Adam Tofilski

Using geometric morphometrics and standard morphometry to discriminate three honeybee subspecies

Honeybee (Apis mellifera) subspecies usually are distinguished by standard morphometry methods, based mainly on multivariate analysis of distances and angles. Recently another method of statistical analysis of shape, geometric morphometrics, has been developed. The new method is based on characteristic points described by Cartesian coordinates. The two methods were used here to discriminate three honeybee subspecies (A. m. mellifera, A. m. carnica and A. m. caucasica) according to forewing venation. Forewing venation was described either by coordinates of 18 vein junctions and centroid size or by 4 distances and 11 angles. All colonies, described by mean of 10 workers, were correctly classified using both methods. In the case of individual wings discrimination, geometric morphometrics was 84.9% successful and standard morphometry was 83.8% successful. The results show that geometric morphometrics is marginally more reliable than standard morphometry for discrimination of honeybee subspecies.ZusammenfassungDie Unterarten der Honigbiene (Apis mellifera) werden üblicherweise unter Verwendung mit Standardmethoden der Morphométrie unterschieden, die überwiegend auf einer multivariaten Analyse von Abständen und Winkeln beruhen. In letzter Zeit wurde als eine weitere Methode die Geometrische Morphometrie entwickelt, die eine statistischen Analyse von durch cartesische Punktkoordinaten charakterisierter Formen verwendet. Beide Methoden wurden hier zur Unterscheidung von drei Unterarten der Honigbienen (A. m. mellifera, A. m. carnica und A. m. caucasica) anhand der Flügeladern verwendet. Die Flügeladerung wurde hierbei entweder durch die Koordinaten von 18 Aderkreuzungspunkten (Abb. 1) und deren Zentroidgröße oder durch 4 Abstände und 11 Flügeladerungswinkel beschrieben. Jede Unterart wurde durch 300 Arbeiterinnen aus 30 Völkern repräsentiert. Alle durch die Mittelwerte von jeweils 20 Arbeiterinnen beschriebene Völker wurden durch beide Methoden richtig klassifiziert (Abb. 2A, B). Einzelne Flügel wurden dagegen von der Geometrische Morphométrie in 83,8 % der Fälle erfolgreich zugeordnet (Abb. 2C), im Falle der Standardmorphomerie waren es 84,9 % (Abb. 2D). Die Ergebnisse zeigen, dass die Geometrische Morphometrie für die Unterscheidung von Unterarten nur geringfügig zuverlässiger ist als die Standardmorphometrie. Die Klassifizierungsfunktionen (Appendix I–IV) und die Mittelwerte der die Flügeladerung beschreibenden Variablen (Appendix V–VI) können zur Unterscheidung der Unterarten genutzt werden.

Nuclear and mitochondrial patterns of introgression into native dark bees (Apis mellifera mellifera) in Poland

Summary The genetic diversity of the north and western European subspecies of honey bee, Apis mellifera mellifera (the “dark bee”) is severely endangered due to hybridization with introduced bees of evolutionary branch C. Genetic variability of native honey bees in the north-eastern part of Poland, including a special isolated breeding zone in the Augustów Forest, has been investigated using mitochondrial DNA and nuclear microsatellites. These involve analysis for alien haplotypes of the tRNAleu-COII region and presence of diagnostic alien alleles respectively, in conjunction with a Bayesian model based approach. We found that approximately 10 to 30% of the nuclear gene pool and 3 to 50% of mitochondria in the studied populations were derived from non-native bees. Our data revealed the presence of hybrids in populations formerly considered to be the most pure populations of dark bees in Poland. We suggest that the Bayesian analysis of admixture based on nuclear microsatellites provides a reliable tool for measuring introgression in dark bees, which should be routinely used for evaluation during conservation programmes.

Partial reproductive isolation between European subspecies of honey bees

Northern Poland is inhabited by native Apis mellifera mellifera (AMM) and the non-native A. m. carnica (AMC) which was introduced by beekeepers. However, hybrids between the two subspecies of honey bee are relatively rare. The lower than expected proportion of hybrids is hypothesised to be related to reproductive isolation between AMM and AMC. To verify this hypothesis, we allowed the AMM and AMC queens to be naturally inseminated in an area inhabited by both AMM and AMC drones. Genotype of the queens and their sexual partners were derived based on random samples of their worker offspring. Assignment of parental genotypes to the two subspecies was performed with a Bayesian clustering method. In colonies headed by AMM queens, workers were fathered mainly by AMM drones. On the other hand, in colonies headed by AMC queens workers were fathered by drones of both subspecies. The partial reproductive isolation reported here between AMM and AMC may facilitate conservation of the declining population of AMM.

Flow cytometry evidence about sperm competition in honey bee (Apis mellifera)

We tested whether flow cytometry can be used for assessment of viability of honey bee (Apis mellifera) sperm. The method was used to detect possible competition between the sperm of different drones. The flow cytometry analysis of semen stained with SYBR-14/propidium iodide revealed significant differences between fresh and freeze-thawed samples. The identification of populations corresponding to viable and nonviable sperm allowed us to assess the sperm viability. The comparison of single-drone semen with mixed semen of two unrelated drones showed that sperm viability was not affected by mixing, but there were differences between mixed and unmixed semen in side scatter, which correlates with shape and optical homogeneity of particles. The proportion of particles in different populations also was affected by mixing of the semen. The results suggest that there are interactions between ejaculates of different drones, possibly related to sperm competition.

