Further contributions to the aleocharine fauna of the Yukon Territory, Canada (Coleoptera, Staphylinidae)

Abstract The aleocharine beetles of the Yukon Territory, Canada are reviewed based on material studied since the most recent survey of the territory in 2008. The present contribution recognizes a fauna of 125 species, of which 9 are new to science, 20 represent new territorial records and one represents a new Canadian record. Seventeen species are considered Holarctic, 6 introduced, and 2 species are of undetermined status (Holarctic or adventive). The Yukon fauna is classified in 32 genera and 8 tribes. The new species are: 1) Acrotona horwoodae Klimaszewski & Godin, sp. n.; 2) Atheta (Microdota) microelytrata Klimaszewski & Godin, sp. n.; 3) Atheta (Microdota) riparia Klimaszewski & Godin, sp. n.; 4) Atheta (Datomicra) whitehorsensis Klimaszewski & Godin, sp. n.; 5) Ocyusa yukonensis Klimaszewski & Godin, sp. n.; 6) Philhygra pseudolarsoniKlimaszewski & Godin, sp. n.; 7) Philhygra terrestris Klimaszewski & Godin, sp. n.; 8) Boreophilia davidgei Klimaszewski & Godin, sp. n.; and 9) Boreophilia herschelensis Klimaszewski & Godin, sp. n.


introduction
Aleocharinae is the largest subfamily of Staphylinidae and embraces a wide variety of morphologically and ecologically diverse species that are poorly documented in Canada. This subfamily is widely distributed in North America and occurs in almost all terrestrial habitats. Most species are found in forests where they occur in leaf litter, under bark, in fungi, in moss and within the nests of ants, mammals and birds. In forest litter, the aleocharine fauna is a dominant group and part of a complex ecological web that is responsible for nutrient cycling, which ultimately contributes to forest productivity and resilience (Buse andGood 1993, Leschen 1993).
Currently, over 400 species of Aleocharinae in 92 genera are recorded from Canada and Alaska (Gouix and Klimaszewski 2007, Majka and Klimaszewski 2010, Klimaszewski et al. 2011. In a checklist of Canadian Coleoptera, Campbell and Davies (1991) recorded 59 species of Aleocharinae from the Yukon Territory. Gouix and Klimaszewski (2007) reported a fauna of 65 aleocharine species and in a more focused study of Yukon material, Klimaszewski et al. (2008) described 6 new species and provided 24 new territorial records, raising the total number of species to 95.
The present paper provides an updated review of aleocharine beetles from the Yukon Territory and constitutes important baseline data for monitoring the impact of invasive species, pollution, natural resource extraction and climate change. Additionally, the information and illustrations contained herein will make it possible to incorporate this diverse subfamily into ongoing Canadian biodiversity inventories including those in the Canadian Arctic.

Materials and methods
Over 1,226 adults of Aleocharinae from the Yukon Territory were studied and most specimens were dissected to examine genitalia. The genital structures were dehydrated in absolute alcohol, mounted in Canada balsam on celluloid microslides and pinned with the specimens from which they originated. Photographs of the entire body and the genital structures were taken using an image processing system (Nikon SMZ 1500 stereoscopic microscope; Nikon Digit-like Camera DXM 1200F) and Adobe Photoshop software.
Morphological terminology mainly follows that used by Seevers (1978), Klimaszewski (1984) and Ashe (2001). The ventral part of the median lobe of the aedeagus is considered to be the part of the bulbus containing the foramen mediale, the entrance of the ductus ejaculatorius and the adjacent ventral part of the tubus of the median lobe with an internal sac and its structures (this part is referred to as the parameral side in some recent publications); the opposite side is referred to as dorsal. In the species descriptions, microsculpture refers to the surface of the upper forebody (head, pronotum and elytra).
In this second recent survey of the Aleocharinae of the Yukon Territory, 125 species in 32 genera and 8 tribes are reported, including two tentative records. Nine species are newly described herein, 20 additional species constitute new territorial records and one species represents a new Canadian record. There are 6 adventive and 17 Holarctic species known from the territory and the status of two other species cannot yet be determined as belonging to either category. Adventive species constitute 4.8% of the total known aleocharine fauna of the Yukon.

