Contributions to the knowledge of Atlantic Canadian Histeridae (Coleoptera)

New records of Histeridae from Atlantic Canada are reported. Th ree species are newly recorded from Prince Edward Island and two from New Brunswick, one of which, the adventive Palearctic Atholus bimaculatus (Linnaeus), is newly recorded from Atlantic Canada as a whole. Th ese new records increase the known histerid fauna of the region to 37 species, 30 native and 7 introduced ones. Th e regional zoogeography of the Histeridae is examined focusing on diff erences between the faunal composition of the various provinces and the possible reasons responsible for these. Th e island faunas of Cape Breton, Prince Edward Island, and insular Newfoundland are examined. All have reduced faunas in comparison with the mainland perhaps as a result of island-associated diminutions, an area eff ect, a paucity of collecting, or a combination of these factors. Th ose of Cape Breton and Prince Edward Island are proportionately similar to those of other families of Coleoptera, whereas that of Newfoundland (only 10% of the mainland fauna) is signifi cantly less, a circumstance that deserves further investigation. Seven species of adventive histerids have been recorded in the region. Th e average dates of fi rst detection of these species are much later than the earliest records of these species in North America and comparatively later than is the case with other suites of adventive species in the Staphylinidae and Carabidae, perhaps as a result of the sparse attention the Histeridae have historically received by coleopterists in the region. Most of the adventive histerids are known to be synanthropic and may have been introduced to the region association with the importation of livestock and materials related to animal husbandry. Th e Histeridae of the region largely fall into one of several trophic guilds: coastal species and those associated with beach-drift material; species associated with bird nests; species associated with mammal nests; myrmecophilous species; saproxylic species found in sub-cortical environments; and generalist species found in a wide variety of decomposing situations.


Introduction
Historically the hister beetles (Histeridae) have been relatively neglected by both taxonomists and ecologists.Many species occur in decaying materials of all kinds, in ant nests, or under the bark of trees, and have received little attention.Th is has been unfortunate since the family is both economically and ecologically signifi cant.Th ose species found in decaying organic matter are predaceous, feeding on fl y larvae, while the sub-cortical species are predaceous on various wood and bark-boring insects.Other species are myrmecophilous and live in association with ants.
Over 3,800 species are known worldwide of which 435 species have been recorded in North America and 135 in Canada (Kovarik and Caterino 2000;Marske and Ivie 2003;Bousquet and Laplante 2006).Twenty-one species were recorded in Atlantic Canada by Davies (1991), although the records of Plegaderus transversus (Say, 1825) and Paromalus bistriatus Erichson, 1834 from Newfoundland were apparently in error.Th ey were not included in the comprehensive review and survey of the Canadian fauna by Bousquet and Laplante (2006) that recorded 36 species from the Atlantic Provinces.In their review 22 species are recorded from New Brunswick, 32 from Nova Scotia, 5 from insular Newfoundland, and 11 from Prince Edward Island.Th e present paper, based on ongoing research on the biodiversity of the Coleoptera of the region, reports new provincial records of fi ve species from Atlantic Canada, including one, Atholus bimaculatus (Linnaeus, 1758), newly recorded for the region.

