-native localities. These diversity indexes results might be related to the occurrence of multiple introductions from genetic distinct areas. Among all haplotypes of the Indian Ocean + Mediterranean Sea cluster, only two were not found in America, what suggests no expressive bottleneck in the introduction from this source. However, a genetic bottleneck might explain the low number of equal haplotypes between the Eastern Indian + Pacific Ocean cluster and the Atlantic range. Only three haplotypes were detected in four specimens out of 87 collected in American localities in comparison to 22 found in the native group. In addition, the molecular and morphological analyses confirmed that a congeneric species, Charybdis variegata, recently recorded on the American coast, is actually another C. hellerii specimen. (AU)

• FAPESP's process: 12/06300-3 - Divesity and genetic structure of the allien swimming crab Charybdis hellerii (A. Milne-Edwards, 1876) as a tool to infer on its introduction in the American coast
• Grantee: Mariana Negri Pereira
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)