Geographic distribution of sex chromosome polymorphism in Anastrepha fraterculus sp. 1 from Argentina

Fine Scale Microevolutionary and Demographic Processes Shaping a Wild Metapopulation Dynamics of the South American Fruit Fly Anastrepha fraterculus

Anastrepha fraterculus (Wiedmann) is an important American pest species. Knowledge of its population dynamics is of particular interest for ecology, evolutionary biology, and management programs. In the present study, phenotypic, genotypic, and spatial data were combined, within the frame of landscape genetics, to uncover the spatial population genetic structure (SGS) and demographic processes of an Argentinian local population from the Yungas ecoregion. Eight simple sequence repeats (SSR) loci and six morphometric traits were analysed considering the hierarchical levels: tree/fruit/individual. Genetic variability estimates were high (H_E = 0.72, R_A = 4.39). Multivariate analyses of phenotypic data showed that in average 52.81% of variance is explained by the tree level, followed by between individuals 28.37%. Spatial analysis of morphological traits revealed a negative autocorrelation in all cases. SGS analysis and isolation by distance based on SSR showed no significant autocorrelation for molecular coancestry. The comparison between phenotypic (P_ST) and molecular (F_ST) differentiation identified positive selection in different fruits for all traits. Bayesian analysis revealed a cryptic structure within the population, with three clusters spatially separated. The results of this study showed a metapopulation dynamics. The genetic background of the components of this metapopulation is expected to change through time due to seasonality, repopulation activities, and high gene flow, with an estimated dispersal ability of at least 10 km. Effective population size (Ne) of the metapopulation was estimated in around 800 flies, and within subpopulations (clusters) Ne was associated with the levels of genetic drift experienced by the founding lineages.

Genetical, Morphological, Behavioral, and Ecological Traits Support the Existence of Three Brazilian Species of the Anastrepha fraterculus Complex of Cryptic Species

Within the Neotropical genus Anastrepha, the nominal species Anastrepha fraterculus is widely distributed from Mexico through northern Argentina. Currently it is believed to comprises a complex of at least eight cryptic species—known as the Anastrepha fraterculus complex (AF complex)—three of which occur in Brazil: A. sp.1 aff. fraterculus, A. sp.2 aff. fraterculus, and A. sp.3 aff. fraterculus. In this study, we present the results of a broad integrated analysis of multiple biological attributes in samples of the three species collected in sympatric areas. Analyses of the mitotic chromosomes confirm that all of them differ in sex chromosomes, and that the relative frequency of the distinct karyotypes is associated with variation in altitude. In these sympatric areas, a single female hybrid karyotype was detected within a significant sample of individuals. Population samples were analyzed for the ribosomal transcribed spacer ITS1, confirming that the three species have specific sequence types. Observations of reproductive behavior under laboratory conditions revealed that A. sp.1 and A. sp.2 mate early in the morning, while A. sp.3 mates in the middle of the day. A bimodal distribution of mating time was observed in the laboratory for hybrids, obtained between A. sp.1 and A. sp.3. In a mating choice experiment, most of the mating pairs were homospecific. In addition, through a list of the most frequent hosts associated with geographical occurrence, a bioclimatic model of their potential distribution was generated. The set of data allowed for the construction of explanatory hypothesis about the observed geographical pattern and the differential use of host fruits. Morphometric analyses of wings clearly demonstrated differences among the three species, for both males and females. Based on a wing image of the A. fraterculus (Wiedemann, 1830) type specimen, the morphometric analysis indicated that the type specimen would correspond to a male of A. sp.2 aff. fraterculus. The information provided by this report is not only useful for taxonomic purposes, but also reveals aspects to be considered in any reconstruction of an evolutionary scenario of the Anastrepha fraterculus complex.

Ecological phylogeography and coalescent models suggest a linear population expansion of Anastrepha fraterculus (Diptera: Tephritidae) in southern South America

This work is a first approach to an integrated view of the genetics, ecology and dispersion patterns of Anastrepha fraterculus in southern South America. We studied the association of genetic variation with geographical patterns and environmental variables to provide insight into the crucial factors that drive the structure and dynamics of fly populations. Data from a 417 bp mitochondrial COII gene fragment from seven Argentinian populations and one South Brazilian population (from five ecoregions grouped in three biomes) were used to identify population clusters using a model-based Bayesian phylogeographical and ecological clustering approach. The sequences were also analysed under a coalescent model to evaluate historical demographic changes. We identified 19 different haplotypes and two clusters differing in all the environmental covariables. The assumption of neutral evolution and constant population size was rejected, and the population growth parameters suggested a linear population expansion starting 2500 years before present. The most likely ancestral location is Posadas, from where A. fraterculus would have expanded southwards and westwards in Argentina. This result is consistent with Holocene changes and anthropic factors related to the expansion of the Tupí–Guaraní culture, 3000–1500 years before present.