The phylogeny of a mutualism: evolution and coadaptation between Trollius and its seed-parasitic pollinators

Interactions between seed-parasitic pollinators and their hosts provide useful model systems for the analysis of evolution of mutualism and potential coevolution between plants and insects. Here I present the systematics, pollination ecology and evolution of one of these interactions. I have documented and analysed the phylogenetic and geographic associations between Trollius (Ranunculaceae: 18 spp.) and Chiastocheta (Diptera: Anthomyiidae; 17 spp.), a host-specific genus of seed-parasitic flies that pollinate their host plants to varying extent. Their interactions are usually facultative mutualisms, but in the specialized T. europaeus three fly species are obligate mutualists and a fourth species is an antagonist. The distribution patterns of fly species among Trollius species suggest that the flies evolved in associations with five highly derived Trollius species, and secondarily colonized four more primitive taxa in the parts of their ranges that overlapped with primary hosts. In general, host specificity is maintained primarily through allopatry, with colonization occurring in regions of overlap between parapatric taxa. Fly speciation has occurred in allopatry, both within and among host taxa. Cospeciation is not evident, but convergent evolution in Trollius flowers of several traits, viz. orange sepals, elongated staminodia and increased carpel number per flower, may be the result of mutualism with Chiastocheta.     

Ecological and historical drivers of diversification in the fly genus Chiastocheta Pokorny

Coevolution is among the main forces shaping the biodiversity on Earth. In Eurasia, one of the best-known plant-insect interactions showing highly coevolved features involves the fly genus Chiastocheta and its host-plant Trollius. Although this system has been widely studied from an ecological point of view, the phylogenetic relationships and biogeographic history of the flies have remained little investigated. In this integrative study, we aim to test the monophyly of the five Chiastocheta eco-morphological groups, defined by Pellmyr in 1992, by inferring a mitochondrial phylogeny. We further apply a new approach to assess the effect of (i) different molecular substitution rates and (ii) phylogenetic uncertainty on the inference of the spatio-temporal evolution of the group. From a taxonomic point of view, we demonstrate that only two of Pellmyr's groups (rotundiventris and dentifera) are phylogenetically supported, the other species appearing para- or polyphyletic. We also identify the position of C. lophota, which was not included in previous surveys. From a spatio-temporal perspective, we show that the genus arose during the Pliocene in Europe. Our results also indicate that at least four large-scale dispersal events are required to explain the current distribution of Chiastocheta. Moreover, each dispersal to or from Asia is associated with a host-shift and seems to correspond to an increase in speciation rates. Finally, we highlight the correlation between diversification and climatic fluctuations, which indicate that the cycles of global cooling over the last million years had an influence on the radiation of the group.     

ECOLOGICAL DIVERSIFICATION AND COMMUNITY STRUCTURE IN THE OLD WORLD LEAF WARBLERS (GENUS PHYLLOSCOPUS): A PHYLOGENETIC PERSPECTIVE

I investigated the historical basis for variation in regional species diversity. I used a molecular phylogenetic analysis within a single genus of birds (the Old World leaf warblers, genus Phylloscopus) in conjunction with ecological studies in Europe, the Himalayas, and Japan to evaluate the importance of historical events in shaping the present constellation of morphology and behavior in the three different regions. The relatively depauperate assemblages have different histories. In Japan, there was invasion of several lineages, which have more closely related species elsewhere in Asia, whereas in Europe there was also limited in situ speciation. Much of the structure of peripheral communities is attributable to invasions from species-rich Asia, with little in situ morphological diversification. Within the Phylloscopus there are several phylogenetic clades with nonoverlapping size distributions. Major ecological and morphological shifts occurred early in the history of diversification within the group, and rarely since.     

