Variable but predictable prey availability affects predator breeding success: natural versus experimental evidence

Food supply is a major source of variation in breeding success for predators, and to what extent individuals are able to cope with temporal variability in food availability remains an outstanding question in life-history studies. We confronted the natural variation in clutch size and breeding success with results from a food supplementation experiment during egg formation, conducted over several contrasted years of natural food supply in an avian specialist predator, the Montagu's harrier Circus pygargus . This raptor mainly preys on common vole Microtus arvalis a cyclic microtine under temperate latitudes. Vole abundance together with timing of breeding accounted for most of the variance in clutch size and number of fledglings. Results from empirical and experimental data were overall in agreement. Fed pairs consistently increased clutch size compared with controls in all experimental years, whereas no effect of food supplementation on egg volume was detected. Supplemented pairs, however, did not fledge significantly more chicks than controls. The costs entailed by the increase in clutch size appear nevertheless to be limited compared with previous studies. Food supply seemed therefore to display sufficient predictability throughout a breeding season to afford individuals the opportunity to adjust their breeding effort to an optimal number of offspring, in agreement with Lack's anticipation hypothesis.     

Breeding systems in a montane tropical cloud forest in Venezuela

The breeding systems, reproductive efficacies and population densities of 75 species of trees, shrubs, perennial herbs and vines in a montane tropical cloud forest in Venezuela are investigated. 56.96% and 44.32% of the trees, versus the other life forms considered, respectively possess obligate outbreeding mechanisms. Two shrubs are non-pseudogamous apomicts. The percentage of dioecy among tree species (31%) is among the highest recorded in tropical forests. Reproductive efficacy is similar under all breeding systems in the forest interior. Obligately outbred taxa are slower recolonizers of a disturbed border as compared with non-obligate outbreeders. Explanations are advanced for the high incidence of dioecy combined with a low level of self-incompatibility among hermaphroditic species. It is concluded that the breeding system spectrum reflects an unpredictable pollination pattern, rather than insufficient pollinator servicing.     

The effects of environmental factors on the virulence of Trichomonas vaginalis

This review focused on potential regulatory mechanisms of Trichomonas vaginalis virulence properties, cytoadherence, cytotoxicity, phagocytosis, hemolysis, induction of apoptosis, and immune evasion in response to environmental factors of the human urogenital tract, iron, zinc, and polyamines. Understanding the multifactorial nature of trichomonal pathogenesis and its regulation may help to unravel the survival strategies of trichomonads and to implement prevention policies, opportune diagnosis, and alternative treatments for control of trichomoniasis.     

Identifying the winter grounds of the recently described Barbary Reed Warbler (Acrocephalus baeticatus ambiguus)

The Iberian and North African populations of reed warblers have been described recently as a separate taxon, ambiguus, forming a sister clade to the Sahelian subspecies minor of African Reed Warbler Acrocephalus baeticatus. Although the breeding range of ambiguus has been identified, the migration strategy of its populations remained unknown. We deployed geolocators and sampled the innermost primary from breeding adults in Spain for stable hydrogen (δ²H) analyses and also analysed stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in feathers collected in two reed warbler taxa (Acrocephalus scirpaceus and Acrocephalus baeticatus ambiguus) in Morocco, to identify the moulting and wintering sites of these populations. Ring recoveries, geolocator tracks and probabilistic assignments to origin from δ²H values indicate that Spanish ambiguus are likely to moult south of the Sahara and winter in West Africa, probably from Mauretania to southern Mali and Ivory Coast. Moroccan ambiguus, however, undergo post-breeding moult north of the Sahara, and possibly then migrate to West Africa. With other populations of ambiguus breeding from Algeria to Libya and probably wintering further east in the Sahelian belt, the Barbary Reed Warbler can therefore be considered a trans-Saharan migrant, with a post-breeding moult strategy that varies between populations, and probably structured according to breeding latitude.     

Placental morphology in two sympatric Andean lizards of the genus Liolaemus (Reptilia: Liolaemidae)

Viviparity is a remarkable feature in squamate sauropsids and it has evolved multiple times in parallel with the formation of a placenta. One example of this repeated evolution of viviparity and placentation occurs in the species‐rich South American genus Liolaemus with at least six independent origins of viviparity. However, evolutionary studies of placentation in this genus are limited by a lack of data on placental morphology. The aim of this study is to describe and compare the microanatomy and vessel diameter (Dv, a function of blood flow) of the placenta using scanning electron microscopy (SEM) and confocal laser scanning microscopy (cLSM) in two sympatric Andean viviparous but highly divergent species, Liolaemus robustus and Liolaemus walkeri. We found interspecific differences in cell types in the chorion, allantois, and omphalopleure that may be explained by divergent phylogenetic history. Time elapsed since divergence may also explain the pronounced interspecific differences in vessel diameter, and within each species, there are strong differences in Dv between tissue locations. Both species show features to improve gas exchange in the chorioallantoic placenta including absence of eggshell, large Dv in the allantois (L. robustus) or embryonic side of the uterus (L. walkeri), and when present, microvillous cells in the allantois (L. walkeri). Both species also show features that suggest transfer of nutrients or water in the omphaloplacenta, including an almost complete reduction of the eggshell, secretive material (L. robustus), or vesicles (L. walkeri) on cell surface uterus, and when present specialized cells in the omphalopleure (L. walkeri). No statistical differences in Dv were found among stages 32–39 in each species, suggesting that a different mechanism, other than enhanced blood flow, might satisfy the increased oxygen demand of the developing embryos in the hypoxic environments of the high Andes. J. Morphol. 276:1205–1217, 2015. © 2015 Wiley Periodicals, Inc.     

Cytological aberrations produced by methotrexate in mouse ascites tumours

The cytological effects have been studied of methotrexate administered in single doses on a hypertriploid ascites tumour in the mouse, which seems to be sensitive to this drug. The drug produced almost total stoppage of the mitotic index, which was maintained for 50 h after administration. The occurrence of fractures in both chromosomes and chromatids in metaphase was the most frequently observed anomaly, sometimes reaching an incidence of 100%. Chromosomal bridges were found in the anaphase in up to 60% of the cells.     

Phenological and morphological differentiation in annual Chaetanthera moenchioides (Asteraceae) over an aridity gradient

Flowering-time, plant longevity and size of capitulum were studied in a common garden experiment on seven populations of annual Chaetanthera moenchioides derived from a strong latitudinal aridity gradient in the mediterranean climate area of Chile. Populations derived from the drier northern part of the latitudinal gradient showed significantly shorter flowering and fruiting phenology and smaller capitula under uniform growing conditions. Water stress experiments performed in the greenhouse induced further phenological hastening and a reduction in number of ray florets per capitulum. Population differentiation and the reaction norms in C. moenchioides agree with the predictions of genetic-assimilation given that the plastic response of the species under water stress mimics phenotypic differentiation that has evolved along the environmental gradient.