Copal is a resin of ritual uses in Mexico that is extracted from several species of trees of the genus Bursera. The effect of traditional management on phenotypical traits of copal trees has not been sufficiently studied. This research analyzed the traditional management and human selection on populations of Bursera bipinnata, and it also examined their influence on the quantity and quality of the resin produced by wild and managed trees. The management of copal was documented through semi-structured interviews and workshops. Samples of 60 trees from six wild and managed populations were selected to quantify the production of resin during two consecutive years. Fresh resin was collected to identify organic volatile compounds through gas chromatography and Principal Components Analysis (PCA); individuals were classified according to the amount and type of organic compounds produced. We identified management strategies from simple harvesting to seeds planting. The criteria of local people for selecting managed trees and seeds are based on the quantity and quality of the resin produced per tree, which were significantly higher in managed than in wild trees: 190.17 ± 329.04 g vs. 29.55 ± 25.50 g (p = 0.003), and 175.88 ± 179.29 g vs. 63.05 ± 53.25 g (p = 0.008) for the production seasons of 2017 and 2018, respectively. Twenty organic volatile compounds were identified, and the PCA showed that managed trees produce higher percentages of compounds associated with scent. The traditional management of Bursera bipinnata involves selective pressures, which generate the differentiation of wild and managed trees that may represent incipient domestication through silvicultural management.

The Hass avocado tree Persea americana cv. Hass was derived from a single hybrid tree of P. americana var. drymifolia and P. americana var. guatemalensis, and it is propagated clonally by grafting. This cultivar is the most widely planted in the world but its profile of secondary metabolites has been studied rarely despite of its importance in plant protection. We illustrate the variability of the volatilome of mature leaves by describing the average chemical composition and the phenotypic variability found in 70 trees. Contrary to the uniformity expected in the Hass cultivar, high variability coefficients were found for most of the 36 detected foliar volatile compounds; furthermore we found six chemotypes grouping the foliar phenotypes of the sampled trees using hierarchical cluster analysis. About 48% of trees were grouped in one chemotype; five chemotypes grouped the remaining trees. The compounds that determined these chemotypes were: estragole, α-farnesene, β-caryophyllene, germacrene D, α-cubebene and eugenol. This striking variation in a cultivar propagated clonally is discussed in terms of somatic mutation.

Three pathogenic fungi of blueberry (Vaccinium spp.) responsible for dieback disease, identified as Pestalotiopsis clavispora, Colletotrichum gloeosporioides and Lasiodiplodia pseudotheobromae, were isolated in the northwestern region of the state of Michoacán, Mexico. The mycelial growth in vitro of these fungi was inhibited by extracts from Lantana hirta, Argemone ochroleuca and Adenophyllum porophyllum, medicinal plants collected in Sahuayo, Michoacán, Mexico. The extracts showed different degrees of inhibition; the most effective were: M5L extract from L. hirta and M6LFr extract from A. ochroleuca, both of which inhibited 100% of the mycelial growth of P. clavispora and C. gloeosporioides; and M4LS extract from A. porophyllum, which inhibited 100% of the mycelial growth of the three pathogens. The extracts were fractionated by thin layer and column chromatography, and the most active fractions were analyzed by gas chromatography-mass spectrometry. The major compounds identified in L. hirta extract were Phytol and α-Sitosterol. The compounds identified in A. ochroleuca were Toluene and Benzene, 1,3-bis(3-phenoxyphenoxy)-. In A. porophyllum, the compound identified was Hexanedioic acid, bis(2-ethylhexyl) ester. These results show the potential of L. hirta, A. ochroleuca and A. porophyllum as a source of antifungal compounds.

