Review of the genus Fontidessus Miller & Spangler, 2008 (Coleoptera, Dytiscidae, Hydroporinae, Bidessini) with description of four new species

Abstract The genus Fontidessus Miller & Spangler, 2008 (Coleoptera: Dytiscidae: Hydroporinae: Bidessini) is reviewed. The genus now includes seven species with three previously described, and four new species described here: F. microphthalmus Miller & Montano, sp. n.; F. bettae Miller & Montano, sp. n.; F. christineae Miller & Montano, sp. n., and F. aquarupe Miller & Montano, sp. n. Each species is diagnosed and described, including the previously known species, based on new specimens and new information. Habitus, male genitalia and other diagnostic features are illustrated for each species. A key to the seven species is provided. Fontidessus species are unique to hygropetric habitats in the Guiana Shield craton of northern South American.


Introduction
Fontidessus Miller & Spangler was introduced to include three new species of diving beetles (Coleoptera: Dytiscidae) from northern South America (Miller and Spangler 2008). Members of the genus are characteristic of habitats where thin films of water flow over the surfaces of bare rock (hygropetric). Northern South America has a relatively rich fauna of hygropetric beetles including numerous diving beetles (Miller and Garcia 2011;Miller and Spangler 2008) and other water beetles (Miller 2009;Short and Garcia 2010;Spangler and Steiner 2005;Valladares and Short 2011). Most of this known diversity is from the western margin of the Guiana Shield. Additional collecting in Venezuela and farther east in the Guiana Shield region (Guyana and Suriname) and examination of collections in Venezuela has revealed additional new species and new distribution records for the described species. Less is known about hygropetric species in the eastern part of the Shield, and the presence of several new species in this recently described genus is tantalizingly suggestive of additional new diversity as this habitat becomes better explored. Two of the original known species were described from only few specimens, and the new material has clarified their morphology and variation considerably. Specimens of most species of Fontidessus are exceptionally small, even for Bidessini, and their male genitalia are complex and tiny with minute, diaphanous structures making critical examination difficult. Because of substantial new information, the entire genus is reviewed here with descriptions of four new species and clarifications of and corrections to the knowledge of distribution, morphology and variation of the three known species.

Materials and methods
Measurements were taken with an ocular scale on a Leica Discovery V8 dissecting microscope. Large and small specimens were measured to assess the range of sizes, and no attempt was made to determine average sizes. Measurements include: 1) total length (TL), 2) greatest width across elytra (GW), 3) greatest width of pronotum (PW), 4) greatest width of head (HW), and 5) distance between eyes (EW). The ratios TL/GW and HW/EW were also calculated and are provided to describe the overall shape and relative size of the eyes, respectively.
Specimens studied for this project are deposited in the Natural History Museum and Biodiversity Research Center, University of Kansas (SEMC, A.E.Z. Short), the National Zoological Collection of Suriname (NZCS, A. Gangadin), the Museo del Instituto de Zoología Agrícola Francisco Fernández Yépez, Universidad Central de Venezuela, Maracay, Venezuela (MIZA, L. Joly), the Center for Biological Diversity, University of Guyana (CSBD), and the Museum of Southwestern Biology Division of Arthropods, University of New Mexico (MSBA, K.B. Miller). Holotype deposition is indicated in the material examined sections for each species. Paratypes are distributed between these collections.
In the following treatments, species are organized according to general similarity (and their appearance in the key that follows), but it is not clear at this time what are the relationships between species of Fontidessus.
