The aquatic Coleoptera of Prince Edward Island , Canada : new records and faunal composition

Th e aquatic Coleoptera (Gyrinidae, Haliplidae, Dytiscidae, Hydrophilidae, Elmidae, Dryopidae, Heteroceridae) of Prince Edward Island, Canada is surveyed. Seventy-two species are now known to occur on Prince Edward Island, 26 of which are added to the island’s faunal list. Th ree species, Gyrinus aquiris LeConte, Oulimnius latiusculus (LeConte), and Helichus striatus LeConte, are removed since there are no voucher specimens or published records to substantiate their presence. Th e name Dineutus horni is designated as an incorrect subsequent spelling of Dineutus hornii Roberts, 1895. Th e composition of the fauna is briefl y discussed, both from regional and zoogeographic perspectives. Th ere is only one introduced species, Helophorus grandis Illiger. Only one third of the aquatic fauna recorded on the neighbouring mainland has been found on Prince Edward Island, perhaps refl ecting an island-associated diminution, the paucity of collecting, an area eff ect, or a combination of all these factors. Th e island faunas of Prince Edward Island, Cape Breton Island, and insular Newfoundland are compared. Prince Edward Island’s is 36% smaller than the others, in contrast with the island’s carabid fauna which is almost identical in magnitude with that of Cape Breton. Th is might refl ect dispersal obstacles, the relative paucity of aquatic habitats on the island, or an insuffi cient collecting eff ort. Further research would be desirable, both to better discern the composition of the province’s fauna, as well as to monitor the health of aquatic ecosystems in relation to anthropogenic activities.


Introduction
Water beetles are important members of many freshwater aquatic ecosystems.Knowledge of this group of insects in the Maritime Provinces, in general, and on Prince Edward Island, in particular, has been fragmentary.Smetana (1974Smetana ( , 1980Smetana ( , 1985Smetana ( , 1988) made important contributions to knowledge of the Hydrophilidae of the region, Oygur and Wolfe (1991) included information from the Maritime Provinces in their revision of the genus Gyrinus (Gyrinidae), and Larson et al. (2000) comprehensively surveyed the Dytiscidae.In the various chapters pertaining to aquatic Coleoptera in Bousquet (1991), 45 species are reported as occurring on the island.Prince Edward Island has, however, been one of the most poorly known jurisdictions in Canada in terms of its beetle fauna.Collecting eff ort has been sparse, and much of the material extant in historical collections has remained unexamined and unidentifi ed.Th e present study makes a contribution towards rectifying this situation by reporting the results of recent collecting of water beetles on the island, as well as the examination of existing historical materials in regional collections.

Methods and conventions
Voucher specimens of water beetles collected on Prince Edward Island and deposited in various collections were examined.Codens of collections (following Evenhuis 2007) referred to in the text are: Note: in some instances specimen records from the UPEI collection are given only for the province as a whole and for the time period 1974-83.Th ese specimens, identifi ed only by catalogue number on their pins, had their detailed collection data recorded in a ledger that was subsequently destroyed by fi re.Geo-referenced location coordinates for all collection sites are provided in Appendix 1.

Gyrinidae
Adults glide on the surface of ponds, lakes, and slow-moving rivers.Th ey often congregate and swim rapidly in circles when alarmed, giving rise to their common name of whirligig.Adults are scavengers, feeding on dead and dying insects on the water surface, whereas larvae are predaceous on insect larvae and nymphs (Roughley 2000a).Dineutus hornii is newly recorded on Prince Edward Island.Species of Dineutus are found on the surface ponds, streams, lakes and rivers where they often form large rafts of individuals (Roughley 2000a).

Dineutus nigrior
Dineutus nigrior is newly recorded on Prince Edward Island.

Gyrinus aquiris LeConte, 1868
Th is species was reported from Prince Edward Island by Roughley (1991a), however, there are no voucher specimens from PEI in any collection consulted, nor was the species listed from the province by Fall (1922) or Oygur and Wolfe (1991).Consequently this species is removed from the faunal list of Prince Edward Island.Newly recorded on Prince Edward Island, this species is found in both lentic (58.8%) and lotic (41.2%) environments (Oygur and Wolfe 1991).Fall, 1922 Prince Edward Island: locality data lost, 1974-1983 Newly recorded on Prince Edward Island, this species is found in both lentic (25.7%) and lotic (74.3%) environments (Oygur and Wolfe 1991).