This research analyzes the connection between highly skilled migration and several determining factors such as migration networks, the prestige of academic institutions and the Gross Domestic Product per capita. The linear regression method has been used to analyze a sample of 207 countries, 25 receiving countries and 182 sending countries from 6 different regions (Africa, Asia, Europe, North America, Central and South America and Oceania). A global analysis including all the countries of the sample and a partial analysis by each world region of origin has been performed. The results at global level showed that migration networks and the prestige of academic institution explain the number of highly skilled immigrants very well. In this sense, prestigious academic institutions of receiving countries imply economic incentives and benefits for skilled migrants. Further, relationships and linkages become an important help for highly skilled migrants. Thus, both would act like external and internal networks attracting highly skilled migrants. Regarding the partial analysis, these factors were also relevant for explaining highly skilled migration, but the results varied depending on each region. In case of Africa and Central & South America, the relevant factor explaining the highly-skilled migration was the prestige of academic institutions of the receiving countries. However, in the regions of Europe, North America, and Oceania results were similar to the global analysis. In Asia all factors were significant.

The international mobility of highly skilled employees in the last few decades has become an essential part of an economy. Simultaneously innovation and its' components have a large effect on the migration of skilled people. The goal of this paper is finding out if a greater degree of innovation in a country has a positive impact on the arrival of highly skilled immigrants. In order to achieve the aforementioned goal and following existing literature on the subject, an analysis on an international level was made regarding the effect of relevant innovation factors (number of patents; research and development funding (as % of GDP) and number of articles in scientific and technical journals) on immigration of highly skilled employees. The results of a regression analysis confirmed a significant relation between the number of patents, articles in scientific and technical journals and number of highly skilled immigrants (HQI). This means that countries with a relatively larger amount of the innovation factors have a great incentive that attracts talented people on an international scale, although in order to achieve this there is the need to promote and maintain a favourable institutional, economic and technological environment.

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Phytochemical diversity (PD) can be considered as a defensive trait; it can operate through single plant secondary metabolites or usually as complex mixtures of them. We tested the more diversity-better defense hypothesis correlating the leaf plant secondary metabolites (PSMs) with the incidence of plant enemies on Hass avocado trees. We expected a negative correlation between the occurrence of plant enemies and PD metrics. Also, as intraspecific PSMs polymorphisms in plant populations are common, we studied the incidence of plant enemies on Hass avocado trees representing chemical variants (chemotypes). We expected a differential incidence of plant enemies among trees grouped by their mono and sesquiterpene + phenylpropanoid chemotypes. We analyzed foliar hexane extracts from 236 trees in 17 orchards by gas chromatography and for the incidence of red mite, thrips, whitefly, avocado branch borer, fruit rot, scab, and peduncle collar blight. The predicted negative correlation between the plant enemies’ incidence and the phytochemical metrics did not occur. To determine the relationship between enemy incidence and chemotypes we grouped the trees by cluster analysis using a matrix of PSMs in each tree. Most trees were grouped under four out of 23 chemotypes. Branch borers attacked trees of low-frequency chemotypes more frequently than trees with common chemotypes. The incidence of five plant enemies was different among the predominant chemotypes. The hypothesis of more diversity-better defense was not supported by the correlations between the phytochemical diversity and the incidence of pests and pathogens in Hass avocado orchards. Based on our results, we hypothesize that phytochemical diversity function as a defensive trait relies more on differentiation among individuals in a population than on the sole increase of chemical diversity. Also, the differential incidence of pests and pathogens on trees classified by their foliar chemotypes implies that these susceptibility or resistance markers represent potential useful tools for Hass avocado orchard pest management.

Secondary sexual traits may convey reliable information about males’ ability to resist pathogens and that females may prefer those traits because their genes for resistance would be passed on to their offspring. In many insect species, large males have high mating success and can canalize more resources to the immune function than smaller males. In other species, males use pheromones to identify and attract conspecific mates, and thus, they might function as an honest indicator of a male's condition. The males of orchid bees do not produce pheromones. They collect and store flower volatiles, which are mixed with the volatile blends from other sources, like fungi, sap and resins. These blends are displayed as perfumes during the courtship. In this study, we explored the relationship between inter‐individual variation in body size and blend composition with the males’ phenoloxidase (PO) content in Euglossa imperialis. PO content is a common measure of insect immune response because melanine, its derived molecule, encapsulates parasites and pathogens. Body size and blend composition were related to bees’ phenolic PO content. The inter‐individual variation in body size and tibial contents could indicate differences among males in their skills to gain access to some compounds. The females may evaluate their potential mates through these compounds because some of them are reliable indicators of the males’ capacity to resist infections and parasites.