Cytogenetic studies on populations of Camponotus rufipes (Fabricius, 1775) and Camponotus renggeri Emery, 1894 (Formicidae: Formicinae)

Abstract

Two valid ant species, Camponotus rufipes and Camponotus renggeri, have recently been the subject of a broad discussion with reference to taxa synonymization. Both species are quite common among the Neotropical myrmecofauna and share some unique traits, such as the shape of the scape and the pilosity patterns of the tibiae and scapes. A single morphological trait can help distinguish these species; however, only a combination of different approaches can enlighten our view of the complex phylogenetic relationships prevailing in the different populations of these two taxa. Therefore, focusing on the taxonomic issues concerning these two species, a cytogenetic survey including 10 populations of C. rufipes and two populations of C. renggeri was performed. In order to better understand the extent of the relationship between C. rufipes and C. renggeri, two common Neotropical Camponotus species, C. atriceps and C. cingulatus were taken as outgroups. All four species of Camponotus that were studied had 2n = 40 chromosomes (4sm+34st+2t); however, the abundance of chromosome rearrangements observed, combined with several chromosome markers, suggest that C. rufipes and C. renggeri are two good distinct species although closely related. The already reported chromosome translocation 2n = 39 (1m+4sm+32st+2t) for C. rufipes has been found in different populations as in the unprecedented chromosome inversions found both in C. rufipes and in C. renggeri populations. Within the C. renggeri chromosome inversions, both the heterozygous state 2n = 40 (1m+3sm+34st+2t) and the homozygous state, 2n = 40 (2m+2sm+34st+2t) were identified. However, only heterozygous specimens for chromosome inversions were found among C. rufipes, with karyotype configurations distinct from those found in C. renggeri, with 2n = 40 (1m+4sm+34st+2t). None of the populations studied showed signs of mosaic individuals. With respect to rDNA clusters, the 18S rDNA seemed to be more restricted inside the genome, as C. renggeri showed four 18S rDNA clusters, whereas, C. rufipes, C. atriceps, and C. cingulatus showed only two clusters. The chromosome locations of the 5S rDNA clusters were pointed for the first time in Formicidae, and showed itself to be more widely spread over the genome. By combining different chromosome banding approaches it was possible to demonstrate the crucial importance that chromosome inversions played on the karyotype evolution within these ants. The results also showed that chromosome translocations might be a consequence of the chromatin dynamic condition observed among Camponotus species. The homozygosis condition found in a C. renggeri from a Brazilian savanna population for chromosome inversions and the contrasting heterozygous condition for a different kind of chromosome inversion in C. rufipes from the Brazilian coastal rainforest, opens the window for a chromosome race hypothesis within the group C. renggeri and C. rufipes. The wide distribution, rich ecological interactions, genetic diversity, and morphological variability among C....

Karyotypic data of five ant taxa from the Brazilian Atlantic rainforest

“…Camponotus (Myrmothrix) atriceps, exhibited 2n=40; 2K=4sm+34st+2a (Fig 2D). Similar karyotypes were observed for individuals collected in the Atlantic rainforest at Ilhéus, Bahia (Mariano et al, 2001) and in the Brazilian Cerrado (Aguiar et al, 2017). Although Mariano et al (2001) used a chromosomal classification different to the present study, it is possible to recognize the same chromosomal pairs in the two localities from the Atlantic rainforest.…”

“…In this study, mensuration of chromosome arms was performed making chromosomal classification more accurate. Considering the difficulties in species identification in Brachymyrmex due to their complex morphology and their extremely small size, molecular cytogenetics can bring important insights in taxonomy as observed in other ant species (Aguiar et al, 2017;Micolino et al, 2019).…”

Cytogenetic data for sixteen ant species from North-eastern Amazonia with phylogenetic insights into three subfamilies

“…Typhlomyrmex rogenhoferi Mayr, 1862 (Mariano et al 2006), Dinoponera lucida Emery, 1901(Mariano et al 2008, Pachycondyla spp. (Mariano et al 2012), and Camponotus rufipes (Fabricius, 1775) (Aguiar et al 2017). However, cytogenetic data can be used to identify cryptic species, which are common in Formicidae (Seifert 2009).…”

Cytogenetic studies in Trachymyrmex holmgreni Wheeler, 1925 (Formicidae: Myrmicinae) by conventional and molecular methods

“…Ant cytogenetics has drawn the attention of myrmecologists (Delabie et al, 2012) and is useful in phylogenetic, taxonomic, evolutionary and conservation applications (e.g., Cristiano et al, 2013;Barros et al, 2015;Santos et al, 2016;Aguiar et al, 2017). Cytogenetic studies in fungus-growing ants are scarce, especially for the so called "lower attine" group (reviewed in Barros et al, 2011).…”

“…In ants from the Neotropical region, the reports of 18S or 45S physical location are available for 25 species (Mariano et al, 2008;Aguiar et al, 2011;Santos et al, 2010Santos et al, , 2016Barros et al, 2012Barros et al, , 2015Barros et al, , 2016Teixeira et al, 2017;Aguiar et al, 2017). The majority of these species present the GC-rich regions coinciding with the nucleolus organizer regions (NORs).…”