Rev. Mus. Argerztzno Czenc. Nat, n.s. l(li:49-52, 1999 Biodiversity in some lentie habitats from southern I. and Hydrophilini (Coleoptera, Ilydrophiloidea)

J. S. DENTON1 and A. OLIVA2

'26 Row Street, Alton, Hants CU34 INY, England, UK. ' Divisi6n Entomologia, Museo Ar.gentina de Ciencias Xaturaies "Bemardino Rivadavia" A". .4. Gallardo 470, 1405 Ruenos Aircs, Argentina

Abstract: Sampics of aquatic Coieopt~rawcre talien from 9 sites in suhiropicaYtemperate southern South- America. A new and several new rcgionvl rccords are reported. The regional affinities ofswimming and crawling Hydraphilidae in lentic habitats are discussed in the context of river basins.

Key words: Hydrophilidae, lentic habitats, biodiversity.

Studies of aquatic tend to concentrate Itatiaia NP straddles the Serra da on lotic habitats, especially mountain streams, Mantiqueira, a peculiar environment, where dry, because organisms adapted to such environments stoney foothills give way to rainforest with a rich are usually very sensitive to alteration of their diversity of species, including epiphytes. Several habitat. Dryopidae were found in streams. However, in Identic water bodies, however, have both this paper we concentrate on the samples taiicn academic and practical interest, as biodiversity in a large stagnant pond some 4 km north of in the major groups of' aquatic Coleoptera Itatiaia (in the grounds of the ilotel Repouso), It (Dytiscidae and Hydrophilidae) is greatest in had a stony substrate with little emergent such environments. In vast areas of South vegetation, and conedined large numbers offish. America, the distinction between permanently, Several species of Herosini are linou~nonly periodically or accidentally flooded lands may be from Ilio de Janeiro, which is close to Itatiaia vital to natural resource management. The NP. This made it all the more important as a pressure to drain wetlands is increasing, so there collecting site. is a real need for more data about biodiversity in The interest of the IberA system lies in its order to identify the most important areas for unique geological formation. The province of conservation. Man-made water bodies, such as Corr-ientes has roughly the shape of a trapeze, rice-fields and &an, lakes (an important source with the broadest side made up by the northern of electric power) should also he considered. limit (marked by the river Parani, which here This paper is based on samples taken by the flows nearly in an East-West direction). senior author during the austral summer of 1995- According to Neiff (1981), the province appears 96. The main targets were two National Parks as a great plain with the highest ground (about in areas of unusual charact,eristics, one, the 200 m above sea level) in the NE and the lower montane Itatiaia National Park (Brazil: Rio de (about 40 m a. s. I.) t,o the SW. The ccrllral claneirostate, on the Serra da Mantiqueiraj, and depression of the IberB covers about 1,200,000 the lowland Ibera National Park (Argentina: ha. Low sandy bars alternate with vast areas, Corrientes province, on the edge of the Ibera flooded either permanently or periodically. The lowlandsj. Other localities were sampled as plain was covered by a Triassic lava flow and travelling allowed, but with special interest for afterwards sufferod marine ingression. During t.hose at or close to National Parks or Nat,ure the Tertiary, the area ofMercedes (whichis close IZeserves. We thank Direccion de Parques to the Ibera National Park) and the eastern part Nacionales, of Argentina, for permission to of the province were raised, while the western collects at Ihera Natural Reserve. The material sector subsided. Finally, during the Quaternary iimm Calilegpta and Ptatiaia was taken outside period there was a raising of the whole land the Parks proper. between the rivers Parana and Uruguay (called 50 Revzsta del Museo Argentzuo de C~enczasNaturnles, n s. I ill

