Invasive species are one of the main threats to biodiversity worldwide and the processes enabling their establishment and persistence remain poorly understood. In generalist consumers, plasticity in ...diet and trophic niche may play a crucial role in invasion success. There is growing evidence that invasive ants, in particular, occupy lower trophic levels in their introduced range compared to the native one, but evidences remain fragmented. We conducted stable isotope analysis at five locations distributed on two continents to infer the trophic position of the invasive ant Formica paralugubris in the native and introduced part of the range. This species forms large colonies and can be a voracious predator while feeding on sugar‐based resources as well. Whereas native populations had trophic positions comparable to that of an omnivore, the introduced populations varied from being honeydew specialists to top predators, or omnivore. Where other ant species co‐occurred, there was no overlap in their trophic niches, and F. paralugubris occupied the lower position, suggesting that trophic displacement may enable the coexistence of different ant species. Taken together, our results suggest that shifts in diet associated with changes in the trophic niche of introduced species might mediate invasion success and enable long‐term coexistence with native species.
In furtive predation, a predator is able to exploit its prey without generating significant defensive behaviors from them. However, in aphidophagous guild, if furtive predator can benefit from ...dilution effects generated by the aphids, they also suffer from intraguild predation from more mobile and active-searching predators. In this context ant-tended aphid colonies might not only represent an important food source but also potentially an enemy-free space for furtive predators if they remain unharmed by ants while other active predators are being repelled. Here we use the furtive predator Aphidoletes aphidimyza and two distinct instars of an active-searching predator, the Asian ladybeetle Harmonia axyridis, to test hypotheses related to predator persistence within aphid colonies in presence of ants. Our results show that persistence rate over time of the furtive predator was not affected by ant presence while it was strongly reduced for both instars of the active-searching predator. Furthermore, when ran in paired trials within ant-tended aphid colonies, furtive predator persistence rate was significantly higher than for active-searching predators, with these latter always leaving the plants quicker. Finally, we tested the importance of predator mobility in detection susceptibility and aggressive responses in ants using mobile and immobile active-searching predators. While the number of antennal palpations was similar for both treatments indicating similar detection rate, the number of ant attacks was significantly higher on mobile individuals highlighting the importance of movement in triggering aggressive responses in ants. Overall our results indicate that furtive predation represents an efficient strategy to limit ant aggressions, while the exclusion of active-searching predators might create an enemy-free space for furtive predators within ant-tended aphid colonies.
The morphology of organisms relates to most aspects of their life history and autecology. As such, elucidating the drivers of morphological variation along environmental gradients might give insight ...into processes limiting species distributions. In eusocial organisms, the concept of morphology is more complex than in solitary organisms. Eusocial insects such as ants exhibit drastic morphological differences between reproductive and worker castes. How environmental selection operates on the morphology of each caste, and whether caste‐specific selection has fitness consequences is largely unknown, but is potentially crucial to understand what limits ant species' distributions.
Here we aimed to examine whether ant shape and body size covaries with climate at the scale of an entire continent, and whether such relationship might be caste specific.
We used 26,472 georeferenced morphometric measurements from 2,206 individual ants belonging to 32 closely related North American species in the genus Formica to assess how ant morphology relates to geographic variation in the abiotic environment.
Although precipitation and seasonality explained some of the geographic variation in morphology, temperature was the best predictor. Specifically, geographic variation in body size was positively related to temperature, meaning that ants are smaller in cold than in warm environments. Moreover, the strength of the relationship between size and temperature was stronger for the reproductive castes (i.e. queens and males) than for the worker caste. The shape of workers and males also varied along these large‐scale abiotic gradients. Specifically, the relative length of workers' legs, thoraxes and antennae positively related to temperature, meaning that they had shorter appendages in cold environments. In contrast, males had smaller heads, but larger thoraxes in more seasonal environments.
Overall, our results suggest that geographic variation in ambient temperature influences the morphology of ants, but that the strength of this effect is caste specific. In conclusion, whereas ant ecology has traditionally focused on workers, our study shows that considering the ecology of the reproductive castes is imperative to move forward in this field.
The size and shape of animals reflect adaptations to the environment in which they occur. When such traits confer fitness advantages, they are considered functional traits. There is ongoing interest in understanding trait–environment relationships along broad‐scale gradients, however these relationships are poorly studied in social organisms. Here the authors report that the strength of trait‐environment relationships in ants is stronger in the reproductive than in the worker caste. This is the first study to show caste‐specific morphological clines in social animals.
Complications of diabetes are now well-known to affect sensory, motor, and autonomic nerves. Diabetes is also thought to be involved in neurodegenerative processes characteristic of several ...neurodegenerative diseases. Indeed, it has been acknowledged recently that hyperglycemia-induced oxidative stress contributes to numerous cellular reactions typical of central nervous system deterioration. The goal of the present study was to evaluate the effects of the polyphenol quercetin and the lignan sesamin on high-glucose (HG)-induced oxidative damage in an in vitro model of dopaminergic neurons, neuronal PC12 cells. When incubated with HG (13.5 mg/mL), neuronal PC12 cells showed a significant increase of cellular death. Our results revealed that quercetin and sesamin defend neuronal PC12 cells from HG-induced cellular demise. An elevated level of reactive oxygen and nitrogen species is a consequence of improved oxidative stress after HG administration, and we demonstrated that this production diminishes with quercetin and sesamin treatment. We also found that quercetin and sesamin elicited an increment of superoxide dismutase activity. DNA fragmentation, Bax/Bcl-2 ratio, nuclear translocation of apoptosis-inducing factor, as well as poly(adenosine diphosphate ADP-ribose) polymerase cleavage were significantly reduced by quercetin and sesamin administration, affirming their antiapoptotic features. Also, HG treatment impacted caspase-3 cleavage, supporting caspase-3-dependent pathways as mechanisms of apoptotic death. Our results indicate a powerful role for these natural dietary compounds and emphasize preventive or complementary nutritional strategies for diabetes control.
