Evolutionary stability in a 400-million-year-old heritable facultative mutualism

Many eukaryotes interact with heritable endobacteria to satisfy diverse metabolic needs. Some of these interactions are facultative symbioses, in which one partner is not essential to the other. Facultative symbioses are expected to be transitional stages along an evolutionary trajectory toward obligate relationships. We tested this evolutionary theory prediction in Ca. Glomeribacter gigasporarum, nonessential endosymbionts of arbuscular mycorrhizal fungi (Glomeromycota). We found that heritable facultative mutualisms can be both ancient and evolutionarily stable. We detected significant patterns of codivergence between the partners that we would only expect in obligate associations. Using codiverging partner pairs and the fungal fossil record, we established that the Glomeromycota-Glomeribacter symbiosis is at least 400 million years old. Despite clear signs of codivergence, we determined that the Glomeribacter endobacteria engage in recombination and host switching, which display patterns indicating that the association is not evolving toward reciprocal dependence. We postulate that low frequency of recombination in heritable endosymbionts together with host switching stabilize facultative mutualisms over extended evolutionary times.     

Gut microbial diversity across a contact zone for California voles: Implications for lineage divergence of hosts and mitonuclear mismatch in the assembly of the mammalian gut microbiome

Gut microbial diversity is thought to reflect the co‐evolution of microbes and their hosts as well as current host‐specific attributes such as genetic background and environmental setting. To explore interactions among these parameters, we characterized variation in gut microbiome composition of California voles (Microtus californicus) across a contact zone between two recently diverged lineages of this species. Because this contact zone contains individuals with mismatched mitochondrial‐nuclear genomes (cybrids), it provides an important opportunity to explore how different components of the genotype contribute to gut microbial diversity. Analyses of bacterial 16S rRNA sequences and joint species distribution modelling revealed that host genotypes and genetic differentiation among host populations together explained more than 50% of microbial community variation across our sampling transect. The ranked importance (most to least) of factors contributing to gut microbial diversity in our study populations were: genome‐wide population differentiation, local environmental conditions, and host genotypes. However, differences in microbial communities among vole populations (β‐diversity) did not follow patterns of lineage divergence (i.e., phylosymbiosis). Instead, among‐population variation was best explained by the spatial distribution of hosts, as expected if the environment is a primary source of gut microbial diversity (i.e., dispersal limitation hypothesis). Across the contact zone, several bacterial taxa differed in relative abundance between the two parental lineages as well as among individuals with mismatched mitochondrial and nuclear genomes. Thus, genetic divergence among host lineages and mitonuclear genomic mismatches may also contribute to microbial diversity by altering interactions between host genomes and gut microbiota (i.e., hologenome speciation hypothesis).     

Communities, populations and individuals of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi in the phylum Glomeromycota are found globally in most vegetation types, where they form a mutualistic symbiosis with plant roots. Despite their wide distribution, only relatively few species are described. The taxonomy is based on morphological characters of the asexual resting spores, but molecular approaches to community ecology have revealed a considerable unknown diversity from colonized roots. Although the lack of genetic recombination is not unique in the fungal kingdom, arbuscular mycorrhizal fungi are probably ancient asexuals. The long asexual evolution of the fungi has resulted in considerable genetic diversity within morphologically recognizable species, and challenges our concepts of individuals and populations. This review critically examines the concepts of species, communities, populations and individuals of arbuscular mycorrhizal fungi.     

Radiation of the polymorphic Little Devil poison frog (Oophaga sylvatica) in Ecuador

Some South American poison frogs (Dendrobatidae) are chemically defended and use bright aposematic colors to warn potential predators of their unpalatability. Aposematic signals are often frequency‐dependent where individuals deviating from a local model are at a higher risk of predation. However, extreme diversity in the aposematic signal has been documented in poison frogs, especially in Oophaga. Here, we explore the phylogeographic pattern among color‐divergent populations of the Little Devil poison frog Oophaga sylvatica by analyzing population structure and genetic differentiation to evaluate which processes could account for color diversity within and among populations. With a combination of PCR amplicons (three mitochondrial and three nuclear markers) and genome‐wide markers from a double‐digested RAD (ddRAD) approach, we characterized the phylogenetic and genetic structure of 199 individuals from 13 populations (12 monomorphic and 1 polymorphic) across the O. sylvatica distribution. Individuals segregated into two main lineages by their northern or southern latitudinal distribution. A high level of genetic and phenotypic polymorphism within the northern lineage suggests ongoing gene flow. In contrast, low levels of genetic differentiation were detected among the southern lineage populations and support recent range expansions from populations in the northern lineage. We propose that a combination of climatic gradients and structured landscapes might be promoting gene flow and phylogenetic diversification. Alternatively, we cannot rule out that the observed phenotypic and genomic variations are the result of genetic drift on near or neutral alleles in a small number of genes.     

