Phylogeography of a Marine Insular Endemic in the Atlantic Macaronesia: The Azorean Barnacle, Megabalanus azoricus (Pilsbry, 1916)

Abstract

The Azorean barnacle, Megabalanus azoricus (Pilsbry, 1916), is a Macaronesian endemic whose obscure taxonomy and the unknown relationships among forms inhabiting isolated Northern Atlantic oceanic islands is investigated by means of molecular analysis herein. Mitochondrial data from the 16S rRNA and COX1 genes support its current species status, tropical ancestry, and the taxonomic homogeneity throughout its distribution range. In contrast, at the intraspecific level and based on control region sequences, we detected an overall low level of genetic diversity and three divergent lineages. The haplogroups α and γ were sampled in the Azores, Madeira, Canary, and Cabo Verde archipelagos; whereas haplogroup β was absent from Cabo Verde. Consequently, population analysis suggested a differentiation of the Cabo Verde population with respect to the genetically homogenous northern archipelagos generated by current oceanographic barriers. Furthermore, haplogroup α, β, and γ demographic expansions occurred during the interglacial periods MIS5 (130 Kya - thousands years ago -), MIS3 (60 Kya), and MIS7 (240 Kya), respectively. The evolutionary origin of these lineages is related to its survival in the stable southern refugia and its demographic expansion dynamics are associated with the glacial-interglacial cycles. This phylogeographic pattern suggests the occurrence of genetic discontinuity informative to the delimitation of an informally defined biogeographic entity, Macaronesia, and its generation by processes that delineate genetic diversity of marine taxa in this area.

De novo innovation allows shark parasitism and global expansion of the barnacle Anelasma squalicola

“…Multiple host species' distributions overlap in waters around South Africa, including two with enormous ranges in the southern hemisphere (Table S1), and this region potentially bridges to the northern hemisphere through a common eastern Atlantic host species (E. spinax). In attempting to estimate time of the earliest haplotype divergence (approximate time of origin of Anelasma as a new species), we obtained from the literature maximum and minimum values for COI and control region mutation rates for related barnacle species, where fossil records or geographical events allowed reliable estimates [7]. The calculated divergence times were found to be between 274,000 and 545,000 ya for the COI gene, and between 408,000 and 811,000 ya for the control region (see Supplemental Experimental Procedures for details).…”

Pelagic Cnidaria and Ctenophora diversity patterns and trends in Macaronesia insular systems (NE Atlantic)

“…Among the three archipelagos, Azores, Madeira and Canary Islands, sister areas tend to change depending on the taxa/phylum used for the biogeography study. For instance, based on the species composition of ichtyofauna (Lloris et al 1991), Cirripedia (Quinteiro et al 2015) and shallow subtidal macroalgae (Sangil et al 2018), the Lusitanian Macaronesia has been divided into two biogeographic areas, one comprising Madeira and the Canary Islands and the other comprising only the Azores. One the other hand, Vanderpoorten et al (2007) and later Tuya and Haroun (2009) featured Azores and Madeira as sister areas based on algae and pteridophyte diversity.…”

Genetic diversity and population structure of the blue jack mackerel Trachurus picturatus across its western distribution

“…These islands, just off the coast of Europe and Africa, are formed by volcanic seamounts and were never part of a continent. This makes the biogeography of the islands very attractive for phylogeographic studies (Quinteiro et al, ; Stefanni et al, ; Whittaker, ). The marine environment is very often characterised as having complex oceanic currents and no physical barriers, which greatly increase a species’ dispersal potential, promoting high gene flow over large scales (Selkoe et al, ).…”

“…These currents, together with the apparent lack of physical barriers, can strengthen the potential for gene flow. Indeed, several phylogeographic studies have reported a low population genetic differentiation in the Macaronesian region for different taxa, including gastropods (De Wolf et al, ), crustaceans (Faria et al, ; Quinteiro et al, ) and fishes (Francisco et al, ; Stefanni et al, ). On the other hand, the Macaronesia archipelagos are also characterised by different upwellings zones, habitat discontinuities and ecotones between areas with different environmental properties and areas with historical sea level drops ( e.g ., Stefanni et al, ).…”