Discovery of a specialist Copelatinae fauna on Madagascar: highly ephemeral tropical forest floor depressions as an overlooked habitat for diving beetles (Coleoptera, Dytiscidae)

Diving beetles are generally aquatic and live submerged in water during larval and adult stages. A few groupshave colonised hygropetric habitats and fewer species still can possibly be referred to as terrestrial. Here wedescribe six new Copelatine species that were mainly found in dry shallow forest floor depressions in the easternand northeastern lowland humid forests of Madagascar. Three new species are described in each of thetwo genera Copelatus and Madaglymbus: Copelatus amphibius sp. nov., Copelatus betampona sp. nov., Copelatuszanatanensis sp. nov., Madaglymbus kelimaso sp. nov., Madaglymbus menalamba sp. nov., and Madaglymbussemifactus sp. nov. Diagnosis, description, known distribution, ecology, and conservation notes areprovided for each species. All species are illustrated with a dorsal habitus image, ventral and lateral views ofthe male penis, and parameres. Photographs of the unusual terrestrial habitats where the species were foundare provided. Madaglymbus menalamba sp. nov. is also documented with macrophotos and videorecordingsof the terrestrial locomotion and behaviour in the field. Although these species should not be classified asterrestrial, or even semi-terrestrial Dytiscidae, they seem to be specialists of very ephemeral aquatic habitatsand stay put instead of disperse when the habitat dries up. It is hypothesised that this lifestyle and behaviouron Madagascar is restricted to the high-precipitation humid forest regions mainly in the east. It may alsorepresent a transition step, or stepping-stone, towards becoming fully terrestrial, a step that the few knownterrestrial Dytiscid taxa once passed through. It is very likely that this type of habitat is overlooked for aquaticbeetles, not only in Madagascar, and the six species herein described may be just the “tip of the iceberg”

Bidessus longistriga Regimbart 1895

Bidessus longistriga Régimbart, 1895 Figs 2C, 3G Bidessus longistriga Régimbart, 1895: 79. Bidessus longistriga – Alluaud 1900: 59. — Zimmermann 1920: 54. — Guignot 1959: 254. — Bistr̂m 1985: 7. — Rocchi 1991: 85. — Nilsson 2001: 115. — Pederzani & Rocchi 2009: 93. — Nilsson & Hajek 2020: 104. Diagnostic characters Head frontally not margined but provided with a shallow, transverse depression slightly posterior to anterior edge of head (between eyes). Pronotum on disc with a broad impunctate area or with a few fine punctures, distinctly sparser than punctures at frontal and posterior edge. Pronotal striae at base deeply impressed. Pronotal striae with a distinct angle (not smoothly curved). Basal striae of elytra long. Sutural lines distinct; anteriorly and posteriorly lines fade away; transformed to row of punctures. Punctures on both side of basal striae of unequal size; distinctly coarser on inner side. Apical sternite with fine, slightly irregular punctures. Female with outline of elytra posteriorly smooth (minor extension absent). Penis in lateral view slender, curved but medially somewhat straightened. Penis apex not distinctly extended (Fig. 3G). Length of body 1.6–1.8 mm. Material examined 283 specimens (BMNH, NHRS, NMW, PBZT / MBC, DEUA) from provinces Antsiranana, Mahajanga, Toliara, Fianarantsoa and Toamasina (see Supplementary File 1). Distribution Endemic species to Madagascar but widely distributed on the island in lowland areas below 800 m a.s.l. (Fig. 4A). Collecting circumstances An apt flier that can be collected at light. At low altitudes on both east and west coast, found in a variety of stagnant waters (rice fields, ponds, pools in riverbeds), and in slow-flowing parts of rivers and canals. Often occurs sympatrically with B. perexiguus.Published as part of Bergsten, Johannes, Ranarilalatiana, Tolotra & Biström, Olof, 2020, A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae), pp. 1-18 in European Journal of Taxonomy 720 on pages 6-8, DOI: 10.5852/ejt.2020.720.1109, http://zenodo.org/record/406835

