Root endophytes are common and genetically highly diverse suggesting important ecological roles. Yet, relative to above-ground endophytes, little is known about them. Dark septate endophytic fungi of the Phialocephala fortinii s.l.-Acephala applanata species complex (PAC) are ubiquitous root colonizers of conifers and Ericaceae, but their ecological function is largely unknown. Responses of Norway spruce seedlings of two seed provenances to inoculations with isolates of four PAC species were studied in vitro. In addition, isolates of Phialocephala subalpina from two populations within and one outside the natural range of Norway spruce were also included to study the effect of the geographic origin of P. subalpina on host response. The interaction of PAC with Norway spruce ranged from neutral to highly virulent and was primarily isolate-dependent. Variation in virulence was much higher within than among species, nonetheless only isolates of P. subalpina were highly virulent. Disease caused by P. subalpina genotypes from the native range of Norway spruce was more severe than that induced by genotypes from outside the natural distribution of Norway spruce. Virulence was not correlated with the phylogenetic relatedness of the isolates but was positively correlated with the extent of fungal colonization as measured by quantitative real-time PCR.

We asked whether pre-(e.g., assortative mating, temporal isolation) or postzygotic (e.g., hybrid inviability, infertility) barriers are more likely to affect the hybridization between Daphnia galeata and Daphnia hyalina. We compared the taxonomic composition of different reproductive stages in the life cycle of D. galeata, D. hyalina, and their hybrids in Greifensee (Switzerland) by using molecular genetic methods. We found evidence for reproductive isolation between taxa and that hybrids in particular, have reduced sexual fitness. The results provide one potential mechanism for parental taxa to remain distinct. F 1 hybrid dominance in Greifensee could be explained by an increased asexual reproduction of hybrids that results in a higher proportion of gravid females compared with the parental D. galeata. The low sexual fitness of hybrids limits the abilities of hybrids to take advantage of diapausing eggs. The lower dispersal ability, including colonization of new habitats, and survival probability during harsh environmental conditions, could, therefore, lead to underestimates of historical hybrid occurrence by using diapausing egg bank reconstructions.Hybridization and introgression are sources of variation that can influence adaptation to new environments and influence speciation in both plant and animal systems (e.g., Anderson and Stebbins 1954). Hybridization is a common phenomenon in both aquatic and terrestrial habitats (reviewed in Dowling and Secor 1997), but seems to be more common among plant species (25% species hybridize) than among animal species (10%, Mallet 2005). It occurs after secondary contact between partially reproductively isolated species and has several potential outcomes. Hybridization can lead to extinction of one or both species (reviewed in Rhymer and Simberloff 1996) to coexistence of parental species and hybrids (Moore 1977) to reinforcement (reviewed in Butlin 1987) or to merging into novel populations of reticulate or polyphyletic origin because of introgressive hybridization (reviewed in Arnold 1992).The evolutionary significance of hybridization depends strongly on the frequency of hybridization events, as well as on hybrid fitness (reviewed in Arnold 1992). Both factors hinge on reproductive isolation mechanisms that can be found in various numbers, combinations, and strengths between the species involved (e.g., Arnold 1997), and be either pre-or postzygotic (reviewed in Avise 1994). Prezygotic isolation mechanisms include cytonuclear incompatibility and a range of behavioral and mechanical mating barriers (e.g., viability selection on migrants, assortative mating, egg-sperm recognition, and timing of reproduction). Postzygotic incompatibilities, on the other hand, comprise reduced hybrid fitness (e.g., offspring viability, fertility) as a consequence of genomic divergence and thus result in incompatibilities. Interactions between parental genomes can lead to a variety of positive and negative epistatic effects on the nuclear and cytonuclear level and result in a set of ...

BackgroundMultiple biologic and targeted synthetic disease-modifying rheumatic drugs (b/tsDMARDs) are approved for the management of rheumatoid arthritis (RA), including TNF inhibitors (TNFi), bDMARDs with other modes of action (bDMARD-OMA) and Janus kinase inhibitors (JAKi). Combination of b/tsDMARDs with conventional synthetic DMARDs (csDMARDs) is recommended, yet monotherapy is common in practice.ObjectiveTo compare drug maintenance and clinical effectiveness of three alternative treatment options for RA management.MethodsThis observational cohort study was nested within the Swiss RA Registry. TNFi, bDMARD-OMA (abatacept or anti-IL6 agents) or the JAKi tofacitinib (Tofa) initiated in adult RA patients were included. The primary outcome was overall drug retention. We further analysed secondary effectiveness outcomes and whether concomitant csDMARDs modified effectiveness, adjusting for potential confounding factors.Results4023 treatment courses of 2600 patients were included, 1862 on TNFi, 1355 on bDMARD-OMA and 806 on Tofa. TNFi was more frequently used as a first b/tsDMARDs, at a younger age and with shorter disease duration. Overall drug maintenance was significantly lower with TNFi compared with Tofa [HR 1.29 (95% CI 1.14 to 1.47)], but similar between bDMARD-OMA and Tofa [HR 1.09 (95% CI 0.96 to 1.24)]. TNFi maintenance was decreased when prescribed without concomitant csDMARDs [HR: 1.27 (95% CI 1.08 to 1.49)], while no difference was observed for bDMARD-OMA or Tofa maintenance with respect to concomitant csDMARDs.ConclusionTofa drug maintenance was comparable with bDMARDs-OMA and somewhat higher than TNFi. Concomitant csDMARDs appear to be required for optimal effectiveness of TNFi, but not for bDMARD-OMA or Tofa.