Mechanisms of allopatric speciation in an Antillean damselfly genus (Odonata, Zygoptera): Vicariance or long-distance dispersal?

We have examined divergence times of the Antillean damselfly genus Hypolestes, to elucidate which mechanism of allopatric speciation, vicariance or long-distance dispersal, could better explain the currently observed disjunct distributions of this genus. Samples of the three extant species of the genus, Hypolestes clara (Jamaica), H. hatuey (Hispaniola) and H. trinitatis (Cuba), were collected. Mitochondrial and nuclear DNA gene fragments were amplified to reconstruct phylogenetic relationships and estimate divergence times in this genus. Hypolestes comprises currently three species, which consist in four geographically and genetically isolated lineages located in Jamaica, Hispaniola, Eastern Cuba and Central Cuba. Results of our analyses suggest that the three species diverged between ∼5.91 and 1.69 mya, and that the separation between the lineages from Central Cuba and Eastern Cuba occurred between ∼2.0 and 0.62 mya. Disjunct distributions in the genus Hypolestes can be better explained by a long-distance dispersal mechanism, since the divergence times of the three species do not coincide with the timeline formation of the geographic barriers between Cuba, Hispaniola and Jamaica. The Cuban lineages of H. trinitatis constitute different molecular operational taxonomic units (MOTU). The elevation of these MOTU to the species category requires the analysis of additional characters.

Hypolestes hatuey sp. nov.: a new species of the enigmatic genus Hypolestes (Odonata, Hypolestidae) from Hispaniola.

Both sexes of Hypolestes hatuey Torres-Cambas, sp. nov. (Odonata: Zygoptera: Hypolestidae) from Hispaniola are described and illustrated here. This newly described species differs from H. trinitatis and H. clara, the other two species within the genus, by the morphology of the genital ligula and male cerci. Females of H. hatuey sp. nov. differ from H. clara by the shape of the female antehumeral stripe and wing venation. Morphological distinctiveness in males is supported by genetic differences in the 16S mitochondrial gene. Following the categories and criteria of the IUCN Red List of Threatened Species, we suggest this species should be listed as Data Deficient (DD), given that available data on its distribution are too limited to assess its risk of extinction.

Influence of temperature on the hydrolysis, acidogenesis and methanogenesis in mesophilic anaerobic digestion: parameter identification and modeling application.

The effect of temperature on the kinetic parameters involved in the main reactions of the anaerobic digestion process was studied. Batch tests with starch, glucose and acetic acid as substrates for hydrolysis, acidogenesis and methanogenesis, respectively, were performed in a temperature range between 15 and 45 degrees C. First order kinetics was assumed to determine the hydrolysis rate constant, while Monod and Haldane kinetics were considered for acidogenesis and methanogenesis, respectively. The results obtained showed that the anaerobic process is strongly influenced by temperature, with acidogenesis exerting the highest effect. The Cardinal Temperature Model 1 with an inflection point (CTM1) fitted properly the experimental data in the whole temperature range, except for the maximum degradation rate of acidogenesis. A simple case-study assessing the effect of temperature on an anaerobic CSTR performance indicated that with relatively simple substrates, like starch, the limiting reaction would change depending on temperature. However, when more complex substrates are used (e.g. sewage sludge), the hydrolysis might become more quickly into the limiting step.

Treatment of low and medium strength sewage in a lab-scale gradual concentric chambers (GCC) reactor.

One of the major challenges of anaerobic technology is its applicability for low strength wastewaters, such as sewage. The lab-scale design and performance of a novel Gradual Concentric Chambers (GCC) reactor treating low (165+/-24 mg COD/L) and medium strength (550 mg COD/L) domestic wastewaters were studied. Experimental data were collected to evaluate the influence of chemical oxygen demand (COD) concentrations in the influent and the hydraulic retention time (HRT) on the performance of the GCC reactor. Two reactors (R1 and R2), integrating anaerobic and aerobic processes, were studied at ambient (26 degrees C) and mesophilic (35 degrees C) temperature, respectively. The highest COD removal efficiency (94%) was obtained when treating medium strength wastewater at an organic loading rate (OLR) of 1.9 g COD/L.d (HRT = 4 h). The COD levels in the final effluent were around 36 mg/L. For the low strength domestic wastewater, a highest removal efficiency of 85% was observed, producing a final effluent with 22 mg COD/L. Changes in the nutrient concentration levels were followed for both reactors.