Diagnosis. Fontidessus differs from other Bidessini by the combination of: 1) a transverse occipital line across the head absent (Figs 1-9), 2) a pair of basal pronotal striae present (Figs 1-9), 3) a basal elytral stria absent (Figs 1-9), 4) an elytral sutural stria faintly present in some specimens (e.g. Figs 4, 5), 5) the anterior clypeal margin unmodified, evenly rounded 6) the elytron without longitudinal carinae, 7) the elytral epipleuron without a transverse carina at the humeral angle, 8) the prosternal process variable in shape (Figs 10-16), but extending to metaventrite, 9) the metatrochanter extremely large relative to the metafemur, approximately 0.6 × length of metafemur (Figs 17-23), 10) overall, the habitus elongate to oval, and the lateral pronotal and elytral margins nearly continuously and shallowly curved (Figs 1-9), and 11) the lateral lobes of the aedeagus two-segmented . In addition, a new character was identified based on new material with better-preserved male genitalia. Species of Fontidessus have a distinctive ventral sclerite associated with the male median lobe. In most species, this sclerite is short and oval (Figs 26B, 28-30B), but in F. toboganensis and F. aquarupe it is elongate (Figs 25B, 27B). In F. microphthalmus, though, the median lobe is complex with large dorsal and ventral portions (Fig. 24). The dorsal part may be homologous with the dorsal sclerite of other taxa. This species is different in several respects from other Fontidessus, and it is possible the ventral portion of the median lobe is, however, not homologous with the ventral sclerite in other taxa. Fontidessus is similar to Spanglerodessus Miller & García, but that genus lacks natatory setae (a possibly derived condition based on life in hygropetric habitats where swimming is not so important) and has a body that is very robust with the lateral pronotal margins extremely broadly expanded and rounded with the lateral margin of the body distinctly discontinuous between the elytron and pronotum. Also, the male median lobe of the single species, S. shorti Miller & García, does not have the distinctive ventral sclerite of Fontidessus. Nevertheless, the two genera appear to be similar. Natural history. All the known species of Fontidessus are hygropetric , and most are known from only one or few localities. They are characteristic of marginal and small aquatic habitats on inselbergs or other rock surfaces (Figs 34,36) and the margins of waterfalls (Fig. 35) in the Guaiana Shield region of northern South America . They can often be extremely abundant in these habitats. Several of the species co-occur, but others are the only known species at some sites (Figs 31-33).
Discussion. Two previously described species, F. ornatus and F. wheeleri, were based on few specimens. Each of the male holotype specimens had been previously dissected, and it clearly appears, based on acquisition and examination of new material, that the male median lobes had been switched between the two and each median lobe suffered some damage during its dissection. Therefore, the incorrect male genitalia were associated with each species in the original descriptions, and the descriptions of these structures were based on somewhat damaged material (Miller and Spangler 2008). This is corrected in the following treatments. Diagnosis. Fontidessus microphthalmus is small (TL = 1.4-1.6 mm), but larger than all species except F. toboganensis, F. bettae, and F. aquarupe which are comparable in size (Figs 1-5). The dorsum is more pale in color than other species (darker along the elytral suture and lighter at the apex, but without distinctive maculae), and the eyes are relatively smaller than other species (Fig. 1, HW/EW = 1.4-1.5). The male genitalia are distinctive. The median lobe has two parts. The dorsal part is extremely broad, apically truncate and medially has a narrow emargination (Fig. 24A). The ventral part is elongate and apically pointed (Fig. 24A). The lateral lobes curve inward apically between the two parts of the median lobe (Fig. 24A).
Male genitalia. Median lobe complex with two sections 1) an elongate ventral structure that is broad and evenly convergent to a narrowly rounded apex in dorsal aspect (Fig. 24A) and slender and evenly convergent to slight curved apex in lateral aspect (Fig. 24B), and 2) an elongate dorsal structure that is very broad, apically broadly truncate and medially narrowly emarginate in dorsal aspect (Fig. 24A) and slender in lateral aspect (Fig. 24B). Lateral lobes elongate, slender with apical segment medially curved between ventral and dorsal portions of median lobe (Fig. 24A).
Variation. No significant variation was observed among the few specimens examined. Etymology. The name of this species is derived from the Greek micro-meaning "small" and ophthalmos meaning "eye" for the relatively small eyes present in this species.
