The origin of the giant ground beetle Aplothorax burchelli on St Helena Island

Some highly isolated oceanic islands harbour endemic ground beetles that have lost the ability to fly. Here, we investigated the origin of the possibly extinct flightless giant ground beetle Aplothorax burchelli on St Helena Island in the South Atlantic. Aplothorax burchelli was initially considered to be a member of the subtribe Calosomina (=genus Calosoma) of the subfamily Carabinae (Coleoptera: Carabidae) closely related to the genus Ctenosta (=Calosoma subgenus Ctenosta), but this proposition was questioned due to its unique external and genital morphology. We conducted a phylogenetic analysis of mitogenome sequences using historical specimens of A. burchelli and samples of representative species of Carabinae. Our analysis of 13 protein-coding gene sequences revealed that A. burchelli is definitely a member of Calosomina, most closely related to a species of Ctenosta. Further analysis using NADH dehydrogenase subunit 5 gene sequences from most groups in Calosomina showed that A. burchelli formed a monophyletic group with Ctenosta species from Africa and Madagascar. Our results suggest that the ancestor of A. burchelli, which had the ability to fly, colonized St Helena from Africa after the emergence of the island 14 Mya, and has since undergone evolutionary changes in conjunction with loss of flight.

Origin and adaptive radiation of the exceptional and threatened bembidiine beetle fauna of St Helena (Coleoptera: Carabidae)

The central peaks of the isolated island of St Helena (south Atlantic Ocean) are home to an extraordinary set of ground beetles of the tribe Bembidiini, which belong to three endemic genus-group taxa. These beetles are strikingly different in overall body form from the many bembidiines found elsewhere in the world. At least some of the St Helena species are likely to be extinct, and all are threatened by habitat destruction and invasive species. Through next-generation sequencing of historical museum specimens, we examine the phylogenetic relationships of the St Helena fauna. We find that, in spite of their morphological disparities, the endemic bembidiines of St Helena form a clade of genetically similar species, with their sister group being Bembidion alsium from the Indian Ocean island of La Réunion, and the sister group of this pair being the African subgenus Omotaphus. We propose that the St Helena Peaks Bembidion are an adaptive radiation that arose from a single dispersal event to St Helena from a now-extinct African lineage (sister to Omotaphus) and that this extinct lineage also served as the ancestral source of B. alsium. Given that the St Helena Peaks Bembidion are deeply nested in the genus Bembidion, we move the three taxa back in that genus as subgenera and provide a new name (Bembidion shepherdae) for the now-homonymous Bembidion wollastoni.

The Mecyclothorax beetles (Coleoptera, Carabidae, Moriomorphini) of Haleakala-, Maui: Keystone of a hyperdiverse Hawaiian radiation

