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Aggression toward competitors is a useful measure of resource ownership and defense in animals, but aggressive behavior is costly. Therefore, it is predicted that animals will display aggression only when the expected benefit to individual fitness exceeds the expected cost. In ants, when conspecific individuals belonging to different colonies encounter each other, fighting occurs, seemingly facultatively. However, the context that influences the expression of ants’ aggressive behavior, especially in the field, is still largely unknown. We investigated the plasticity of aggressiveness toward non-nestmates in Diacamma sp. from Japan. Our field experiment clearly showed that the same foragers that were aggressive toward non-nestmates in the vicinity of their nest changed to be non-aggressive at greater distances from the nest. Furthermore, the size of the colony to which the foragers belonged weakly but significantly affected their aggressiveness: foragers belonging to larger colonies behaved more aggressively toward non-nestmates. We discuss the possible adaptive significance of the observed facultative aggression between conspecific non-nestmates. Digital video images related to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo190618ds01a and http://www.momo-p.com/showdetail-e.php?movieid=momo190618ds02a.

Carrion is a valuable resource exploited not only by obligate scavengers but also by a wide variety of facultative scavengers. These species provide several important ecosystem services which can suffer if the scavenger community composition is altered, thus reducing the ecosystem provided. We studied the response of the Mediterranean facultative scavenger community to the exclusion of larger scavenger species (red fox Vulpes vulpes, European badger Meles meles, and wild boar Sus scrofa) using an exclusion fence permeable to small scavenger species (mainly Egyptian mongoose Herpestes ichneumon, common genet Genetta genetta, and stone marten Martes foina). The exclusion of dominant facultative scavengers led to a significant reduction in the amount of carrion consumed and an increase in carrion available for smaller species and decomposers, over a longer period of time. Although carrion consumption by the non-excluded species increased inside the exclusion area relative to the control area, it was insufficient to compensate for the carrion not eaten by the dominant scavengers. Of the small scavenger species, only the Egyptian mongoose significantly increased its carrion consumption in the exclusion area, and was the main beneficiary of the exclusion of dominant facultative scavengers. Therefore, altering the facultative scavenger community in Mediterranean woodlands can reduce the efficiency of small carcass removal and benefit other opportunistic species, such as the Egyptian mongoose, by increasing the carrion available to them. This interaction could have substantial implications for disease transmission, nutrient cycling, and ecosystem function., This study has been possible as a result of the CGL2013-40975-R and RTI2018-099609-B-C22 projects, from the I + D + I National Plan funded by the Spanish Ministry of Economy and Competitiveness and by the Ministry of Science, Innovation and Universities, and also of project (SBPLY-19-180501-000138) funded by the Junta de Comunidades de Castilla la Mancha. Jorge Tobajas is the recipient of an FPI PhD scholarship (BES-2014-068987) funded by the Spanish Ministry of Economy and Competitiveness., Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.

Protected areas are central to the conservation of biodiversity across the globe. However, their performance, especially in relation to highly mobile species, is largely dependent on the socio-ecological characteristics of the landscape that surrounds them. Here, we assess the patterns of avian scavenger distribution, including both obligate (i.e., vultures) and facultative (corvids and other raptors) scavenger species, inside and outside of protected areas. We contrast the situation between an African area, which has protected areas surrounded by mostly subsistence stockbreeding (KwaZulu-Natal Province, South Africa) and a European area, which has protected areas surrounded by commercial farming (Ebro Valley, Spain). We found large differences between the two areas. In the South African area, the richness and abundance of vultures, but not of facultative scavengers, were higher inside than outside of protected areas; as a result, the richness and abundance of vultures were negatively related to the distance to the nearest protected area in South Africa. In contrast, the richness and abundance of vultures in the Spanish area were similar inside and outside of protected areas. We obtained similar results when focusing solely on presence and abundance of Gyps vultures. The contrasting effects of protected areas in the distribution of avian scavengers, especially vultures, in the studied areas may be due to differences in agro-systems and socio-economical models that lead to differential availability of ungulate carcasses. We suggest that carrion shortage in the subsistence farming systems in the South African area, whereby domestic livestock carcasses are generally used by householders and thus rarely become available to vultures, should be considered alongside poisoning prevention to help conserve African vulture populations., MM was supported by postdoctoral grants from the Spanish Ministry of Education (Plan Nacional de I+D+i 2008–2011), the Severo Ochoa Program for Centres of Excellence in R+D+I (SEV-2012-0262) and the Ramón y Cajal Program (RYC-2015-19231). ACA was supported by a contract Juan de la Cierva Incorporación (IJCI-2014-20744) from the Spanish Ministry of Economy and Competitiveness and a postdoctoral contract Programa Viçent Mut of Govern Balear, Spain (PD/039/2017). The study was partly supported by the Spanish Ministry of Science and Innovation through projects CGL2012-40013-C02-02, CGL2015-66966-C2-1-R and CGL2017-89905-R, and ERDF funds.

