The origin of the giant ground beetleAplothorax burchellion St Helena Island

Abstract

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.

HyRAD-X Exome Capture Museomics Unravels Giant Ground Beetle Evolution

“…1100 species) ( Jiroux 2006 ; Takami and Sota 2006; Cavazzuti 2010 ; Bruschi 2013 ; Deuve 2019 ). Furthermore, the monotypic genus Aplothorax Waterhouse, 1841 endemic to the Atlantic island of St Helena, considered extinct since the 1970s ( Gray et al 2019 ), is classified within the subfamily but without a robust tribal placement ( Jeannel 1940 ; Prüser and Mossakowski 1998 ; Bruschi 2013 ; but see Sota et al 2020 ). In addition to ranking among the most popular of beetles owing to their often elegant and attractive appearance ( Fabre 1901 ; Chatenet 1986 ), the Carabinae include some of the largest and bulkiest ground beetles, including species in the subgenus Carabus ( Procerus ) Dejean, 1826 that attain 6 cm in length ( Cavazzuti 1989 ), and can be termed ‘giant ground beetles’ accordingly.…”

“…2001 ; Sota and Vogler 2001 , 2003 ; Su et al 2003 , 2005 ; Osawa et al. 2004 ; Sota and Ishikawa 2004; Su, Imura, Okamoto, Kim, et al 2004 ; Su, Imura, Okamoto, and Osawa 2004 ; Sota et al 2005 ; Andújar et al 2012a ; Andújar et al 2012b ; Deuve et al 2012 ; Deuve and Faille 2013 ; Muñoz-Ramírez 2015 ; Muñoz-Ramírez et al 2016 ; Imura et al 2018 ; Toussaint and Gillett 2018 ; Sota et al 2020 ). An early attempt to employ RAD-sequencing within the genus Carabus L., 1758 aimed to construct a molecular phylogeny of the charismatic subgenus Carabus ( Chysocarabus ) Thomson, 1875, indicating that a potential strength of such an approach is the inference of relationships at the intrageneric level ( Cruaud et al 2014 ).…”

“…This approach was successfully pursued for phylogenetic inference within Japanese Carabus (e.g., Takahashi et al 2014 ; Fujisawa et al 2019 ). However, very few studies have focused on intertribal relationships (but see Osawa et al 2004 ; Toussaint and Gillett 2018 ; Sota et al 2020 ). Based upon preliminary analyses of Sanger sequencing or mitogenome data, the snail-eating beetles (Cychrini) have been shown to be sister to the rest of the subfamily, followed by Ceroglossini and Pamborini, which together form an apparent Gondwanan stock, that is in turn sister to Carabini (comprising the diverse genera Carabus and Calosoma Weber 1801) ( Imura et al 2018 ; Toussaint and Gillett 2018 ; Sota et al 2020 ).…”

“…However, very few studies have focused on intertribal relationships (but see Osawa et al 2004 ; Toussaint and Gillett 2018 ; Sota et al 2020 ). Based upon preliminary analyses of Sanger sequencing or mitogenome data, the snail-eating beetles (Cychrini) have been shown to be sister to the rest of the subfamily, followed by Ceroglossini and Pamborini, which together form an apparent Gondwanan stock, that is in turn sister to Carabini (comprising the diverse genera Carabus and Calosoma Weber 1801) ( Imura et al 2018 ; Toussaint and Gillett 2018 ; Sota et al 2020 ). Jeannel (1940) hypothesized that Aplothorax is a close relative of the Afrotropical subgenus Calosoma ( Ctenosta ) Motschulsky, 1865 and this placement was recently supported by analysis of mitogenomes ( Sota et al 2020 ).…”

“…Based upon preliminary analyses of Sanger sequencing or mitogenome data, the snail-eating beetles (Cychrini) have been shown to be sister to the rest of the subfamily, followed by Ceroglossini and Pamborini, which together form an apparent Gondwanan stock, that is in turn sister to Carabini (comprising the diverse genera Carabus and Calosoma Weber 1801) ( Imura et al 2018 ; Toussaint and Gillett 2018 ; Sota et al 2020 ). Jeannel (1940) hypothesized that Aplothorax is a close relative of the Afrotropical subgenus Calosoma ( Ctenosta ) Motschulsky, 1865 and this placement was recently supported by analysis of mitogenomes ( Sota et al 2020 ). The genus Calosoma is unique in this subfamily of predominantly brachypterous flightless species, for containing a significant proportion of fully winged and flight-capable species ( Bruschi 2013 ).…”