Molecular taxonomy of endemic coastalLigiaisopods from the Hawaiian Islands: re-description ofL. hawaiensisand description of seven novel cryptic species

Abstract

Past phylogeographic work has shown Ligia hawaiensis, a coastal isopod species endemic to the Hawaiian Islands, to be a paraphyletic complex of several highly genetically divergent yet morphologically cryptic lineages. Despite the need for a taxonomic revision of this species, the lack of morphological differentiation has proven an impediment to formally describe new Ligia species in the region. Molecular characters and species delimitation approaches have been successfully used to formally describe cryptic species in other crustacean taxa, suggesting they may aid taxonomic revisions of L. hawaiensis. Herein, various distance- and tree-based molecular species delimitation approaches are applied on a concatenated dataset comprised of both mitochondrial and nuclear gene sequences of L. hawaiensis and L. perkinsi, a terrestrial species endemic to the Hawaiian archipelago. Results of these analyses informed a taxonomic revision leading to the redescription of L. hawaiensis and the description of seven new cryptic species on the basis of molecular characters: L. dante, L. eleluensis, L. honu, L. kamehameha, L. mauinuiensis, L. pele, and L. rolliensis. These coastal Ligia species from the Hawaiian archipelago appear to be largely limited to single islands, where they appear largely constrained to volcanic rift zones suggesting allopatric events at local scales may drive diversification for poorly dispersing organisms in the Hawaiian coastlines. Additional work remains needed to fully assess the role of said events; however, the description of these novel species underscore their potential to aid in studies of local diversification of marine organisms in Hawai‘i. Lastly, this represents the first application of molecular taxonomic approaches to formally describe genetic lineages found in Ligia isopods as species, underscoring the promise these methods hold to taxonomic revisions in other species in the genus shown to harbor cryptic genetic lineages.

Redescription of Tylos maindroni Giordani Soika, 1954 (Crustacea, Isopoda, Oniscidea) based on SEM and molecular data

“…The low level of diversification herein reported between individuals of T. maindroni collected at Persian Gulf locations stands in contrast with those reported for other coastal oniscid taxa (Khalaji-Pirbalouty and Raupach , 2016Raupach et al 2014;Hurtado et al 2017;Santamaria et al 2017;Greenan et al 2018;Hurtado et al 2018;Santamaria 2019), including other Tylos species (Hurtado et al 2013). For instance, the molecular characterizations of Tylos populations from the Gulf of California showed genetic differentiation in COI sequences ranging from 3.6 to 17.3%, indicating long-standing isolation of the populations in the region as well as the possible presence of cryptic species (Hurtado et al 2013).…”

“…A later work by Taiti and Ferrara (1991) suggested that T. maindroni ’s geographic range extends into the Persian Gulf, including locations on the coasts of Kuwait and Iran, but additional work remains necessary to clarify the status of this species and its geographic range. Additionally, considering the high levels of genetic divergence reported in several coastal isopod taxa ( Hurtado et al 2013 ; Khalaji-Pirbalouty and Raupach 2014 , 2016 ; Raupach et al 2014 ; Hurtado et al 2017 ; Santamaria et al 2017 ; Greenan et al 2018 ; Hurtado et al 2018 ; Santamaria 2019 ), it would be important to determine if T. maindroni harbors cryptic diversity in its native range.…”

Phylogeographic analysis of Ligidium japonicum (Isopoda: Ligiidae) and its allied species reveals high biodiversity and genetic differentiation in the Kanto region, Japan

“…Khalaji‐Pirbalouty & Wägele 2010). Given our results, however, there might be huge cryptic diversity within morphologically similar and even completely identical groups, which is also suggested by other phylogenetic analyses of Ligia isopods in Hawaii (Santamaria 2019), California and Mexico (Markow & Pfeiler 2010) and East Asia (Yin et al . 2013).…”

Surprisingly high genetic divergence of the mitochondrial DNA barcode fragment (COI) within Central European woodlice species (Crustacea, Isopoda, Oniscidea)

“…Considering the previous discussed aspects, however, additional morphological and/or nuclear DNA sequence data are essential for a verification of truly distinct lineages. For freshwater and terrestrial isopods, a few studies demonstrated such integrative taxonomic approaches ( McGaughran et al 2005 ; Santamaria et al 2017 ; Santamaria 2019 ). In terms of the analyzed taxa, no previous studies discussed the existence of cryptic species, and all specimens were checked and determined carefully before molecular works started.…”