The Mecyclothorax carabid beetle fauna of Haleakalā volcano, Maui Island, Hawai‘i is taxonomically revised, with 116 species precinctive to Haleakalā recognized, 74 newly described. Species are classified into 14 species groups, with the newly described species arrayed as follows: 1, Mecyclothoraxconstrictus group with Mecyclothoraxperseveratussp. n.; 2, Mecyclothoraxobscuricornis group with Mecyclothoraxnotobscuricornissp. n., Mecyclothoraxmordaxsp. n., Mecyclothoraxmordicussp. n., Mecyclothoraxmanducussp. n., Mecyclothoraxambulatussp. n., Mecyclothoraxmontanussp. n., Mecyclothoraxwaikamoisp. n., Mecyclothoraxpooulisp. n., and Mecyclothoraxahulilisp. n.; 3, Mecyclothoraxrobustus group with Mecyclothoraxaffinissp. n., Mecyclothoraxanchisteussp. n., Mecyclothoraxconsanguineussp. n., Mecyclothoraxantaeussp. n., Mecyclothoraxcymindulussp. n., and Mecyclothoraxhaydenisp. n.; 4, Mecyclothoraxinterruptus group with Mecyclothoraxbradycelloidessp. n., Mecyclothoraxanthracinussp. n., Mecyclothoraxarthurisp. n., Mecyclothoraxmedeirosisp. n., Mecyclothoraxinconscriptussp. n., and Mecyclothoraxfoveolatussp. n.; 5, Mecyclothoraxsobrinus group with Mecyclothoraxfoveopunctatussp. n.; 6, Mecyclothoraxovipennis group with Mecyclothoraxsubtilis Britton & Liebherr, sp. n., Mecyclothoraxpatulussp. n., Mecyclothoraxpatagiatussp. n., Mecyclothoraxstrigosussp. n., Mecyclothoraxtakumiaesp. n., Mecyclothoraxparapicalissp. n., Mecyclothoraxmauiaesp. n., Mecyclothoraxsubternussp. n., Mecyclothoraxflaviventrissp. n., Mecyclothoraxcordaticollarissp. n., and Mecyclothoraxkrushelnyckyisp. n.; 7, Mecyclothoraxargutor group with Mecyclothoraxommatoplaxsp. n., Mecyclothoraxsemistriatussp. n., Mecyclothoraxrefulgenssp. n., Mecyclothoraxargutulussp. n., Mecyclothoraxplanipennissp. n., Mecyclothoraxplanatussp. n., and Mecyclothoraxargutuloidessp. n.; 8, Mecyclothoraxmicrops group with Mecyclothoraxmajorsp. n., Mecyclothoraxxestossp. n., Mecyclothoraxorbiculussp. n., and Mecyclothoraxcontractussp. n.; 9, Mecyclothoraxscaritoides group with Mecyclothoraxscaritessp. n., Mecyclothoraxtimberlakeisp. n., Mecyclothoraxcrassuloidessp. n., Mecyclothoraxcrassulussp. n., Mecyclothoraxgracilicollissp. n., and Mecyclothoraxdisparsp. n.; 10, Mecyclothoraxhaleakalae group with Mecyclothoraxreiteratussp. n., Mecyclothoraxsplendidussp. n., Mecyclothoraxbacrionissp. n., and Mecyclothoraxsimpulumsp. n.; 11, Mecyclothoraxvitreus group with Mecyclothoraxkipwillisp. n., Mecyclothoraxkipahulusp. n., Mecyclothoraxkaumakanisp. n., and Mecyclothoraxkuikisp. n.; 12, Mecyclothoraxmontivagus group with Mecyclothoraxrexsp. n.; 13, Mecyclothoraxducalis group with Mecyclothoraxaquilussp. n., Mecyclothoraxinvisitatussp. n., Mecyclothoraxlongiduxsp. n., and Mecyclothoraxbreviduxsp. n.; and 14, Mecyclothoraxpalustris group with Mecyclothoraxhephaestoidessp. n., Mecyclothoraxoculellussp. n., Mecyclothoraxbicolorissp. n., Mecyclothoraxbicoloratussp. n., Mecyclothoraxbilobatussp. n., Mecyclothoraxpalustroidessp. n., Mecyclothoraxfilipoidessp. n., Mecyclothoraxnanunctussp. n., Mecyclothoraxtauberorumsp. n., and Mecyclothoraxpausp. n.Mecyclothoraxinteger Sharp, stat. n. is recognized as a species distinct from Mecyclothoraxinterruptus Sharp. Because type series for species described by Blackburn, Karsch, and Sharp are most often divided among geographically remote collections, lectotypes are designated to stabilize the nomenclature. The radiation includes numerous cryptic sibling species best diagnosed using male genitalia, and photographs are used to represent the male genitalic variability observed among numerous dissected individuals. The large number of new species is based on substantial new collections made from all quarters of the mountain. The dense geographic sampling allows fine-scale discrimination of species boundaries, elucidating the geographic disjunctions that are associated with speciation within this hyperdiverse radiation. Disjunctions between closely related species precinctive to various areas of the mountain are not congruent across the different lineages of the radiation, indicating differential responses by the various lineages to past geological and geographical events. Of the 62 1’ latitude × 1’ longitude grid cells on Haleakalā that are occupied by Mecyclothorax beetles, 22 house 10 or more species, and 9 house 20 or more species. This substantial level of sympatry, associated with occupation of diverse microhabitats by these beetles, provides ample information useful for monitoring biodiversity of the natural areas of Haleakalā.