Dead wood decomposition begins immediately after tree death and involves a large array of invertebrates. Ecological successions are still poorly known for saproxylic organisms, particularly in boreal ...forests. We investigated the use of dead wood as nesting sites for ants along a 60-yr postfire chronosequence in northeastern coniferous forests. We sampled a total of 1,625 pieces of dead wood, in which 263 ant nests were found. Overall, ant abundance increased during the first 30 yr after wildfire, and then declined. Leptothorax cf. canadensis Provancher, the most abundant species in our study, was absent during the first 2 yr postfire, but increased steadily until 30 yr after fire, whereas Myrmica alaskensis Wheeler, second in abundance, was found at all stages of succession in the chronosequence. Six other species were less frequently found, among which Camponotus herculeanus (Linné), Formica neorufibarbis Emery, and Formica aserva Forel were locally abundant, but more scarcely distributed. Dead wood lying on the ground and showing numerous woodborer holes had a higher probability of being colonized by ants. The C:N ratio was lower for dead wood colonized by ants than for noncolonized dead wood, showing that the continuous occupation of dead wood by ants influences the carbon and nitrogen dynamics of dead wood after wildfire in northern boreal forests.
Lors d’un projet de recherche en foresterie, une gyne (reine) de la fourmi parasite Myrmica lampra a été capturée dans la région du Lac-Saint-Jean, au Québec. Cette découverte agrandit le territoire ...connu de cette espèce, rarement observée jusqu’à présent.
Ground-nest densities and nesting habits of 13 ant species were quantified in five postfire age classes (1, 9, 23, 47, and 79 yr old) in the lichenâspruce woodland of Quebec, Canada. There were no ...significant differences in ant nest densities between age-classes (average of 163 nests/ha), but there were significant differences in ant community structure. Ant communities were dominated by Formica podzolica, F. aserva, F. hewetti, and Myrmica detritinodis, which accounted for 77% of occupied nests. Some species (e.g., F. podzolica) were specialists in their nesting habits, whereas others (e.g., F. aserva) were generalists and built their nest in a variety of substrates. Nest densities of F. aserva correlated with several habitat factors, but these correlations could have been spurious because they were not related to this speciesâ nesting habits. However, significant positive correlations found between Camponotus herculeanus and Leptothorax canadensis and coarse woody debris (CWD) may be biologically significant, because these two species nested exclusively within CWD. Nest densities of M. detritinodis and M. fracticornis were relatively high in the youngest and the oldest age classes, resulting in a negative correlation with CWD. We suggest that the distribution of these two species is caused by their preference for older forests to a high rate of fire survival and possibly to competitive release in the year after disturbance. According to canonical correspondence analysis, at least 75% of the variation in ant species cannot be explained by the habitat factors measured. Future research should include, therefore, experimental manipulations to determine the extent to which other factors, such as interspecific interactions, may structure ant communities in lichenâspruce woodland.
The ant (Hymenoptera: Formicidae) fauna of the Mont St. Hilaire Biosphere Reserve, Québec, was surveyed in 2002 and 2003. Although overall species richness was high, 10 of 40 total ant species ...collected were limited to anthropogenically disturbed habitats within the reserve. While only 2 of these 10 species (Tetramorium caespitum (L.) and Lasius niger (L.)) can definitively be considered introduced, areas altered by human activity (representing a small fraction of the reserve’s total area) possess nearly as many unique species as the reserve’s old-growth forest. Although further research will be necessary to determine the consequences of such changes in community structure, this study shows the importance of specifying the extent of biodiversity surveys within protected habitats to more accurately monitor the effectiveness of conservation efforts.
Ground-nest densities and nesting habits of 13 ant species were quantified in five postfire age classes (1, 9, 23, 47, and 79 yr old) in the lichen–spruce woodland of Quebec, Canada. There were no ...significant differences in ant nest densities between age-classes (average of 163 nests/ha), but there were significant differences in ant community structure. Ant communities were dominated by Formica podzolica, F. aserva, F. hewetti, and Myrmica detritinodis, which accounted for 77% of occupied nests. Some species (e.g., F. podzolica) were specialists in their nesting habits, whereas others (e.g., F. aserva) were generalists and built their nest in a variety of substrates. Nest densities of F. aserva correlated with several habitat factors, but these correlations could have been spurious because they were not related to this species’ nesting habits. However, significant positive correlations found between Camponotus herculeanus and Leptothorax canadensis and coarse woody debris (CWD) may be biologically significant, because these two species nested exclusively within CWD. Nest densities of M. detritinodis and M. fracticornis were relatively high in the youngest and the oldest age classes, resulting in a negative correlation with CWD. We suggest that the distribution of these two species is caused by their preference for older forests to a high rate of fire survival and possibly to competitive release in the year after disturbance. According to canonical correspondence analysis, at least 75% of the variation in ant species cannot be explained by the habitat factors measured. Future research should include, therefore, experimental manipulations to determine the extent to which other factors, such as interspecific interactions, may structure ant communities in lichen–spruce woodland.
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