Results
Aeletes politus (LeConte, 1853) Aeletes politus is newly recorded on Prince Edward Island.There are scattered records from throughout the Maritime Provinces, although it has not been recorded on Cape Breton Island (Fig. 1).It is known in Canada from Ontario, Quebec, New Brunswick, and Nova Scotia (with an isolated record from westcentral Alberta), and occurs south to Florida in the United States.It is found in forest floor litter, log litter, bracket fungi, tree holes, and compost (Bousquet and Laplante 2006).The above record from a brackish marsh represents an unusual habitat for this species, possibly attracted to the site by accumulations of decomposing litter.19.VII.2001, 14.VII.2002, 17.VIII.2002, 18.VIII.2002,Dryocoetes aff aber, Ips borealis, and Polygraphus rufi pennis burrows in Picea rubens, (7, CGMC).
Paromalus teres is newly recorded on Prince Edward Island.Th e species is generally distributed in the Maritime Provinces, although few records are known from New Brunswick (Fig. 1).It has been recorded in Canada from the Northwest Territories, Alberta, Ontario, Quebec, New Brunswick, and Nova Scotia and occurs in neighbouring states in the United States from Minnesota to New York and Connecticut.It is found under the bark of dead spruces and pines (Bousquet and Laplante 2006).Margarinotus faedatus is newly recorded on Prince Edward Island.Th e species is widely distributed in the Maritime Provinces (Fig. 1).It has been recorded in Canada from Ontario, Quebec, New Brunswick, and Nova Scotia, and occurs south to Texas and Georgia in the United States.It is found in decaying organic matter such as carrion, dung, and rotten mushrooms (Bousquet and Laplante 2006).
Hister curtatus is newly recorded in New Brunswick.Th is species has been recorded in Canada from southern Manitoba, Ontario, and Quebec as well as from Sable Island and from one site on the mainland (Lake Little, Halifax County) of Nova Scotia (Fig. 1).It is found in leaf litter and carrion (Bousquet and Laplante 2006).(Linnaeus, 1758) New Brunswick: Saint John Co.: Saint John, 27.III.1898,P. R. McIntosh, NBM.

Atholus bimaculatus
Atholus bimaculatus is newly recorded in New Brunswick and in Atlantic Canada.Th is introduced, Palearctic hister beetle has been recorded in Canada from British Columbia east to southern Québec (Bousquet and Laplante 2006).In Europe, it is known throughout the continent east to at least southern and central Russia (Yélamos and Lackner 2007).It is now almost cosmopolitan in distribution and is found in dung and decaying vegetable matter (Bousquet and Laplante 2006).

Discussion
Th ese new records increase the known histerid fauna of New Brunswick to 24 species (20 native and 4 adventive), that of Prince Edward Island to 14 species (12 native and 2 adventive), and that of the Atlantic Canada to 37 species (30 native and 7 adventive) (Table 1).

Regional zoogeography
Examining the composition of the fauna, several trends become apparent.Four native species, Plegaderus confusus Bousquet & Laplante, 1999, Geomysaprinus moniliatus (Casey, 1916), Hypocaccus bigener (LeConte, 1844) and Hister abbreviatus Fabricius, 1775, have been found in New Brunswick but not in Nova Scotia.Th ey are candidates for species that have, for climatic or other environmental reasons, reached the limit of their distribution in New Brunswick, or which have found the Northumberland Strait and/or the isthmus of Chignecto as obstacles to geographical dispersal.Alternatively, they could be present but have remained undetected.Th ey represent 13.3% of the native histerid fauna, very similar to the 12.4% of the native elaterid fauna (Majka and Johnson 2008) and 13.5% of the native carabid fauna (Majka et al. 2007) found in New Brunswick but not in Nova Scotia.
Th ere are ten native species, Gnathoncus barbatus Bousquet & Laplante, 2006, Platysoma lecontei Marseul, 1853, Platysoma defi ciens (Casey, 1924), Margarinotus cognatus (LeConte, 1844), Margarinotus confusus Wenzel, 1944, Margarinotus egregius (Casey, 1916), Margarinotus marginicollis (LeConte, 1845), Margarinotus stygicus (LeConte, 1845), Spilodiscus arcuatus (Say, 1825), and Atholus perplexus (Le-Conte, 1863), which have been found in Nova Scotia and not in New Brunswick.It is probable that many of these occur in New Brunswick but have not been detected as a result of the comparative paucity of collecting eff ort in the latter province.However, two species, M. stygicus and S. arcuatus, have not otherwise been recorded in Atlantic Canada nor from Québec.Th e Nova Scotia populations of both appear to be disjunct and isolated from the balance of the range of these species.Margarinotus stygicus, associated with mammal nests, is otherwise found in the United States north to southern Ontario and Rhode Island, whereas S. arcuatus is a primarily coastal species ranging from the Florida panhandle north to New Hampshire (Bousquet and Laplante 2006).It is possible that these species may have colonized Nova Scotia from the New England states (northeastern U.S.A.) across post-glacial, emergent land-bridges and island chains that existed between Cape Cod, Georges Bank, and the continental shelf of Nova Scotia from circa 14,500 to 8,000 years BP (King 1996).Th is mechanism is well documented in the case of Nova Scotia's coastal-plain fl ora (Keddy and Wisheu 1989).

