Plant microbiomes are shaped by forces working at different spatial scales. Environmental factors determine a pool of potential symbionts while host physiochemical factors influence how those microbes associate with distinct plant tissues. These scales are seldom considered simultaneously, despite their potential to interact. Here, we analyze epiphytic microbes from nine Hibiscus tiliaceus trees across a steep, but short, environmental gradient within a single Hawaiian watershed. At each location, we sampled eight microhabitats: leaves, petioles, axils, stems, roots, and litter from the plant, as well as surrounding air and soil. The composition of bacterial communities is better explained by microhabitat, while location better predicted compositional variance for fungi. Fungal community compositional dissimilarity increased more rapidly along the gradient than did bacterial composition. Additionally, the rates of fungal community compositional dissimilarity along the gradient differed among plant parts, and these differences influenced the distribution patterns and range size of individual taxa. Within plants, microbes were compositionally nested such that aboveground communities contained a subset of the diversity found belowground. Our findings indicate that both environmental context and microhabitat contribute to microbial compositional variance in our study, but that these contributions are influenced by the domain of microbe and the specific microhabitat in question, suggesting a complicated and potentially interacting dynamic.

The genus Caeculus Dufour (Prostigmata, Caeculidae) contains 19 previously described species, most of which are found in North America, and for which no comprehensive phylogenetic treatment exists. Here, one new species from Alberta, Canada, is described: Caeculus cassiopeiae Bernard & Lumley, sp. nov., and another caeculid known to be present in Canada is documented. The new species is characterized within the genus with a character state matrix, from which an updated key is produced. A systematic analysis of all 20 species based on morphological and geographical distribution traits obtained from literature represents the first phylogenetic review of the genus.

We describe Bulasconotus scaccarius sp. nov., a new species of cylindrical bark beetle (Zopheridae: Colydiinae: Synchitini), elevating the number of described species in its genus to two. Despite discovering this species in Hawaii, we suspect, based on collections and survey data, that it is endemic to the South Pacific archipelago of Vanuatu and has only recently arrived in Hawaii. Evidence of the diet of closely related genera indicates that the new species may be a predator of ambrosia beetles (Curculionidae: Scolytinae), conceivably posing a risk to those that are endemic to Hawaii.

Populations and communities are known to respond to abiotic conditions, but the forces determining the distribution of particular insect pests are sometimes overlooked in the process of developing control methods. Bark and ambrosia beetles (Curculionidae: Scolytinae) are important pests of crops, forestry, and ecosystems worldwide, yet the factors that influence their success are unknown for many species. The Hawaiian archipelago is host to over three dozen invasive scolytines, many of which occur on Kauaʻi and are pests of agriculture. We analyzed scolytine community dynamics at two coffee estates: a hand-harvested site in a tropical wet forest and a mechanically harvested site in a tropical dry savanna. Our regression analyses show overall scolytine abundance was negatively correlated with rainfall, as were four species: the tropical nut borer (Hypothenemus obscurus), H. brunneus, Cryphalus longipilus, and Xyleborinus andrewesi. These relationships contributed to the compositions of the communities being markedly dissimilar despite having the same species richness. Multivariate analysis found no influence from temperature or harvest method on community dynamics. This information can be valuable for the timing of pest control methods, for predicting the success of possible new scolytine arrivals on Kauaʻi, and for forecasting how these species may spread with climate change.

A global shuffling of biodiversity is underway, propelled by human transport across natural dispersal barriers. We review the dissolution of biogeographic isolation, showing that modern biotic mixing is global, accelerating, and characterized by a diversity of nonnative species. Strategies to curb introductions now exist, but understanding how impacts accumulate with additional invasions remains critical. To characterize the consequences of this Great Shuffle, we first synthesize evidence that multiple invaders, including those with modest effects, can collectively inflict substantial ecological harm. Second, we review paleontological studies of prehistoric biotic exchanges showing how the number of species exchanged and the spatial extent of mixing correlate with long-term consequences. Because modern invasions are occurring more frequently and over broader scales than ancient events, their consequences may be more severe. By integrating contemporary and prehistoric insights, we highlight research needs and offer a framework for understanding the cumulative and long-term impacts of multispecies invasions.