Discussion
The present survey increased the known Yukon aleocharine fauna from 95 to 125 species (Klimaszewski et al. 2008) and represents a significant contribution to the documentation of Canada's entomofauna. Recent baseline surveys of Aleocharinae in other regions of Canada reported 203 species from the Maritime Provinces of Canada, of which 174 have been recorded in the past decade (Majka and Klimaszewski 2010), and 172 species from Newfoundland and Labrador (Klimaszewski et al. 2011).
Intensive sampling of the aleocharine fauna of the Yukon is continuing by the second author and undoubtedly many more species will be discovered in the future. The study of the Yukon fauna is particularly significant for understanding the shift in some species distributions in response to climate warming and for establishing baseline biodiversity data for northern Canada. Additionally, the occurrence of a species in the Yukon Territory otherwise known only from the eastern part of the country provides some evidence for a natural Holarctic distribution. Therefore, a survey of the biodiversity of the Yukon also contributes to our knowledge of species suspected of being adventive.

Checklist of Aleocharinae species in the Yukon Territory
(* adventive species, ** Holarctic species, NTR=new territorial record for the Yukon Territory, NCR=new Canadian record; taxa in phylogenetic order). Etymology. Yukonensis -a Latin adjective derived from the Yukon Territory, Canada.
Distribution. This native Nearctic species is known only from the type locality in the Yukon.
Bionomics. Two adults were collected in July.

Origin Nearctic Distribution
Canada: NL, NB, MB, YT Comments. The two females are tentatively identified as G. criddlei but a male is needed for positive confirmation of this species in the Yukon Territory. Paratype (female). Same data as the holotype (ECW).

Acrotona horwoodae
Etymology. This species name is dedicated to Denise Horwood, wife of the second author, who assisted him in numerous aleocharine sample collections.
Bionomics. The specimens were found by sifting forest litter in May. Comments. The shape of the median lobe of the aedeagus and the spermatheca of A. horwoodae are different from all recorded species of Nearctic Acrotona, and they are generally similar to those of the Palaearctic species A. aterrima Gravenhorst, which is brown and has a much broader body. YT  Comments. Two additional Amischa morphotypes were recognized in the Yukon material on the basis of external body characters and the shape of the spermatheca. They are not included in this account because they are difficult to associate with any of the recorded species. The first morphospecies is represented by three narrowly elongate bicoloured specimens with the head and 4-5 basal abdominal tergites almost black, with the pronotum brown and the appendages and posterior of the elytra light brown, and with the spermathecal capsule moderately elongate with a moderately long apical invagination. The second morphospecies is represented by three specimens, which are broader, with the body uniformly dark brown to almost black, and the spermathecal capsule broader and shorter apically and with a longer apical invagination. Both groups have the apex of tergite 8 deeply notched. We need more specimens and representatives of both sexes to establish the status of these morphotypes. Etymology. The specific name derives from the name of the type locality, which is Whitehorse, Yukon.
This species is similar externally to Atheta (Dimetrota) hampshirensis Bernhauer and Atheta (Datomicra) dadopora Thomson but differs in the shape of the spermatheca and median lobe of the aedeagus, and has a broader body than the latter species.
Distribution. This native Nearctic species is known only from the type locality in the Yukon Territory.
This species bears some superficial external similarity to Geostiba and Emmelostiba but has typical Atheta-like genitalia.
Distribution. This native Nearctic species is known only from the type locality in the Yukon Territory.
Bionomics. Adults were found in aspen, alder and willow litter in March, May and September. Etymology. The name of this species derives from the Latin adjective riparius, -a, -um, in allusion to the wet litter where the types were found.
This species differs from other Nearctic Microdota by the combination of body shape, strongly punctate surface and the shape of the median lobe of the aedeagus and spermatheca.
Distribution. This native Nearctic species is known only from the Yukon Territory but it is probably more widely distributed in northern Canada.
Bionomics. The two males were captured in September in wet, organic litter and the female was found in mushrooms in mid-August. Figs 141, 314a-c, 442, in Klimaszewski et al. 2011 Distribution.
The following combination of characters distinguishes this species from other congeners: narrow, subparallel and uniformly black body, integument of forebody matte and with dense microsculpture, median lobe of aedeagus narrow apically and spermatheca S-shaped.
Distribution. This Nearctic species is known only from the type locality on Herschel Island, Yukon.
Bionomics. Adults were collected in June and July on an alluvial fan.
Comments. This species is superficially similar to B. nomensis Casey (=B. caseyiana Lohse) but differs by its uniformly black body and aedeagus with evenly narrow apical part of median lobe in lateral view. Etymology. Named for Douglas Davidge, biological technician (ECW), who supported the second author in his work for 20 years.
The following combination of characters distinguishes this species from other congeners: body narrow, subparallel and brown, with pronotum, elytra and legs lighter, antennae yellowish, surface of forebody moderately glossy and with dense microsculpture, and spermatheca short and S-shaped.
Distribution. This Nearctic species is known only from the type localities in the Yukon Territory.
Bionomics. Adults were collected from May to September from soil and organic litter.
Comments. This species may be easily distinguished by the unique shape of the spermatheca.