The ambrosia symbiosis is specific in some species and promiscuous in others: evidence from community pyrosequencing

Symbioses are increasingly seen as dynamic ecosystems with multiple associates and varying fidelity. Symbiont specificity remains elusive in one of the most ecologically successful and economically damaging eukaryotic symbioses: the ambrosia symbiosis of wood-boring beetles and fungi. We used multiplexed pyrosequencing of amplified internal transcribed spacer II (ITS2) ribosomal DNA (rDNA) libraries to document the communities of fungal associates and symbionts inside the mycangia (fungus transfer organ) of three ambrosia beetle species, Xyleborus affinis, Xyleborus ferrugineus and Xylosandrus crassiusculus. We processed 93 beetle samples from 5 locations across Florida, including reference communities. Fungal communities within mycangia included 14–20 fungus species, many more than reported by culture-based studies. We recovered previously known nutritional symbionts as members of the core community. We also detected several other fungal taxa that are equally frequent but whose function is unknown and many other transient species. The composition of fungal assemblages was significantly correlated with beetle species but not with locality. The type of mycangium appears to determine specificity: two Xyleborus with mandibular mycangia had multiple dominant associates with even abundances; Xylosandrus crassiusculus (mesonotal mycangium) communities were dominated by a single symbiont, Ambrosiella sp. Beetle mycangia also carried many fungi from the environment, including plant pathogens and endophytes. The ITS2 marker proved useful for ecological analyses, but the taxonomic resolution was limited to fungal genus or family, particularly in Ophiostomatales, which are under-represented in our amplicons as well as in public databases. This initial analysis of three beetle species suggests that each clade of ambrosia beetles and each mycangium type may support a functionally and taxonomically distinct symbiosis.     

Characterization of Small,Mononuclear Blood Cells from Salmon Having High Phagocytic Capacity and Ability to Differentiate into Dendritic like Cells

Phagocytes are the principal component of the innate immune system, playing a key role in the clearance of foreign particles that include potential pathogens. In vertebrates, both neutrophils and mononuclear cells like monocytes, macrophages and dendritic cells are all professional phagocytes. In teleosts, B-lymphocytes also have potent phagocytic ability. We have isolated a population of small (<5 µm), mononuclear blood cells from Atlantic salmon (Salmo salar L.) not previously characterized. In order to identify them, we have performed morphological, gene expression, flow cytometry, cytochemical, ultrastructural and functional analyses. Interestingly, they highly express the gene encoding CD83, the most characteristic cell surface marker for dendritic cells in mammals, and MHC class II limited to professional antigen presenting cells. They did not express genes nor did they have cell markers for B-cells, T-cells, monocytes/macrophages or neutrophils as shown by qRT-PCR, flow cytometry and immunoblotting. A remarkable feature of these cells is their potent phagocytic capacity. Their oxygen-independent killing mechanism, as shown by intense acid phosphatase staining, is supported by lack of respiratory burst and myeloperoxidase activity and the acid phosphatase''s sensitivity to tartrate. They show a high level of morphological plasticity, as, upon stimulation with mitogens, they change morphology and obtain branching protrusions similarly to dendritic cells. We suggest, based on our findings, that the small, round cells described here are progenitor cells with potential to differentiate into dendritic like cells, although we can not exclude the possibility that they represent a novel cell type.     

Resource use of insect seed predators during general flowering and seeding events in a Bornean dipterocarp rain forest

Insect seed predators of 24 dipterocarp species (including the genera ot Dipterocarpus, Dryobalanops and Shorea) and five species belonging to the Moraceae, Myrtaceae, Celastraceae and Sapotaceae were investigated. In a tropical lowland dipterocarp forest in Sarawak, Malaysia, these trees produces seeds irregularly by intensely during general flowering and seeding events in 1996 and/or 1998. Dipterocarp seeds were preyed on by 51 insect species (11 families), which were roughly classified into three taxonomic groups: smaller moths (Trotricidae, Pyralidae, Crambidae, Immidae, Sesiidae, and Cosmopterigidae), scolytids (Scolydae) and weevils (Curdulionidae, Apionidae, Anthribidae, and Attelabidae). Although the host-specificity of invertebrate seed predators has been assumed to be high in tropical forests, it was found that the diet ranges of some insect predators were relatively wide and overlapped one another. Most seed predators that were collected in both study years changes their diets between general flowering and seeding events. The results of cluster analyses based on the number of adult of each predator species that emerged from 100 seeds of each tree species, suggested that the dominant species was not consistent, alternating between the two years.     

The origin and radiation of Macaronesian beetles breeding in Euphorbia: the relative importance of multiple data partitions and population sampling

Species-level phylogenies derived from many independent character sources and wide geographical sampling provide a powerful tool in assessing the importance of various factors associated with cladogenesis. In this study, we explore the relative importance of insular isolation and host plant switching in the diversification of a group of bark beetles (Curculionidae: Scolytinae) feeding and breeding in woody Euphor biaspurges. All species in the genus Aphanarthrumare each associated with only one species group of Euphorbia(succulents or one of three different arborescent groups), and the majority of species are endemic to one or several of the Macaronesian Islands. Hence, putative mechanisms of speciation could be assessed by identifying pairs of sister species in a phylogenetic analysis. We used DNA sequences from two nuclear and two mitochondrial genes, and morphological characters, to reconstruct the genealogical relationships among 92 individuals of 25 species and subspecies of Aphanarthrumand related genera. A stable tree topology was highly dependent on multiple character sources, but much less so on wide population sampling. However, multiple samples per species demonstrated one case of species paraphyly, as well as deep coalescence among three putative subspecies pairs. The phylogenetic analyses consistently placed the arborescent breeding and West African--Lanzarote-distributed species A. armatumin the most basal position in Aphanarthrum, rendering this genus paraphyletic with respect to Coleobothrus. Two major radiations followed, one predominantly African lineage of succulent feeding species, and one island radiation associated with arborescent host plants. Sister comparisons showed that most recent divergences occurred in allopatry on closely related hosts, with subsequent expansions obscuring more ancient events. Only 6 out of 24 cladogenetic events were associated with host switching, rendering geographical factors more important in recent diversification.     