Haliplus canadensis
Th e species was recorded from Prince Edward Island by Vondel (2005), however, the collection data for this species have not previously been published.Th e species was recorded from Prince Edward Island by Vondel (2005), however, the collection data for this species have not previously been published.Th e species was recorded from Prince Edward Island by Vondel (2005), however, the collection data for this species have not previously been published.
Peltodytes edentulus is newly recorded on Prince Edward Island.

Dytiscidae
Th e Dytiscidae are a diverse and species-rich family of predaceous water beetles.Th ey occur in many aquatic environments.Newly recorded on Prince Edward Island, this species is found in springs, small, creeks occasionally along the margins of small rivers on mineral substrates or in mats of vegetation at the edge of fl owing water (Larson et al. 2000).Newly recorded on Prince Edward Island, this species is found in sun-warmed, permanent lentic habitats in dense aquatic vegetation (Larson et al. 2000).Hatch, 1963 Queens Co.: locality data lost, VII.1979, L.S. Th ompson, (1, ACPE).

Rhantus wallisi
Newly recorded on Prince Edward Island, this species is found in ponds in wooded areas, in sun-warmed, vegetation-rich margins (Larson et al. 2000).Newly recorded on Prince Edward Island, this species is found in shallow, warm permanent ponds and sedge marshes; specimens have also been taken in beaver ponds and at the edges of slow-moving boreal streams (Larson et al. 2000).
Newly recorded on Prince Edward Island, this species is found in a variety of ponds and marshes, in particular those with sedges; it is an avid predator of early spring mosquito larvae (Larson et al. 2000).(Say, 1823) Kings Co.: Souris, 29.VI.1993,L.S. Th ompson, (1, ACPE).

Acilius mediatus
Newly recorded on Prince Edward Island, this species is found in small forest pools, generally with bare, peaty bottoms; also in pools or adjacent to slow-fl owing, brown-water streams (Larson et al. 2000).

Hydrophilidae
Th e aquatic members of the Hydrophilidae (the present account does not treat terrestrial species in the subfamily Sphaeridiinae) occur in a wide variety of aquatic environments, most of them in standing water and lentic habitats.Most species are scavengers, feeding on various kinds of decaying plant material, or else they feed on living plants such as algae (Smetana 1988).Newly recorded on Prince Edward Island, this species favours temporary pools and muddy or weedy margins of ponds or lakes (Smetana 1988).

Helophorus grandis
Th is adventive, Palaearctic species was fi rst reported in North America by Darlington (1927).Smetana (1985) examined specimens from as early as 1904 from Montreal, although Brown (1940)  Newly recorded on Prince Edward Island, this Holarctic species is found in a wide range of lotic and lentic environments, however, shallow temporary pools with plenty of vegetation are preferred (Smetana 1988).Newly recorded on Prince Edward Island, the species favours a wide variety of aquatic habitats favouring margins of deeper waters, particularly those with sandy bottoms and lots of debris (Smetana 1988).Newly recorded on Prince Edward Island.It is found in both lotic and lentic environments, however, little is known about its habitat preferences (Smetana 1988).
Newly recorded on Prince Edward Island, this species is found in both lotic and lentic environments, however, little is known about its habitat preferences (Smetana 1988).Newly recorded on Prince Edward Island, this species favours shallow standing water or margins of slow-fl owing creeks with vegetation.It is also frequently found in semi-aquatic habitats (Smetana 1988).
Th e zoogeographic status of this species is unclear.Smetana (1988) regarded it as an apparently Palaearctic species introduced to North America.He also drew attention to the fact that it appeared that two species, A. lutescens (Stephens 1829) and A. limbata, were being confused under the name of A. limbata in North America.Albrecht Komarek (pers.comm.), who is revising the genus worldwide, points out that while A. limbata and A. lutescens are readily separable in Europe, North American specimens cannot unambiguously be assigned to either species.He believes that North American specimens may represent a separate, undescribed "cryptic" species in the lutescens complex.Morphological examinations cannot resolve the problem and it may require molecular phylogenetic analysis in order to discern the nature of this "species."Th us, in the present treatment, I provisionally treat it as a Nearctic species in the lutescens complex whose status has yet to be fully discerned.Cheary, 1971 Prince Edward Island: locality data lost, 1974-1983, (1, UPEI); Queens Co.: St. Patricks, 14.VII.2002,C.G. Majka, in wet moss beside small stream, (1, CGMC).

