Continental-scale migration patterns and origin of Helicoverpa zea (Lepidoptera: Noctuidae) based on a biogeochemical marker.

Insect migrations have ecological and economic impacts, particularly in agriculture. However, there is limited knowledge about the migratory movements of pests at the continental scale, which is an important factor influencing the spread of resistance genes. Understanding the migratory patterns of economic pests, like Helicoverpa zea (Boddie), is essential for improving Integrated Pest Management (IPM) and Insect Resistance Management (IRM) strategies. In this study, we used stable hydrogen isotopic ratios in wing tissue as a biogeochemical marker to examine migratory patterns and estimate the native origins of H. zea individuals collected across a wide latitudinal gradient in North America. Samples collected at higher latitudes (Ontario, Canada and Minnesota, USA) exhibited a greater proportion (60%-96%) of nonlocal individuals, with an increased probability of origin from the southeastern United States. Populations from mid-latitudes (Florida, North Carolina, and South Carolina) showed a blend of local and nonlocal (40%-60%) individuals. Finally, 15% of the southernmost population individuals (Puerto Rico) were classified as migratory, with some having a probability of origin at higher latitudes (>30°). Overall, our results provide evidence of a northward spring/summer migration of H. zea in North America and underscore the significance of the southeastern United States as a hub for genetic flow. In addition, based on stable hydrogen isotopic ratios, there is strong evidence of reverse (southward) migration of H. zea from the continental United States to Puerto Rico. Our study highlights the implications for IPM and IRM programs and the need for management strategies that account for both northward and southward migration patterns.

Interactions between large-scale and local factors influence seed predation rates and seed loss.

Herbivores often have highly variable impacts on plant fecundity. The relative contribution of different environmental factors operating at varying spatial scales in affecting this variability is often unclear. We examined how density-dependent seed predation at local scales and regional differences in primary productivity are associated with variation in the magnitude of pre-dispersal seed predation on Monarda fistulosa (Lamiaceae). Within M. fistulosa populations growing in a low-productivity region (LPR), Montana, USA, and a high-productivity region (HPR), Wisconsin, USA, we quantified the magnitude of pre-dispersal seed predation among individual plants differing in seed head densities. Out of a total of 303 M. fistulosa plants that were surveyed, we found half as many herbivores in seed heads in the LPR (n = 133 herbivores) compared to the HPR (n = 316). In the LPR, 30% of the seed heads were damaged in plants with low seed head density, while 61% of seed heads were damaged in plants with high seed head density. Seed head damage was consistently high in the HPR (about 49% across the range of seed head density) compared to the LPR (45% across a range of seed head density). However, the proportion of seeds per seed head that were destroyed by herbivores was nearly two times higher (~38% loss) in the LPR compared to HPR (22% loss). Considering the combined effects of probability of damage and seed loss per seed head, the proportion seed loss per plant was consistently higher in the HPR regardless of seed head density. Nevertheless, because of greater seed head production, the total number of viable seeds produced per plant was higher in HPR and high-density plants, despite being exposed to greater herbivore pressure. These findings show how large-scale factors can interact with local-scale factors to influence how strongly herbivores suppress plant fecundity.

Environmental variables drive plant species composition and distribution in the moist temperate forests of Northwestern Himalaya, Pakistan.

By assessing plant species composition and distribution in biodiversity hotspots influenced by environmental gradients, we greatly advance our understanding of the local plant community and how environmental factors are affecting these communities. This is a proxy for determining how climate change influences plant communities in mountainous regions ("space-for-time" substitution). We evaluated plant species composition and distribution, and how and which environmental variables drive the plant communities in moist temperate zone of Manoor valley of Northwestern Himalaya, Pakistan. During four consecutive years (2015-2018), we sampled 30 sampling sites, measuring 21 environmental variables, and recording all plant species present in an altitudinal variable range of 1932-3168 m.a.s.l. We used different multivariate analyses to identify potential plant communities, and to evaluate the relative importance of each environmental variable in the species composition and distribution. Finally, we also evaluated diversity patterns, by comparing diversity indices and beta diversity processes. We found that (i) the moist temperate zone in this region can be divided in four different major plant communities; (ii) each plant community has a specific set of environmental drivers; (iii) there is a significant variation in plant species composition between communities, in which six species contributed most to the plant composition dissimilarity; (iv) there is a significant difference of the four diversity indices between communities; and (v) community structure is twice more influenced by the spatial turnover of species than by the species loss. Overall, we showed that altitudinal gradients offer an important range of different environmental variables, highlighting the existence of micro-climates that drive the structure and composition of plant species in each micro-region. Each plant community along the altitudinal gradient is influenced by a set of environmental variables, which lead to the presence of indicator species in each micro-region.

Response of plant physiological attributes to altitudinal gradient: Plant adaptation to temperature variation in the Himalayan region.

Plants have evolved several metabolic pathways as a response to environmental stress like low temperatures. In this perspective, it is paramount to highlight physiological mechanisms of plant responses to changing environments. To determine the impact of cold stress on the physiological attributes of high altitude plant natives, i.e. Pedicularis punctata and Plantago major, we studied the protein, sugar and proline contents, as well as abscisic acid (ABA) and indoleacetic acid (IAA) in leaves collected from three different altitudinal ranges in Himalayan region of Pakistan. Leaves were collected at the initial blooming phase from each altitudinal range i.e. 2400-2500 m, 2950-3250 m and 3500-3550 m. Temperature decreases with an increase in the altitude which induces cold acclimation. Both plant species showed significant variation in the concentrations of the ecophysiological attributes evaluated at the different collection altitudes. The concentrations of all compounds except for IAA increased as temperature decreased and altitude increased. IAA showed an opposite response, that is, the concentrations of this phytohormone decreased with decreasing temperature and increasing altitude. We showed that temperature significantly affected the physiological attributes of Pedicularis punctata and Plantago major in the Himalayan region, which works as a proxy for understanding the plant responses to climate change. As per survival and risk assessment, underlying physiological mechanisms of plant response (understory plants) to changing environments (altitude and temperature ranges) revealed adaptation in the chilling environments. Further studies are needed to completely understand how the studied plants photosynthetic characteristics are affected by altitudinal gradient.