Evolution of cuticular hydrocarbon diversity in ants

The cuticular hydrocarbons (CHCs) of ants provide important cues for nestmate and caste recognition. There is enormous diversity in the composition of these CHCs, but the manner in which this diversity has evolved is poorly understood. We gathered data on CHC profiles for 56 ant species, relating this information to their phylogeny. We deduced the mode of evolution of CHC profiles by reconstructing character evolution and then relating the number of changes in CHC components along each branch of the phylogeny to the length of the branch. There was a strong correlation between branch length and number of component changes, with fewer changes occurring on short branches. Our analysis thereby indicated a gradual mode of evolution. Different ant species tend to use specific CHC structural types that are exclusive of other structural types, indicating that species differences may be generated in part by switching particular biosynthetic pathways on or off in different lineages. We found limited, and contradictory, evidence for abiotic factors (temperature and rainfall) driving change in CHC profiles.

Seasonal changes in the diet of the long-nosed bandicoot (Perameles nasuta) assessed by analysis of faecal scats and of stable isotopes in blood

The diet of long-nosed bandicoots (Perameles nasuta) on the central coast of New South Wales, Australia, was examined over two summers and two winters using a combination of faecal scat analysis for food fragments and stable isotope analysis (ratios of ¹³C/¹²C and ¹⁵N/¹⁴N) of blood. Isotope ratios in blood overlapped most strongly with those in invertebrate prey, and varied much less between seasons than did those in most dietary items, suggesting that the assimilated diet of long-nosed bandicoots is dominated by invertebrates throughout the year. Invertebrate remains dominated collected faeces in both seasons, even though the availability of invertebrate prey was higher in summer. Thus both techniques indicated that long-nosed bandicoots were primarily insectivorous year-round. Faecal scat analysis indicated that invertebrate eggs were more abundant in summer than winter. At a finer scale, spiders, orthopterans, lepidopteran larvae, ants, leaf material (non-grass monocot) and seeds were more abundant in summer, while cicada larvae, roots, fungi, grass leaves and Acacia bract (small modified leaves appearing as scales) were more abundant in winter. Subterranean foods (cicada larvae, plant roots and hypogeous fungi) were more abundant in winter and more abundant in the diet of males than of either lactating or non-lactating females.

Letters to a young scientist by Edward O. Wilson : interview

I am an early- to mid-career researcher, and Letters to a Young Scientist struck a chord with me from the very first page. The journey from amateur enthusiast to professional scientist is an exciting, challenging and often difficult one, and Edward Wilson - a Pulitzer prizewinner and one of the world's greatest entomologists - is well qualified to guide and advise the new generation. Written as a collection of letters filled with anecdotes and well-considered advice, this book is inspired by the author's experience of the journey from being a young boy enthused by ants to an eminent scholar. Like many in his field, Wilson's education began when he was a child fascinated by insects in the garden (my own summers spent excavating ant nests feel somewhat validated). He traces his progression through formal education to the establishment of his own scientific research programme.

An ant colony system based on the physarum network

The Physarum Network model exhibits the feature of important pipelines being reserved with the evolution of network during the process of solving a maze problem. Drawing on this feature, an Ant Colony System (ACS), denoted as PNACS, is proposed based on the Physarum Network (PN). When updating pheromone matrix, we should update both pheromone trails released by ants and the pheromones flowing in a network. This hybrid algorithm can overcome the low convergence rate and local optimal solution of ACS when solving the Traveling Salesman Problem (TSP). Some experiments in synthetic and benchmark networks show that the efficiency of PNACS is higher than that of ACS. More important, PNACS has strong robustness that is very useful for solving a higher dimension TSP.

A multi-objective ant colony optimization algorithm based on the physarum-inspired mathematical model

Multi-objective traveling salesman problem (MOTSP) is an important field in operations research, which has wide applications in the real world. Multi-objective ant colony optimization (MOACO) as one of the most effective algorithms has gained popularity for solving a MOTSP. However, there exists the problem of premature convergence in most of MOACO algorithms. With this observation in mind, an improved multiobjective network ant colony optimization, denoted as PMMONACO, is proposed, which employs the unique feature of critical tubes reserved in the network evolution process of the Physarum-inspired mathematical model (PMM). By considering both pheromones deposited by ants and flowing in the Physarum network, PM-MONACO uses an optimized pheromone matrix updating strategy. Experimental results in benchmark networks show that PM-MONACO can achieve a better compromise solution than the original MOACO algorithm for solving MOTSPs.

