Dominant predators mediate the impact of habitat size on trophic structure in bromeliad invertebrate communities.

Local habitat size has been shown to influence colonization and extinction processes of species in patchy environments. However, species differ in body size, mobility, and trophic level, and may not respond in the same way to habitat size. Thus far, we have a limited understanding of how habitat size influences the structure of multitrophic communities and to what extent the effects may be generalizable over a broad geographic range. Here, we used water-filled bromeliads of different sizes as a natural model system to examine the effects of habitat size on the trophic structure of their inhabiting invertebrate communities. We collected composition and biomass data from 651 bromeliad communities from eight sites across Central and South America differing in environmental conditions, species pools, and the presence of large-bodied odonate predators. We found that trophic structure in the communities changed dramatically with changes in habitat (bromeliad) size. Detritivore : resource ratios showed a consistent negative relationship with habitat size across sites. In contrast, changes in predator: detritivore (prey) ratios depended on the presence of odonates as dominant predators in the regional pool. At sites without odonates, predator: detritivore biomass ratios decreased with increasing habitat size. At sites with odonates, we found odonates to be more frequently present in large than in small bromeliads, and predator: detritivore biomass ratios increased with increasing habitat size to the point where some trophic pyramids became inverted. Our results show that the distribution of biomass amongst food-web levels depends strongly on habitat size, largely irrespective of geographic differences in environmental conditions or detritivore species compositions. However, the presence of large-bodied predators in the regional species pool may fundamentally alter this relationship between habitat size and trophic structure. We conclude that taking into account the response and multitrophic effects of dominant, mobile species may be critical when predicting changes in community structure along a habitat-size gradient.

Choosing between good and better: optimal oviposition drives host plant selection when parents and offspring agree on best resources.

Insect preferences for particular plant species might be subjected to trade-offs among several selective forces. Here, we evaluated, through laboratory and field experiments, the feeding and ovipositing preferences of the polyphagous leafminer Liriomyza huidobrensis (Diptera: Agromyzidae) in relation to adult and offspring performance and enemy-free space. Female leafminers preferred laying their eggs on Vicia faba (Fabaceae) over Beta vulgaris var. cicla (Chenopodiaceae), in both laboratory and field choice experiments, although no oviposition preference was observed in no-choice tests. Females fed more often on B. v. var. cicla (no-choice test) or showed no feeding preference (choice test), even when their realized fecundity was remarkably higher on V. faba. Offspring developed faster, tended to survive better, and attained bigger adult size on the preferred host plant. Also, a field experiment showed higher overall parasitism rates for leafminers developing on B. v. var. cicla, with a nonsignificant similar tendency in field surveys. According to these results, host plant selection by L. huidobrensis appears to be driven mainly by variation in host quality. Moreover, the consistent oviposition choices for the best host and the labile feeding preferences observed here, suggest that host plant selection might be driven by maximization of offspring fitness even without a conflict of interest between parents and offspring. Overall, these results highlight the complexity of decisions performed by phytophagous insects regarding their host plants, and the importance of simultaneous evaluation of the various driving forces involved, in order to unravel the adaptive significance of female choices.

Evaluacion clinica de las lesiones condrales de rodilla tratadas mediante tecnica de microfracturas / Clinical evaluation of chondral lesiones of the knee treated with microfracture technique

Introducción: Las lesiones osteocondrales de la rodilla son tratadas con diferentes técnicas, con resultados diversos. Realizamos una valoración clínica de pacientes tratados con la técnica de microfracturas con el objetivo de evaluar los resultados clínicos, la eficacia de la técnica y la relación costo-beneficio en comparación con otras. Materiales y métodos: Realizamos un estudio retrospectivo descriptivo de 20 pacientes con lesión condral de tipo 4 en la rodilla tratados mediante la técnica de microfracturas con dos años de seguimiento mínimo, evaluados mediante la prueba de Lysholm y radiografías. Resultados: Con la prueba de Lysholm obtuvimos resultados excelentes (30 por ciento) en pacientes jóvenes en los que se realizaron perforaciones más plásticas de LCA y meniscectomía, muy buenos (25 por ciento) en pacientes de mediana edad en los cuales se realizaron perforaciones en el condilo interno más meniscectomía, buenos (15 por ciento) en pacientes de mediana edad en los que se realizaron perforaciones en el condilo externo más meniscectomía y regulares (30 por ciento) cuando se realizaron perforaciones en la articulación femororrotuliana y en lesiones condrales en beso. Conclusiones: Dada la simplicidad de la técnica, su bajo costo, la posibilidad de realizarla junto con otras cirugías y considerando los resultados clínicos y radiológicos obtenidos, creemos que es una muy buena opción de tratamiento para las lesiones condrales de tipo 4, tanto en el compartimiento externo como interno, no así en la articulación femororrotuliana y en las lesiones en beso