The analysis of ecological networks is generally bottom‐up, where networks are established by observing interactions between individuals. Emergent network properties have been indicated to reflect ...the dominant mode of interactions in communities that might be mutualistic (e.g., pollination) or antagonistic (e.g., host–parasitoid communities). Many ecological communities, however, comprise species interactions that are difficult to observe directly. Here, we propose that a comparison of the emergent properties from detail‐rich reference communities with known modes of interaction can inform our understanding of detail‐sparse focal communities. With this top‐down approach, we consider patterns of coexistence between termite species that live as guests in mounds built by other host termite species as a case in point. Termite societies are extremely sensitive to perturbations, which precludes determining the nature of their interactions through direct observations. We perform a literature review to construct two networks representing termite mound cohabitation in a Brazilian savanna and in the tropical forest of Cameroon. We contrast the properties of these cohabitation networks with a total of 197 geographically diverse mutualistic plant–pollinator and antagonistic host–parasitoid networks. We analyze network properties for the networks, perform a principal components analysis (PCA), and compute the Mahalanobis distance of the termite networks to the cloud of mutualistic and antagonistic networks to assess the extent to which the termite networks overlap with the properties of the reference networks. Both termite networks overlap more closely with the mutualistic plant–pollinator communities than the antagonistic host–parasitoid communities, although the Brazilian community overlap with mutualistic communities is stronger. The analysis raises the hypothesis that termite–termite cohabitation networks may be overall mutualistic. More broadly, this work provides support for the argument that cryptic communities may be analyzed via comparison to well‐characterized communities.
Many species–species interactions are difficult to observe directly. Here we propose that comparing the network topology of these obfuscated communities to the network topology of well‐studied, detail‐rich communities will provide insight into the structure of the obfuscated communities. We examine termite mound cohabitation as a case study; the analysis raises the hypothesis that the interactions contained therein may be overall mutualistic.
A quantitative catalogue of the parasitoids (almost exclusively Chalcidoidea) and inquiline Cynipidae recorded in the western Palaearctic from galls induced on Quercus by Cynipidae (Cynipini) is ...presented. Quantitative and national data are included with bibliographic references to almost all records published in 2011 and earlier. The catalogue is followed by two checklists, firstly one of the Chalcidoidea with numbers of each species recorded from each type of host gall (galls of the sexual and asexual generations of the host gall wasps are listed separately), and secondly one of inquiline Cynipidae with host galls. Compared to non-oak gall wasps, the Cynipini support a much larger parasitoid and especially inquiline fauna, and this fauna is very largely restricted at the species level to Cynipini galls. About one hundred chalcidoid species are recorded from galls of Cynipini, distributed over six families: Pteromalidae and Eulophidae (29 species each), Torymi-dae (21 species), Eurytomidae (10 species), Eupelmidae (8 species) and Ormyridae (at least 2 species). Polyphagy is usual in the chalcidoid parasitoids, most species having a broad host gall range, but quantitatively the fauna of each type of oak gall is rather characteristic and is strongly influenced by gall morphology, situation on the tree, season of growth and host tree species. These and other extrinsic factors restrict the full exploitation of the chalcidoids' potential host gall range.
The possession of an efficient communication system and an ability to distinguish between young stages are essential attributes that enable eusocial insects to live in complex integrated societies ...1–4. Although ants communicate primarily via chemicals, it is increasingly clear that acoustical signals also convey important information, including status, between adults in many species 5–9. However, all immature stages were believed to be mute 7. We confirm that larvae and recently formed pupae of Myrmica ants are mute, yet once they are sclerotized, the pupae possess a fully functioning stridulatory organ. The sounds generated by worker pupae were similar to those of workers but were emitted as single pulses rather than in the long sequences characteristic of adults; both induced the same range and intensity of benevolent behaviors when played back to unstressed workers. Both white and sclerotized pupae have a higher social status than larvae within Myrmica colonies, but the latter’s status fell significantly after they were made mute. Our results suggest that acoustical signals supplant semiochemicals as a means of identification in sclerotized pupae, perhaps because their hardened integuments block the secretion of brood pheromones or because their developing adult secretions initially differ from overall colony odors 5, 10.
