Peyerimhoffia jaschhoforum (Diptera, Sciaridae), a new deadwood inhabiting species from Canada

Abstract A new species of black fungus gnat from Canada, Peyerimhoffia jaschhoforum sp. n., is presented with a description, illustrations, biotope information and a brief discussion of the placement and concept of the genus Peyerimhoffia. P. jaschhoforum is characterized by a unique gonostylar structure where the apex is hollowed but not enclosed and contains a mass of mega setae housed within. P. jaschhoforum was reared from decomposing jack pine (Pinus banksiana Lamb.) deadwood using both in-situ and ex-situ photoeclectors. We documented three additional specimens originating from Fennoscandia that resemble P. jaschhoforum but differ based on a broader tegmen, placement of setigerous papillae behind the tegmen and the fused intercoxal area. Based on this, these specimens are assigned to a new subspecies, Peyerimhoffia jaschhoforum fennoscandica ssp. n.


Introduction
The Holarctic genus Peyerimhoffia Kieffer, 1903 was defined by , who presented a key and described several new species. Since then, additional closely related species have been placed within Peyerimhoffia (Hippa and , Vilkamaa et al. 2013, Shi et al. 2014, Rudzinski and Baumjohann 2009, Rudzinski and Baumjohann 2012 including species formerly included in the Corynoptera crassistylata group sensu Menzel and Mohrig (2000). However the concept of the genus in its current state is disputed with authors continuing to include crassistylata group species in Corynoptera (Menzel et al. 2011, Shin et al. 2013. Until a new analysis of the phylogenetic relationships between representatives is presented, we follow the concept of Vikamaa and Hippa. The following paper presents a new, slightly deviant addition to the genus, Peyerimhoffia jaschhoforum sp. n. and with coeval description of a Northern European subspecies, Peyerimhoffia jaschhoforum fennoscandica ssp. n.

Materials and methods
Thirty five specimens of the new species were collected in Ontario, Canada. Nine male specimens were collected from a jack pine (Picea banksiana) log (Fig. 1a) on the 22 July 2013 and again on the 6 August 2013 located in a closed canopy jack pine forest (47.572 -82.859) near Chapleau, Ontario, Canada. The log (29 cm ø) was in the early stages of decay (decay class 1 based on Rouvinen et al. 2002), with well intact bark. Six other specimens were collected from a similar log (decay class 1, 22cm ø) in the same forest. Two specimens were collected on the 22 July 2013, 6 August 2013 and 19 August 2013 respectively. All specimens were collected using in-situ photoeclectors (Fig. 1b) identical to those described in (Work and Hibbert 2011). Twenty male specimens were also collected from 70 cm log sections taken from a neighboring closed canopy jack pine forest (47.636 -83.243). These specimens were reared from logs in sonotubes between 19 May and 14 September 2013. Eighteen specimens were reared from a log section in advanced stages of decay (decay class 4, 9.5 cm ø). Two additional specimens were reared from separate log sections in advanced stages of decay (decay class 4, 17 cm ø). These specimens were collected from a broader study examining the ecological impacts of intensive biomass harvesting on saproxylic biodiversity. European specimens were collected by Catrin and Mathias Jaschhof in boreal mixed forests during expeditions in Northern Europe. Two specimens were taken with an aspirator and one with a sweep net.
Specimens were sorted using Nikon SMZ800 or Hertel & Reuss STE-5R stereo microscopes and stored in 70% ethanol. Type specimens were selected, dehydrated in 96% ethanol, dissected and slide mounted in Euparal or in Canada Balsam. Specimens were observed under an ISO9001 compound microscope with magnifications of 40×, 100× and 400×.
Specimens were photographed using a MCA-510 USB microscope camera by TUCSEN (Xintu Photonics Co., Ltd.). Between 15-40 images taken at different focal lengths were merged with the aid of the Public Domain Software CombineZP using the method "Weighted Average". Using GIMP software version 2.8.0., the colour images were converted to greyscale, contrast, and brightness were enhanced and a filter was applied to accentuate the outlines. After manual redrawing of the printed images and a subsequent greyscale scanning at 600 DPI, the final retouch was accomplished again using GIMP. We used scanning electron microscopy (Hitachi S-3400N Scanning Electron Microscope) to characterize the hypopygium. Prior to taking photos, the male gonostyli were dissected from the gonocoxites in 70% alcohol, transferred to 96% ethanol and dried. Gonostyli and gonocoxites were mounted on a single 12.7 mm aluminium specimen stub with epoxy resin and coated with platinum in preparation for secondary electron imaging. All photos were taken at an 11-19 mm working distance from the specimen. Species descriptions were prepared using DELTA (DEscription Language for TAxonomy) (Dallwitz et al. 1999). The following acronyms correspond to the museums and collections where specimens reside: The typical environment for P. jaschhoforum and the method of trapping used. a: One of the logs at Superior forest where nine specimens including the holotype were found. b: Two in-situ photoeclectors primed for use in Superior forest.