Bidessus Sharp 1882

<p> <b> <i>Key to species of</i> Bidessus <i>on Madagascar</i></b> </p> <p>1. Elytral stria long, approximately half the length of elytron (Figs 1A, 2C)...................................... 2</p> <p>– Elytral stria short, distinctly shorter than half the length of elytron (Figs 1 B–D, 2A–B)................ 3</p> <p> 2. Elytral stria straight (Fig. 1A); female ventrite with a deep, longitudinal furrow; female elytron posteriorly with a distinct, lateral extension (Fig. 1A)...... <i>B. apicidens</i> Biström & Sanfilippo, 1986</p> <p> – Elytral stria sinuate (Fig. 2C); female ventrite simple, no longitudinal furrow; female elytron posteriorly smooth, lacks extension.................................................. <i>B. longistriga</i> Régimbart, 1895</p> <p> 3. Small species (max. length 1.5 mm); elytra with distinct, longitudinal, pale markings (Fig. 2B)....................................................................................................................... <i>B. perexiguus</i> Kolbe, 1883</p> <p>– Larger species (length 1.5–2.0 mm); elytra predominantly dark, sometimes with minor, vague, pale markings (Figs 1 B–D, 2A)............................................................................................................... 4</p> <p> 4. Frontal transverse depression of head transformed to four minor, slightly vague, tubercles (Fig. 1B)................................................................................................. <i>B.</i> cf. <i>ceratus</i> Guignot, 1941</p> <p>– Frontal transverse depression of head not transformed to small tubercles (depression laterally distinct, medially vague)................................................................................................................... 5</p> <p> 5. Head and pronotum mainly pale, testaceous (Fig. 1D)................... <i>B.</i> cf. <i>nero</i> Gschwendtner, 1933</p> <p>– Head distinctly darker than pronotum (Figs 1C, 2A)....................................................................... 6</p> <p> 6. Elytral stria longer (approximately <b>⅓</b> of elytron length); body shape broad (Fig. 1C); pronotum extensively pale (dark markings reduced to narrow areas close to frontal and posterior edges) (Fig. 1C); antenna pale (Fig. 1C).................................................................... <i>B. anjozorobe</i> sp. nov.</p> <p> – Elytral stria short (less than <b>⅓</b> of elytron length); body shape slender (Fig. 2A); pronotum extensively dark (pale markings reduced to quite narrow medial area, often divided into two separate spots) (Fig. 2A); antenna segments 4–11 dark (Fig. 2A)................................. <i>B. nesioticus</i> Guignot, 1956</p>Published as part of <i>Bergsten, Johannes, Ranarilalatiana, Tolotra & Biström, Olof, 2020, A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae), pp. 1-18 in European Journal of Taxonomy 720</i> on page 3, DOI: 10.5852/ejt.2020.720.1109, <a href="http://zenodo.org/record/4068355">http://zenodo.org/record/4068355</a&gt

Bidessus ceratus Guignot 1941

<i>Bidessus</i> cf. <i>ceratus</i> Guignot, 1941 <p>Figs 1B, 3B</p> <p> <i>Bidessus ceratus</i> Guignot, 1941: 31.</p> <p> <i>Bidessus ceratus</i> – Guignot 1959: 257. — Bistr̂m 1985: 20. — Rocchi 1991: 85. — Nilsson 2001: 114. — Pederzani & Rocchi 2009: 93. — Nilsson & Hajek 2020: 104.</p> Diagnostic characters <p>Head frontally not margined. Slightly posterior to frontal edge with slight depression and anterior to it with three (sometimes four) transversely located, slight but clearly distinguishable tubercles. Pronotum on disc with a rather broad impunctate area. Pronotal striae distinct but not strongly impressed; striae angled and sinuate. Basal striae of elytra distinct but comparatively short. Sutural lines present but quite weakly developed; anteriorly they end clearly before reaching frontal edge of elytra; posteriorly they are transformed to a row of separate punctures slightly behind middle of elytra. Punctures on each side of elytral striae almost similar; fine, slightly irregularly distributed and somewhat sparse. Ventrite apically with distinct and quite dense punctures. Female with outline of elytra posteriorly smooth (minor process absent). Penis (lateral aspect) comparatively robust, evenly curved; (dorsal aspect), quite broad. Penis apex not distinctly extended (Fig. 3B).</p> <p>Length of body 1.8–2.0 mm.</p> Material examined <p>MADAGASCAR • 5 specs; “envir. de Perinet riv. Farimbany” [around Perinet, Farimbany river]; “(Q 800)” [800 m a.s.l.]; 18 Jul. 1970; N. Sanfilippo leg.; FMNH.</p> Distribution <p> A species as tentatively defined here distributed in East Africa and Madagascar (see Biström 1985). In Madagascar only known from Moramanga and Analamazaotra NP in east central parts (Fig. 4D). However, Pederzani & Rocchi (2009) identified seven specimens collected in southern Madagascar by Gerecke & Goldschmidt in 2001 as <i>B. ceratus</i> (specimens housed at BMNH and NMW). The series, which we have not studied, was collected north of Ranopiso (25.05° S, 46.67° E) near the southern part of Andohahela NP and ca 35 km west of Taolanaro.</p> Collecting circumstances <p>According to label information sampled at 800–1000 m a.s.l.</p> Taxonomic observation <p> <i>Bidessus ceratus</i> is described from Uganda in eastern continental Africa. When the <i>B. sharpi</i> species group was revised (Bistr̂m 1985), specimens from Madagascar were considered to belong to this species. There are, however, features, which indicate the existence of a separate species in Madagascar. No fresh specimens in ethanol are at present available for DNA analyses and accordingly the earlier interpretation is retained.</p>Published as part of <i>Bergsten, Johannes, Ranarilalatiana, Tolotra & Biström, Olof, 2020, A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae), pp. 1-18 in European Journal of Taxonomy 720</i> on pages 5-6, DOI: 10.5852/ejt.2020.720.1109, <a href="http://zenodo.org/record/4068355">http://zenodo.org/record/4068355</a&gt