Genetic processes in arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi (Glomeromycota) colonize roots of the majority of land plants and facilitate their mineral nutrient uptake. Consequently, AM fungi play an important role in terrestrial ecosystems and are becoming a component of sustainable land management practices. The absence of sexual reproductive structures in modern Glomeromycota combined with their long evolutionary history suggest that these fungi may represent an ancient asexual lineage of great potential interest to evolutionary biology. However, many aspects of basic AM fungal biology, including genome structure, within-individual genetic variation, and reproductive mode are poorly understood. These knowledge gaps hinder research on the mechanisms of AM fungal interactions with individual plants and plant communities, and utilization of AM fungi in agricultural practices. I present here the current state of research on the reproduction in AM fungi and indicate what new findings can be expected in the future.     

Evolution of sociality in spiders leads to depleted genomic diversity at both population and species levels

Across several animal taxa, the evolution of sociality involves a suite of characteristics, a “social syndrome,” that includes cooperative breeding, reproductive skew, primary female‐biased sex ratio, and the transition from outcrossing to inbreeding mating system, factors that are expected to reduce effective population size (Ne). This social syndrome may be favoured by short‐term benefits but come with long‐term costs, because the reduction in Ne amplifies loss of genetic diversity by genetic drift, ultimately restricting the potential of populations to respond to environmental change. To investigate the consequences of this social life form on genetic diversity, we used a comparative RAD‐sequencing approach to estimate genomewide diversity in spider species that differ in level of sociality, reproductive skew and mating system. We analysed multiple populations of three independent sister‐species pairs of social inbreeding and subsocial outcrossing Stegodyphus spiders, and a subsocial outgroup. Heterozygosity and within‐population diversity were sixfold to 10‐fold lower in social compared to subsocial species, and demographic modelling revealed a tenfold reduction in Ne of social populations. Species‐wide genetic diversity depends on population divergence and the viability of genetic lineages. Population genomic patterns were consistent with high lineage turnover, which homogenizes the genetic structure that builds up between inbreeding populations, ultimately depleting genetic diversity at the species level. Indeed, species‐wide genetic diversity of social species was 5–8 times lower than that of subsocial species. The repeated evolution of species with this social syndrome is associated with severe loss of genomewide diversity, likely to limit their evolutionary potential.     

Evidence for the evolution of native plant response to mycorrhizal fungi in post‐agricultural grasslands

Plant–microbe interactions play an important role in structuring plant communities. Arbuscular mycorrhizal fungi (AMF) are particularly important. Nonetheless, increasing anthropogenic disturbance will lead to novel plant–AMF interactions, altering longstanding co‐evolutionary trajectories between plants and their associated AMF. Although emerging work shows that plant–AMF response can evolve over relatively short time scales due to anthropogenic change, little work has evaluated how plant AMF response specificity may evolve due to novel plant–mycorrhizal interactions. Here, we examine changes in plant–AMF interactions in novel grassland systems by comparing the mycorrhizal response of plant populations from unplowed native prairies with populations from post‐agricultural grasslands to inoculation with both native prairie AMF and non‐native novel AMF. Across four plant species, we find support for evolution of differential responses to mycorrhizal inocula types, that is, mycorrhizal response specificity, consistent with expectations of local adaptation, with plants from native populations responding most to native AMF and plants from post‐agricultural populations responding most to non‐native AMF. We also find evidence of evolution of mycorrhizal response in two of the four plant species, as overall responsiveness to AMF changed from native to post‐agricultural populations. Finally, across all four plant species, roots from native prairie populations had lower levels of mycorrhizal colonization than those of post‐agricultural populations. Our results report on one of the first multispecies assessment of local adaptation to AMF. The consistency of the responses in our experiment among four species provides evidence that anthropogenic disturbance may have unintended impacts on native plant species'' association with AMF, causing evolutionary change in the benefit native plant species gain from native symbioses.     

