Biology subjects

Hadrava, J.

Publications and source records attributed to Hadrava, J..

5 recordsLinked to original sources

bioRxiv2021

Individual-level specialisation and interspecific resource partitioning in bees revealed by pollen DNA metabarcoding

It is increasingly recognised that intraspecific variation in traits, such as morphology, behaviour, or diet is both ubiquitous and ecologically important. While many species of predators and herbivores are known to display high levels of between-individual diet variation, there is a lack of studies on pollinators. It is important to fill in this gap because individual-level specialisation of flower-visiting insects is expected to affect their efficiency as pollinators with consequences for plant reproduction. Accordingly, the aim of our study was to quantify the level of individual-level specialisation and foraging preferences, as well as interspecific resource partitioning, across different temporal scales in three co-occurring species of bees of the genus Ceratina (Hymenoptera: Apidae: Xylocopinae), C. chalybea, C. nigrolabiata, and C. cucurbitina. We conducted a field experiment where we provided artificial nesting opportunities for the bees and combined a short-term mark-recapture study with the dissection of the bees nests to obtain repeated samples from individual foraging females and complete pollen provisions from their nests. Hence, we could study variation of the composition of pollen collected by the bees at different temporal scales. We used DNA metabarcoding based on the ITS2 locus to identify the composition of the pollen samples. We found that the composition of pollen carried on the bodies of female bees and stored in the brood provisions in their nests significantly differed among the three co-occurring species. At the intraspecific level, individual females consistently differed in their level of specialisation and in the composition of pollen carried on their bodies and stored in their nests. Our study thus provides evidence of consistent individual-level specialisation in pollinators across multiple temporal scales. We also demonstrate that higher generalisation at the species level stemmed from larger among-individual variation in diets as observed in other types of consumers, such as predators. Our study thus reveals how specialisation and foraging preferences of bees change from the scale of individual foraging bouts to complete pollen provisions accumulated in their nests over their lifetime. Such multi-scale view of foraging behaviour is necessary to improve our understanding of the functioning of plant-flower visitor communities.

ecology↗

bioRxiv2021

Are plants in sown flower strips suitable for communities of wild bees? Pollination network approach in conservation biology

O_LIDrastic reductions of insect diversity and abundance are observed in the highly fragmented agricultural landscapes of central Europe. Declines of pollinators may have detrimental effects on the reproduction of wild insect-pollinated plants as well as the yield of crops. In order to mitigate such impacts, sown flower strips on arable land within Agri-Environment Climate Schemes (AECS) are supported across EU countries. However, it is not clear whether sown flower strips provide equivalent benefits to wild flower-visiting insects as semi-natural habitats. C_LIO_LIHere, we apply plant-pollinator network approach to evaluate the function of sown flower strips for the communities of wild bees. We compared the structural characteristics and the robustness of plant-pollinator networks in sown flower strips and nearby semi-natural habitats. We also quantified the importance of individual plant species for bees based on simulations of plant-pollinator extinction cascades. C_LIO_LIWe found that assemblages of plants and pollinators were less diverse in sown flower strips than in semi-natural habitats, more generalized, and more nested. However, we did not find any significant differences in network robustness to plant-pollinator coextinctions. Further, simulations revealed a large variation in the functional importance among plant species from both habitats. C_LIO_LIWe conclude that although the analysis of network robustness suggested that plants in the sown flower strips and semi-natural habitats were functionally equivalent, this masked important differences among the two habitats. From the conservation point of view, semi-natural habitats were superior in supporting a more diverse community of solitary bees and bumblebees. C_LI

ecology↗

bioRxiv2021

Scarcity of hosts for gregarious parasitoids indicates an increase of individual offspring fertility by reducing their own fertility

The gregarious parasitoid strategy allows multiple larvae to complete development in a single host due to their tolerance and/or lower mobility and thus flexibly adjust their reproductive potential amidst changing environmental conditions. Reproductive success is generally measured as the number of each mothers offspring. We propose that with scarcity of host, for gregarious parasitoids is important the view on the fertility not only of a mother but also of her offspring (F1 generation). Due to the body size-fitness correlation, each female deliberately adjusts the clutch size, determining the offspring body size and their reproductive potential. In our study, using Anaphes flavipes as a model species, we showed that under a limited number of hosts, the females reduced their fertility. We propose that the lower fertility of mothers can cause higher fertility in the F2 generation using a larger offspring body while halving fertility. The females increase their individual offsprings fertility by reducing their own fertility. Moreover, we showed that with a scarcity of hosts, the mothers increased the number of their female offspring, and thus, they obtained more offspring in the F2 generation. Additionally, other costs and benefits of the gregarious strategy in relation to superparasitism were tested and discussed.

zoology↗

bioRxiv2021

A new two-generation approach to the population dynamics of gregarious parasitoids

Parasitoids, as important natural enemies, help maintain balance in natural ecosystems. Their population dynamics is generally predicted from the number of individuals. Here, using gregarious parasitoids as models, we show that this traditional approach omits one important parameter: the mothers manipulation of offspring fertility due to the clutch size-body size- fertility correlation. As a result of this correlation, when females deliberately adjust the number of offspring laid in a host, they determine not only the number but also the body sizes and reproductive potentials of those offspring. For the first time in the model species Anaphes flavipes, we determined the parasitoids offspring fertility from clutch size. Using this, we experimentally clarified the advantage of specific clutch size combinations and we show that identical fertility in the F1 generation can lead to distinctly different fertility values in the F2 generation. Even with the same number of hosts, lower fertility in the F1 generation can cause higher fertility in the F2 generation. Based on these results, we propose a novel two-generation approach which includes the clutch size-body size-fertility correlation. Our novel approach provides a new perspective for determining the individual fitness levels of gregarious parasitoids with new options for the modelling of parasitoid population dynamics.

zoology↗

bioRxiv2021

Female manipulation of offspring sex ratio in the gregarious parasitoid Anaphes flavipes from a new two-generation approach

Both theoretical and empirical work suggests that offspring sex ratio has important consequences on fitness. Within insects, gregarious parasitoids with haplodiploid sex determination represent an ideal model for studying the decision-making process behind the assignment of offspring sex. To gain insight into the offspring sex ratio of gregarious parasitoids, we performed experiments on Anaphes flavipes, interpreting our results through a two-generation approach. We confirm the existence of a relationship between offspring sex ratio and clutch size: the proportion of males increases with larger clutch size. Based on this finding, we assumed that the proportion of males among one females offspring would also increase with external factors such as a low population density of the host or the presence of the hosts predator, which may pressure the mothers to lay a higher-sized clutch. Contrary to our initial expectations, we show that if it is the pressure of external factors that leads to an increase in clutch size, these larger clutches tend to be more female-biased and the overall offspring sex ratio of a particular female does not change. While in our previous work, we showed that higher clutch sizes reduce body sizes of the offspring and their future fertility, here we conclude that the differences in fertility affect the offspring sex ratio. Taken together, we highlight our two-generation approach which reveals that while the above external factors do not affect the sex ratio of A. flavipes in the F1 generation, they do have an effect in the F2 generation.

zoology↗