Distribution and habitat. The species is known from two sites, one on the Auyan Tepui of the Gran Sabana of Venezuela, and the other on Kasikasima in the Sipilawini District of Suriname ( Fig. 31) suggesting that the species may be characteristic of the Guyana Highlands. The specimens from Suriname are clearly hygropetric (Fig. 34), but the habitat is not known for the Venezuela specimens which were collected in an "intercept trap".
Comments. This is a problematic species. It is, in many ways, like other species of Fontidessus, but the male median lobe is unusually modified and the "ventral sclerite" is either absent or the large ventral part (Fig. 24) is homologous with that structure in the other species. Also, the eyes are quite small (Fig. 1). In some ways, it approaches Spanglerodessus shorti Miller and García in being broad, but its shape and structure, with the median lobe divided into two portions and the dorsal portion apically emarginate, is much more like species of Fontidessus.

Diagnosis.
Fontidessus aquarupe is small (TL = 1.5-1.7 mm), but larger than all Fontidessus species except F. toboganensis and F. bettae, which are comparable in size (Figs 1-5). The dorsum is dark with diffuse yellow maculae on the pronotum and elytron. The male genitalia are distinctive. The median lobe is broad and apically broadly pointed and curved dorsad (Fig. 24A, C). The ventral sclerite is long and broad, and apically subtruncate with distinct lateral pointed lobes (Fig. 24B). The lateral lobes are basally broad and apically are elongate and slender (Fig. 25A, D). The prosternal process is relatively broad, flattened and apically narrowly rounded (Fig. 11).
Coloration. Head dark brown; pronotum dark brown, black along anterior and posterior margins, with yellow transverse macula on each side anterior to middle (Fig. 2); elytron brown with diffuse pale areas anteriorly and with posterior extensions along lateral margins and near suture, apex with triangular pale area (Fig. 2). Ventral surfaces black to dark red-brown except prothorax, including prosternal process, yellow; antennae and appendages yellow to yellow-brown.
Variation. Specimens vary in the extent of dorsal coloration, particularly the extent to which the anterior diffuse elytral macula extends posteriorly along the lateral and sutural margins.
Etymology. This species is named aquarupe from the Latin, aqua, meaning "water", and rupe, meaning "rock" or "cliff" since specimens are known from hygropetric habitats.  Diagnosis. Fontidessus bettae is small (TL = 1.4 mm), but larger than all species except F. toboganensis, F. aquarupe, and F. microphthalmus, which are comparable in size (Figs 1-5). The dorsal maculae are distinctive. The elytron has a transverse, welldemarcated yellow macula near the anterior margin and a smaller, subapical yellow macula (Fig. 3). The anterior macula does not have medial or lateral posterior extensions along the disc (Fig. 3) as is often the case in F. tambopaticus (Fig. 5). The eyes in F. bettae are larger (Fig. 3, HW/EW = 1.5-1.6) than in F. microphthalmus (Fig. 1, HW/EW = 1.4-1.5). The male median lobe terminates in a narrow, pointed apex with only small lateral hyaline lobes (Fig. 26).
Coloration. Head brown, pronotum dark brown along anterior and posterior margins with prominent yellow transverse region near anterior margin, darker yellow brown medially (Fig. 3); elytron brown with distinct, well-defined, yellow, transverse but slightly oblique macula near base and yellow triangular shaped macula near apex (Fig. 3). Ventral surfaces of thorax and abdomen dark brown to black except prosternum, prosternal process, propleuron and pronotal epipleuron yellow-brown; appendages yellow to yellow-brown.
Sculpture and structure. Head with very fine, inconspicuous, irregular punctation, surface between punctures shiny with distinct microsculpture in the form of small cells; eyes medium in size (Fig. 3, HW/EW = 1.5-1.6). Pronotal surface similar to that of head; with posterior angles obtuse; lateral bead narrow, of even width throughout; pronotal striae finely incised, extending nearly 1/2 distance across pronotum (Fig. 3). Elytron with anterolateral angle obtuse, not extended anteriorly (Fig. 3); surface similar to pronotum. Prosternal process moderately broad, lateral margins evenly curved, apex of process narrowly rounded (Fig. 12); metacoxae impunctate, but with distinct microreticulation; metacoxal process with lateral lobe minute. Pro-and mesotarsi relatively narrow in both male and female, but slightly broader in male. Metatrochanter very large in relation to metafemur (Fig. 19).