Cyto‐nuclear discordance suggests complex evolutionary history in the cave‐dwelling salamander,Eurycea lucifuga

Our understanding of the evolutionary history and ecology of cave‐associated species has been driven historically by studies of morphologically adapted cave‐restricted species. Our understanding of the evolutionary history and ecology of nonrestricted cave species, troglophiles, is limited to a few studies, which present differing accounts of troglophiles’ relationship with the cave habitat, and its impact on population dynamics. Here, we used phylogenetics, demographic statistics, and population genetic methods to study lineage divergence, dates of divergence, and population structure in the Cave Salamander, Eurycea lucifuga, across its range. In order to perform these analyses, we sampled 233 individuals from 49 populations, using sequence data from three gene loci as well as genotyping data from 19 newly designed microsatellite markers. We find, as in many other species studied in a phylogeographic context, discordance between patterns inferred from mitochondrial relationships and those inferred by nuclear markers indicating a complicated evolutionary history in this species. Our results suggest Pleistocene‐based divergence among three main lineages within E. lucifuga corresponding to the western, central, and eastern regions of the range, similar to patterns seen in species separated in multiple refugia during climatic shifts. The conflict between mitochondrial and nuclear patterns is consistent with what we would expect from secondary contact between regional populations following expansion from multiple refugia.     

Genetic variability in a population of arbuscular mycorrhizal fungi causes variation in plant growth

Different species of arbuscular mycorrhizal fungi (AMF) alter plant growth and affect plant coexistence and diversity. Effects of within-AMF species or within-population variation on plant growth have received less attention. High genetic variation exists within AMF populations. However, it is unknown whether genetic variation contributes to differences in plant growth. In our study, a population of AMF was cultivated under identical conditions for several generations prior to the experiments thus avoiding environmental maternal effects. We show that genetically different Glomus intraradices isolates from one AMF population significantly alter plant growth in an axenic system and in greenhouse experiments. Isolates increased or reduced plant growth meaning that plants potentially receive benefits or are subject to costs by forming associations with different individuals in the AMF population. This shows that genetic variability in AMF populations could affect host-plant fitness and should be considered in future research to understand these important soil organisms.     

Niche shifts and range expansions along cordilleras drove diversification in a high‐elevation endemic plant genus in the tropical Andes

The tropical Andes represent one of the world's biodiversity hot spots, but the evolutionary drivers generating their striking species diversity still remain poorly understood. In the treeless high‐elevation Andean environments, Pleistocene glacial oscillations and niche differentiation are frequently hypothesized diversification mechanisms; however, sufficiently densely sampled population genetic data supporting this are still lacking. Here, we reconstruct the evolutionary history of Loricaria (Asteraceae), a plant genus endemic to the Andean treeless alpine zone, based on comprehensive population‐level sampling of 289 individuals from 67 populations across the entire distribution ranges of its northern Andean species. Partly incongruent AFLP and plastid DNA markers reveal that the distinct genetic structure was shaped by a complex interplay of biogeography (spread along and across the cordilleras), history (Pleistocene glacial oscillations) and local ecological conditions. While plastid variation documents an early split or colonization of the northern Andes by at least two lineages, one of which further diversified, a major split in the AFLP data correlate with altitudinal ecological differentiation. This suggests that niche shifts may be important drivers of Andean diversification not only in forest–alpine transitions, but also within the treeless alpine zone itself. The patterns of genetic differentiation at the intraspecific level reject the hypothesized separation in spatially isolated cordilleras and instead suggest extensive gene flow among populations from distinct mountain chains. Our study highlights that leveraging highly variable markers against extensive population‐level sampling is a promising approach to address mechanisms of rapid species diversifications.     

Effects of gene flow on phenotype matching between two varieties of Joshua tree (Yucca brevifolia; Agavaceae) and their pollinators

In animal‐pollinated plants, local adaptation to pollinator behaviour or morphology can restrict gene flow among plant populations; but gene flow may also prevent divergent adaptation. Here, we examine possible effects of gene flow on plant–pollinator trait matching in two varieties of Joshua tree (Agavaceae: Yucca brevifolia). The two varieties differ in strikingly in floral morphology, which matches differences in the morphology of their pollinators. However, this codivergence is not present at a smaller scale: within the two varieties of Joshua tree, variation in floral morphology between demes is not correlated with differences in moth morphology. We use population genetic data for Joshua tree and its pollinators to test the hypotheses that gene flow between Joshua tree populations is structured by pollinator specificity, and that gene flow within the divergent plant–pollinator associations ‘swamps’ fine‐scale coadaptation. Our data show that Joshua tree populations are structured by pollinator association, but the two tree varieties are only weakly isolated – meaning that their phenotypic differences are maintained in the face of significant gene flow. Coalescent analysis of gene flow between the two Joshua tree types suggests that it may be shaped by asymmetric pollinator specificity, which has been observed in a narrow zone of sympatry. Finally, we find evidence suggesting that gene flow among Joshua tree sites may shape floral morphology within one plant–pollinator association, but not the other.     

