Distribution, Invasion History, and Ecology of Non-native Pine Bark Beetles (Coleoptera: Curculionidae: Scolytinae) in Southern South America.

The growth of international trade, coupled with an expansion of large-scale pine plantations in South America during the second half of the twentieth century, has significantly increased the opportunities for the invasion of forest insects. Bark beetles (Coleoptera: Curculionidae, Scolytinae) are a large and diverse group of insects, commonly recognized as one of the most important tree mortality agents in coniferous forests worldwide and an important group among invasive forest species. In this study, we combined data from field sampling with published records of established non-native pine bark beetles, to describe their distribution and invasion history in pine plantations across southern South America, reviewing the available information on their phenology and host range. We obtained records of established populations of six Eurasian species distributed in two major regions: the southwest region comprises plantations in Chile and the Argentine Patagonia, with four bark beetle species: Hylastes ater, Hylastes linearis, Hylurgus ligniperda, and Orthotomicus laricis; the northeastern zone includes northeastern Argentina, Uruguay, and southern Brazil, and includes three bark beetle species: Cyrtogenius luteus, H. ligniperda, and O. erosus. The establishment of non-native populations across the study area began in the 1950s, and from the 1980s onwards, there has been an exponential increase in introductions. We predict that several of these species will continue spreading across South America and that new species will continue arriving. We highlight the importance of international collaboration for early detection and management of non-native pine bark beetles.

Mating success at elevated temperature is associated to thermal adaptation in a set of recombinant inbred lines of Drosophila melanogaster.

In insects, mating ability at elevated temperature can be relevant for adaptation to heat-stressed environments and global warming. Here, we examined copulation latency (T1), copulation duration (T2), and mating frequency (T3, an index of mating success) in two related sets of recombinant inbred lines (RIL) in Drosophila melanogaster at both elevated (33 °C) and benign (25 °C) temperatures. One of these RIL sets (RIL-SH2) was shown to be consistently more resistant in both heat knockdown and heat-shock survival assays than its related set (RIL-D48) in previous studies. Negative correlations across RILs were found between T1 and T3 in this study. Flies from the heat-resistant set of RIL (RIL-SH2) were better able to mate at elevated temperature than flies from the heat-susceptible set (RIL-D48). Quantitative trait locus (QTL) mapping identified temperature-dependent QTLs for all traits (T1, T2 and T3) on all the three major chromosomes. Mating success at elevated temperature was found to be influenced by multiple QTLs. At elevated temperature, several QTLs for mating traits co-localized with QTLs that were previously associated with thermotolerance. The genetic basis for T1, T2 and T3 at the elevated temperature was found to be largely different from the genetic basis controlling the variation for mating success at benign temperature, as there was only a very low (or even null) number of QTLs overlapping across temperatures.

Heat knockdown resistance and chill-coma recovery as correlated responses to selection on mating success at high temperature in Drosophila buzzatii.

Reproduction and related traits such as mating success are strongly affected by thermal stress. We tested direct and correlated responses to artificial selection in replicated lines of Drosophila buzzatii that were selected for mating success at high temperature. Knockdown resistance at high temperature (KRHT) and chill-coma recovery (CCR) were tested as correlated selection responses. Virgin flies were allowed to mate for four hours at 33°C in three replicated lines (S lines) to obtain the selected flies and then returned at 25°C to lay eggs. Other three replicated lines were maintained at 25°C without any selection as control (C lines). After 15 selection generations, KRHT and CCR were measured. Both traits were assessed in flies that did not receive any hardening pretreatments as well as in flies that were either heat or cold hardened. Thermotolerance traits showed significant correlated responses with higher KRHT in S than in C lines, both with a heat-hardening pretreatment and without a heat-hardening pretreatment. CCR time was longer in S than in C lines both with a cold-hardening pretreatment and without a cold-hardening pretreatment. Hardening treatments improved both KRHT and CCR in all cases excepting KRHT in C lines. Overall, KRHT and CCR showed an antagonistic pattern of correlated responses to our selection regime, suggesting either pleiotropy or tightly linked trait-specific genes partially affecting KRHT and CCR.

Negative genetic correlation between longevity and its hormetic extension by dietary restriction in Drosophila melanogaster.

Longevity is a highly malleable trait which is influenced by many genetic and environmental factors including nutrition. Mild stress of dietary restriction (DR) is often beneficial by extending longevity in many organisms. Here, DR-induced effects on longevity were tested for genetic variation in a set of recombinant inbred lines (RIL) in D. melanogaster. Genetic variability was significant in the longevity response following a DR-treatment across RIL, with detrimental effects in several RIL but beneficial effects in other RIL. One quantitative trait locus (QTL) was consistently significant in the middle of chromosome 2 for DR-induced changes in longevity, including hormesis (an increase in longevity by DR). Another QTL co-localized with a previously found QTL for starvation resistance in females. Several other QTL were also significant on most chromosomal arms. Longevity in controls was negatively correlated to DR effects across RIL for longevity in females, the sex showing higher DR-induced hormesis. This negative genetic correlation highlights the importance to further investigate the effects of genetic variation in the strength of DR-induced hormesis in longevity and its sex-specificity.