Comparative phylogeography of mutualists and the effect of the host on the genetic structure of its partners

Whether or not species participating in specialized and obligate interactions display similar and simultaneous demographic variations at the intraspecific level remains an open question in phylogeography. In the present study, we used the mutualistic nursery pollination occurring between the European globeflower Trollius europaeus and its specialized pollinators in the genus Chiastocheta as a case study. Explicitly, we investigated if the phylogeographies of the pollinating flies are significantly different from the expectation under a scenario of plant–insect congruence. Based on a large‐scale sampling, we first used mitochondrial data to infer the phylogeographical histories of each fly species. Then, we defined phylogeographical scenarios of congruence with the plant history, and used maximum likelihood and Bayesian approaches to test for plant–insect phylogeographical congruence for the three Chiastocheta species. We show that the phylogeographical histories of the three fly species differ. Only Chiastocheta lophota and Chiastocheta dentifera display strong spatial genetic structures, which do not appear to be statistically different from those expected under scenarios of phylogeographical congruence with the plant. The results of the present study indicate that the fly species responded in independent and different ways to shared evolutionary forces, displaying varying levels of congruence with the plant genetic structure. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 1021–1035.     

Using AFLP to resolve phylogenetic relationships in a morphologically diversified plant species complex when nuclear and chloroplast sequences fail to reveal variability

Inferring phylogenetic relationships among closely related plant species is often difficult due to the lack of molecular markers exhibiting enough nucleotide variability at this taxonomic level. Moreover, gene tree does not necessary represent the true species tree because of random sorting of polymorphic alleles in different lineages. A solution to these problems is to use many amplified fragment length polymorphisms (AFLP) distributed throughout the whole genome, to infer cladistic and phenetic among-species relationships. Phylogenetic relationships among interfertile species of Trollius L. (Ranunculaceae) were investigated using nuclear DNA (ITS1+5.8S rRNA+ITS2) and chloroplast DNA (trnL intron and trnL-trnF intergene spacer) sequences, and AFLP markers. ITS sequences were not informative at the intrageneric level, but confirmed the sister relationship between Trollius and Adonis genera, and provided new information on the phylogenetic relationships among five Ranunculaceae genera. Chloroplast DNA was more informative among Trollius species, but not consistent with the sections previously described. AFLP proved to be a powerful tool to resolve the complex genetic relationships between the morphological entities constituting the genus Trollius. Although as much as 76.1% of the total AFLP variability was found within a priori defined morphological groups, the remaining 23.9% variability differentiating groups was sufficient to generate congruent and robust cladistic and phenetic trees. Several morphological traits, independent from those used to define groups, were mapped onto the molecular phylogeny, and their evolution discussed in relation to the absence/presence of pollinator-seed parasite Chiastocheta flies.     

多倍化——白刺属的系统分类、进化特征及应用前景

在回顾白刺属研究历史的基础上,根据白刺属种间染色体倍数特征并结合形态学、生物地理学等方面的研究文献,提出新的白刺属种间分类系统：二倍体组(2n= 2X=24) 和四倍体组 (2n=4X=48)。多倍化(2X→4X)是白刺属内种间进化的基本特征。白刺属的起源中心可能是古地中海沿岸地区;中亚及我国西北地区是白刺属的现代分布中心。并指出将该属作为模式系统开展荒漠植物分子生态学研究的前景。     

Extended phylogeny of Aquilegia: the biogeographical and ecological patterns of two simultaneous but contrasting radiations

Studies of the North American columbines (Aquilegia, Ranunculaceae) have supported the view that adaptive radiations in animal-pollinated plants proceed through pollinator specialisation and floral differentiation. However, although the diversity of pollinators and floral morphology is much lower in Europe and Asia than in North America, the number of columbine species is similar in the three continents. This supports the hypothesis that habitat and pollinator specialisation have contributed differently to the radiation of columbines in different continents. To establish the basic background to test this hypothesis, we expanded the molecular phylogeny of the genus to include a representative set of species from each continent. Our results suggest that the diversity of the genus is the result of two independent events of radiation, one involving Asiatic and North American species and the other involving Asiatic and European species. The ancestors of both lineages probably occupied the mountains of south-central Siberia. North American and European columbines are monophyletic within their respective lineages. The genus originated between 6.18 and 6.57 million years (Myr) ago, with the main pulses of diversification starting around 3 Myr ago both in Europe (1.25–3.96 Myr ago) and North America (1.42–5.01 Myr ago). The type of habitat occupied shifted more often in the Euroasiatic lineage, while pollination vectors shifted more often in the Asiatic-North American lineage. Moreover, while allopatric speciation predominated in the European lineage, sympatric speciation acted in the North American one. In conclusion, the radiation of columbines in Europe and North America involved similar rates of diversification and took place simultaneously and independently. However, the ecological drivers of radiation were different: geographic isolation and shifts in habitat use were more important in Europe while reproductive isolation linked to shifts in pollinator specialisation additionally acted in North America.     