Many epiphytic plants have associated with ants to gain nutrients. Here, we report a novel type of ant–plant symbiosis in Fiji where one ant species actively and exclusively plants the seeds and fertilizes the seedlings of six species of Squamellaria (Rubiaceae). Comparison with related facultative ant plants suggests that such farming plays a key role in mutualism stability by mitigating the critical re-establishment step. Mutualisms are common in nature. In Fiji, a species of ant selects, disperses and fertilizes an epiphytic plant in an exclusive symbiosis. This represents a novel example of plant farming by ants.

We investigate the feeding responses of the red fox (Vulpes vulpes) at a regional scale to different densities of European wild rabbit (Oryctolagus cuniculus) in central–southern Spain. Rabbit abundance indices were obtained in 86 localities during summer 2002. The diet of the fox was studied by analysis of 114 scats collected in 47 of these localities. The feeding response of the fox was examined by a representation of the dry weight percent of rabbit in the diet as a function of the abundance of rabbits; this used data only from those localities where at least 3 scats were collected (70 fox scats from 18 localities). We evaluated the relationship between rabbit abundance and the diversity of the diet of the fox. The feeding patterns of red foxes approximated to Holling’s type III functional response, typical of opportunistic predators. There was a negative relationship between the diversity of the fox’s diet and the abundance of rabbits. Therefore, the fox apparently behaves as a facultative predator, feeding on rabbits when they are abundant and shifting to other prey (and hence a more diverse diet) when rabbits are scarce. These findings are the first step towards understanding the potential role of red foxes in regulating rabbit populations in central–southern Spain., MDM was supported by a I3P grant funded by the European Social Fund through the “Consejo Superior de Investigaciones Científicas” (CSIC). JFS was supported by a FPI grant from the Spanish Ministry of Education and Science. Funding was provided by the projects CGL 2005-02340/BOS by the Spanish Ministry of Education and Science and PAI06-170 by the regional government of Castilla-La Mancha.

Intra-colony odor variability can disturb ants’ ability to discriminate against intruders. The evolutionary relevance of this phenomenon can be revealed by studies on colonies of slave-making ants in which the parasite, and not the host, is subject to selection pressures associated with living in a mixed colony. We examined how the European facultative slave-making species Formica sanguinea and its F. fusca slaves perform in discriminating ants from alien colonies. Results of behavioral assays showed that slave-maker ants respond with hostility to conspecific individuals from alien colonies but are relatively tolerant to alien slaves. Furthermore, the behavior of slaves indicated a limited ability to discriminate ants from alien parasitic colonies. The subdivision of colony fragments into mixed and species-separated groups demonstrated that contact with the parasite is necessary for F. fusca slaves to be re-accepted by former nestmates after a period of separation from the stock colony. The results presented in this paper are consistent with the following hypotheses: (1) F. sanguinea ants, as opposed to their slaves, are adapted to discriminate alien individuals in the conditions of odor variability found in a mixed-species colony, (2) the recognition of slaves by F. sanguinea ants involves a dedicated adaptive mechanism that prevents aggression toward them, (3) the odor of slaves is strongly influenced by the parasite with beneficial effect on the colony integrity. Electronic supplementary material The online version of this article (doi:10.1007/s00040-016-0493-z) contains supplementary material, which is available to authorized users.