► We present first evidence that mature, brown pupae of Myrmica ants can stridulate ► Pupal calls are similar to those of worker ants but different in structure ► Behavioral experiments show mute brown pupae lose their high status among the brood ► Stridulating rescues their elevated status as part of communication between castes
We examine phylogenetic relationships within the Synergus complex of herbivorous inquiline gallwasps (Hymenoptera; Cynipidae; Synergini) associated with cynipid host galls on oak, a biologically ...diverse group whose genus-level morphological taxonomy has long been considered stable but whose species level taxonomy is problematic. We incorporate data for over 70% of recognised Western Palaearctic species in five morphology-based genera (Ceroptres, Saphonecrus, Synergus, Synophrus, Ufo), comprising sequence for two mitochondrial loci (coxI, cytb) and one nuclear locus (28S D2). In particular, we assess the evidence for monophyly of two long-established, morphology-defined sections within the genus Synergus that differ in a range of biological traits. To aid analyses of ecological interactions within oak cynipid communities, we also consider the utility of cytochrome oxidase I (coxI) DNA barcodes in the oak inquilines. In this assessment, we do not assume that species are delineated at a single threshold value of sequence divergence for a single gene, but examine concordance in the composition of molecular operational Taxonomic units (MOTUs) across a range of sequence divergences in each gene and across genes. We also assess the impact of sampling effort on MOTU stability.
Phylogenetic reconstructions for all three loci support monophyly for Synergus and Synophrus, but reject monophyly for Saphonecrus and for the two sections within Synergus. The suites of traits associated with the two sections of the genus Synergus are thus homoplasious. All three loci also reject monophyly for three Synergus species (S. hayneanus, S. pallipes, S. umbraculus). Sequences for each locus identify robust MOTUs that are largely concordant across loci for a range of cut-off values. Though many MOTU’s correspond to recognised Linnean species, there is significant, multigene disagreement between groupings supported by morphology and sequence data, with both allocation of different morphospecies to the same MOTU and allocation of the same morphospecies to multiple MOTUs, regardless of cut-off value. Our results imply that while DNA barcoding has considerable utility within this group, morphology-based identification needs major revision at both genus and species levels. Further, lifehistory traits currently attributed to single morphospecies probably confound attributes of multiple lineages. Revealing patterns of character state evolution in Synergus requires collection of new host association and life history data explicitly linked to DNA barcode data for the specimens concerned.
Maculinea (= Phengaris) species of butterfly have complex life‐styles in which the larvae feed briefly on specific foodplants before entering the final instar, after which they live as social ...parasites within Myrmica ant colonies and acquire 98–99% of their ultimate biomass by either preying on ant brood (predatory species) or being fed by worker ants (cuckoo species). Cuckoo species demonstrate two growth forms, whereby some individuals develop to pupate in 11 months and others remain 23 months in the nest, a strategy that in theory represents the most efficient exploitation of resources within Myrmica societies. Early studies suggested that development rates in Maculinea rebeli (referred to by other authors as the xerophilous form of Maculinea alcon) were not plastic but represented an unusual fixed polymorphism, in which eggs were genetically predetermined as 1‐ or 2‐year larvae.
We tested this idea in lab experiments using M. rebeli from the French Hautes‐Alpes, with these results: (i) the growth strategy of every individual larva is pre‐determined by the mother either genetically or, less probably, during oogenesis. (ii) Intra‐nest competition and host fitness affects survival and growth but does not influence the inherent growth strategy. (iii) The ratio of 1‐ and 2‐year developing larvae is initially about 50:50, although differential survival in crowded nests may alter the ratio of surviving individuals. (iv) All females tested laid eggs that hatched into both 1‐ or 2‐year developers. (v) Growth patterns vary between different regions. Larvae from the Spanish Pyrenees initially grow less than those from the Alps, with a smaller initial differentiation between the size classes.
The larvae of cuckoo species of Maculinea butterfly have two growth forms when they exploit Myrmica ant nests: some individuals develop to pupate in 11 months, others take 23 months.
Unusually in biology, this trait is not plastic but represents a fixed polymorphism. Individuals females lay a 50:50 mixture of eggs that are genetically predetermined as spiepr132 1‐spiepr132 or spiepr132 2‐spiepr132 year spiepr132 larvae.
Host fitness and competition within nests affect the survival and growth of each morph but do not influence the inherent growth strategy. Precise growth patterns vary between different regions.
Numerous invertebrates inhabit social insect colonies, including the hoverfly genusMicrodon, whose larvae typically live as brood predators.Formica lemaniant colonies apparently endureMicrodon ...mutabilisinfections over several years, despite losing a considerable fraction of young, and may even produce more gynes. We present a model for resource allocation within polygynous ant colonies, which assumes that whether an ant larva switches development into a worker or a gyne depends on the quantity of food received randomly from workers. Accordingly,Microdonpredation promotes gyne development by increasing resource availability for surviving broods. Several model predictions are supported by empirical data. (i) Uninfected colonies seldom produce gynes. (ii) Infected colonies experience a short-lived peak in gyne production leading to a bimodal distribution in gyne production. (iii) Low brood∶worker ratio is the critical mechanism controlling gyne production. (iv) Brood∶worker ratio reduction must be substantial for increased gyne production to become noticeable.