Enochrus ochraceus
Newly recorded on Prince Edward Island, this species prefers shallow water with abundant organic debris (Smetana 1988).Newly recorded on Prince Edward Island, this is a common species, abundant in a wide range of aquatic habitats (Smetana 1988).Newly recorded on Prince Edward Island, this species is found in a wide range of aquatic habitats, particularly shallow, stagnant pools with plant debris; also in swampy habitats and Sphagnum bogs (Smetana 1988).Newly recorded on Prince Edward Island, this species prefers running water habitats in places protected from currents (Smetana 1988).

Dryopidae
Th e aquatic species of this family found in North America are riparian where they are found crawling on various substrates in streams.Adults and larvae are herbivorous (Shepard 2002b).LeConte, 1852 Although this species was recorded from Prince Edward Island by LeSage (1991b) there are no voucher specimens in any collection consulted, nor are there published records of this species from the province.It is not listed as occurring in PEI by Brown (1983a).Laurent LeSage (pers.comm.) was unable to determine the source of the original report.Consequently this species is removed from the faunal list of Prince Edward Island.

Lantenarius brunneus
Th e species was recorded from Prince Edward Island by LeSage (1991a), however, the collection data for this species has not previously been published.

Discussion
Seventy-two species of water beetles are known from Prince Edward Island: ten gyrinids, six haliplids, 40 dytiscids, 14 hydrophilids, four elmids, and one heterocerid (Table 1).Of these, 26 species are newly recorded from Prince Edward Island: fi ve gyrinids, one haliplid, six dytiscids, and 14 hydrophilids.Th ree species, Gyrinus aquiris LeConte, Oulimnius latiusculus (LeConte), and Helichus striatus LeConte, have been removed from the faunal list of Prince Edward Island since no voucher specimens or published records of these species on PEI could be located.Th ere are records of 49 species from Queens County, 39 from Kings County and 16 from Prince County.Th ese regional diff erences may be attributable to variations in collecting eff ort between these three portions of the province.Alternatively they may refl ect anthropogenic infl uences on the fauna since Prince County is the most heavily farmed portion of the island and in recent years the area has experienced a number of well-documented fi sh-kills due to pesticide run off .
Th e composition of the fauna refl ects that of the Maritime Provinces as a whole.All the species found on Prince Edward Island have also been recorded in Nova Scotia, and all but six [Dinetus assimilis Kirby, Haliplus canadensis Wallis, Peltodytes tortulosus Roberts, Copelatus glyphicus (Say), Hygrotus turbidus (LeConte), and Lantenarius brunneus (Melsheimer)] have also been recorded in New Brunswick.Th e absence of these six species in the latter province is likely attributable to a lack of collection eff ort in New Brunswick, a relatively poorly investigated province within Canada in terms of its beetle fauna.In general, Prince Edward Island's fauna appears to be relatively homogeneous in composition.For example, of the 40 species of Dytiscidae found on Prince Edward Island, all are broadly distributed in the Atlantic Maritime Ecozone and all 40 are also found in the neighbouring Boreal Shield and Mixed Plains Ecozones (Larson et al. 2000).
Th e Nearctic component of the fauna is made up of 64 species (89%), the Holarctic component of 7 species (10%), and the introduced, Palaearctic component of one species (1%).Th e proportion of Holarctic Carabidae on Prince Edward Island (10.5%) is very similar (Majka et al. 2008), however, the proportion of adventive aquatic species in comparison to the overall adventive beetle fauna of Prince Edward Island (21.2%, unpublished data) is very slight.
As is typical in the case with island faunas, that of Prince Edward Island is diminished in comparison with that of the neighbouring mainland.Table 2 indicates that the 71 native water beetles found on Prince Edward Island are only 34% of the  Larson et al. (2000), Larson and Roughley (1991), LeSage (1991aLeSage ( , 1991bLeSage ( , 1991c)), Roughley (1991aRoughley ( , 1991bRoughley ( , 1991c)), Smetana (1988), Vondel (2005) Majka et al. (2008) found that despite signifi cantly diff erent land areas, and diff erent distances to the neighbouring continental mainland, the island faunas of Prince Edward Island (with a land area of 5,660 km 2 and 13 km from the mainland) and insular Newfoundland (with a land area of 111,390 km 2 , 18 km distant from Labrador and 110 km from Cape Breton Island), are very similar (144 and 148 species respectively) despite diff erences in composition.Th e fauna of Cape Breton Island (with a land area of 10,311 km 2 and 1.5 km from the mainland) was 16% greater consisting of 170 species.In the case of aquatic beetles the situations is reversed.Table 2 indicates that the size of the Cape Breton and Newfoundland faunas are very similar (111 and 114 species respectively), whereas that of Prince Edward Island is 36% smaller consisting of 72 species.Th is diff erence could be due to several factors.It could be that the 13+ km wide Northumberland Strait has been a barrier to the dispersal of some species of aquatic Coleoptera; or the comparative lack of certain aquatic habitats on the island (which has only one freshwater lake and only relatively short watersheds); or the comparative lack of collecting on Prince Edward Island; or a combination of all these factors.Th ere are, however, more than 800 millponds and a large number of springs on the island, many of which have been little or not at all investigated in terms of their aquatic beetle fauna.Further research in these habitats may yield additional species for the Prince Edward Island fauna.
As a rather diff erent point of comparison, there have been 14 species of water beetles recorded on Sable Island (Table 2) which is circa 50 km 2 in area and is 160 km from the Nova Scotia mainland, although one of these species, Hydrophilus triangularis Say, was recorded only as a stray (Wright 1989).
Helophorus grandis is the only adventive water beetle found on Prince Edward Island and it is noteworthy that the collection from 1923 establishes a new early timeline for this species in the Maritime Provinces.Its collection in pitfall traps in agricultural fi elds may be indicative of a mode of introduction.Brown (1950) and Lindroth (1957) developed the theory that ships' dry ballast was a probable source of entry of many adventive ground-dwelling Coleoptera.It is possible that H. grandis might belong to the suite of adventive beetles that were introduced to North America via this mechanism.
Almost all of the knowledge that we have about the Prince Edward Island aquatic beetle fauna has been acquired recently.Of the 72 species recorded to date, all but eight (Gyrinus affi nis, Gyrinus bifarius, Laccophilus m. maculosus Say, Ilybius angustior (Gyllenhal), Colymbetes sculptilis Harris, Rhantus binotatus (Harris), Acilius semisulcatus Aubé, and Helophorus grandis) have fi rst been recorded in the last 50 years (and these eight species have also been recorded subsequently).Th us the very limited historical information on these aquatic insects on the island means that it is not possible to determine historical population trends.

