Different patterns of retinal cone topography in two genera of rodents,Mus and Apodemus

Recently, we have reported the peculiar topographic separation of shortwave- and middlewave-sensitive (S and M) cones in the retina of the common house mouse (Mus musculus) and in a number of inbred laboratory mouse strains derived from the same species. In an attempt to follow the phylogeny of the complementary cone fields, we have investigated the retina of other mouse-like rodents. Two monoclonal anti-visual pigment antibodies, OS-2 and COS-1, specific to the S and M cones, respectively, have been used to identify the two cone types. Immunocytochemistry on retinal sections and on whole-mount preparations have shown that, as in the house mouse, the two cone types in the mound builder mouse (Mus spicileugus) occupy opposite halves of the retina. In contrast, in the wood mouse (Apodemus sylvaticus), both cone types are scattered uniformly across the whole retinal surface. Another distinguishing feature between the two genera is the frequency of the S cones. Whereas their density in the Mus species is above 7 000/mm² in the S-field, the maximum density of the S cones in A. sylvaticus is one order of magnitude smaller. In another species of this genus (the herb field mouse, A. microps), the S cones are completely missing.     

Yersinia Yop-Specific IgA antibodies in Hungarian blood donors

Sera of 112 healthy Hungarian blood donors were tested for the presence of Yersinia enterocolitica and Y. pseudotuberculosis-specific agglutinins by tube agglutination, and for that of yersinia outer membrane protein (Yop)-specific IgA antibodies by ELISA. The positive results of this latter assay were confirmed by immunoblot. Only one sample gave a positive agglutination reaction with Y. enterocolitica antigen (group 03) and four exhibited an equivocal reaction with Y. pseudotuberculosis antigens (groups II and IV). Contrary to the low incidence of agglutinins, 15.1% of the samples showed a positive Yop-specific IgA reaction, while further 5.3% samples fell into the equivocal range by ELISA (17 and 6 specimens, respectively). Eleven of these samples (9.8% of all specimens tested) were also positive by immunoblot for the presence of Yop-specific IgA antibodies. These data suggest a higher incidence of yersinia infections than the 1.0-1.4 per 10(5) population predicted on the basis of stool culture results.     

Major plant communities of the Carson Desert (Nevada), North America's coldest and driest desert

This paper describes the vegetation of the Carson Desert (Nevada, USA) based on a phytosociological analysis of its major plant associations, as determined by the Braun-Blanquet method. Diagnostic tables, climatic, edaphic, and biogeographical data were used to establish floristic affinities among identified plant communities and to interpret their distributions in zonal gradients. Their syntaxonomic positions in the classes Allenrolfeetea occidentalis and Artemisio tridentatae–Juniperetea osteospermae, and in the new class Sarcobatetea vermiculati were also established. Three associations (Atriplici confertifoliae–Sarcobatetum baileyi, Atriplici canescentis–Psorothamnetum polydenii, and Suaedo moquinii–Sarcobatetum vermiculati) are described here for the first time along with the order Sarcobatetalia vermiculati and the alliance Sarcobation vermiculati.     

Dispersal of non-myrmecochorous plants by a “keystone disperser” ant in a Mediterranean habitat reveals asymmetric interdependence

In contrast to other plant–animal mutualisms, seed dispersal interactions, and particularly seed dispersal by ants, are generally considered asymmetric, non-specialized relationships in which dispersers depend less on plants than vice versa. Although myrmecochory is well understood in many terrestrial ecosystems, dispersal of non-elaiosome-bearing seeds by ants has barely been studied outside the Neotropics. Aphaenogaster senilis, a common ant in Southern Spain, collects a great variety of non-myrmecochorous diaspores along with insect prey. At our study site, fleshy fruits of Arum italicum, Phillyrea angustifolia and Pistacia lentiscus represent up to one-fourth of the items collected by A. senilis from June to November. However, they are mostly ignored by other ants. In the laboratory, the addition of A. italicum fruits to A. senilis insect-based diet increased male production and both worker and queen pupae size. Seeds were transported up to 8 m away from the mother plant and deposited in a favorable habitat allowing a relatively high proportion of germination. Given important differences in seed production between species, our data suggest that A. senilis removes virtually all seeds of A. italicum, but a negligible fraction of P. lentiscus seeds. We conclude that in contrast to the common view, dispersal of non-myrmecochorous Mediterranean plants by ants might be an important phenomenon. Keystone disperser ants like A. senilis probably obtain an important fitness advantage from non-myrmecochorous diaspore collection. However, plant benefit may vary greatly according to the amount of seeds per individual plant and the existence of alternative dispersal agents.     

More rapid shift to a benthic niche in larger Gadus morhua juveniles

Trophic use by Atlantic cod Gadus morhua juveniles was examined early and late in the shift from pelagic to benthic habitats. Changes in the proportion of pelagic copepods, estimates of benthic prey indicated by isotope mixing models and stable‐isotope values between sample periods suggested a gradual shift towards a benthic niche. Values of the trophic proxies, however, changed most markedly in the largest juvenile group, suggesting a more rapid trophic niche shift, and in turn competitive advantage, of larger juveniles.     

Tibor Jermy (1917–2014)

Throughout the course of their evolution, plants have acquired a wide range of chemical and mechanical defenses to protect against herbivores. Ehrlich & Raven's coevolutionary theory suggests that this diversification of defensive traits is driven by the strong impact of novel traits on insect herbivores. However, the impact of plant defenses on insects is difficult to compare between related plant species due to variation in environmental and biotic conditions. We standardized these factors as far as possible by analyzing the effects of chemical and mechanical defensive traits on insects in a local community of 11 Salicaceae species growing in sympatry, and their leaf‐chewing herbivores. Defensive traits (salicylates, flavonoids, tannins, trichomes, and leaf toughness) were generally not inter‐correlated, with the exception of a negative correlation between salicylates and trichomes. The content of salicylates, a novel group of defensive metabolites in the Salicaceae, was correlated with low herbivore diversity and high host specificity. Despite these effects, the phylogeny of the studied species shows loss of salicylates in some Salix species instead of their further diversification. This could be due to salicylates not decreasing the overall abundance of herbivores, despite accounting for up to 22% of the dry leaf mass and therefore being costly. The defense of low‐salicylate willow species is thus probably maintained by other defensive traits, such as trichomes. Our study shows that the balance between costs and benefits of defensive traits is not necessarily in favor of novel compounds and illustrates a process, which may lead to the reduction in a defensive trait.