EVALUATION OF THE CHEMICAL COMPOSITION AND ALLELOPATHIC POTENTIAL OF ESSENTIAL OILS FROM THREE SPECIES OF ASTERECEAE AGAINST SEED GERMINATION AND SEEDLING VIGOR OF LETTUCE

The allelopathic properties of the essential oils have been exploited because they are biodegradable natural compounds that can be used in combination or as prototypes for new bioherbicides. The objectives of this study were to chemically characterize the essential oils from B. dracunculifolia, C. bonariesis and T. diversifolia and to evaluate their allelopathic potential. The essential oils were extracted by hydrodistillation and their chemical compositions were determined by GC-MS. Allelopathic activities were determined by methods that evaluate the effects of volatile compounds and direct contact of those compounds on the seed germination and seedling vigor of lettuce. The principal constituents of the essential oil from B. dracunculifolia were limonene, trans-nerolidol and β-pinene; those in the oil from C. bonariesis were limonene, trans-β-ocimene and cis-verbenol (4.4%); and those in the oil from T. diversifolia were β-pinene, α-pinene and limonene. Minor differences in the germination and vigor of lettuce seedlings were observed when they were exposed to the volatile essential oils from the leaves of the three species of the Asteraceae family. However, upon direct contact with these oils, those of C. bonariesis presented the greatest allelopathic potential, which was attributed to its higher content of oxygenated monoterpenes

Genetic Diversity and Population History of a Critically Endangered Primate, the Northern Muriqui (Brachyteles hypoxanthus)

Social, ecological, and historical processes affect the genetic structure of primate populations, and therefore have key implications for the conservation of endangered species. The northern muriqui (Brachyteles hypoxanthus) is a critically endangered New World monkey and a flagship species for the conservation of the Atlantic Forest hotspot. Yet, like other neotropical primates, little is known about its population history and the genetic structure of remnant populations. We analyzed the mitochondrial DNA control region of 152 northern muriquis, or 17.6% of the 864 northern muriquis from 8 of the 12 known extant populations and found no evidence of phylogeographic partitions or past population shrinkage/expansion. Bayesian and classic analyses show that this finding may be attributed to the joint contribution of female-biased dispersal, demographic stability, and a relatively large historic population size. Past population stability is consistent with a central Atlantic Forest Pleistocene refuge. In addition, the best scenario supported by an Approximate Bayesian Computation analysis, significant fixation indices (ΦST = 0.49, ΦCT = 0.24), and population-specific haplotypes, coupled with the extirpation of intermediate populations, are indicative of a recent geographic structuring of genetic diversity during the Holocene. Genetic diversity is higher in populations living in larger areas (>2,000 hectares), but it is remarkably low in the species overall (θ = 0.018). Three populations occurring in protected reserves and one fragmented population inhabiting private lands harbor 22 out of 23 haplotypes, most of which are population-exclusive, and therefore represent patchy repositories of the species' genetic diversity. We suggest that these populations be treated as discrete units for conservation management purposes