Chemical communication plays a major role in the organisation of ant societies, and is mimicked to near perfection by certain large blue (Maculinea) butterflies that parasitise Myrmica ant colonies. ...The recent discovery of differentiated acoustical communication between different castes of ants, and the fact that this too is mimicked by the butterflies, adds a new component of coevolutionary complexity to a fascinating multitrophic system of endangered species, and it could inspire new ways to engage the public in their conservation.
1. In 2002 Microdon myrmicae, a social parasite of Myrmica ants, was taxonomically separated from Microdon mutabilis. The original study in the U.K. found Microdon myrmicae to be specific to one ant ...species, Myrmica scabrinodis, yet it became apparent that the range of Microdon myrmicae includes at least the western Palaearctic. 2. Current knowledge of the European distributions of both Microdon myrmicae and Microdon mutabilis in Europe is reviewed. Also, in detailed studies of two Polish populations, Microdon myrmicae was found to survive equally well with two Myrmica ant species. We examine, however, the possibility that this reflects the presence of two separate Microdon species, each connected to one species of Myrmica. 3. Forty populations of Microdon myrmicae and 37 populations of Microdon mutabilis are currently known in Europe. All the populations in central and southern Europe that were visited after the separation of the two species were identified as Microdon myrmicae, while Microdon mutabilis' recognised range is now restricted to the British Isles and Scandinavia. Myrmica scabrinodis was found to host Microdon myrmicae in 26 out of 31 populations investigated. Four other Myrmica species were identified to the host Microdon myrmicae: Myrmica gallienii (eight populations), Myrmica rubra (four), Myrmica vandeli (one), and Myrmica sabuleti (one). Microdon myrmicae occurs in waterlogged grassland habitats, mainly of the 'Molinietum' type, resulting in a patchy distribution relative to its host ants. 4. In two populations Myrmica scabrinodis and Myrmica gallienii are both abundant and rear Microdon myrmicae in equal proportions. Microdon myrmicae pupae from Myrmica gallienii nests were heavier and the anterior respiratory organs were of significantly different shape. In contrast, the comparisons of Microdon myrmicae pupae among all other populations showed no significant differences, suggesting only one species throughout the European range.
1. Biological invasions involving continuous range expansion differ from discontinuous introductions in that invaded and native ranges remain connected, potentially allowing pursuit of range ...expanding species by their natural enemies. The establishment in Britain of eight alien herbivorous gall wasps (Hymenoptera: Cynipinae) provides a rare opportunity to study continuous range expansion and natural enemy recruitment in a guild of related and ecologically similar species. 2. Four aliens (Andricus kollari, A. quercuscalicis, A. lignicolus, and A. corruptrix) reached the UK before 1990, while four more recent invaders (A. aries, A. grossulariae, A. lucidus, and Aphelonyx cerricola) reached Britain by 2000. We provide the first parasitoid records for the recent invaders, update community development for the earlier set, and use dates of first record to estimate rates of spread for all eight species. 3. While the recent invaders are restricted to southern and eastern England, three of the early invaders have reached northern Scotland. From their origins in southern England, invading gall wasps have expanded their distributions across the UK at mean rates ranging from 1.4 km/year to >20 km/year. Variation in range expansion rate was not related to life history differences, including voltinism or host oak association. 4. All species have recruited native parasitoid enemies since their arrival, and we found no evidence of pursuit by non‐native natural enemies from continental Europe. Our results suggest that over timescales predicted for rapid climate change, herbivore/parasitoid communities are unlikely to expand their range as sets of interacting species. Rather, we expect host range expansions to trigger local reassembly of communities.
An emerging problem in conservation is whether listed morpho-species with broad distributions, yet specialized lifestyles, consist of more than one cryptic species or functionally distinct forms that ...have different ecological requirements. We describe extreme regional divergence within an iconic endangered butterfly, whose socially parasitic young stages use non-visual, non-tactile cues to infiltrate and supplant the brood in ant societies. Although indistinguishable morphologically or when using current mitochondrial and nuclear sequence-, or microsatellite data, Maculinea rebeli from Spain and southeast Poland exploit different Myrmica ant species and experience 100 per cent mortality with each other's hosts. This reflects major differences in the hydrocarbons synthesized from each region by the larvae, which so closely mimic the recognition profiles of their respective hosts that nurse ants afford each parasite a social status above that of their own kin larvae. The two host ants occupy separate niches within grassland; thus, conservation management must differ in each region. Similar cryptic differentiation may be common, yet equally hard to detect, among the approximately 10 000 unstudied morpho-species of social parasite that are estimated to exist, many of which are Red Data Book listed.
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