Do island plant populations really have lower genetic variation than mainland populations? Effects of selection and distribution range on genetic diversity estimates

Ecological and evolutionary studies largely assume that island populations display low levels of neutral genetic variation. However, this notion has only been formally tested in a few cases involving plant taxa, and the confounding effect of selection on genetic diversity (GD) estimates based on putatively neutral markers has typically been overlooked. Here, we generated nuclear microsatellite and plastid DNA sequence data in Periploca laevigata, a plant taxon with an island–mainland distribution area, to (i) investigate whether selection affects GD estimates of populations across contrasting habitats; and (ii) test the long‐standing idea that island populations have lower GD than their mainland counterparts. Plastid data showed that colonization of the Canary Islands promoted strong lineage divergence within P. laevigata, which was accompanied by selective sweeps at several nuclear microsatellite loci. Inclusion of loci affected by strong divergent selection produced a significant downward bias in the GD estimates of the mainland lineage, but such underestimates were substantial (>14%) only when more than one loci under selection were included in the computations. When loci affected by selection were removed, we did not find evidence that insular Periploca populations have less GD than their mainland counterparts. The analysis of data obtained from a comprehensive literature survey reinforced this result, as overall comparisons of GD estimates between island and mainland populations were not significant across plant taxa (N = 66), with the only exception of island endemics with narrow distributions. This study suggests that identification and removal of markers potentially affected by selection should be routinely implemented in estimates of GD, particularly if different lineages are compared. Furthermore, it provides compelling evidence that the expectation of low GD cannot be generalized to island plant populations.     

RIBOSOMAL RNA GENE DIVERSITY,EFFECTIVE POPULATION SIZE,AND EVOLUTIONARY LONGEVITY IN ASEXUAL GLOMEROMYCOTA

Arbuscular mycorrhizal fungi (phylum Glomeromycota) are among the oldest and most successful symbionts of land plants. With no evidence of sexual reproduction, their evolutionary success is inconsistent with the prediction that asexual taxa are vulnerable to extinction due to accumulation of deleterious mutations. To explore why Glomeromycota defy this prediction, we studied ribosomal RNA (rRNA) gene evolution in the Claroideoglomus lineage and estimated effective population size, N_e, in C. etunicatum. We found that rRNA genes of these fungi exhibit unusual and complex patterns of molecular evolution. In C. etunicatum, these patterns can be collectively explained by an unexpectedly large N_e combined with imperfect genome‐wide and population‐level rRNA gene repeat homogenization. The mutations accumulated in rRNA gene sequences indicate that natural selection is effective at purging deleterious mutations in the Claroideoglomus lineage, which is also consistent with the large N_e of C. etunicatum. We propose that in the near absence of recombination, asexual reproduction involving massively multinucleate spores typical for Glomeromycota is responsible for the improved efficacy of selection relative to drift. We postulate that large effective population sizes contribute to the evolutionary longevity of Glomeromycota.     

Ecological and evolutionary drivers of haemoplasma infection and bacterial genotype sharing in a Neotropical bat community

Most emerging pathogens can infect multiple species, underlining the importance of understanding the ecological and evolutionary factors that allow some hosts to harbour greater infection prevalence and share pathogens with other species. However, our understanding of pathogen jumps is based primarily around viruses, despite bacteria accounting for the greatest proportion of zoonoses. Because bacterial pathogens in bats (order Chiroptera) can have conservation and human health consequences, studies that examine the ecological and evolutionary drivers of bacterial prevalence and barriers to pathogen sharing are crucially needed. Here were studied haemotropic Mycoplasma spp. (i.e., haemoplasmas) across a species‐rich bat community in Belize over two years. Across 469 bats spanning 33 species, half of individuals and two‐thirds of species were haemoplasma positive. Infection prevalence was higher for males and for species with larger body mass and colony sizes. Haemoplasmas displayed high genetic diversity (21 novel genotypes) and strong host specificity. Evolutionary patterns supported codivergence of bats and bacterial genotypes alongside phylogenetically constrained host shifts. Bat species centrality to the network of shared haemoplasma genotypes was phylogenetically clustered and unrelated to prevalence, further suggesting rare—but detectable—bacterial sharing between species. Our study highlights the importance of using fine phylogenetic scales when assessing host specificity and suggests phylogenetic similarity may play a key role in host shifts not only for viruses but also for bacteria. Such work more broadly contributes to increasing efforts to understand cross‐species transmission and the epidemiological consequences of bacterial pathogens.     

