Belongs within: Dytiscidae.
Contains: Paroster, Sternopriscus, Nirripirti, Hydrovatini, Bidessini, Vatellini, Hyphydrus, Hydroporus.
The Hydroporinae is a clade of diving beetles distinguished from others in the family Dytiscidae by their pseudotetramerous pro- and mesotarsi (the fourth tarsal segment is much reduced, so that it appears absent). Hydroporines are divided between several tribes, with Laccornis supported as the sister group of all other hydroporines by its retention of laterotergites in the female genitalia (Miller 2001). The Methlini have the metafemur reaching the metacoxal lobe, and terga VII and VIII modified with tergum VIII posteriorly acute with dorsal and ventral lobes, the dorsal lobe forming a trifid structure.
The Hyphydrini lack posteromedial lobes on the metacoxae, and have the metatarsal claws unequal in length in both sexes, with the posterior claw shorter than the anterior (Miller 2001). Some authors have divided this group between the Hyphydrini sensu stricto, with an apically narrow, acute prosternal process, and the Pachydrini, in which the prosternal process is apically broad and truncate, but the latter was nested within the former by the analysis of Miller (2001). Members of Pachydrini and the genus Desmopachria share fusion of the metacoxae with the first abdominal ventrite.
The Hydroporini is an assemblage of mostly Holarctic diving beetles, with a group of species found in Australia. The monophyly of this group as generally recognised was not resolved by Miller (2001), who found it to be at least paraphyletic with regard to the Vatellini. The latter are characterised by a prosternal process that is completely excluded from the metasternum, metepisterna not reaching the mesocoxal cavities, and female genitalia with a heavily sclerotised, triangular process extending off the posterior end of the spermatheca (Miller 2001). Members of the Hydroporini include Necterosoma, a primarily Australian genus of diving beetles with outlying species in New Caledonia and Timor, with distinctly pentamerous protarsi, a small subapical spine on each elytron, and males with protibiae notched on the inner side.
Boreonectes: diversity hidden underwater
Published 12 November 2018
The beetle in the photo below (copyright Joakim Pansar) may or may not be Boreonectes griseostriatus. This small diving beetle, a few millimetres in length, has been regarded in the past as widespread with a distribution spanning the Holarctic region. However, in recent years it has become apparent that this single widespread species may actually be a number of more localised species in a skin.
This possibility had been considered for a while. In 1890, a Norwegian entomologist recognised distinct montane and coastal species, noting a tendency for the former to the neatly striped whereas the latter was more blotchy. Later authors, however, rejected this distinction. In 1953, a Russian author expressed the view that B. griseostriatus “varies markedly in many characters; all attempts to establish subspecies and varieties are unjustified, because almost all varieties are connected by transitions” (Angus et al. 2015). In its overall appearance, B. griseostriatus is a a fairly undistinguished small diving beetle. Most of the body surface is densely and finely punctate both dorsally and ventrally, and it lacks some of the modifications found in other diving beetles such as lateral grooves on the pronotum or sucker-hairs on the male tarsi (Angus 2010). This latter feature, offhand, is an adaptation that assists males who have it in clinging to the backs of females during mating. Their functionality would be much reduced in punctate species such as B. griseostriatus because the the uneven surface of the female would prevent the suckers from getting a grip, and phylogenetic studies suggest that their absence in Boreonectes may represent a secondary loss. I don’t know if the Boreonectes males do anything to make up for their absence; maybe they just have to grip tighter.
The complicated nature of B. griseostriatus‘ identity became really apparent in the 2000s when karyotypic studies on European specimens identified several different chromosomal races, distinct not only in chromosome topography but also in number, that may represent distinct species. The original B. griseostriatus of lowland Sweden possesses a karyotype of thirty pairs of autosomal chromosomes plus the X sex chromosome (sex is determined in this genus by an X0/XX system where males have one copy of the X chromosome and females have two, with no Y chromosome). Boreonectes multilineatus, the Scandinavian montane species, has 28 autosomal pairs. Other species have fewer. It appears likely that a similar thing is happening in Boreonectes to the situation I described in an earlier post for the bat genus Rhogeessa where mutations lead to chromosomes becoming fused or split. It is notable in this regard that Angus (2010) found several specimens of B. ibericus from Morocco that were heterozygous for a chromosomal fusion, so that a single fused chromosome was paired meiotically with distinct chromosomes 1 and 24.
