Distyly is a floral polymorphism characterized by the presence of two discrete morphs with reciprocal positioning of anthers and stigmas in flowers on different plants in the same population. For a distylous system to function effectively, the presence of suitable pollinators that transfer pollen from the two morphs (a short-styled S-morph and a long-styled L-morph) on separate locations of their body is required. In this study, we surveyed pollinator communities visiting flowers of the distylous Primula veris in two different natural habitats (grassland and forest). Previous research has shown differences in the positioning of the anthers and stigmas between flowers of forest and grassland populations, possibly impacting on patterns of pollen transfer and seed set. To test this hypothesis, we measured anther–stigma separation in the two habitats, assessed pollen uptake on the head and proboscis of each of the pollinator species observed, and compared stigmatic pollen deposition and subsequent seed set between short-styled and long-styled flowers of P. veris. More specifically, we tested the hypothesis that the ratio of pollen morph uptake by pollinators is related to the length of their proboscis and to differences in floral morphology and that this in turn is related to the efficiency with which legitimate pollen is deposited on S- and L-morph stigmas. The forest and grassland P. veris populations contained distinct pollinator communities. Pollen from L-morph flowers was more abundantly deposited on the proboscis than on the head of the pollinator, whereas the opposite was observed for pollen of short-styled flowers. Tongue length seemed to be a determining characteristic for the predisposition of a pollinator for pollen uptake of a certain pollen morph on the proboscis or head. Proboscis length was positively correlated with proportional uptake of pollen of long-styled flowers, but negatively correlated with the uptake of pollen of short-styled flowers on the head. Long-styled stigmas captured more pollen grains in total, but short-styled stigmas contained proportionally more legitimate pollen. Pollen proficiencies were higher in the grassland habitat, but seed set did not significantly differ between habitats. Overall, these results suggest that that long- and short-tongued insects complement each other in the legitimate pollination of a distylous plant species and that differences in floral morphology do not impact on reproductive success.

The Mediterranean fruit fly,Ceratitis capitata(Weidemann), is considered one of the most significant tephritid pest species worldwide and is an exotic species in most of its range. Here, we investigated polymorphism at 14 microsatellite loci for a total of 126 populations ofC. capitatafrom six geographical regions, applying network theory and cluster analyses. Analyses revealed nine distinct modules for the Central American region and one in each of the remaining five regions. Bayesian cluster analysis revealed that the highest level of genetic partitioning corresponds with the presence of 3 well-defined genetic clusters. Our results confirm the African origin for Mediterranean populations based on genetic diversity and suggest a direct invasion ofC. capitatafrom the Mediterranean to Central-America. South American populations show links with Central-America, but also exhibit indications of direct admixture with the European cluster. Additionally, the network analysis proposes a South American origin for the Madeiran and Hawaiian flies. Cluster analysis corroborates the hypothesis of a Mediterranean origin for Australian samples. Our work provides novel insights regarding the migration history of Medfly worldwide.

An increasing number of invasive fruit fly pests are colonizing new grounds. With this study, we aimed to uncover the invasion pathways of the oriental fruit fly, Bactrocera dorsalis into the islands of the Indian Ocean. By using genome‐wide SNP data and a multipronged approach consisting of PCA, ancestry analysis, phylogenetic inference, and kinship networks, we were able to resolve two independent invasion pathways. A western invasion pathway involved the stepping‐stone migration of B. dorsalis from the east African coast into the Comoros, along Mayotte and into Madagascar with a decreasing genetic diversity. The Mascarene islands (Reunion and Mauritius), on the contrary, were colonized directly from Asia and formed a distinct cluster. The low nucleotide diversity suggests that only a few genotypes invaded the Mascarenes. The presence of many long runs of homozygosity (ROH) in the introduced populations is indicative of population bottlenecks, with evidence of a more severe bottleneck for populations along the western migration pathway than on the Mascarene islands. More strict phytosanitary regulations are recommended in order to prevent the further spread of B. dorsalis.

Adaptive radiation occurs when species diversify rapidly to occupy an array of ecological niches. As opportunities for parasite infection and transmission may greatly vary among these niches, adaptive radiation is expected to be associated with a turnover of the parasite community. As major agents of natural and sexual selection, parasites may play a central role in host diversification. The study of parasite turnover may thus be of general relevance and could significantly improve our understanding of adaptive radiation. In this study, we examined the parasite faunas of eleven species belonging to the tribe Tropheini, one of several adaptive radiations of cichlid fishes in Lake Tanganyika. The most parsimonious ancestral foraging strategy among the Tropheini is relatively unselective substrate browsing of aufwuchs. Several lineages evolved more specialized foraging strategies, such as selective combing of microscopic diatoms or picking of macro‐invertebrates. We found that representatives of these specialized lineages bear reduced infection with food‐web‐transmitted acanthocephalan helminths, but not with parasites with a direct life cycle. Possibly, the evolution of selective foraging strategies entailed reduced ingestion of intermediate invertebrate hosts of acanthocephalans. We conclude that some species belonging to the Tropheini virtually escape acanthocephalan infection as a by‐product of trophic specialization.

The Mediterranean fruit fly (Ceratitis capitata) is a globally invasive species and an economically significant pest of fruit crops. Understanding the evolutionary history and local climatic adaptation of this species is crucial for developing effective pest management strategies. We conducted a comprehensive investigation using whole genome sequencing to explore (i) the invasion history of C. capitata with an emphasis on historical admixture and (ii) local climatic adaptation across African, European, Central, and South American populations of C. capitata. Our results suggest a stepwise colonization of C. capitata in Europe and Latin America in which Mediterranean and Central American populations share an ancestral lineage. Conversely, South American invasion history is more complex, and our results partly suggest an old secondary invasion into South America from Europe or a colonization of South America directly from Africa, followed by admixture with an European lineage. Throughout its invasive range, C. capitata is challenged with diverse climatic regimes. A genome wide association study identified a relationship between allele frequency changes and specific bioclimatic variables. Notably, we observed a significant allele frequency shift related to adaptation to cold stress (BIO6), highlighting the species’ ability to rapidly adapt to seasonal variations in colder climates.

Genetic divergence by environment is a process whereby selection causes the formation of gene flow barriers between populations adapting to contrasting environments and is often considered to be the onset of speciation. Nevertheless, the extent to which genetic differentiation by environment on small spatial scales can be detected by means of neutral markers is still subject to debate. Previous research on the perennial herb Primula veris has shown that plants from grassland and forest habitats showed pronounced differences in phenology and flower morphology, suggesting limited gene flow between habitats. To test this hypothesis, we sampled 33 populations of P. veris consisting of forest and grassland patches and used clustering techniques and network analyses to identify sets of populations that are more connected to each other than to other sets of populations and estimated the timing of divergence. Our results showed that spatial genetic variation had a significantly modular structure and consisted of four well-defined modules that almost perfectly coincided with habitat features. Genetic divergence was estimated to have occurred about 114 generations ago, coinciding with historic major changes in the landscape. Overall, these results illustrate how populations adapting to different environments become structured genetically within landscapes on small spatial scales.