All monogonont rotifers have a diapause stage (=resting egg, RE), which allows them to endure unfavourable periods and to disperse across non-aquatic boundaries. However, recent research has shown that REs may often develop spontaneously within a few days, which seems to partly offset these adaptive explanations. In this study, I determined the minimum duration of RE development in a Brachionus calyciflorus Pallas 1766 strain in relation to other life-history variables. RE development took at least 72 h, but 50 % of those REs that hatched within the first week did so in a much synchronized manner, within 72–82 h. By contrast, amictic egg development took 11 h, while REs that had been previously stored in the cold/dark for weeks, hatched within 21 h if exposed to warm/light conditions. I discuss the fitness consequences of such fast RE development and whether it can ameliorate the costs of sex in this system. I also propose a conceptual model of RE development, which assumes two obligatory phases of pre- and post-diapause development and a facultative phase of dormancy. The latter phase may be missing in spontaneously developing REs.

Background Culex pipiens pipiens plays an important role in the transmission of several vector-borne pathogens such as West Nile virus (WNV) in North America. Laboratory and field studies suggest that this species is ornithophilic but because of genetic hybridization with sibling species during the active mosquito season, it may occasionally feed on mammals. Adult female Cx. p. pipiens undergo a facultative diapause and may serve as an overwintering mechanism for WNV. To determine the effect of diapause on the innate host preference of Cx. p. pipiens emerging from winter hibernation, we conducted host-choice experiments using bird and mammal hosts. Methods Mosquitoes were reared under non-diapause induced (NDI), diapause induced (DI), and field collected from overwintering (OW) hibernaculae. They were released into a large mesh enclosure housing two lard can traps, and given a choice between feeding on a dove or a rat. Results Host seeking Cx. p. pipiens were four times more likely to feed on the dove than the rat, regardless of experimental conditions. Under NDI conditions, Cx. p. pipiens were (p

13 pages, 6 figures, 4 tables., [Background] Specialised leaf-eating is almost universally regarded as the ancestral state of all ruminants, yet little evidence can be cited in support of this assumption, apart from the fact that all early ruminants had low crowned cheek teeth. Instead, recent years have seen the emergence evidence contradicting the conventional view that low tooth crowns always indicate leaf-eating and high tooth crowns grass-eating., [Results] Here we report the results of two independent palaeodietary reconstructions for one of the earliest deer, Procervulus ginsburgi from the Early Miocene of Spain, suggesting that despite having lower tooth crowns than any living ruminant, this species included a significant proportion of grass in its diet., [Conclusion] The phylogenetic distribution of feeding styles strongly supports that leaf-grass mixed feeding was the original feeding style of deer, and that later dietary specialization on leaves or grass occurred independently in several lineages. Evidence for other ruminant clades suggests that facultative mixed feeding may in fact have been the primitive dietary state of the Ruminantia, which would have been morphologically expressed only under specific environmental factors., Excavations were funded and supported by the Cultural Heritage Department of the government of Aragón. This research was supported by the Spanish Ministerio de Educación y Ciencia (CGL 2004-00400, CGL2005-03900/BTE and grant AP2003-0468) and by the government of Aragón (E05).