"Mesopotamia"in Argentina, andmade up by the material is kept in the collection of the senior provinces of Misiones, Corrientes and Entre author, with the exception of four specimens that Rios), and the river Parani settled into the new proved a new species (see Oliva, 1998), and of bed, which ii a geological fault. two more that represented new geographical Neiff (1981) describes six basic types of lentic records, and which are kept at the Museo water bodies in NE Argentina: Argentino de Ciencias Naturdlcs. These are a) lsolated ponds; primary productivity high; marked with asterisks. accumulation of dead organic matter low. Substrate sandy. Relatively young; water comes partly from superficial draining, partly from phreatic circulation. On the north-western sector 1. Brazil: State of Rio de Janeiro: Itatiaia. Large of the province. stagnant pond, rocky suhstrate, a little emergent b) Isolated ponds; low primary productivity. vegetation; Gyrinids on surface; many Fish On fine-grained soil with a high calcium and observed. 5/11/1995. sulphate contents. On the Cham plain. rnari.aritinusu Oliva. 1998 c) Isolated ponds; primary productivity high, Hemiosus rnoreirai Orchymont, 19214' bv vascular nlants: acumnlation of dead oreanic- Oerallus anicatus Orchvmont. 1940 matter high. Substrate sandy or clayey-sandy; a Trop~sterr~usovalzs Castelnau, 1840 superficial horizon of varying thickness (0.1-2.0 mm) of ooze ofvegetal origin. Water transparent 2. Argentina: Province of Misiones: Puerto (Secchi disk 70.100% total depth), amber- Iguazu. 1211 111995. Shaded stagnant forest pool. coloured because of organic content, of low saline apicipalpis Chevrolat, 1834 content, rarely with thermic stratification save Helobata cossyphoides (Bruch, 1915) in densely veget,ated sectors near the shore. Very rich in insects. Free water made up only 20% 3. Argentina: Province of Misiones (Dpto. around 1980, and it may have decreased due to Candeiaria): Martires. Road bridge, about 19 km the advance of "esteros". However, the NIi; of Santa Ana. Shallow, weedy marshy pool combination of lentic waters and sandy in a grazed field, with many emergent tussocks; substrates is very unusual outside this system; remarkably rich in insects. 15-1611V1995. this sort ofwater body is the most interesting to Berosus minimus Knisch, 1921 Berosus reticulatw Knisch, 1921 assess biodiversity. Derallusparanensis Oliva, 1981 d) Pools connected to streams and rivers; Tropisternus setiger (Germar, 1824) primary productivity high, by vascular plants; acumulation of organic matter low. Mainly 4. Argentina: Province of Gorrientes: Ibera. Camp around the Parana-Paraguay system. site near Laguna Iberi; shallow seasonal pools c) "Esteros": permanently flooded, densely in flooded fields C'bairado" sensu Neiff); also a vegetated areas; substrate originated by the deep, permanent lake with weeds C'estero" sensu remains of dead plants, with numerous pores Neiff?. lV1.995. bearing water of phreatic (in less quantity Berosus minimus pluvial) origin, acid and of a higher saline content Berosus corumhanus Knisch, 1921" than water of other ponds. Berosus patruelis Berg, 1887 f) "Baiiados": seasonally flooded areas, Berosus pedregalensis Jensen-Haarup, 1910 including some used for rice growing and others Berosus reticulatus used as pastures in dry season. Flooding may be Berosus decolor Knisch, 1924 due to river spates or to rain. angustus Sharp, 1882 Among several Eamilies of aquatic Tropisternus lateralis limbatus (Brulli., 1837) Tropisternus collaris (F., 1775) sampled, the Hydrophilidae have been chosenfor Enochrus uulgaris (Steinheil, 1869) a first paper, and within this family, the two main aquatic tribes, namely Berosini and Hydrophilini 5. Argentina: Province of Buenos Aires: San (sensu Hansen, 1991). Clemente del Tufl. Weed-choked ponds fringcd with tall emergent vegetation. 25/11/1995. MATERIAL AND METHODS Berosus festiuus Berg, 1887 Berosus coelacanthus Oliva, 1989 The insects were netted, killed and dry- Berosus pedregalensis mounted in the usual manner, and the Tropisternus setiger characteristics oi' the environment noted. The Tropisternus ignoratus Knisch Denton & Oliuu: Hydrophzlidae from lentic habitats 51