Tracing the origin of a cryptic invader: phylogeography of the Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) species complex

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Cryptic genetic variation in an inbreeding and cosmopolitan pest,Xylosandrus crassiusculus,revealed using ddRADseq

Each year new exotic species are transported across the world through global commerce, causing considerable economic and ecological damage. An important component of managing invasion pathways is to identify source populations. Some of the most widespread exotic species are haplodiploid ambrosia beetles. The ability to mate with siblings (inbreed) and their transportable food source (symbiotic fungus) have enabled them to colonize most of the world and become pests of plant nurseries, lumber, and forests. One of the fastest spreading ambrosia beetles is Xylosandrus crassiusculus. In order to discover the source populations of this globally invasive species, track its movement around the world, and test biogeographical scenarios, we combined restriction site‐associated DNA sequencing (RADseq) with comprehensive sampling across the species native and introduced range. From 1,365 genotyped SNP loci across 198 individuals, we determined that in its native range, X. crassiusculus is comprised of a population in Southeast Asia that includes mainland China, Thailand, and Taiwan, and a second island population in Japan. North America and Central America were colonized from the island populations, while Africa and Oceania were colonized from the mainland Asia, and Hawaii was colonized by both populations. Populations of X. crassiusculus in North America were genetically diverse and highly structured, suggesting (1) numerous, repeated introductions; (2) introduction of a large founding population; or (3) both scenarios with higher than expected outcrossing. X. crassiusculus, other wood‐boring insects, and indeed many other pests with unusual genetic structure continue to spread around the world. We show that contemporary genetic methods offer a powerful tool for understanding and preventing pathways of future biosecurity threats.     

Phylogeny of haplo–diploid,fungus‐growing ambrosia beetles (Curculionidae: Scolytinae: Xyleborini) inferred from molecular and morphological data

Cognato, A. I., Hulcr, J., Dole, S. A. & Jordal, B. H. (2010). Phylogeny of haplo‐diploid, fungus‐growing ambrosia beetles (Curculionidae: Scolytinae: Xyleborini) inferred from molecular and morphological data. —Zoologica Scripta, 40, 174–186. The ambrosia beetle tribe Xyleborini currently contains 30 genera and approximately 1200 species which are distributed throughout worldwide forests with most diversity located in the tropics. They also represent the most invasive scolytines in North America. Despite economic concerns and biological curiosity with this group, a comprehensive understanding of generic boundaries and the evolutionary relationship among species is lacking. In this study, we include 155 xyleborine species representing 23 genera in parsimony and Bayesian analyses using 3925 nucleotides from mitochondrial (COI) and nuclear genomes (28S, ArgK, CAD, EF‐1α) and 39 morphological characters. The phylogenies resulting from the parsimony analyses, which treated gap positions either as missing or fifth character states, and the Bayesian analysis were generally similar. Clades with high support or posterior probabilities were found in all trees, while those with low support were not recovered by all analyses. Fourteen of the 23 genera were monophyletic although not all relationships among the genera were resolved. We show monophyly of several species groups associated with particular morphological and biological characters and suggest recognition of these groups as genera. Most interesting was the monophyly of South and Central American species representing several genera. This finding suggests recent and fast radiation of xyleborines in the New World accompanied by morphological and biological diversification.     

Origin and evolution of fungus farming in wood-boring Coleoptera – a palaeontological perspective

Insect–fungus mutualism is one of the better-studied symbiotic interactions in nature. Ambrosia fungi are an ecological assemblage of unrelated fungi that are cultivated by ambrosia beetles in their galleries as obligate food for larvae. Despite recently increased research interest, it remains unclear which ecological factors facilitated the origin of fungus farming, and how it transformed into a symbiotic relationship with obligate dependency. It is clear from phylogenetic analyses that this symbiosis evolved independently many times in several beetle and fungus lineages. However, there is a mismatch between palaeontological and phylogenetic data. Herein we review, for the first time, the ambrosia system from a palaeontological perspective. Although largely ignored, families such as Lymexylidae and Bostrichidae should be included in the list of ambrosia beetles because some of their species cultivate ambrosia fungi. The estimated origin for some groups of ambrosia fungi during the Cretaceous concurs with a known high diversity of Lymexylidae and Bostrichidae at that time. Although potentially older, the greatest radiation of various ambrosia beetle lineages occurred in the weevil subfamilies Scolytinae and Platypodinae during the Eocene. In this review we explore the evolutionary relationship between ambrosia beetles, fungi and their host trees, which is likely to have persisted for longer than previously supposed.     

Red cell 2,3-DPG, ATP, and mean cell volume in highly trained athletes. Effect of long-term submaximal exercise

20 male elite long distance runners were compared to a control group of blood donors to determine the effect of training on red blood cells. The acute effects of exercise on red cells were investigated in 11 of the runners following a race of 15-30 km. The runners had elevated resting values of red cell 2,3-DPG (P less than 0.05) and mean cell volume (P less than 0.01); blood Hb and ATP were not different from concentrations in the control group. The red cell status of the athletes may be explained by an increased proportion of young erythrocytes in runners. No statistically significant changes in red cell 2,3-DPG, ATP, mean cell volume or blood Hb were found post exercise.