A phylogenetic analysis of Doronicum (Asteraceae, Senecioneae) based on morphological, nuclear ribosomal (ITS), and chloroplast (trnL-F) evidence.

A phylogenetic analysis of the Old World genus Doronicum (26 species, 4 subspecies) based on sequence data of the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA, the chloroplast spacer trnL-F, and morphology is presented. Congruence among the three data sets was explored by the computing of several indices, all of which suggest homogeneity between only the two molecular matrices. We argue that the morphological data set contains poor phylogenetic signal and advocate simultaneous analysis of the three data sets (total evidence approach) so that morphological characters are tested for homology by congruence with molecular data. The resulting phylogenetic hypothesis allows several well-supported conclusions including the placement of a Corsican endemic (D. corsicum), sister to the remainder of the genus, and the inference that an early southern European or Mediterranean diversification took place in the genus. Shifts in morphological characters (e.g., homocarpy to heterocarpy) are confirmed to have evolved several times. Results from comparative studies of sequence data of the chloroplast gene ndhF support inclusion of Doronicum in tribe Senecioneae.     

Molecular phylogeny and historical biogeography of the genus Tuber, the 'true truffles'

Aim Various data sets and methods of analysis were combined to produce the first comprehensive molecular phylogeny of the genus Tuber and to analyse its biogeography. Location Europe, North Africa, China, Asia, North America. Methods Phylogenetic relationships among Tuber species were reconstructed based on a data set of internal‐transcribed spacer (ITS) sequences and various phylogenetic inference methods, specifically maximum parsimony, Bayesian analysis and neighbour joining. Tajima’s relative rate test showed that Tuber 18S rRNA, 5.8S rRNA, 5.8S‐ITS2 rRNA and β‐tubulin sequences evolved in a clock‐like manner. These genes, combined or not, were employed for molecular clock estimates after construction of linearized trees using mega 3.1. We reconstructed ancestral areas in the Northern Hemisphere by means of a dispersal–vicariance analysis (diva 1.1) based on current distribution patterns of the genus Tuber determined from the literature. Results The resulting molecular phylogeny divided the genus Tuber into five distinct clades, in agreement with our previously published studies. The Puberulum, Melanosporum and Rufum groups were diversified in terms of species and geographical distribution. In contrast, the Aestivum and Excavatum groups were less diversified and were located only in Europe or North Africa. Using a global molecular clock analysis, we estimated the divergence times for the origin of the genus and for the origin of several groups. diva inferred nine dispersal events and suggested that the ancestor of Tuber was originally present in Europe or was widespread in Eurasia. Equally optimal distributions were obtained for several nodes, suggesting different possible biogeographical patterns. Main conclusions Our analyses identified several discrepancies with the classical taxonomy of the genus, and we propose a new phylogenetic classification. According to molecular clocks, the radiation of the genus Tuber could have started between 271 and 140 Ma. Used in combination with the results obtained from time divergence estimates, this allows us to propose two equally probable scenarios of intra‐ and inter‐continental diversification of the genus according to the geographic distribution of the most recent common ancestor in Europe or Eurasia. The biogeographical patterns imply intra‐continental dispersal events between Europe and Asia and inter‐continental dispersal events between North America and Europe or Asia, which are compatible with land connections during the Tertiary.     