Diagnosis
P. jaschhoforum (Fig. 4a) is instantly recognizable by its long, drawn-out tegmen (Fig.  2a, e) that extends up to the base of the gonostyles. It also has a characteristic set of megasetae-like bristles (3-4) that are bunched together and slotted into the underside/ ventral part of the hollow apical tooth which is reminiscent of an upturned canoe (Figs  2b, 3b, c). On one of the paratypes we examined, the ventromesial sclerotization of the gonostylus was ruptured (Fig. 2b). This forced the megasetae-like bristles out from the sheath-like tooth that normally houses the bristles (Fig. 3b, c). When viewed with a fibre-optic lamp or otherwise, these setae may be visible within the tooth giving the illusion of surface topography/texture on the tooth. P. jaschhoforum can be separated from most similar looking species by the absence of long specialized setae and megasetae on the inner-sides of the gonostyles.

Etymology
Peyerimhoffia jaschhoforum is named in honour of Catrin and Mathias Jaschhof in recognition of their work on Sciaroidea and who collected provisional specimens from Northern Europe.

Distribution
Boreal zone of Nearctic Region.

Ecology
P. jaschhoforum appears to be associated with both early and advanced stages of decaying deadwood. In early stages of decomposition larvae most likely reside underneath the bark as interior wood is still intact. The affinity with deadwood likely explains why this species and other Peyerimhoffia species tend to be collected at and around ground level close to the soil surface . Peyerimhoffia species also tend to be some of the most minute Sciaridae potentially inferring poor dispersal ability. This suggests that Malaise traps may be relatively inefficient in sampling these species.

Taxon discussion
P. jaschhoforum appears to be a transitional form between the true Peyerimhoffia species such as P. vagabunda which have reduced palpi and a practically undifferentiated tibial organ and Peyerimhoffia s.l., formerly the Corynoptera crassistylata group. In P. jaschhoforum, the narrowly elongated gonostyles resembles Peyerimhoffia species such as P. thula, P. collina and P. semicurvata. The setigerous papillae behind the tegmen possibly suggests a relation with P. alpina, also belonging to the former Corynoptera crassistylata group sensu Menzel and Mohrig (2000). For these reasons, we placed it in the genus Peyerimhoffia.
In the current concept of Peyerimhoffia sensu , the absence or reduction of long, specialized setae may mislead the observer and suggest P. jaschhoforum is not part of Peyerimhoffia. However, modification on the mesial side of the gonostyles has been found in other enigmatic species, such as P. sepei . In P. jaschhoforum, we record the first reduction in these specialized setae. When compared to P. alpina, the sole Nearctic Peyerimhoffia species described to date, P. jaschhoforum differs in that the intercoxal area is not fused and the tegmen is narrower and longer. However the absence of long specialized setae at the inner side of the gonostyles isolates this species from all other potential congeners. Given the small size and the absence of recognizable characters, additional genetic characters will be helpful to correctly position P. jaschhoforum in a phylogeny. The interesting makeup of the gonostylar tooth and associated setae merits larger comparisons across the true Peyerimhoffia and Peyerimhoffia s.l. using scanning electron microscopy (SEM

Description and Diagnosis
The main characters are basically the same as in the nominate subspecies described above. Referring mainly to (Fig. 5), P. j. fennoscandica differs in the following ways: • the hypopygium is slightly larger • the apical tooth is narrower and hooked • the gonostyles are more tumid • the intercoxal area is fused and U-shaped • the first palpomere contains 1-3 bristles • the tegmen is broader and shorter with darkened lateral edges • the setigerous papillae are centrally located behind the tegmen when viewing ventrally

Etymology
The subspecies was named after the region Fennoscandia where it has been collected.

Distribution
Boreal zone of Palaearctic Region.

Ecology
The method used to collect specimens of P. j. fennoscandica was non-substrate specific (aspirator and sweep-net). It is therefore difficult to comment on its ecology. As it was found in mixed subalpine forest it appears to be forest associated but any deadwood associations are unconfirmed until more substrate specific sampling is carried out.