Conclusions
Despite the many additions to the faunal list of Prince Edward Island, the preceding account clearly represents only a preliminary treatment of the aquatic beetles of the province.Th e comparative dearth of collecting means that it is likely that additional species remain to be found.As well, the detailed distribution of these species on the island remains to be discerned.Yves Alarie at Laurentian University has been conducting surveys on Prince Edward Island and it is to be expected that the results of his work will yield additional information.As well, D. Giberson and her students at the University of Prince Edward Island, continue to investigate aquatic habitats, programs that will also doubtless yield important comparative information on aquatic insects and invertebrates.Prince Edward Island has experienced a long history of anthropogenic activities, which in the past 60 years has included the extensive use of insecticides and other biocides.Ongoing surveying of populations of aquatic insects such as beetles, may provide avenues of monitoring the health of aquatic ecosystems and of environmental change.

Table 2 .
Composition of the Maritime Provinces aquatic Coleoptera Majka et al. (2008)2006)2006)ation from Newfoundland is provided as a basis of comparison.*excluding the Sphaeridiinae fauna (209 species) recorded in the Maritime Provinces.Th is may represent an island-associated diminution, the paucity of collecting, an area effect, or a combination of all these factors.In comparison,Majka and McCorquodale (2006)found that Prince Edward Island had 39% of the native Maritime Provinces fauna of Coccinellidae,Majka and Jackman (2006)found 40% of Maritime species of Mordellidae,Majka et al. (2007)found 32% of the native Maritime Cerambycidae, andMajka et al. (2008)found 49% of the native Maritime Carabidae that occur on Prince Edward Island.In an examination of the native Carabidae of insular portions of Atlantic Canada,