Externally, however, these genetically distinct species remain all but indistinguishable. There may be a tendency for one species to be larger than another, or towards slightly different genital morphologies, but these differences are not distinct enough or consistent enough to provide a reliable guide to identification. Which, if you don’t have access to fresh specimens allowing a karyotype spread, is a problem.
Systematics of Hydroporinae
Characters (from Miller 2001): Prosternum and prosternal process strongly declivitous; pro- and mesotarsi pseudotetramerous in both sexes; scutellum usually not externally visible; median lobe usually bilaterally symmetrical; larva with clypeal margin produced anteriorly.
<==Hydroporinae [Actobaenidae, Hydroporini, Hygrotini, Hyphydrini] |--MethliniM01 | |--Methles cribratellusM01 | `--Celina Aubé 1837VB21, RL01 [incl. Hydroporomorpha Babington 1841RL01] | |--C. aculeataR89 | |--C. angustataR89 | `--C. hubbelliM01 `--+--Laccornis Gozis 1914VB21, RL01 [incl. Agaporus Zimmermann 1919RL01; LaccorniniM01] | |--L. difformisM01 | |--L. oblongusM01 | `--L. pacificusM01 `--+--+--HydrovatiniVB21 | `--+--PachydriniM01 | | |--Heterhydrus sudanensisM01 | | `--Pachydrus Sharp 1882VB21, RL01 | | |--P. globosus Sharp 1882 [incl. P. cribratus]FS90 | | |--P. obesusR89 | | `--P. princepsRL01 | `--Desmopachria Babington 1841M01, RL01 | |--D. dispersaM01 | `--+--D. bifasciataM01 | |--D. challetiM01 | |--D. convexaM01 | |--D. mendozanaM01 | |--D. ovalisM01 | |--D. striolaM01 | |--D. volatidiscaM01 | `--D. youngiM01 `--+--+--BidessiniVB21 | `--+--+--+--‘Hydroporus’ paugusM01 | | | `--Sanfilippodytes Franciscolo 1979M01, S86 | | | |--*S. sbordonii Franciscolo 1979RL01, S86 | | | `--‘Hydroporus’ vilisRL01 | | `--VatelliniVB21 | `--Necterosoma Macleay 1871VB21, LM87 | |--N. penicillatum (Clark 1862) (see below for synonymy)LM87 | |--N. aphrodite Watts 1978LM87 | |--N. darwini (Babington 1841) [=Hydroporus darwini]LM87 | |--N. dispar (Germar 1848) [=Hydroporus dispar]LM87 | |--N. regulare Sharp 1882 [incl. N. arcuatum Sharp 1882]LM87 | |--N. schmelzi Sharp 1882LM87 | |--N. susanna Zwick 1979LM87 | |--N. thoreyi (Clark 1862) [=Hydroporus thoreyi]LM87 | `--N. undecimlineatum (Babington 1841) (see below for synonymy)LM87 `--+--+--HyphydrusVB21 | `--+--GraptodytesVB21 | | |--G. flavipesM01 | | |--G. granularisM01 | | `--G. pictusVB21 | `--Porhydrus lineatusVB21 `--+--+--HerophydrusM01 | `--Hygrotus Stephens 1828VB21, RL01 | | i. s.: H. (Leptolambus) impressopunctatusVB21 [=H. (Coelambus) impressopunctatusM01] | | H. novemlineatusRL01 | | H. quinquelineatusC01 | |--H. laccophilinusM01 | `--+--H. inaequalisM01 | |--H. sayiM01 | `--H. versicolorM01 `--+--HydroporusVB21 `--Stictotarsus Zimmermann 1919VB21, RL01 [incl. Trichonectes Guignot 1941RL01] |--S. corpulentusM01 |--S. duodecimpustulatusVB21 |--S. griseostriatusM01 `--S. striatellusM01 