Arthropod and oligochaete assemblages from grasslands of the southern Kenai Peninsula, Alaska

Abstract

BackgroundBy the end of this century, the potential climate-biome of the southern Kenai Peninsula is forecasted to change from transitional boreal forest to prairie and grasslands, a scenario that may already be playing out in the Caribou Hills region. Here, spruce (Picea × lutzii Little [glauca × sitchensis]) forests were heavily thinned by an outbreak of the spruce bark beetle (Dendroctonus rufipennis (Kirby, 1837)) and replaced by the native but invasive grass species, Calamagrostis canadensis (Michx.) P. Beauv. As part of a project designed to delimit and characterize potentially expanding grasslands in this region, we sought to characterize the arthropod and earthworm communities of these grasslands.We also used this sampling effort as a trial of applying high-throughput sequencing metabarcoding methods to a real-world inventory of terrestrial arthropods.New informationWe documented 131 occurrences of 67 native arthropod species at ten sites, characterizing the arthropod fauna of these grasslands as being dominated by Hemiptera (60% of total reads) and Diptera (38% of total reads). We found a single exotic earthworm species, Dendrobaena octaedra (Savigny, 1826), at 30% of sites and one unidentified enchytraeid at a single site. The utility of high-throughput sequencing metabarcoding as a tool for bioassessment of terrestrial arthropod assemblages was confirmed.

Using climate envelope models to identify potential ecological trajectories on the Kenai Peninsula, Alaska

“…Seedling recruitment for white and Lutz spruce decreased significantly when bluejoint reedgrass litter exceeded a threshold of 60% [30]. Unprecedented spruce mortality in the aftermath of beetle attack, coupled with human-caused grassland fires in spring, have promoted extensive grasslands on the northwestern slope of the Caribou Hills [48]. In fact, it was this qualitative shift in fire regime from canopy fires in late summer to grass fires in spring that prompted the Alaska Division of Forestry to change the official start of the statewide fire season from 1 May to 1 April in 2006.…”

Responding to Ecosystem Transformation: Resist, Accept, or Direct?

“…in an Alaskan ecosystem that supports 14 native tree species (Morton 2017). Extensive deforestation on the southern peninsula caused by spruce bark beetles, coupled with wildfire, has prompted the Kenai National Wildlife Refuge to consider introducing foundation species (Record et al 2018) to promote higher biodiversity via niche, structural, and compositional diversification in this developing novel (albeit depauperate) grassland ecosystem (Bowser et al 2017). This approach could be manifested as the use of prescribed fire and the introduction of a nonnative grazer such as wood bison Bison bison athabascae to steward the system towards a richer grassland, or the planting of nonnative trees that are resistant to spruce bark beetle (e.g., P. contorta) to promote a more resilient forest ecosystem.…”

Application of propylene glycol in DNA-based studies of invertebrates

“…Likewise, actively collected single specimens or -in a few cases -invertebrate bulk samples were fixed with PG (e.g. Bowser et al 2017Bowser et al , 2019Cordero et al 2017;Jusino et al 2019;Robinson et al 2020;. This taxonomically widespread application mimics the use of PG in traditional non-DNA-based research and application domains (primarily pitfall trapping; see Hohbein and Conway 2018) now entering the molecular field.…”

“…Systematic studies analysing the impact of PG fixation and preservation in the context of HTS are widely lacking. Still, first case studies indicate a high applicability of PG fixation for short read amplicon sequencing (metabarcoding; Bowser et al 2017Bowser et al , 2019Lefort et al 2017;Jusino et al 2019;Robinson et al 2020). In particular Robinson et al (2020) tested the effect of PG antifreeze fixation of homogenised mock communities and benthic bulk samples.…”