Formica

The title of the work, Formica, speaks both to the work’s insect motif – formica is Latin for ant - but also to the 2-dimensional nature of the projection screen – Formica is also a kind of decorative laminate surface. This is Grennan’s second video installation work commissioned specifically for the Kingston Art Centre’s Bridge Space. Following on from the first project - which transformed a dilapidated 3rd story pedestrian corridor into a virtual swimming pool - this work continues to explore the residual meanings of the corridor as a liminal, in-between, or non-space. The new work seeks to again reply aesthetically and poetically to the site’s external setting dominated as it is by the heavy commuter traffic along the Nepean Highway. Scale is central to the work. In Formica, Grennan constructs a scaled-down Perspex replica of the walk-bridge, and with the help of Patrick Honan and Museum Victoria (where Patrick, an entomologist, is head of live exhibits), he populates the corridor with live Bull Ants. The work records these colossal ants as they negotiate the non-space of the corridor and fulfil their metaphorical roles as standardised commuters. With nowhere to go, however, the ants subvert this assigned role and exhibit far more nuanced and individuated behaviour as they investigate, probe, prevaricate, dawdle, or preen idly as though performing some insectile version of Waiting for Godot.

A rank-based ant system algorithm for solving 0/1 knapsack problem

The 0/1 Knapsack Problem (KP), which is a classical NP-complete problem, has been widely applied to solving many real world problems. Ant system (AS), as one of the earliest ant colony optimization (ACO) algorithms, provides approximate solutions to 0/1 KPs. However, there are some shortcomings such as low efficiency and premature convergence in most AS algorithms. In order to overcome the shortcomings of AS, this paper proposes a rank-based AS algorithm, denoted as RAS to solve 0/1 KP. Taking advantages of the ranked ants with a higher profit, the pheromone of items will be updated with better solutions in RAS. Experimental results in different datasets show that this new kind of AS algorithm can obtain a higher efficiency and robustness when solving 0/1 KP.

Social structure and landscape genetics of the endemic New Caledonian ant Leptomyrmex pallens Emery, 1883 (Hymenoptera: Formicidae: Dolichoderinae), in the context of fire-induced rainforest fragmentation

Habitat fragmentation is a major threat to biodiversity, as it can alter ecological processes at various spatial and trophic scales. At the species level, fragmentation leading to the isolation of populations can trigger reductions in genetic diversity, potentially having detrimental effects on population fitness, adaptability and ultimately population persistence. Leptomyrmex pallens is a widespread rainforest ant endemic to New Caledonia but now confined to habitat patches that have been fragmented by anthropogenic fire regimes over the last 200 years. We investigated the social structure of L. pallens in the Aoupinié region (c.a. 4900 ha), and assessed the impacts of habitat fragmentation on its population genetic structure. Allele frequencies at 13 polymorphic microsatellite loci were compared among 411 worker ants from 21 nests distributed across the region. High within-nest relatedness (r = 0.70 ± 0.02), and a single queen found in 38 % of the nests by pedigree analysis indicate that the species is monogynous to weakly polygynous. Estimates of gene flow and genetic structure across the region were subsequently determined using a combined dataset of single workers per nest and of unrelated foraging workers. These estimates coupled with a comprehensive landscape genetic analysis revealed no evidence of significant population structure or habitat effects, suggesting that the Aoupinié region harbours a single panmictic population. In contrast, analyses of mitochondrial DNA sequence data revealed a high degree of genetic structuring, indicating limited maternal gene flow and suggesting that gene flow among nests is driven primarily by winged males. Overall these findings suggest that fire-induced habitat fragmentation has had little impact on the population dynamics of L. pallens. Additional studies of less mobile species should therefore be conducted to gain further insights into fire related disturbances on the unique biodiversity and function of New Caledonian ecosystems.