6. Argentina: Province of Salta: J. V. Gonzilez. 3. Martires: interesting only as intermediate Enochrw uulgaris locality record for the three species. Berosus minimus is a widespread species, but this 7. Argentina: Province of Jujuy: Calilegna. Bare appears to be the first record of it ibr Misiones pools with silty substrate among shingle bars of province. B. reticulatus in Misiones came from river, undoubtedly inundated during spates. 11 the eastern tip of the province (Oliva, 1989). 1996. Derallus paranensis is known from the middle Berosus auriceps Boheman, 1859 and lower course of the river Parana, from the Berosus reticulatus Knisch, 1921 NW ofArgentina, SE of Bolivia and northern half Hemiosus bruchi Knisch, 1924 of Paraguay (Oliva, 1981). Tropisternus jlauescens, Orchymont, 1922 4. lbera: B, corumbanus is a new record for Enochrus circumcinctw (Bruch, 1915) Argentina (Oliva, 1997). The fact that it was fo'nd with such species as 8.pedregalensis, B. 8. Bolivia: Department of Sanla Cruz: (Prov. patruelis andB. reticulatus shows this species to Sara): Buena Vista. Weedy marsh dykes (near be allied with young water bodies rich in organic ria Surutu) 27/1/1996. matt.er. The species obtained at the Ibera station Berosus holdl~a~~siKnisch, 1921 Berosus truncalipennis Castelnau, 1840 are interesting rather as intermediate locality Tropisternus collaris records than because of any peculiarity of their habitat preference. This is to be expected from 9. Bolivia: Department of Santa Cruz: Sajta. seasonal ponds. As to Laguna Iberi itself, Stagnant forest pool, open and free of weeds. 20/ Tropistel-nus colluris was oxtsemely abundant V1996. among the vegetated fringes. Many species were Berosus holdhausi also abundant in ponds connected to river Berosus auriceps systems. In fact, the sort of pools sampled in this Enochrus obsoletus (Brnch, 1915) expedition were perhaps not the most Tropisternl~slaevis (Sturm, 1826) representative of this extensive and unusual wetland system. DISCUSSION Certain species, notably members of the genus Hemiosus, are associated with sandy 1. Itatiaia: although not large, the sample substrates. One species is widespread in the provided some important records, including a province of Entre Rios, south of Corrientes; new species ofBerosus, and the first specimen of another two have been found at Misiones, one of Hemiosus moreirai known outside the type- which appears also in liruguay (Oliva, 1994).No material from Rio de Janeiro. Both species are information is available for Corrientes, but it is remarkable, with a smooth dorsal surface likely that some species occur in ponds with compared to related species. It may be added that sandy substrate, which do occur in the province. Hemiosi~sdimorphus Orchymont, 1940, known It would be or'interest to know whether the only from Rio de Janeiro (type-locality) and Santa psammophilous fauna of Corrientes resembles Catharina, is also remarkable by a smooth dorsal that ofMisiones at the North-east or that of Entre surface. Old records 1abelled"Rio de Janeiro"may Rios at the South. More extensive sampling is well refer to the hinterland of the province rather needed. than the city and its immediate environs. 5. San Clemente del Tnyii: a bathing resort Thenew species is unique, with a subglobular on the Atlantic coast, near the month of the Ilia shape recalling that of Derallus. Conversely, de la Plata. A large network of marsh dykes and Derallus anicatus, which was found in this seasonally floodedground occurs in the low-lying sample, is a large species (c. 4 mm) with smooth hinterland. The sample shows high diversity elytral disk. The size and sculpture might be without having a special fauna. Both Berosus adaptative to avoid predation by fishes. The pedregalensis and Tropisternus setiger are quite smaller species of Der<~llus(2-2.5 mm) would common pioneer species. Berosus fistiuus andB. presumably be easily snapped up. coelacanthus