The effects of the invasive Harrisia cactus mealybug (Hypogeococcus sp.) and exotic lianas (Jasminum fluminense) on Puerto Rican native cacti survival and reproduction

Genomic and ecological evidence shed light on the recent demographic history of two related invasive insects

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.

Whole-Plant Seedling Functional Traits Suggest Lianas Also Support “Fast-Slow” Plant Economics Spectrum

Lianas are predicted to perform better than trees during seasonal drought among tropical forests, which has substantial implications for tree and forest dynamics. Here, we use whole-plant trait comparison to test whether lianas allocated on the resource acquisitive end of the continuum of woody plant strategies. We measured morphological and biomass allocation traits for seedlings of 153 species of trees and lianas occurring in a tropical forest in Thailand during the dry season. We first compared trait differences between lianas and trees directly, and then classified all species based on their trait similarities. We found that liana seedlings had significantly higher specific leaf areas and specific stem lengths than co-occurring tree seedlings. Trait similarity classification resulted in a liana-dominated cluster and a tree-dominated cluster. Compared to the tree-dominated cluster, species in the liana-dominated cluster were characterized by a consistent pattern of lower dry matter content and cheaper and more efficient per dry mass unit investment in both above- and below-ground organs. The consistency of all organs operating in tandem for dry matter content, together with optimized investment in them per mass unit, implied that the lianas and trees can be highly overlapped on the strategy gradient of the resource acquisition continuum.

Natural Enemies of the Harrisia Cactus Mealybug and Other Hypogeococcus Species (Hemiptera: Pseudococcidae) in Puerto Rico: Identification and Taxonomic Notes on Primary and Secondary Parasitoids

Primary and secondary parasitoids of Hypogeococcus spp. (Hemiptera: Pseudococcidae) on Cactaceae, Amaranthaceae, and Portulacaceae were reported from field surveys conducted in Puerto Rico, USA, since 2009. Resident natural enemies of the Harrisia cactus mealybug (HCM), Hypogeococcus sp., which is devastating native cacti in Puerto Rico and threatening cacti in the adjacent Caribbean islands, were documented prior to the planned introductions of non-native biological control agents from South America against this pest. Two species of Encyrtidae (Hymenoptera: Chalcidoidea) were recorded as primary parasitoids of the HCM on Cactaceae: Leptomastidea hypogeococci Triapitsyn, which was the most common, and Anagyrus quilmes Triapitsyn, Logarzo & Aguirre. Another primary parasitoid, Acerophagus sp. near nubilipennis Dozier (Encyrtidae), was also reared from a different Hypogeococcus sp. on Amaranthaceae and Portulacaceae. Hyperparasitoids, usually via L. hypogeococci, included Prochiloneurus narendrani Noyes & Triapitsyn (Encyrtidae), Pachyneuron sp. (Hymenoptera: Pteromalidae), Chartocerus elongatus (Girault), and Chartocerus niger (Ashmead) (Hymenoptera: Signiphoridae). Cheiloneurus chrisiantorresi Triapitsyn sp. n. (Encyrtidae) is newly described and illustrated; its status as a suspect hyperparasitoid of Hypogeococcus sp. on Amaranthaceae and Portulacaceae, along with that of Cheiloneurus sp., will need to be verified. The recorded HCM predators include one species of Chamaemyiidae (Diptera), Leucopina bella (Loew), and three species of Coccinellidae (Coleoptera): Cryptolaemus montrouzieri Mulsant, Decadiomus austrinus (Gordon), and Scymnobius flavifrons (Melsheimer).