Geographic pattern of genetic variation in the European globeflower Trollius europaeus L. (Ranunculaceae) inferred from amplified fragment length polymorphism markers

The distribution of genetic variation and the phylogenetic relationships between 18 populations of the arctic-alpine plant Trollius europaeus were analysed in three main regions (Alps, Pyrenees and Fennoscandia) by using dominant AFLP markers. Analysis of molecular variance revealed that most of the genetic variability was found within populations (64%), although variation among regions (17%) and among populations within regions (19%) was highly significant (P < 0.001). Accordingly, the global fixation index FST averaged over loci was high (0.39). The among-population differentiation indicates restricted gene flow, congruent with limited dispersal of specific globeflower's pollinating flies (Chiastocheta spp.). Within-population diversity levels were significantly higher in the Alps (mean Nei's expected heterozygosity HE = 0.229) than in the Pyrenees (HE= 0.197) or in Fennoscandia (HE = 0.158). This finding is congruent with the species-richness of the associated flies, which is maximum in the Alps. We discuss the processes involved in shaping observed patterns of genetic diversity within and among T. europaeus populations. Genetic drift is the major factor acting on the small Pyrenean populations at the southern edge of T. europaeus distribution, while large Fennoscandian populations result probably from a founder effect followed by demographic expansion. The Alpine populations represent moderately fragmented relics of large southern ancestral populations. The patterns of genetic variability observed in the host plant support the hypothesis of sympatric speciation in associated flies, rather than recurrent allopatric speciations.     

Evolution of mutualism between globeflowers and their pollinating flies

Plant/seed-eater pollinators mutualisms involve a plant pollinated by an insect whose larvae develop by eating a fraction of host-plant seeds. The outcome of the interaction therefore depends on the number of ovules fertilized by adult visits and the number of seeds destroyed by larvae. Among the very few cases of such mutualisms reported so far is the globeflower-globeflower flies mutualism, which is unique in that it involves several congeneric fly species (Chiastocheta genus) coexisting within a single host-plant species, Trollius europaeus. These species exhibit contrasted oviposition behaviors resulting in a more or less beneficial outcome for the plant. We designed an adaptive dynamics model to investigate how morphological traits of globeflower could affect the evolution of oviposition in its pollinating flies. Three fly traits (flower age at oviposition, clutch size and the level of avoidance of already parasitized flowers) and one plant trait (closed or open corolla) were examined. Whatever the shape of the flower, evolutionary branching occurs between early and late ovipositing flies, driven by strong competition among larvae within a fruit. Once this branching occurred, the closed shape of the corolla is likely to offer a better protection to eggs of early but not of late ovipositing flies. The difference in egg survival results in higher competition among early larvae and thus selects for decreased clutch size in early flies. This can be seen as a first step in the evolution of a mutualistic behavior. The prediction of our model fits field observations of fly behavior, giving theoretical support to the hypothesis of fly sympatric speciation within its host plant. Moreover, flower closed globe shape can be positively selected in globeflowers as it results in a reduction of parasitism strength. This last evolution therefore leads to a stable mutualism between globeflowers and globeflower flies.     

Molecular phylogeny and historical biogeography of the Holarctic wetland leaf beetle of the genus Plateumaris

Leaf beetles of the genus Plateumaris inhabit wetlands across the temperate zone of the Holarctic region. To explore the phylogeographic relationships among North American, East Asian, and European members of this genus and the origin of the species endemic to Japan, we studied the molecular phylogeny of 20 of the 27 species in this genus using partial sequences of mitochondrial cytochrome oxidase subunit I (COI) and the 16S and nuclear 28S rRNA genes. The molecular phylogeny revealed that three species endemic to Europe are monophyletic and sister to the remaining 11 North American and six Asian species. Within the latter clade, North American and Asian species did not show reciprocal monophyly. Dispersal-vicariance analysis and divergence time estimation revealed that the European and North America-Asian lineages diverged during the Eocene. Moreover, subsequent differentiation occurred repeatedly between North American and Asian species, which was facilitated by three dispersal events from North America to Asia and one in the opposite direction during the late Eocene through the late Miocene. Two Japanese endemics originated from different divergence events; one differentiated from the mainland lineage after differentiation from the North American lineage, whereas the other showed a deep coalescence from the North American lineage with no present-day sister species on the East Asian mainland. This study of extant insects provides molecular phylogenetic evidence for ancient vicariance between Europe and East Asia-North America, and for more recent (but pre-Pleistocene) faunal exchanges between East Asia and North America.     

