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Seed germination from fruits of Pilosocereus royenii that are uninfested (and healthy), lightly infested, and severely infested by Hypogeococcus sp. and from fruits growing on tumors caused by Hypogeococcus sp. A. Average cumulative percentage of germinated seeds per plant by observation day. B. Seed germination rates expressed as number of new seedlings between sampling intervals; negative numbers indicate higher seedling mortality compared to germination (or negative germination rate), positive numbers indicate a net germination rate growth, and 0's represent no net growth in the number of seedlings (either there was no mortality and no germination, or they cancel each other).
Source publication
We evaluated the impact of the Harrisia Cactus Mealybug (HCM), Hypogeococcus sp. (Hemiptera: Pseudococcidae), on seed germination of Pilosocereus royenii (Cactaceae) in Puerto Rico. Mature fruits were collected from individuals of P. royenii at various levels of HCM infestation, ranging from completely healthy plants to fruits growing directly on H...
Citations
Novel host plant–insect interactions often arise from human-mediated introductions of potential hosts to areas inhabited by native insects, or invasive insects to regions with suitable hosts. These novel interactions may drive ecological and evolutionary change in native species. Here we investigate the role of the introduction of the prickly pear Opuntia ficus-indica on the demographic history of the native moth Cactoblastis cactorum. The latter became a pest in its native range after the introduction of the economically cultivated prickly pear. We evaluated potential scenarios of long-term population size changes by applying a demographic simulation framework to a large set of high-throughput sequence data. We sampled populations of the cactus moth from regions of historical incidence of prickly pear crop, in central and northwestern Argentina. To shed insight into the shared history of the exotic cactus/native moth system we integrated the historical records of the introduction of O. ficus-indica in South America into the demographic simulation. We also included a null hypothesis of stable population and/or ancient population changes. Our results reveal population size changes in both Quaternary and contemporary C. cactorum populations. Simulations pointed to a recent population expansion that coincided with the hypothesis of the introduction of the prickly pear after the arrival of Europeans in South America. The presence of the new host during the last centuries apparently prompted the expansion of C. cactorum. Overall, our results are of interest to understand the ongoing impact of introduced species and the complex ecological adjustments of native insects that occur with the introduction of new hosts.
Graphical Abstract
Hypogeococcus pungens is a species complex native to southern South America that is composed of at least five putative species, each one specialized in the use of different host plants. Two of these undescribed species were registered as invasive in Central and North America: Hyp-C is a cactophagous mealybug that became an important pest that threatens endemic cactus species in Puerto Rico, and Hyp-AP feeds on Amaranthaceae and Portulacaceae hosts, but does not produce severe damage to the host plants. We quantified genomic variation and investigated the demographic history of both invasive species by means of coalescent-based simulations using high throughput sequencing data. We also evaluated the incidence of host plant infestation produced by both species and used an ecological niche modeling approach to assess potential distribution under current and future climatic scenarios. Our genetic survey evinced the footprints of strong effective population size reduction and signals of genetic differentiation among populations within each species. Incidence of plant attacks varied between species and among populations within species, with some host plant species preferred over others. Ecological niche modeling suggested that under future climatic scenarios both species would expand their distribution ranges in Puerto Rico. These results provide valuable information for the design of efficient management and control strategies of the Puerto Rican cactus pest and shed light on the evolutionary pathways of biological invasions.
