We update the global assessment of seed dispersal by ants and test the hypothesis that the body size of seed-dispersing ant species varies with latitude in the same way as dispersal distance. We ...compiled all published data about seed dispersal distance by myrmecochory through March, 2011. We then broke the data down by vegetation type, geography and taxonomy. We also compiled data on body size (body length) of the seed-dispersing ant species from the studies consulted. Based on 7889 observations, the mean dispersal distance was 1.99 m, although the curve has a long tail extending to 180 m. Considering the mean dispersal distance by ant species and study as independent data, the mean dispersal distance was 2.24 ± 7.19 m (n = 183). Shorter distances are associated with smaller ant species, while the tail of the dispersal curve is due to larger ant species. The mean dispersal distance of myrmecochorous seeds dispersed by ants decreased with increasing latitude, but there was no significant relationship between the body size of dispersing ant species and latitude (i.e. myrmecochorous seed-dispersing ant species do not follow Bergmann's rule). In 1998 we made three predictions: 1) the dispersal distances of the Southern Hemisphere will decrease with as more data from mesophyllous vegetation are obtained; 2) assuming that ant nest density is higher at lower latitudes, the differences in distances between hemispheres would probably decrease with more data; and 3) numerical differences between dispersal distances in mesophyllous and sclerophyllous vegetation zones would increase with more data. The results obtained since 1998 support the only the third prediction. The dispersal distances in mesophyllous vegetation zones are shorter than in the sclerophyllous vegetation zones, and the difference between 1998 have increased. The differences in dispersal distances between hemispheres are consistent with the avoidance of parent-offspring competition (escape hypothesis).
In social species, the presence of several reproductive individuals can generate conflict. In social insects, as queen number increases, individual oviposition rate may decrease because of direct and ...indirect behavioural and/or chemical interactions. Understanding the factors that mediate differences in queen fecundity should provide insight into the regulation and maintenance of highly polygynous insect societies, such as those of the invasive Argentine ant (Linepithema humile). In this study, we investigated (1) whether differences in the oviposition rates of Argentine ant queens exposed to polygynous conditions could result from interactions among them; (2) whether such differences in fecundity stemmed from differences in worker attention; and (3) whether polygynous conditions affected the cuticular hydrocarbon profiles of queens (CHCs). We found that differences in queen fecundity and CHC profiles observed under polygynous conditions disappeared when queens were exposed to monogynous conditions, suggesting some form of reproductive inhibition may exist when queens cohabit. These differences did not seem to arise from variation in worker attention because more fecund queens were not more attractive to workers. Levels of some CHCs were higher in more fecund queens. These CHCs are associated with greater queen productivity and survival. Our findings indicate that such compounds could be multifunctional queen pheromones.
Competition among queens in polygynous societies may result in queen executions or conflicts over personal reproduction. Understanding the factors that mediate the executions of ant queens should ...provide insight into how queen numbers are regulated in polygynous insect societies. The Argentine ant is a widespread invasive species that displays secondary polygyny, and workers execute 90% of their nestmate queens each spring. In this study, we investigated: (1) whether ambient temperature, queen number, and protein deprivation have an effect on queen executions and (2) whether workers select the queens slated for execution based on their cuticular hydrocarbon (CHC) profiles. We found that the percentage of queens executed was positively correlated with temperature and queen number but that protein deprivation did not play a role. As for queen fate, the levels of some CHCs were higher in surviving queens. One of these CHCs is associated with queen productivity (i.e egg-laying rate and ovarian index) suggesting that workers execute the least productive queens. Our findings suggest that chemical cues related to fertility signaling may mediate queen executions in Argentine ants.
