N,N'-dibenzyl-4,13-diaza-18-crown-6 (A) and bis[(benzo-15-crown-5)-4'-ylmethyl] pimelate (B) were tested as coatings for two piezoelectric crystals for potassium quantification. Both sensors showed stability, reversibility and sensitivity characteristics that allowed their use in quantitative analysis. However, compound A is much more sensitive to potassium than B. Compound A also shows a larger relative sensitivity for potassium with regard to sodium than B. A pharmaceutical sample of known composition was analysed both by an acoustic wave sensor with a crystal coated with compound A and by conductivity. No statistically significant difference in the median of the results was found (alpha = 0.05), although precision is superior for the conductivity methodology. Performance of the sensor in terms of frequency stability and selectivity was improved by the incorporation of PVC, a plasticizer and a lipophilic salt in the coating composition. Limits of detection found for potassium were 1.92 ppm, or 1.75 ppm for a crystal with a frequency decrease due to coating of 2.9 kHz or 3.9 kHz, respectively. Selectivity coefficients (fixed interference 80 ppm) for potassium over Na, Ca, Al, Zn, Mg, and Fe ranged from 0.103 to 0.332.

Species-rich ecosystems as tropical forests are extremely vulnerable to anthropogenic destruction. Most tropical plant species rely on animals to disperse their seeds. However, patterns of mutualistic interactions have rarely been explored, and seed dispersal networks are still poorly studied in Africa. Here, we examine how forest edges’ (FE) seed dispersal networks differ from the mature forest (MF) at a West African sub-humid tropical forest within the National Park of Cantanhez (Guinea-Bissau). Additionally, we explore species’ roles within the network. MF had higher fruit availability, more frugivore visitors, and plant–frugivore interactions. Network structure was quite similar between habitats, showing signs of redundancy, and some robustness to species’ extinction. FE was more nested, modular, and specialized, whereas MF had higher connectance, interaction evenness, and robustness to extinction. Most species were generalists, but large-bodied frugivores prevailed at MF. FE showed a higher vulnerability, mostly to the loss of trees. Trees are key, keeping the structure of both networks. Large-bodied frugivores and fruiting-tree species that work as network connectors should thus be the focus of active conservation management in these forests. Only viable populations of these species will ensure a good performance of the seed dispersal network, promoting the natural regeneration of the ecosystem.

Hyla molleri is well adapted to arboreal microhabitats, which are used among breeding seasons. This species is common in wetlands across the Iberian Peninsula and is therefore vulnerable to the loss and degradation of these ecosystems. Due to its secretive habits, the knowledge about the ecology of H. molleri, outside the breeding season, is still scarce. Using artificial refuges as a proxy to natural refuges, we studied how H. molleri uses arboreal microhabitats near reproductive areas and which environmental drivers influence refuge colonisation. We installed 70 PVC pipe refuges in isolated trees and tree patches. Pairs of pipes were installed at two different heights and monitored fortnightly, for four consecutive days, for one year. Each sampling day, we registered the values of variables related with seasonality, microhabitat, dominant plant species, weather and site fidelity. We recorded 2234 individual colonization events by H. molleri, including 516 multiple colonization events, with a maximum of nine individuals in a single refuge. Refuges that were colonized before were more likely to be colonized again. Additionally, colonization was lower in spring and summer and higher in tree clusters than in isolated trees. We found no significant differences on the height or temperature of colonized versus non-colonized refuges. Our results highlight the importance of adequate arboreal microhabitats and the need for the conservation of terrestrial habitats around breeding areas. We also show that artificial refuges can be useful for H. molleri and similar species, namely for habitat improvement or the implementation of citizen-science and monitoring programs.

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