Hydroporinae incertae sedis: Carabhydrus Watts 1978LM87 [CarabhydriniM01] |--*C. monteithi Watts 1978LM87 |--C. andreas Zwick 1981LM87 |--C. niger Watts 1978LM87 |--C. plicatus Watts 1978LM87 `--C. stephanieae Watts et al. 2007WM13 LaccornellusM01 CanthyporusM01 Kintingka Watts & Humphreys 1999BW04 `--K. kurutjutu Watts & Humphreys 1999BW04 Dimitshydrus Uéno 1996BW04 `--D. typhlops Uéno 1996BW04 Hyphovatus Wewalka & Biström 1994NR97 `--*H. dismorphus (Biström 1984) [=Hyphydrus dismorphus]NR97 HerocerasRL01 HyphoporusRL01 PseudhydrovatusRL01 Coelambus Thomson 1860M01, RL01 |--C. nigrescens [=Hygrotus (Coelambus) nigrescens]M01 |--C. patruelis [=Hygrotus (Coelambus) patruelis]M01 |--C. sellatus [=Hygrotus (Coelambus) sellatus]M01 `--C. unguicularis [=Hygrotus (Coelambus) unguicularis]M01 DeronectesM01 Haideoporus Young & Longley 1976S86 `--H. texanus Young & Longley 1976S86 Siettitia Abeille de Perrin 1904S86 |--*S. balsetensis Abeille de Perrin 1904AP04 `--S. avenionensis Guignot 1925S86 Morimotoa Uéno 1957S86 |--M. gigantea Uéno 1996BW04 |--M. morimotoi Uéno 1996BW04 `--M. phraetica Uéno 1957BW04 |--M. p. phraeticaS86 `--M. p. miurai Uéno 1957S86 ParosterLM87 Chostonectes Sharp 1882LM87 |--*C. gigas (Boheman 1858) [=Hydroporus gigas; incl. Hyphydrus humeralis Clark 1862]LM87 |--C. johnsonii (Clark 1862) [=Hydroporus johnsonii; incl. C. latus Sharp 1882]LM87 |--C. nebulosus (Macleay 1871) [=Hydroporus nebulosus]LM87 `--C. sharpi Sharp 1882LM87 Antiporus Sharp 1882LM87 |--*A. femoralis (Boheman 1858) [=Hydroporus femoralis]LM87 |--A. bakewellii (Clark 1862) [=Hydroporus bakewellii; incl. A. curtulus Sharp 1882]LM87 |--A. blakei (Clark 1862) [=Hydroporus blakeii]LM87 |--A. gilbertii (Clark 1862) [=Hydroporus gilbertii]LM87 |--A. interrogationis (Clark 1862) [=Hydroporus interrogationis]LM87 |--A. simplex Watts 1978LM87 `--A. wilsoni Watts 1978LM87 Hypodes Watts 1978 [=Tiporus Watts 1985]LM87 |--*H. undecimmaculatus (Clark 1862) [=Hydroporus undecimmaculatus, *Tiporus undecimmaculatus]LM87 |--H. alastairi Watts 1978 [=Tiporus alastairi]LM87 |--H. centralis Watts 1978 [=Tiporus centralis]LM87 |--‘Hydroporus’ collaris Hope 1842 (see below for synonymy)LM87 |--H. denticulatus Watts 1978 [=Tiporus denticulatus]LM87 |--H. giuliani Watts 1978 [=Tiporus giuliani]LM87 |--H. josepheni Watts 1978 [=Tiporus josepheni]LM87 `--H. tambreyi Watts 1978 [=Tiporus tambreyi]LM87 SternopriscusLM87 Barretthydrus Lea 1927LM87 |--*B. geminatus Lea 1927LM87 |--B. stepheni Watts 1978LM87 `--B. tibialis Lea 1927LM87 Megaporus Brinck 1943 [=Macroporus Sharp 1882 non Uhler 1875]LM87 |--*M. hamatus (Clark 1862) [=Hydroporus hamatus, *Macroporus hamatus; incl. Ma. lateralis Sharp 1882]LM87 |--M. fischeri Mouchamps 1964LM87 |--M. gardenerii (Clark 1862)LM87 (see below for synonymy) |--M. howittii (Clark 1862)LM87 (see below for synonymy) |--M. nativigi Mouchamps 1964LM87 |--M. ruficeps (Sharp 1882) [=Macroporus ruficeps]LM87 |--M. solidus (Sharp 1882) [=Macroporus solidus; incl. Ma. dilatatus Régimbart 1908]LM87 `--M. wilsoni Mouchamps 1964LM87 NirripirtiBW04 Iberoporus Castro & Delgado 2001BW04 `--I. cermenius Castro & Delgado 2001BW04 Siamoporus Spangler 1996BW04 `--S. deharbengi Spangler 1996BW04 Stygoporus Larson & LaBonte 1994BW04 `--*S. oregonensis Larson & LaBonte 1994NR97 Hydrocolus Larson et al. 2000RL01 |--H. deflatusRL01 |--‘Hydroporus’ oblitusRL01 `--H. picicornisRL01 Lioporeus Guignot 1950 [incl. Falloporus Wolfe & Matta 1981]RL01 Rhithrodytes Bameul 1989NR97 `--*R. crux (Fabricius 1792) [=Dytiscus crux]NR97 Nebrioporus Régimbart 1906M01, RL01 [incl. Potamonectes Zimmermann 1921RL01, Zimmermannius Guignot 1941NR97] `--N. macronychusM01 Heterosternuta Strand 1935M01, RL01 (see below for synonymy) |--H. pulcherM01 [=Hydroporus pulcherRL01] `--H. wickhamiM01 Oreodytes Seidlitz 1887M01, RL01 (see below for synonymy) |--O. congruusM01 |--O. natrixBM06 |--O. obesusM01 |--O. quadrimaculatusRL01 `--O. scitulusM01 Neoporus Guignot 1931M01, RL01 [incl. Circinoporus Guignot 1945RL01] |--N. clypealisM01 |--N. dimidiatusM01 |--N. solitariusM01 |--N. superiorisM01 `--N. undulatusM03 [=Hydroporus undulatusRL01]
Heterosternuta Strand 1935M01, RL01 [incl. Heterosternus Zimmermann 1919 (preoc.)RL01, Heterostethus Falkenström 1938 (preoc.)RL01]
‘Hydroporus’ collaris Hope 1842 [=Tiporus collaris; incl. H. gravidus Clark 1862, H. thoracicus Schaum 1847]LM87
Megaporus gardenerii (Clark 1862)LM87 [=Hydroporus gardeneriiLM87, Macroporus gardneriM96; incl. H. brunnipennis Macleay 1871LM87]
Megaporus howittii (Clark 1862)LM87 [=Hydroporus howittiiLM87, Macroporus howittiM96; incl. H. foveiceps Macleay 1871LM87]
Necterosoma penicillatum (Clark 1862) [=Hydroporus penicillatus; incl. N. costipenne Lea 1899, *N. vittipenne Macleay 1871]LM87
Necterosoma undecimlineatum (Babington 1841) [=Hydroporus undecimlineatus; incl. N. flavicolle Macleay 1871, H. wollastonii Clark 1862]LM87
Oreodytes Seidlitz 1887M01, RL01 [incl. Deuteronectes Guignot 1945RL01, Nectoporus Guignot 1950RL01, Neonectes Balfour-Browne 1944RL01]
*Type species of generic name indicated
References
[AP04] Abeille de Perrin, E. 1904. Description d’un coléoptère hypogé français. Bulletin de la Société Entomologique de France 9 (15): 226–228.
Angus, R. B. 2010. Boreonectes gen. n., a new genus for the Stictotarsus griseostriatus (De Geer) group of sibling species (Coleoptera: Dytiscidae), with additional karyosystematic data on the group. Comparative Cytogenetics 4 (2): 123–131.
Angus, R. B., E. M. Angus, F. Jia, Z.-N. Chen & Y. Zhang. 2015. Further karyosystematic studies of the Boreonectes griseostriatus (De Geer) group of sibling species (Coleoptera, Dytiscidae)—characterisation of B. emmerichi (Falkenström, 1936) and additional European data. Comparative Cytogenetics 9 (1): 133–144.