Island faunas
Th e native island faunas of Cape Breton (10 species, i.e., 33% of the native fauna), with a land area of 10,311 km 2 and 1.5 km from the mainland, Prince Edward Island (11 species, i.e., 37%), with a land area of 5,660 km 2 and 13 km from the mainland, and insular Newfoundland (3 species, i.e. 10%), with a land area of 111,390 km 2 , 18 km distant from Labrador and 110 km from Cape Breton Island, are reduced in comparison with the mainland fauna.Th is may represent island-associated diminutions, an area eff ect, a paucity of collecting, or a combination of these factors.In comparison, 58% of native Carabidae and 50% of native Elateridae of the Maritime Provinces have been recorded on Cape Breton, and 47% of the region's native Carabidae and 38% of the Elateridae have been recorded on Prince Edward Island (Majka and Johnson 2008;Majka et al. 2007bMajka et al. , 2008)).Th ere are no species found on any of these islands that are not also present on the mainland.Th e native histerid fauna of insular Newfoundland (3 species, i.e. 10%) appears to be particularly impoverished.In comparison, 47% of the native Carabidae of Atlantic Canada have been recorded on Newfoundland (Majka et al. 2007b).It is unclear if this low representation is as a result of insuffi cient collecting or if other factors are responsible.Two of the native species, Hypocaccus fraternus (Say, 1825) and Baeckmanniolus dimidiatipennis (LeConte, 1824), are coastal species associated with beach drift (see below) while Paromalus teres is a saproxylic species found under the bark of coniferous trees.It may be that many North American histerids are less tolerant of colder, northern environmental circumstances.Bousquet and Laplante (2006) record only three histerids from the Yukon Territory, four from the Northwest Territories (all native species), and none from Nunavut or Labrador from a Canadian fauna of 135 species.Hypocaccus fraternus and B. dimidiatipennis have only been recorded in the extreme southwest of Newfoundland whereas P. teres is known only from the Avalon peninsula in the southeast of the province.
Th e beetle faunas of smaller islands in the region have been comparatively little investigated.Majka et al. (in press) reported H. fraternus in beach-drift material from Scatarie Island (2 km from the Nova Scotia coast) and Ogden and Majka (unpublished data) have found H. fraternus and B. dimidiatipennis in beach-drift material on Brier Island (1 km from the Nova Scotia coast).Wright (1989) recorded both species on sand beaches, as well as under carrion and horse dung, on Sable Island (160 km from the Nova Scotia coast).As halo-tolerant beach-drift inhabitants, these two species would appear to be able to disperse readily, either aerially or on fl oating material, to coastal and island environments.Wright (1989) also recorded Hister curtatus as common on Sable Island, a rather surprising discovery given the apparent scarcity of this species in the region as a whole.In discussing the mite (Acari) fauna of Sable Island Majka et al. (2007a) raise the possibility that such Sable Island "relict species" may have arrived there via post-glacial island chains and land bridges across the continental shelf and have subsequently been isolated by rising sea-levels, a circumstance which may also apply to the population of H. curtatus present there.