Genetic diversity and host plant preferences revealed by simple sequence repeat and mitochondrial markers in a population of the arbuscular mycorrhizal fungus Glomus intraradices

Arbuscular mycorrhizal fungi (AMF) are important symbionts of plants that improve plant nutrient acquisition and promote plant diversity. Although within-species genetic differences among AMF have been shown to differentially affect plant growth, very little is actually known about the degree of genetic diversity in AMF populations. This is largely because of difficulties in isolation and cultivation of the fungi in a clean system allowing reliable genotyping to be performed. A population of the arbuscular mycorrhizal fungus Glomus intraradices growing in an in vitro cultivation system was studied using newly developed simple sequence repeat (SSR), nuclear gene intron and mitochondrial ribosomal gene intron markers. The markers revealed a strong differentiation at the nuclear and mitochondrial level among isolates. Genotypes were nonrandomly distributed among four plots showing genetic subdivisions in the field. Meanwhile, identical genotypes were found in geographically distant locations. AMF genotypes showed significant preferences to different host plant species (Glycine max, Helianthus annuus and Allium porrum) used before the fungal in vitro culture establishment. Host plants in a field could provide a heterogeneous environment favouring certain genotypes. Such preferences may partly explain within-population patterns of genetic diversity.     

Relatedness among arbuscular mycorrhizal fungi drives plant growth and intraspecific fungal coexistence

Arbuscular mycorrhizal fungi (AMF) form symbioses with most plant species. They are ecologically important determinants of plant growth and diversity. Considerable genetic variation occurs in AMF populations. Thus, plants are exposed to AMF of varying relatedness to each other. Very little is known about either the effects of coexisting AMF on plant growth or which factors influence intraspecific AMF coexistence within roots. No studies have addressed whether the genetics of coexisting AMF, and more specifically their relatedness, influences plant growth and AMF coexistence. Relatedness is expected to influence coexistence between individuals, and it has been suggested that decreasing ability of symbionts to coexist can have negative effects on the growth of the host. We tested the effect of a gradient of AMF genetic relatedness on the growth of two plant species. Increasing relatedness between AMFs lead to markedly greater plant growth (27% biomass increase with closely related compared to distantly related AMF). In one plant species, closely related AMF coexisted in fairly equal proportions but decreasing relatedness lead to a very strong disequilibrium between AMF in roots, indicating much stronger competition. Given the strength of the effects with such a shallow relatedness gradient and the fact that in the field plants are exposed to a steeper gradient, we consider that AMF relatedness can have a strong role in plant growth and the ability of AMF to coexist. We conclude that AMF relatedness is a driver of plant growth and that relatedness is also a strong driver of intraspecific coexistence of these ecologically important symbionts.     

Spatial soil heterogeneity has a greater effect on symbiotic arbuscular mycorrhizal fungal communities and plant growth than genetic modification with Bacillus thuringiensis toxin genes

Maize, genetically modified with the insect toxin genes of Bacillus thuringiensis (Bt), is widely cultivated, yet its impacts on soil organisms are poorly understood. Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with plant roots and may be uniquely sensitive to genetic changes within a plant host. In this field study, the effects of nine different lines of Bt maize and their corresponding non‐Bt parental isolines were evaluated on AMF colonization and community diversity in plant roots. Plants were harvested 60 days after sowing, and data were collected on plant growth and per cent AMF colonization of roots. AMF community composition in roots was assessed using 454 pyrosequencing of the 28S rRNA genes, and spatial variation in mycorrhizal communities within replicated experimental field plots was examined. Growth responses, per cent AMF colonization of roots and AMF community diversity in roots did not differ between Bt and non‐Bt maize, but root and shoot biomass and per cent colonization by arbuscules varied by maize cultivar. Plot identity had the most significant effect on plant growth, AMF colonization and AMF community composition in roots, indicating spatial heterogeneity in the field. Mycorrhizal fungal communities in maize roots were autocorrelated within approximately 1 m, but at greater distances, AMF community composition of roots differed between plants. Our findings indicate that spatial variation and heterogeneity in the field has a greater effect on the structure of AMF communities than host plant cultivar or modification by Bt toxin genes.     