look very much alike, and may be The presence of Tropisternus ovalis is distinguished by small morpholo@cal characters remarkable, as this species is usually associated of the ventral structures and of the male with floating plants, especially Salvinia spp. genitaiia. Intriguingly, when both species occur 2. Ignazu: the singie species recorded is together, each one usually shows a different widespread in the Northeast of Argentina. degree of sclerotizing. San Clemente del TuyO is 52 Reulsta del Museo Argentlno de Ccenclus Naturales, n. s. 1 (1) just south of the 36"s parallel, whichis the known Proper studies of Riodiversity in lentic southern limit for B. coelacanthus. Berg's species habitats, especially areas threatened by draining extends further south, at least to General Hoca schemes andlor global climate changes, require in the province of Rio Negro, at 39'5. methodically prepared expeditions, and an 6. J. V. Gonzilez: a locality of no special appropiate level of funding. interest, save in that it is placed just within the Chaco plain. Enochrus vulgaris is a very common, pioneering species. ACKNOWLEDGEMENTS 7. Calilegua: the environment is characteristic of the NW and centre ofArgentina, We thank Dr Axel 0. Bachmann (Museo and both Berosus auriceps and Hemiosus bruchi argentino de Ciencias naturales) for are commonly found there (Oliva, pers, obs.). R. determination of the species of Tropisternus, and reticulati~sis a pioneering species confined in Dr. Liliana Fernindez (Facultad de Ciencias Argentina to the northern half of the country naturales y Museo, La Plata) for determination (Oliva, 1989). Tropisternus flauescens is a of the Acidocerina. widespread, rather pioneering species common in the Andean highlands, although there are some records from low altitudes. BIBLIOGRAPHY 8. Buena Vista: the vast flat area of Santa Cruz is continuous with the Chaco-Pampean Hanscn, M. 1991. The Hydrophiloid Beetles. plain. The wat,er- fauna reseinbles that of Phylogeny, Clasification and a Revisiorr of the Corumbi and the Mato Grosso iowiands, rather eenera (Coleontera. Hvdrouhiloideu).". Bioloc.- S'iirLfirr 40 1-367 than that of'the Andes. Xolff, J J 1981 Panorama de 10s cuemos dc arua. del 9. Sajta: a forest pool is always interesting. nordeste argentino. Symposia VI Jornadas arg. Berosus holdhausz is rarely abundant, but ranges Zooi. (I.uPlaia, 18-'23 Oct 1981j.lII.Ecologia: 115- from Corumbi in Brazil: Mato Grosso (from 151 where it was first described) to Argentina: La Oliva, A. 1981. El genero Dernllus Sharp en la Kioja: Iliar, c. 30"30'S (Oliva, 1989). it had been Argentina (Coieoptera, Hydrophilidae), Reuta Soc. recorded from ZI Cidrai (Santa Cruz ent, erg. 40(1-4): 285-296 department). Most of the previous records are - 1989. El genero rrosus (Coleoptera: Gom tree-less areas. At Sajta the beetles were Hydrophiiidaejen AinBrica dei Sur. Kevta Mus. arg. G(4): fdund in flooded wheel-ruts in a small forest Cs net. (Ent.), 67-235. Bueiios Aires. - 1.904.A revision ofthe genus Herniosus Sharp, 1882 clearing. It is likely that lhis is a pioneering in South America (Coleoptera: Hydrophilidaej. species olnew pools devoid of fish, where its poor Bull. Annls Soc. r. beige Ent. , j30 (7-9): 267-303 swimming ability (due to coarse dorsal sculpture - 1997. Rerosus coru,nba,cus Knisch, 1921 and sturdy shape; Oliva, 1989) is less important. (Coleoptera, Hydrophilidae) iiueva cita para la Argentina. Physis (Buenos Aires) B: 18. - 1998 A new species of Brrosus 1,caeh from CONCLUSION Soutl~easternBrazil (Coleoptera: I-Iydrophilidae), with some colnments on the possible evolutiol~aly The study of lentic habitats throws some light pressme of Hydrodynamics factors. Bull. Annls Soe. r. belxe Ent.131 (3):239-246. on distribution as related to river haL' sins. Thus, species described from Corumbi appear in Iberi because of the coniiection through the Recibido: 15-Xi-1997 river Paraguay. Aceptado: 2-X-1998