Adventive species
Seven species of adventive histerids have been recorded in the region (Table 2).Th e introductions of these species to North America evidently took place a considerable time ago since all seven are known from the continent from dates ranging from 1825 to 1862 with the mean date of fi rst detection being 1839.In contrast, these species in Atlantic Canada have been recorded only much more recently.With the exception of Atholus bimaculatus, which was recorded in New Brunswick in 1898, the other six species have only been fi rst detected in the region between 1948 and 1993 (mean = 1960), on average 121 years later than in North America.In contrast, of the 79 species of adventive Staphylinidae known in the Maritime Provinces, the mean date of their fi rst detection in North America is 1904, whereas the mean date of fi rst detection in the region is 1967, on average 63 years later (derived from Majka and Klimaszewski 2008).For the 35 adventive Carabidae found in the Maritime Provinces, the mean date of fi rst detection in North America is 1916 whereas the mean date of fi rst detection in the region is 1943, a diff erence of only 27 years (derived from Majka et al. 2007b).Th ese diff erences are probably in large measure attributable to the diff erent degrees of attention and collecting eff ort that these families have received in Atlantic Canada.Th e Carabidae have historically been much more extensively investigated than either the Staphylinidae or the Histeridae.Lindroth (1957) and Brown (1950) both proposed that dry-ballast shipments commencing in the early 17th century and continuing until the early 19th century, were responsible for the introduction of many Carabidae and other species of Coleoptera frequenting coastal environments.However, in his extensive survey of the seven principal sites in southwestern England where dry ballast originated, Lindroth (1957) found only one histerid, Margarinotus purpurascens (Herbst, 1792).Th is species is known in Canada only from southwestern British Columbia (Bousquet and Laplante 2006).
In contrast, at least four of the adventive histerids found in Atlantic Canada, Gnathoncus rotundatus (Kugelann, 1792), Dendrophilus punctatus (Herbst, 1792), Carcinops pumilo (Erichson, 1834), and Margarinotus merdarius (Hoff man, 1803) are synanthropic species associated with stables, hen houses, mills, granaries, and similar areas related to the husbandry of animals, or with the storage of dried products (Bousquet and Laplante 2006).Atholus bimaculatus, M. merdarius, and Margarinotus brunneus (Fabricius, 1775) are associated with dung, carrion, and decaying vegetation while Gnathoncus communis (Marseul, 1862) is found in bird nests.Th e synanthropic habits of these species suggest that they may have been introduced to the region, and to the continent, in association with the importation of livestock and materials related to animal husbandry.In this regard, D. punctatus is an apparent anomaly.Although in Europe it is most frequently found in bird nests, granaries, and mills, in North America it seems to be primarily a saproxylic species found under bark and in deciduous tree hollows (Bousquet and Laplante 2006).Possibly, in the New World, it has reverted to ancestral, pre-synanthropic habits.

Habits and habitats
Examining the environment column of Table 1, 28 species of Histeridae are predators found in saprophytic environments (dung, carrion, decaying vegetation, decomposing fungi, etc.); eight are saproxylic species, predators in subcortical or decaying wood environments; and one, Psiloscelis planipes (LeConte, 1852), is probably a myrmecophilous species associated with ant nests.Th e "habitat" column of Table 1 provides further bionomic details with respect to these species, indicating that a variety of habitats are utilized.
Although specifi c information with respect to P. planipes is lacking, other species in this genus are associated with ants.Adults capture and feed on ants (Kovarik and Caterino 2000).

Conclusions
Although Bousquet and Laplante's (2006) survey and revision was a milestone in terms of developing an understanding of the Canadian histerid fauna, it is evident that there is more to be learned with respect to this interesting and important family in Atlantic Canada.Th e Histeridae of New Brunswick remain relatively little investigated and it is likely that many additional species remain to be found there.Th e dearth of species recorded from Newfoundland is unusual and further fi eldwork is required to ascertain if this is due to a genuine paucity of species, or is an artifact of insuffi cient collecting.
of collections examined and referred to in this study are:

Table 2 .
Dates of fi rst detection of adventive Histeridae in Atlantic Canada