Detection of a novel intracellular microbiome hosted in arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) are important members of the plant microbiome. They are obligate biotrophs that colonize the roots of most land plants and enhance host nutrient acquisition. Many AMF themselves harbor endobacteria in their hyphae and spores. Two types of endobacteria are known in Glomeromycota: rod-shaped Gram-negative Candidatus Glomeribacter gigasporarum, CaGg, limited in distribution to members of the Gigasporaceae family, and coccoid Mollicutes-related endobacteria, Mre, widely distributed across different lineages of AMF. The goal of the present study is to investigate the patterns of distribution and coexistence of the two endosymbionts, CaGg and Mre, in spore samples of several strains of Gigaspora margarita. Based on previous observations, we hypothesized that some AMF could host populations of both endobacteria. To test this hypothesis, we performed an extensive investigation of both endosymbionts in G. margarita spores sampled from Cameroonian soils as well as in the Japanese G. margarita MAFF520054 isolate using different approaches (molecular phylotyping, electron microscopy, fluorescence in situ hybridization and quantitative real-time PCR). We found that a single AMF host can harbour both types of endobacteria, with Mre population being more abundant, variable and prone to recombination than the CaGg one. Both endosymbionts seem to retain their genetic and lifestyle peculiarities regardless of whether they colonize the host alone or together. These findings show for the first time that fungi support an intracellular bacterial microbiome, in which distinct types of endobacteria coexist in a single cell.     

Mycoheterotrophic interactions are not limited to a narrow phylogenetic range of arbuscular mycorrhizal fungi

The majority of achlorophyllous mycoheterotrophic plant species associate with arbuscular mycorrhizal fungi (AMF). Previous studies have shown that some species are highly specialized towards narrow lineages of AMF and have suggested that only particular lineages of these fungi are targeted by mycoheterotrophic plants. To test this hypothesis, we analyzed all available partial SSU sequences of AMF associated with mycoheterotrophic plants including data from 13 additional specimens from French Guiana, Gabon and Australia. Sequences were assigned to 'virtual taxa' (VT) according to the MaarjAM database. We found that 20% of all known Glomeromycota VT are involved in mycoheterotrophic interactions and the majority of associations involve Glomeraceae (Glomus Group A) fungi. While some mycoheterotrophic plant species have been found growing with only a single VT, many species are able to associate with a wide range of AMF. We calculated significant phylogenetic clustering of Glomeromycota VT involved in mycoheterotrophic interactions, suggesting that associations between mycoheterotrophic plants and AMF are influenced by the phylogenetic relationships of the fungi. Our results demonstrate that many lineages of AMF are prone to exploitation by mycoheterotrophic plants. However, mycoheterotrophs from different plant lineages and different geographical regions tend to be dependent on lineages of AMF that are phylogenetically related.     

Genetic diversity and structuring across the range of a widely distributed ladybird: focus on rear‐edge populations phenotypically divergent

Population genetics and phenotypic structures are often predicted to vary along the geographic range of a species. This phenomenon would be accentuated for species with large range areas, with discontinuities and marginal populations. We herein compare the genetic patterns of central populations of Coccinella septempunctata L. with those of two phenotypically differentiated populations considered as rear‐edge populations and subspecies based on phenotype (Algeria and Japan). According to the central‐marginal model and expected characteristics of rear‐edge populations, we hypothesize that these rear‐edge populations have (1) a reduced genetic diversity, resulting from their relative isolation over long periods of time, (2) a higher population genetic differentiation, explained by low contemporary gene flow levels, and (3) a relationship between genetic diversity characteristics and phenotypes, due to historical isolation and/or local adaptation. Based on genotyping of 28 populations for 18 microsatellite markers, several levels of regional genetic diversity and differentiation are observed between and within populations, according to their localization: low within‐population genetic diversity and higher genetic differentiation of rear‐edge populations. The genetic structuring clearly dissociates the Algerian and Eastern Asia populations from the others. Geographical patterns of genetic diversity and differentiation support the hypothesis of the central‐marginal model. The pattern observed is in agreement with the phenotypic structure across species range. A clear genetic break between populations of Algeria, the Eastern Asia, and the remaining populations is a dominant feature of the data. Differential local adaptations, absence of gene flow between marginal and central populations, and/or incapacity to mate after colonization, have contributed to their distinct genotypic and phenotypic characteristics.