Influence of pollen deprivation on the fore wing asymmetry of honeybee workers and drones

Environmental stress during development can be linked to changes in morphological traits of the organism such as increased fluctuating asymmetry. In suboptimal conditions, like food deprivation, developmental stability may be perturbed, because organisms are not able to buffer disturbances caused by stressors and, in effect, greater degrees of asymmetry can arise during development. In this study, honeybee workers and drones were reared in colonies with limited and unlimited access to pollen. The developmental instability of the workers and drones in these colonies was assessed using the asymmetry of their fore wing venation. Both workers and drones showed a similar directional asymmetry of size—in favour of the right wing—and significant, but dissimilar, differences of wing shape. Limited access to pollen caused some differences in the fluctuating asymmetry of size and shape in pollen-deprived workers and drones compared to the control bees. However, more pronounced differences were found due to replication than to pollen deprivation itself.

Citizen monitoring of invasive species: wing morphometry as a tool for detection of alien Tetropium species

The increasing threat of alien wood‐boring insect has resulted in the initiation of large‐scale monitoring programmes. These programmes are most often based on pheromone‐bailed traps, which allow the early detection and monitoring of invasive species. This approach is expensive because it entails the processing and accurate identification of large numbers of specimens. One of the most often suggested solutions to this problem is citizen participation in the monitoring of invasive species. Such an approach has the potential for reducing costs as well as providing data from a larger number of sites. However, citizens vary in taxonomic expertise and experience which can result in identification errors. This may be particularly important in the case of wood borers which include many morphologically similar species. In this study, we develop and discuss a semi‐automated method of identifying four morphologically similar and invasive Tetropium spp. wood borers as a potential tool for citizen‐based monitoring programmes. Identification is based on wing measurements and requires neither specialist knowledge nor expensive equipment. The method correctly identified the species of Tetropium with an error ranging from 1.3% for T. fuscum to 7.5% for T. cinnamopterum. We found that experience level of the individual user was not essential for correct identification; on average, inexperienced volunteers correctly identified the Tetropium species in 93% of cases. Further development of this method may be a significant step to overcoming the taxonomical impediment to citizen monitoring of taxonomically challenging groups of insects.

Within- and Between-Species Variation of Wing Venation in Genus Monochamus (Coleoptera: Cerambycidae)

We have described the morphological variation of five Western Palaearctic species of Monochamus Dejean, 1821. The variation was assessed using wing measurements. Special emphasis was placed on the differences between Monochamus sartor (F., 1787) and Monochamus urussovii (Fischer-Waldheim, 1805). There was an interesting pattern of variation between the two species. Individuals of M. sartor from the Carpathians differed markedly from individuals of M. urussovii from Siberia, but individuals from north-eastern Poland were intermediate between those two populations. The intermediate individuals were more similar to the Siberian M. urussovii than to the Carpathian M. sartor despite the relatively large geographic distance between north-eastern Poland and Siberia. The occurrence of the intermediate individuals in north-eastern Poland may be the effect of hybridization between M. urussovii and M. sartor, which might have occurred after secondary contact between the two species in the Holocene.

Forewing structure of the solitary bee Osmia bicornis developing on heavy metal pollution gradient

Wild bees in natural conditions can develop under various environmental stressors. Heavy metal pollution of the environment is one of the most widely studied stressors in insects, yet its effect is poorly described in bees. We have measured how pollution of the environment along a zinc, cadmium and lead contamination gradient in Poland affects bee development, using red mason bees (Osmia bicornis) as a model and their forewing asymmetry measures to assess possible developmental instabilities. We have also described wing asymmetry measures in the red mason bee—an important managed pollinator species—for the first time. The development of bee larvae in a contaminated environment did not affect forewing asymmetry measures, but it did lead to a negative correlation of wing size with contamination in females. Bees also showed a clear change in their asymmetry measures between various seasons, suggesting other, unknown environmental factors affecting wing asymmetry more than pollution. Sexes were found to have different forewing shape and size, larger females having larger forewings than the smaller males. The direction of size asymmetry was in favour of the left side in both sexes and also shape differences between the left and right wings showed similar tendencies in males and females. The levels of forewing shape and size asymmetry were smaller in females, making them the more symmetrical sex.

There are still Bee Trees in Europe

In Europe honey bees are considered as domesticated animals. Beekeepers provide them with hives, feed them, protect against parasites and manage them extensively. However, the number of colonies in central and northern Europe is declining, Feral colonies of honey bees once present in Europe have also seen a sharp decline in recent years.

Elytra reduction may affect the evolution of beetle hind wings

Beetles are one of the largest and most diverse groups of animals in the world. Conversion of forewings into hardened shields is perceived as a key adaptation that has greatly supported the evolutionary success of this taxa. Beetle elytra play an essential role: they minimize the influence of unfavorable external factors and protect insects against predators. Therefore, it is particularly interesting why some beetles have reduced their shields. This rare phenomenon is called brachelytry and its evolution and implications remain largely unexplored. In this paper, we focused on rare group of brachelytrous beetles with exposed hind wings. We have investigated whether the elytra loss in different beetle taxa is accompanied with the hind wing shape modification, and whether these changes are similar among unrelated beetle taxa. We found that hind wings shape differ markedly between related brachelytrous and macroelytrous beetles. Moreover, we revealed that modifications of hind wings have followed similar patterns and resulted in homoplasy in this trait among some unrelated groups of wing-exposed brachelytrous beetles. Our results suggest that elytra reduction may affect the evolution of beetle hind wings.