[BW04] Balke, M., C. H. S. Watts, S. J. B. Cooper, W. F. Humphreys & A. P. Vogler. 2004. A highly modified stygobiont diving beetle of the genus Copelatus (Coleoptera, Dytiscidae): taxonomy and cladistic analysis based on mitochondrial DNA sequences. Systematic Entomology 29: 59–67.
[BM06] Bergsten, J., & K. B. Miller. 2006. Taxonomic revision of the Holarctic diving beetle genus Acilius Leach (Coleoptera: Dytiscidae). Systematic Entomology 31: 145–197.
[C01] Csiki, E. 1901. Bogarak [Coleopteren]. In: Horváth, G. (ed.) Zichy Jenő Gróf Harmadik Ázsiai Utazása [Dritte Asiatische Forschungsreise des Grafen Eugen Zichy] vol. 2. Zichy Jenő Gróf Harmadik Ázsiai Utazásának Állattani Eredményei [Zoologische Ergebnisse der Dritten Asiatischen Forschungsreise des Grafen Eugen Zichy] pp. 75–120. Victor Hornyánszky: Budapest, and Karl W. Hierseman: Leipzig.
[FS90] Fleutiaux, E., & A. Sallé. 1890. Liste des coléoptères de la Guadeloupe et descriptions d’espèces nouvelles. Annales de la Société Entomologique de France, 6e série 9: 351–484.
[LM87] Lawrence, J. F., B. P. Moore, J. E. Pyke & T. A. Weir. 1987. Zoological Catalogue of Australia vol. 4. Coleoptera: Archostemata, Myxophaga and Adephaga. Australian Government Publishing Service: Canberra.
[M96] Masters, G. 1896. Catalogue of the described Coleoptera of Australia. Supplement, part II. Dytiscidae, Gyrinidae, Hydrophyllidae, Staphylinidae, Pselaphidae, Paussidae, Silphidae, Scaphididae, Histeridae, Phalacridae, Nitidulidae, Trogositidae, Colydiidae, Cucujidae, Cryptophagidae, Lathridiidae, Mycetophagidae, Dermestidae, Byrrhidae, Parnidae, Heteroceridae. Proceedings of the Linnean Society of New South Wales 21 (Suppl.): 695–754.
[M01] Miller, K. B. 2001. On the phylogeny of the Dytiscidae (Insecta: Coleoptera) with emphasis on the morphology of the female reproductive system. Insect Systematics and Evolution 32: 45–92.
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[NR97] Nilsson, A. N., & R. E. Roughley. 1997. The genus- and family-group names of the Dytiscidae—additions and corrections. Beiträge zur Entomologie 47 (2): 359–364.
[R89] Régimbart, M. 1889. Enumération des Haliplidae, Dytiscidae et Gyrinidae recueillis par M.r le Prof. L. Balzan dans l’Amérique méridionale et description de quelques autres espèces voisines. Annali del Museo Civico di Storia Naturale di Genova, Serie 2a, 7: 256–268.
[RL01] Roughley, R. E., & D. J. Larson. 2001. Dytiscidae Leach, 1815. In: Arnett, R. H., Jr & M. C. Thomas (eds) American Beetles vol. 1. Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia pp. 156–186. CRC Press: Boca Raton.
[S86] Spangler, P. J. 1986. Insecta: Coleoptera. In: Botosaneanu, L. (ed.) Stygofauna Mundi: A Faunistic, Distributional, and Ecological Synthesis of the World Fauna inhabiting Subterranean Waters (including the Marine Interstitial) pp. 622–631. E. J. Brill/Dr W. Backhuys: Leiden.
[VB21] Vasilikopoulos, A., M. Balke, S. Kukowka, J. M. Pflug, S. Martin, K. Meusemann, L. Hendrich, C. Mayer, D. R. Maddison, O. Niehuis, R. G. Beutel & B. Misof. 2021. Phylogenomic analyses clarify the pattern of evolution of Adephaga (Coleoptera) and highlight phylogenetic artefacts due to model misspecification and excessive data trimming. Systematic Entomology 46: 991–1018.
[WM13] Watts, C. H. S., & J. McRae. 2013. Limbodessus bennetti sp. nov., the first stygobitic Dytiscidae (Coleoptera) from the Pilbara region of Western Australia. Records of the Western Australian Museum 28 (2): 141–143.