Radiocarbon analysis reveals expanded diet breadth associates with the invasion of a predatory ant

Alien ants spreading through Europe: Brachyponerachinensis and Nylanderiavividula in Italy

The number of known alien ant species throughout Europe has been steadily increasing during the last few decades and Italy has been no exception, with four new taxa reported in the last five years. Here, we document new data on the Asian needle ant Brachyponerachinensis (Emery, 1895), an invasive alien species whose first establishment in Europe was detected in the southern Italian city of Naples in 2022 and which has now been found near Lake Como in northern Italy, representing the second European record, about 730 km distant from the first. Furthermore, we report for the first time the presence of Nylanderiavividula (Nylander, 1846) in the country, based on specimens collected both in Rome and near Lake Como. This is at least the second Nylanderia species established in the country after N.jaegerskioeldi, first reported in 2018. Unlike B.chinensis, N.vividula is not considered an ecological and health threat in the invaded range and is already known to occur in several other European countries. While only a few introduced ants in Europe are considered serious ecological, economic or health threats, the increasing circulation of several alien species and the poor ability to swiftly track their movements and detect their establishment can render management very difficult.

Declines of bees and butterflies over 15 years in a forested landscape

Despite growing concerns about pollinator declines,^1,2,3,4 evidence that this is a widespread problem affecting entire communities remains limited.⁵ There is a particular shortage of pollinator time series from relatively undisturbed natural habitats, such as forests, which are generally thought to provide refuge to biodiversity from anthropogenic stressors.⁶ Here, we present the results from standardized pollinator sampling over 15 years (2007-2022) at three relatively undisturbed forested locations in the southeastern United States. We observed significant declines in the richness (39%) and abundance (62.5%) of bees as well as the abundance of butterflies (57.6%) over this time period. Unexpectedly, we detected much stronger declines in the richness and abundance of above-ground-nesting bees (81.1% and 85.3%, respectively) compared with below-ground-nesting bees. Even after dropping the first or last year of sampling, which happened to yield the greatest and lowest numbers of pollinators, respectively, we still detected many of the same negative trends. Our results suggest that sharp declines in pollinators may not be limited to areas experiencing direct anthropogenic disturbances. Possible drivers in our system include increasing mean annual minimum temperatures near our study sites as well as an invasive wood-nesting ant that has become increasingly widespread and abundant in the region over the course of this study.

Intraspecific differences in the invasion success of the Argentine ant Linepithema humile Mayr are associated with diet breadth

The Argentine ant, Linepithema humile Mayr, has spread to almost all continents. In each introduced region, L. humile often forms a single large colony (supercolony), the members of which share the haplotype "LH1", despite the presence of other supercolonies with different genetic structures. However, the mechanisms underlying the successful invasion of LH1 ants are unclear. Here, we examined whether diet breadth differs between more successful (LH1) and less successful (LH2, LH3, LH4) L. humile supercolonies in Japan to better understand the processes responsible for invasion success. The standard ellipse areas (SEAs) of δ13C and δ15N and their ranges (CR and NR) were used as diet breadth indices. The SEAs of LH1 were much larger than those of the less successful supercolonies despite no differences in the baseline SEAs of arthropods within the supercolony habitats, indicating that the invasion success of a supercolony is associated with its diet breadth. Furthermore, LH1 had a broader CR than the other supercolonies, suggesting that which might be derived from superior resource exploitation ability. Our study highlights the importance of focusing on intraspecific differences in diet breadth among supercolonies when assessing organisms that can potentially invade and become dominant in new habitats.

Host use diversification during range shifts shapes global variation in Lepidopteran dietary breadth

Niche breadths tend to be greater at higher latitudes. This pattern is frequently assumed to emerge from the cumulative effects of multiple, independent local adaptation events along latitudinal environmental gradients, although evidence that generalization is more beneficial at higher-latitude locations remains equivocal. Here I propose an alternative hypothesis: that latitudinal variation in niche breadths emerges as a non-adaptive consequence of range shift dynamics. Based on analysis of a global dataset comprising more than 6,934 globally distributed dietary records from 4,410 Lepidopteran species, this hypothesis receives robust support. Population-level dietary niche breadths are better explained by the relative position of the population within its geographic range and the species' poleward range extent than by the latitude of diet observation. Broader diets are observed closer to poleward range limits and in species that have attained higher latitudes. Moreover, latitudinal variation in diet breadth is more prominent within and among species undergoing rapid, contemporary range shifts than for species with more stable ranges. Together these results suggest that latitudinal patterns in niche breadth represent a transient and emergent property of recent geographic range dynamics and need not require underlying gradients in selective agents or fitness trade-offs. The results have wide-ranging implications for global ecology and for anticipating changes in host use during ongoing distributional shifts of pests and disease vectors.