Morphological and molecular data confirm species assignment and dispersal of the genusLigia(Crustacea: Isopoda: Ligiidae) along northeastern coastal China and East Asia

Abstract

The morphological traits and mitochondrial genes of sympatric sea slaters from the genus Ligia were analysed from samples collected along northeastern coastal China and adjacent coastal East Asia to assign the species and to obtain interpretations of their distributions. Using 338 sequences and 199 diagnoses of 16S polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) from 331 specimens sampled from 26 localities, and homological sequences from counterparts from South Korea and the west coast of the USA, we assigned these taxa into two distinct species, Ligia exotica and Ligia cinerascens. Both species are recovered as two monophyletic clades in the robust phylogenetic hypothesis presented here. The northern boundaries of these species in China and the Korean peninsula are more southern than those of counterparts in Japan. Ligia exotica in northeastern coastal China is further split into two geographical subclades (B1 and B2), coexisting near 35°N. The distribution range of L. cinerascens covers the whole range of L. exotica subclade B1. Counterparts in Japan show a similar pattern. Oceanic rafting, shipping, damming and planting of seaweed are proposed as the media for the contemporary connectivity among populations of Ligia species inhabiting coastal China.

Cryptic biodiversity and phylogeographic patterns of SeychelloisLigiaisopods

“…Lastly, individuals from Cousine Island exhibit COI K2P divergences of 4.5–5.3% when compared to other localities (Mahé and Silhouette) within the inner islands. Interestingly, this pattern is similar to those previously reported for Seychellois herpetofauna from the inner islands (Rocha, Harris & Posada, 2011; Rocha, Posada & Harris, 2013; Silva et al, 2010) and to reports of cryptic diversity for other Ligia species, including L. occidentalis (Eberl et al, 2013; Hurtado, Mateos & Santamaria, 2010), L. hawaiensis (Santamaria et al, 2013; Taiti et al, 2003), L. baudiniana (Santamaria, Mateos & Hurtado, 2014), L. exotica and L. cinerascens (Yin et al, 2013), and L. oceanica (Raupach et al, 2014). The sum of our findings thus suggest the presence of 2–3 putative cryptic species of Ligia in the Seychelles: Aldabra Ligia being one, and those of Cousine and Silhouette + Mahé representing one or two putative species.…”

Phylogeographical analysis ofLigia oceanica(Crustacea: Isopoda) reveals two deeply divergent mitochondrial lineages

“…Molecular studies of other Ligia species from North America and East Asia also revealed similar deep mitochondrial divergences (Jung et al ., ; Hurtado, Mateos & Santamaria, ; Markow & Pfeiler, ; Eberl, ; Eberl et al ., ; Yin et al ., ). In the case of Ligia occidentalis from the Pacific coast of North America, recent molecular studies also imply the existence of cryptic species (Eberl et al ., ).…”

Out of Asia: Mitochondrial evolutionary history of the globally introduced supralittoral isopod Ligia exotica

“…and L. italica in the Mediterranean basin (Hurtado et al unpublished cinerascens extends further north into the Kuril Islands (Yin et al, 2013) (Eberl, 2013) and L. oceanica (Raupach et al, 2014). Within the L. exotica clade, Clade B, which is mostly restricted to temperate areas, exhibits comparatively lower genetic diversity (maximum K2P divergence = 2.0%) than clades C and D, which occur in warmer regions.…”

“…leading Yin et al (2013) (2) determine whether further molecular diversity is found in these clades; and (3) shed light on the evolutionary and invasion history of L. exotica.…”

“…Finally, a third D2 haplotype was observed in Brazil (Praia de Calhetas, Cabo de Santo Agostinho, Pernambuco), Uruguay, as well as in Taiwan.Multiple divergent lineages and taxonomic uncertaintyThe L. exotica clade is comprised of highly divergent lineages, which probably represent multiple species. Using morphological characters (i.e., number of segments in the second antenna flagellum, uropod, characters of the telson and the shape of the appendix masculina on the second pleopod of adult males),Yin et al (2013) concluded that members of clades B and D in our phylogenetic tree correspond to L. exotica (they did not examine members of clades A and…”