Host‐associated genetic differentiation in a seed parasitic weevil Rhinusa antirrhini (Coleptera: Curculionidae) revealed by mitochondrial and nuclear sequence data

Plant feeding insects and the plants they feed upon represent an ecological association that is thought to be a key factor for the diversification of many plant feeding insects, through differential adaptation to different plant selective pressures. While a number of studies have investigated diversification of plant feeding insects above the species level, relatively less attention has been given to patterns of diversification within species, particularly those that also require plants for oviposition and subsequent larval development. In the case of plant feeding insects that also require plant tissues for the completion of their reproductive cycle through larval development, the divergent selective pressure not only acts on adults, but on the full life history of the insect. Here we focus attention on Rhinusa antirrhini (Curculionidae), a species of weevil broadly distributed across Europe that both feeds on, and oviposits and develops within, species of the plant genus Linaria (Plantaginaceae). Using a combination of mtDNA (COII) and nuclear DNA (EF1‐α) sequencing and copulation experiments we assess evidence for host associated genetic differentiation within R. antirrhini. We find substantial genetic variation within this species that is best explained by ecological specialisation on different host plant taxa. This genetic differentiation is most pronounced in the mtDNA marker, with patterns of genetic variation at the nuclear marker suggesting incomplete lineage sorting and/or gene flow between different host plant forms of R. antirrhini, whose origin is estimated to date to the mid‐Pliocene (3.77 Mya; 2.91–4.80 Mya).     

Evolution of oviposition strategies and speciation in the globeflower flies Chiastocheta spp. (Anthomyiidae)

Trollius europaeus (Ranunculaceae) is involved in an intimate interaction with several species of Chiastocheta flies (Anthomyiidae) that are both seed predators and pollinators. In this paper, we analyse the oviposition strategy of the six Chiastocheta species found to coexist on T. europaeus in 19 populations from the French Alps. We show that the species are not equivalent in their oviposition behaviour: C. rotundiventris usually deposits no more than one egg per flower in first-day flowers whereas C. dentifera aggregates its eggs on fruits and thus does not contribute to pollination at all; the four remaining species deposit eggs sequentially during the flowering period from the 2nd to the 7th day. Hence, the outcomes of the interaction in terms of net seed production for the plant greatly depend on the Chiastocheta species visiting it, ranging from a mutualistic to a purely parasitic interaction. We assessed mitochondrial divergence between Chiastocheta spp. by sequencing a 1320-bp mitochondrial DNA fragment. The low divergence observed between species (0–4.15%) suggests that genus diversification took place recently. Unlike in other plant–insect systems where diversification is usually thought to be driven by cospeciation or host shifts, we propose that Chiastocheta speciation took place within the host plant. Basal separation of a particularly mutualistic species provided favourable conditions for plant specialization on this seed-parasite as a pollinator early in the evolution of the association. The parasitic species ovipositing on fruits derived from a species ovipositing on flowers. Diversification of the intermediate strategies probably occurred in relation with the Pleistocene climatic events, reproductive isolation between species being reinforced by niche partitioning for oviposition and/or sexual selection.     

Monophyletic clades of Macaranga‐pollinating thrips show high specificity to taxonomic sections of host plants

