Colonization of Marginal Host Plants by Seed Beetles (Coleoptera: Chrysomelidae): Effects of Geographic Source and Genetic Admixture

On the fast track: hybrids adapt more rapidly than parental populations in a novel environment

Rates of hybridization are predicted to increase due to climate change and human activity that cause redistribution of species and bring previously isolated populations into contact. At the same time climate change leads to rapid changes in the environment, requiring populations to adapt rapidly in order to survive. A few empirical cases suggest hybridization can facilitate adaptation despite its potential for incompatibilities and deleterious fitness consequences. Here we use simulations and Fisher's Geometric model to evaluate the conditions and time frame of adaptation via hybridization in both diploids and haplodiploids. We find that hybrids adapt faster to new environments compared to parental populations in nearly all simulated scenarios, generating a fitness advantage that can offset intrinsic incompatibilities and last for tens of generations, regardless of whether the population was diploid or haplodiploid. Our results highlight the creative role of hybridization and suggest that hybridization may help contemporary populations adapt to the changing climate. However, adaptation by hybrids may well happen at the cost of reduced biodiversity, if previously isolated lineages collapse into one.

Identification and distribution of leafrollers (Lepidoptera, Tortricidae) associated with berries (Rosaceae) cultivated in Mexico

Berries are agricultural products of great economic interest for Mexico, and their production has increased in recent years; however, crops are affected by tortricid leafrollers. From August 2019 to April 2021 in Michoacán and Guanajuato, Mexico, a study was conducted to determine the species of tortricids associated with blackberries (Rubus spp. L.), raspberries (Rubus idaeus L.) and strawberries (Fragaria × ananassa Duch.), as well as their altitudinal distribution. In 12 orchards located in these states, shoots, leaves and flowers infested by larvae were collected. The species were identified by male genitalia and were determined taxonomically as Amorbia cuneana (Walsingham, 1879), Argyrotaenia montezumae (Walsingham, 1914) and Platynota sp. Walker, 1859, found at elevations from 1290 to 2372 m. The most abundant species were A. cuneana and A. montezumae. Generally, these tortricids prefer to feed on tender vegetative parts of the plant, but the economic impact they have is not known. It is worth mentioning that the number of species found is lower than those reported in other countries, but it is necessary to broaden the study area to other berry-producing regions to determine whether their distribution is wider.

Disparate genetic variants associated with distinct components of cowpea resistance to the seed beetle Callosobruchus maculatus

Polygenic genome-wide association mapping identified two regions of the cowpea genome associated with different components of resistance to its major post-harvest pest, the seed beetle Callosobruchus maculatus. Cowpea (Vigna unguiculata) is an important grain and fodder crop in arid and semi-arid regions of Africa, Asia, and South America, where the cowpea seed beetle, Callosobruchus maculatus, is a serious post-harvest pest. Development of cultivars resistant to C. maculatus population growth in storage could increase grain yield and quality and reduce reliance on insecticides. Here, we use a MAGIC (multi-parent, advanced-generation intercross) population of cowpea consisting of 305 recombinant inbred lines (RILs) to identify genetic variants associated with resistance to seed beetles. Because inferences regarding the genetic basis of resistance may depend on the source of the pest or the assay protocol, we used two divergent geographic populations of C. maculatus and two complementary assays to measure several aspects of resistance. Using polygenic genome-wide association mapping models, we found that the cowpea RILs harbor substantial additive-genetic variation for most resistance measures. Variation in several components of resistance, including larval development time and survival, was largely explained by one or several linked loci on chromosome 5. A second region on chromosome 8 explained increased seed resistance via the induction of early-exiting larvae. Neither of these regions contained genes previously associated with resistance to insects that infest grain legumes. We found some evidence of gene-gene interactions affecting resistance, but epistasis did not contribute substantially to resistance variation in this mapping population. The combination of mostly high heritabilities and a relatively consistent and simple genetic architecture increases the feasibility of breeding for enhanced resistance to C. maculatus.