Background Soils harbour high diversity of obligate as well as facultative chemolithoautotrophic bacteria that contribute significantly to CO2 dynamics in soil. In this study, we used culture dependent and independent methods to assess the community structure and diversity of chemolithoautotrophs in agricultural and coastal barren saline soils (low and high salinity). We studied the composition and distribution of chemolithoautotrophs by means of functional marker gene cbbL encoding large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase and a phylogenetic marker 16S rRNA gene. The cbbL form IA and IC genes associated with carbon fixation were analyzed to gain insight into metabolic potential of chemolithoautotrophs in three soil types of coastal ecosystems which had a very different salt load and sulphur content. Results In cbbL libraries, the cbbL form IA was retrieved only from high saline soil whereas form IC was found in all three soil types. The form IC cbbL was also amplified from bacterial isolates obtained from all soil types. A number of novel monophyletic lineages affiliated with form IA and IC phylogenetic trees were found. These were distantly related to the known cbbL sequences from agroecosystem, volcanic ashes and marine environments. In 16S rRNA clone libraries, the agricultural soil was dominated by chemolithoautotrophs (Betaproteobacteria) whereas photoautotrophic Chloroflexi and sulphide oxidizers dominated saline ecosystems. Environmental specificity was apparently visible at both higher taxonomic levels (phylum) and lower taxonomic levels (genus and species). The differentiation in community structure and diversity in three soil ecosystems was supported by LIBSHUFF (P = 0.001) and UniFrac. Conclusion This study may provide fundamentally new insights into the role of chemolithoautotrophic and photoautotrophic bacterial diversity in biochemical carbon cycling in barren saline soils. The bacterial communities varied greatly among the three sites, probably because of differences in salinity, carbon and sulphur contents. The cbbL form IA-containing sulphide-oxidizing chemolithotrophs were found only in high saline soil clone library, thus giving the indication of sulphide availability in this soil ecosystem. This is the first comparative study of the community structure and diversity of chemolithoautotrophic bacteria in coastal agricultural and saline barren soils using functional (cbbL) and phylogenetic (16S rDNA) marker genes.

Background Non-essential facultative endosymbionts can provide their hosts with protection from parasites, pathogens, and predators. For example, two facultative bacterial symbionts of the pea aphid (Acyrthosiphon pisum), Serratia symbiotica and Hamiltonella defensa, protect their hosts from parasitism by two species of parasitoid wasp. Previous studies have not explored whether facultative symbionts also play a defensive role against predation in this system. We tested whether feeding on aphids harboring different facultative symbionts affected the fitness of an aphid predator, the lady beetle Hippodamia convergens. Results While these aphid faculative symbionts did not deter lady beetle feeding, they did decrease survival of lady beetle larvae. Lady beetle larvae fed a diet of aphids with facultative symbionts had significantly reduced survival from egg hatching to pupation and therefore had reduced survival to adult emergence. Additionally, lady beetle adults fed aphids with facultative symbionts were significantly heavier than those fed facultative symbiont-free aphids, though development time was not significantly different. Conclusions Aphids reproduce clonally and are often found in large groups. Thus, aphid symbionts, by reducing the fitness of the aphid predator H. convergens, may indirectly defend their hosts’ clonal descendants against predation. These findings highlight the often far-reaching effects that symbionts can have in ecological systems.

The rate of gene loss was studied in the facultative pathogens, E. coli and Shigella, and was found to be greater in the more niche-limited Shigella. This is demonstrated to be due to a genome-wide reduction in the effectiveness of selection., Background Obligate pathogenic bacteria lose more genes relative to facultative pathogens, which, in turn, lose more genes than free-living bacteria. It was suggested that the increased gene loss in obligate pathogens may be due to a reduction in the effectiveness of purifying selection. Less attention has been given to the causes of increased gene loss in facultative pathogens. Results We examined in detail the rate of gene loss in two groups of facultative pathogenic bacteria: pathogenic Escherichia coli, and Shigella. We show that Shigella strains are losing genes at an accelerated rate relative to pathogenic E. coli. We demonstrate that a genome-wide reduction in the effectiveness of selection contributes to the observed increase in the rate of gene loss in Shigella. Conclusion When compared with their closely related pathogenic E. coli relatives, the more niche-limited Shigella strains appear to be losing genes at a significantly accelerated rate. A genome-wide reduction in the effectiveness of purifying selection plays a role in creating this observed difference. Our results demonstrate that differences in the effectiveness of selection contribute to differences in rate of gene loss in facultative pathogenic bacteria. We discuss how the lifestyle and pathogenicity of Shigella may alter the effectiveness of selection, thus influencing the rate of gene loss.