Thrips (Thysanoptera) have been recorded as pollinators of various plant species, but they are mostly regarded to be of low ecological relevance. In Southeast Asia, thrips were recently discovered to pollinate flowers of several taxonomic sections of the pioneer tree genus Macaranga (Euphorbiaceae), which is particularly well known as an ant‐plant, and for its importance in early forest succession. The lack of taxonomic treatment and of knowledge about systematic relationships among extant thrips, however, has prevented firm conclusions on the specificity of this plant–pollinator interaction. Here, results from sequencing of the mitochondrial cytochrome oxidase subunit support our previous morphospecies concept of Macaranga flower thrips, and confirm the genetic identity of five recently described species. They were remarkably all assigned to the genus Dolichothrips (Phlaeothripidae), which typically consists of phytophagous species. In addition, the molecular data revealed one cryptic species. A first phylogenetic tree of the Dolichothrips associated with Macaranga provides insights into their systematic position. In particular, we identify monophyly of all important Macaranga pollinator species, all species being largely specific to particular taxonomic host plant sections. Our results suggest a closely matched diversification of pollinating thrips with Macaranga trees. This adds a novel type of association to thrips pollinator–plant interactions, which have been so far documented as single‐species interactions or generalist thrips species visiting multiple plant taxa.     

Origin and evolution of African Polystoma (Monogenea: Polystomatidae) assessed by molecular methods

Among Polystomatidae (Monogenea), the genus Polystoma, which mainly infests neobatrachian hosts, is the most diverse and occurs principally in Africa, from where half the species have been reported. Previous molecular phylogenetic studies have shown that this genus originated in South America, and later colonised Eurasia and Africa. No mention was made on dispersal corridors between Europe and Africa or of the origin of the African Polystoma radiation. Therefore, a molecular phylogeny was inferred from ITS1 sequences of 21 taxa comprising two species from America, seven representatives from Europe and 12 from Africa. The topology of the phylogenetic tree reveals that a single event of colonisation took place from Europe to Africa and that the putative host carrying along the ancestral polystome is to be found among ancestral pelobatids. Percentage divergences estimates suggest that some presumably distinct vesicular species in unrelated South African anurans and some neotenic forms found in several distinct hosts in Ivory Coast, could, in fact, belong to two single polystome species parasitising divergent hosts. Two main factors are identified that may explain the diversity of African polystomes: (i), we propose that following some degree of generalism, at least during the juvenile stages of both hosts and parasites, distinctive larval behaviour of polystomes engenders isolation between parasite populations that precludes sympatric speciations; (ii), cospeciation events between Ptychadena hosts and their parasites are another factor of diversification of Polystoma on the African continent. Finally, we discuss the systematic status of the Madagascan parasite Metapolystoma, as well as the colonisation of Madagascar by the host Ptychadena mascareniensis.     

Distribution pattern and radiation of the European subterranean genus Verhoeffiella (Collembola,Entomobryidae)

One of the most striking features of obligate subterranean species is their narrow distribution ranges. These prevail not only at specific, but often also at generic level. However, some subterranean genera have continental scale and disjunct distribution, which challenges their monophyly and questions the scenarios of their origin and colonization. In our study, we investigated the subterranean collembolan genus Verhoeffiella, currently known from five remote karst regions of Europe. Four nuclear and one mitochondrial genes were assembled to reveal the evolutionary history of the genus. We tested the monophyly of the genus, explored its relationship with putative surface relatives, and its temporal patterns of molecular diversification. The phylogeny revealed a complex relationship of Verhoeffiella with surface species Heteromurus nitidus and partially disentangled the biogeographical question of its disjunct distribution. Further on, several lineages of Verhoeffiella were recognized in the Dinarides, showing highly underestimated diversity and, compared with the number of described species, a sevenfold increase in the number of MOTUs. The radiation is relatively recent, with the events triggering the diversification linked to the Messinian salinity crisis and Pleistocene climatic shifts. The combination of this extensive subterranean radiation and close evolutionary links with epigean relatives makes Verhoeffiella an exceptional case within the subterranean fauna of temperate areas, which significantly contributes to our understanding of subterranean colonization and diversification patterns.     

