Recent speciation and secondary contact in endemic ants

Abstract

Gene flow is the main force opposing divergent selection, and its effects are greater in populations in close proximity. Thus, complete reproductive isolation between parapatric populations is not expected, particularly in the absence of ecological adaptation and sharp environmental differences. Here, we explore the biogeographical patterns of an endemic ant species, Cataglyphis floricola, for which two colour morphs (black and bicolour) coexist in parapatry throughout continuous sandy habitat in southern Spain. Discriminant analyses of six biometric measurements of male genitalia and 27 cuticular hydrocarbons reveal high differentiation between morphs. Furthermore, the low number of shared alleles derived from nuclear markers (microsatellites) between the morphs at their contact zone suggests the absence of recent gene flow. Mitochondrial DNA (COI) phylogenetic analysis and median‐joining networks show that the black morph is basal to the bicolour morph, with unique haplotypes recovered for each morph. Mismatch distribution analysis and Bayesian skyline plots suggest that they are undergoing different demographic changes, with the bicolour and black morphs at demographic equilibrium and expansion, respectively. Thus, our results show complete reproductive isolation between the two colour morphs as evidenced from genetic, chemical and morphological data. We suggest that these divergence events could be explained by historical vicariance during the Pleistocene, in which reproductive traits experienced strong divergent selection between the morphs initiating or culminating speciation.

Macaronesian islands as promoters of diversification in amphipods: The remarkable case of the family Hyalidae (Crustacea, Amphipoda)

“…It is acknowledged that the present‐day Macaronesia is only the residual of a larger complex that now is submerged for a major part (Fernández‐Palacios et al, ). The emerged seamounts since the beginning of the Palaeogene (60 Myr) until the Pleistocene, now eroded and submerged, could have played two different roles: first as stepping stones, allowing the dispersion between the different archipelagos of the Macaronesia and the mainland (Chevolot, Hoarau, Rijnsdorp, Stam, & Olsen, ; Fernández‐Palacios et al, ; Van Den Broeck, Breugelmans, De Wolf, & Backeljau, ); second, allowing the allopatric differentiation and later a secondary contact between the diverged lineages (Jowers et al, ). Moreover, the possible role of Macaronesia region as refugium during Pleistocene glaciations was documented before for groups of marine invertebrates such as limpets and sponges (Sá‐Pinto, Branco, Sayanda, & Alexandrino, ; Xavier, Soest, Breeuwer, Martins, & Menken, ).…”

Social Life in Arid Environments: The Case Study of Cataglyphis Ants

“…For instance, in C. cursor, the distribution of genetic variability varies across habitats that differ in patchiness (43). Whatever the relative importance of geographical barriers and of restricted dispersal abilities, high genetic differentiation has been detected within populations over relatively short distances (43,78,79). This sets the scene for high levels of genetic and phenotypic divergence among populations that could be driven by either drift or natural selection and could ultimately lead to allopatric speciation.…”

“…This sets the scene for high levels of genetic and phenotypic divergence among populations that could be driven by either drift or natural selection and could ultimately lead to allopatric speciation. For instance, in southern Spain, molecular evidence suggests that recent (<1 Myr) allopatric speciation between C. floricola and C. tartessica occurred without ecological niche segregation (78). The relatively restricted range of some Cataglyphis species and their absence from most Mediterranean islands also support the idea of restricted dispersal, which, together with their thermophilous foraging activities, suggests Cataglyphis species likely retain a strong genetic signal of the impact of long-term environmental changes in the region in which they live.…”

Evolutionary reduction of female dispersal in Cataglyphis desert ants

“…This sets the stage for phenotypic and genetic differentiation among populations, leading to increased opportunities for allopatric or parapatric divergence within a given area. The recent speciation (< 1 Myr) between C. floricola and C. tartessica, two species living in parapatry across continuous sandy habitat in southern Spain, lends credence to this hypothesis (Jowers et al, 2014).…”