A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae)

We review the species of Bidessus of Madagascar and describe Bidessus anjozorobe sp. nov. from material collected in Anjozorobe forest. Anjozorobe is part of the Anjozorobe-Angavo Protected Area, which is an important corridor of transition forest between typical eastern humid forests and the residual sub-humid forest of the Central Highlands. Bidessus longistriga Régimbart, 1895 and Bidessus perexiguus Kolbe, 1883 are widespread but endemic low-altitude species on Madagascar. Bidessus nesioticus Guignot, 1956 is an alpine species described from near the peak of the Ankaratra mountain massifs at 2500 m a.s.l. We recollected the species for the first time since its description, in Ankaratra and in a new area above 2000 m a.s.l. in the Andringitra mountain further south. Bidessus cf. nero Gschwendtner, 1933 is tentatively recorded for Madagascar for the first time but further studies are needed to test the status of mainland and insular populations. Bidessus apicidens Biström & Sanfilippo, 1986 has not been recollected on Madagascar since 1970. All species are endemic to Madagascar except potentially Bidessus cf. ceratus and Bidessus cf. nero described from Uganda and the Democratic Republic of the Congo, respectively. The older records of the two non-endemic species Bidessus complicatus Sharp, 1904 and Bidessus ovoideus Régimbart, 1895 on Madagascar could not be verified

Bidessus apicidens Bistrom & Sanfilippo 1986

<i>Bidessus apicidens</i> Biström & Sanfilippo, 1986 <p>Figs 1A, 3A</p> <p> <i>Bidessus apicidens</i> Biström & Sanfilippo, 1986: 46.</p> <p> <i>Bidessus apicidens</i> – Rocchi 1991: 85. — Nilsson 2001: 114. — Nilsson & Hajek 2020: 104.</p> Diagnostic characters <p> Head frontally not margined. Slightly posterior to frontal edge with a shallow, transverse depression, which medially is vague but still clearly discernible. Pronotum on disc with fine to very fine and sparse punctures (no clearly impunctate area). Pronotal striae at base strongly impressed; striae sinuate (not angled). Basal elytral striae quite long (length of stria almost half the length of elytra). Sutural lines in part vague; frontally and especially, posteriorly the lines are transformed to rows of punctures. Moreover, posteriorly, sutural row fades away; mixed with ordinary elytra punctures. Punctures on each side of elytral striae unequal; between sutural line and elytral stria punctures quite coarse, dense but somewhat irregularly distributed; outside elytral stria punctures distinctly finer and somewhat sparser. Last ventrite of female with a distinct, medial depression which is delimited by distinct, narrow and longitudinal keels. Female elytra outline posteriorly with a small but distinct, lateral expansion (unique character in <i>Bidessus</i> of Madagascar). Penis in lateral view quite slender, curved but medially slightly straightened. Penis apex not distinctly extended (Fig. 3A).</p> <p>Length of body 1.7 mm.</p> Material examined <p> <b>Paratype</b></p> <p>MADAGASCAR • 1 ♀; “envir. de Moramanga” [around Moramanga]; “(Q. 1000 c.a)” [1000 m a.s.l.]; 21 Jul. 1970; N. Sanfilippo leg.; FMNH.</p> Distribution <p>Endemic species to Madagascar and only known from around Antsirabe and Moramanga (Fig. 4D). Collecting circumstances poorly known. Sampled at mid (1000 m a.s.l.) and high (1600 m a.s.l.) elevations. Only two specimens are so far known.</p>Published as part of <i>Bergsten, Johannes, Ranarilalatiana, Tolotra & Biström, Olof, 2020, A new species of Bidessus from Anjozorobe-Angavo and a review of Malagasy Bidessus (Coleoptera, Dytiscidae), pp. 1-18 in European Journal of Taxonomy 720</i> on pages 3-5, DOI: 10.5852/ejt.2020.720.1109, <a href="http://zenodo.org/record/4068355">http://zenodo.org/record/4068355</a&gt