Phylogenetic relationships, biogeography and speciation in the avian genus Saxicola

The avian genus Saxicola is distributed throughout Africa, Asia, Europe and various islands across Oceania. Despite the fact that the group has great potential as a model to test evolutionary hypotheses due to the extensive variability in life history patterns recorded between and within species, the phylogenetic relationships among species and subspecies of this genus are poorly understood. We undertook a systematic investigation of the relationships within this genus with three main objectives in mind, (1) to test the monophyly of the genus; (2) to ascertain geographical origin and dispersal sequence; and (3) to test for monophyly within the most morphologically diverse species, S. torquata and S. caprata. We studied sequence data from the mitochondrial cytochrome b gene from 11 of the 12 recognized species and 15 of the 45 described subspecies. Four clades, two exclusively Asian, one Eurasian, and the fourth encompassing Eurasia and Africa, were identified. Based on our analyses, monophyly of the genus Saxicola is not supported and an Asian origin for the genus can be inferred. Results from DIVA analyses, tree topology and nodal age estimates suggest independent colonisation events from Asia to Africa and from Asia to the Western Palearctic, with the Sahara desert acting as a natural barrier for S. torquata. Subspecies and populations of S. torquata are not monophyletic due to S. tectes, S. dacotiae and S. leucura grouping within this complex. Subspecies and populations of S. caprata are monophyletic. Importantly, within S. torquata and S. caprata, slight morphological traits and plumage colour pattern differences used to recognize subspecies are indicative of the greater cryptic diversification that has occurred within this genus.     

Taxonomic review and phylogenetic analysis of central European Eresus species (Araneae: Eresidae)

Ladybird spiders ( Eresus spp.) have attracted scientific interest since the 18th century, but taxonomical knowledge of the genus is unsatisfactory. Early classification based on colour and size variation divided European Eresus into numerous species. These were later lumped into one predominant morphospecies, Eresus niger / E. cinnaberinus , which could be found from Portugal to Central Asia. Here, we perform a major revision of Eresus from northern and central Europe using morphological, phenological, habitat, distribution and molecular data. Three species, E. kollari , E. sandaliatus and E. moravicus sp. n. were distinguished. The name E. niger (originally Aranea nigra ) cannot be used as the name A. nigra was used for a previous spider species. The name E. cinnaberinus is considered a nomen dubium . The three species differ in size, colour pattern, shape of prosoma and copulatory organs, phenology, and have slightly different habitat requirements. No morphologically intermediate forms were recorded. In contrast to distinct morphology and phenology, the genus is genetically complex. Genetically, the mitochondrial haplotypes of E. sandaliatus and E. moravicus sp. n. are monophyletic, whereas those of E. kollari are paraphyletic. Eastern central European E. kollari is likely a hybrid lineage between E. sandaliatus and the monophyletic western central European E. kollari . Because eastern and western European E. kollari are morphologically and phenologically indistinguishable, we did not formally split them. However, detailed population-based research in the future may partition E. kollari into additional species.     

Local‐ to continental‐scale variation in the richness and composition of an aquatic food web

Aim We investigated patterns of species richness and composition of the aquatic food web found in the liquid‐filled leaves of the North American purple pitcher plant, Sarracenia purpurea (Sarraceniaceae), from local to continental scales. Location We sampled 20 pitcher‐plant communities at each of 39 sites spanning the geographic range of S. purpurea– from northern Florida to Newfoundland and westward to eastern British Columbia. Methods Environmental predictors of variation in species composition and species richness were measured at two different spatial scales: among pitchers within sites and among sites. Hierarchical Bayesian models were used to examine correlates and similarities of species richness and abundance within and among sites. Results Ninety‐two taxa of arthropods, protozoa and bacteria were identified in the 780 pitcher samples. The variation in the species composition of this multi‐trophic level community across the broad geographic range of the host plant was lower than the variation among pitchers within host‐plant populations. Variation among food webs in richness and composition was related to climate, pore‐water chemistry, pitcher‐plant morphology and leaf age. Variation in the abundance of the five most common invertebrates was also strongly related to pitcher morphology and site‐specific climatic and other environmental variables. Main conclusions The surprising result that these communities are more variable within their host‐plant populations than across North America suggests that the food web in S. purpurea leaves consists of two groups of species: (1) a core group of mostly obligate pitcher‐plant residents that have evolved strong requirements for the host plant and that co‐occur consistently across North America, and (2) a larger set of relatively uncommon, generalist taxa that co‐occur patchily.