In insect societies, chemical communication plays an important role in colony reproduction and individual social status. Many studies have indicated that cuticular hydrocarbons (CHCs) are the main ...chemical compounds encoding reproductive status. However, these studies have largely focused on queenless or monogynous species whose workers are capable of egg laying and have mainly explored the mechanisms underlying queen-worker or worker-worker reproductive conflicts. Less is known about what occurs in highly polygynous ant species with permanently sterile workers. Here, we used the Argentine ant as a model to examine the role of CHCs in communicating reproductive information in such insect societies. The Argentine ant is unicolonial, highly polygynous, and polydomous. We identified several CHCs whose presence and levels were correlated with queen age, reproductive status, and fertility. Our results also provide new insights into queen executions in the Argentine ant, a distinctive feature displayed by this species in its introduced range. Each spring, just before new sexuals appear, workers eliminate up to 90% of the mated queens in their colonies. We discovered that queens that survived execution had different CHC profiles from queens present before and during execution. More specifically, levels of some CHCs were higher in the survivors, suggesting that workers could eliminate queens based on their chemical profiles. In addition, queen CHC profiles differed based on season and species range (native vs. introduced). Overall, the results of this study provide new evidence that CHCs serve as queen signals and do more than just regulate worker reproduction.
► Ants play an important role in monitoring ecosystem health. ► A successful ant monitoring protocol requires efficient sampling methods. ► The use of hand collecting methodologies makes more ...effective ant sampling. ► Large ant sizes in Mohago pine forests simplify rapid ant assessments. ► This information improves the application of RBA protocols adapted to management goals.
Ants are good indicators of ecosystem health and therefore a good choice for rapid terrestrial bioassessments (RBAs) in land management. However, the application of these rapid protocols is unfeasible until efficient sampling methodologies adapted to management goals have been developed. Taking into account the need to improve tools to synthesize broad-scale RBA, the aim of this study is to search for a simple and efficient ant sampling protocol suitable to assess changes in ant assemblages taking, as an example, the specific case of the management of selective logging activities in public pine forests of the central Iberian Peninsula. Ants were sampled at eighteen sites. Each one corresponded to a tranzón, a quadrangular unit of management. In our case all the tranzones had similar areas (25–30ha). Ants were sampled at each site using two methods: pitfall traps and hand collecting. Ant species richness (number of species) and the Shannon diversity index (H) were compared both for sampling method and for sample point. The Shannon diversity index was not considered as a biodiversity index, but a measure of entropy (uncertainty or information content) like in its original proposed sense. In both comparisons, hand collecting was the method that achieved a greater ant species collection and greater diversity indexes, and therefore, a higher information content, suggesting that it is the best choice to use for ant RBA protocols in the particular case of temperate forest habitats. This is an important issue for land managers of these forests in order to detect changes in ant assemblages between logging events. Moreover, the relatively large ant sizes reported in the Mohago pine forests in comparison with ant species across the whole Iberian Peninsula make the process of ant collection and recognition easier, simplifying forest management through the elaboration of simple protocols for rapid ant bioassessments (RBAs). Overall, this information greatly improves the current application of rapid ant assessment protocols for monitoring the recovery status of these temperate forests.
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•In the Argentine ant there are permanent and temporal colonies.•Queens from permanent colonies exhibit higher oviposition rates and δ15N values.•The ovarian structure of queens from ...both kinds of colonies is similar.•Higher oviposition rates seem to be related with a higher carnivorous diet.•Colony permanence seems to be the main factor responsible of higher oviposition rates.
Polydomy associated with unicoloniality is a common trait of invasive species. In the invasive Argentine ant, colonies are seasonally polydomous. Most follow a seasonal fission–fussion pattern: they disperse in the spring and summer and aggregate in the fall and winter. However, a small proportion of colonies do not migrate; instead, they inhabit permanent nesting sites. These colonies are large and highly polydomous. The aim of this study was to (1) search for differences in the fecundity of queens between mother colonies (large and permanent) and satellite colonies (small and temporal), (2) determine if queens in mother and satellite colonies have different diets to clarify if colony size influences social organization and queen feeding, and (3) examine if colony location relative to the invasion front results in differences in the queen’s diet. Our results indicate that queens from mother nests are more fertile than queens from satellite nests and that colony location does not affect queen oviposition rate. Ovarian dissections suggest that differences in ovarian morphology are not responsible for the higher queen oviposition rate in mother vs. satellite nests, since there were no differences in the number and length of ovarioles in queens from the two types of colonies. In contrast, the higher δ15N values of queens from mother nests imply that greater carnivorous source intake accounts for the higher oviposition rates.
After the publication of this work in 'Genome Biology, 2016, 17:43', the autors was noticed that the mapping between column 1 and 2 in the Additional file 7 - Table S5 was incorrect
► We studied the process of pine forest recovery by focusing on ant assemblages. ► Selective logging does not produce dramatic changes in diversity or ant assemblages. ► The ant assemblages need at ...least 8
years to recover. ► An ant functional group approach provides interesting information to managers.
Pine forests on the northern plateau of the Iberian Peninsula have a long history of use, exploitation, and management. Current management practices consist of selective logging with relatively short periods of time between logging events. The main objective of this study is to detect changes in ant assemblages in the short time periods between selective logging activities. Ants were sampled at 44 sites considering three grouping categories of time periods after the last timber extraction: short (<4
years), medium (4–8
years) and long (>8
years). After selective logging the number of ant species increases as the forest recovers. A look at the differences between the assemblages when the analysis shifts from the species-specific level to functional groups showed differences between the short and long categories. This indicates that in certain circumstances the functional groups may be more informative of the functional restructuring of the ant assemblages in a disturbed habitat. Ant species from three functional groups display significant indicative values (Opportunist, Hot Climate Specialists and Subordinate Camponotini) in the medium- and long-time-after-logging categories:
Messor capitatus (HCS) for medium-time category sites; and
Aphaenogaster iberica (Op),
Camponotus cruentatus (SC) and,
Cataglyphis velox (HCS) for long-time category sites. No indicator species were found for the early stages of recovery. This information may also be of interest to managers because it reduces the number of data elements of the recovery status of these forests, and can be translated into monitoring protocols. The continued exploitation of these forests leads to an ant fauna that reflects this change. The results show that ant assemblages need at least 8
years to recover since only after that much time there is an emergence of Subordinate Camponotinae, a behaviorally dominant and low stress-tolerant functional group. This selective logging maintains the relative diversity and structure of ant assemblages.
The influence of temperature on the developmental times and survival of insects can largely determine their distribution. For invasive species, like the Argentine ant, Linepithema humile Mayr ...(Hymenoptera: Formicidae), these data are essential for predicting their potential range based on mechanistic models. In the case of this species, such data are too scarce and incomplete to make accurate predictions based on its physiological needs. This research provides comprehensive new data about brood survival and developmental times at a wide range of temperatures under laboratory conditions. Temperature affected both the complete brood development from egg to adult worker and each of the immature stages separately. The higher the temperature, the shorter the development times. Brood survival from egg to adult was low, with the maximum survival rate being only 16% at 26° C. Temperature also affected survival of each of the immature stages differently: eggs were negatively affected by high temperatures, while larvae were negatively affected by low temperatures, and the survival of pupae was apparently independent of environmental temperature. At 32° C no eggs survived, while at 18° C less than 2% of the eggs hatched into larva. The data from the present study are essential for developing prediction models about the distribution range of this tramp species based on its physiological needs in relation to temperature.
Reproductive division of labor in eusocial insects is a striking example of a shared genetic background giving rise to alternative phenotypes, namely queen and worker castes. Queen and worker ...phenotypes play major roles in the evolution of eusocial insects. Their behavior, morphology and physiology underpin many ecologically relevant colony-level traits, which evolved in parallel in multiple species.
Using queen and worker transcriptomic data from 16 ant species we tested the hypothesis that conserved sets of genes are involved in ant reproductive division of labor. We further hypothesized that such sets of genes should also be involved in the parallel evolution of other key traits. We applied weighted gene co-expression network analysis, which clusters co-expressed genes into modules, whose expression levels can be summarized by their 'eigengenes'. Eigengenes of most modules were correlated with phenotypic differentiation between queens and workers. Furthermore, eigengenes of some modules were correlated with repeated evolution of key phenotypes such as complete worker sterility, the number of queens per colony, and even invasiveness. Finally, connectivity and expression levels of genes within the co-expressed network were strongly associated with the strength of selection. Although caste-associated sets of genes evolve faster than non-caste-associated, we found no evidence for queen- or worker-associated co-expressed genes evolving faster than one another.
These results identify conserved functionally important genomic units that likely serve as building blocks of phenotypic innovation, and allow the remarkable breadth of parallel evolution seen in ants, and possibly other eusocial insects as well.
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