Variation. There is some minor variation in the extent and distinctiveness of the dorsal maculae, but relatively little variation among the few specimens examined.
Etymology. This species is named to honor the second author's grandmother, Elizabeth (Betty) Baca, who deeply inspired her to live well and seek knowledge.
Distribution and habitat. Fontidessus bettae is known only from the type series in the Gran Sabana of Venezuela (Fig. 31). It was collected from "waterfall seeps", a hygropetric habitat along the margin of a waterfall (Fig. 35) Diagnosis. Although small for diving beetles, this species is relatively large for the genus (Figs 4, 5, TL = 1.5-1.6 mm). The prosternal process is moderately broad and parallel-sided and has the apex broadly truncate (Fig. 13). The male genitalia are distinctive with the median lobe elongate, slender and broadly recurved in lateral aspect (Fig. 27C). There is an elongate ventral sclerite that fits into the ventral groove of the median lobe (Figs 27B, C). Specimens are variable in coloration with specimens from Suriname indistinctly marked with maculae (Fig. 4) and specimens from Venezuela marked with diffuse but distinctive maculae on the elytra (Fig. 5).
Coloration. Head yellow brown, pronotum yellow brown, brown medially along posterior margin; elytron brown with the following yellow maculae: 1) a basal macula in a band extending from lateral to sutural margins, posterior margin of macula irregular, often with medial extension posteriorly along elytral suture, 2) a lateral longitudinal macula at humeral angle, 3) a narrow longitudinal macula along lateral margin medially, and 4) a subtriangular subapical macula (Figs 4, 5). Many specimens with elytral maculae reduced or indistinct (Fig. 4). Ventral surfaces of thorax and abdomen brown except prosternum, prosternal process, propleuron and pronotal epipleuron yellow-brown; appendages yellow to yellow-brown.
Variation. This species exhibits considerable variability in the extent of yellow coloration on the dorsal surface. Specimens from Venezuela are usually heavily marked with yellow maculae and fasciae on the elytron and have the pronotum and head yellow (Fig. 5). Specimens from Suriname, in contrast, have the elytral maculae reduced and very indistinct and the head and pronotum darker (Fig. 4).
Distribution and habitat. Fontidessus toboganensis is known from the extreme western margin of the Guayana Shield in the area around Puerto Ayacucho, Venezuela and from a few localities in Suriname (Fig. 32). In both areas it is extremely common and abundant in hygropetric habitats. The broadly disjunct distribution and differences in coloration suggest the possibility that the two populations are different species, but the male genitalia are shaped the same and the body is similarly shaped and sized. This is similar to F. ornatus which is also darker and less maculate in eastern localities than in western ones, though that species is also known from localities in between.
Material examined. ~627 specimens from the following localities: Diagnosis. Fontidessus christineae is extremely small (<1.2 mm) and very dark testaceous dorsally with only some diffuse, transverse yellow margins on the pronotum (Fig.  6). The male median lobe terminates apically in two broadly lobate rami (Fig. 28).
Coloration. Head dark red-brown, lighter anteriorly, pronotum dark red-brown along anterior and posterior margins with indistinct yellow-red transverse region across anterior half, darker yellow brown medially (Fig. 6); elytron dark red-brown (Fig. 6). Ventral surfaces of thorax and abdomen dark brown to dark red-brown except prosternum, prosternal process, propleuron and pronotal epipleuron red-brown; appendages yellow to yellow-brown.
Sculpture and structure. Head with very fine, inconspicuous, irregular punctation, surface between punctures shiny with distinct microsculpture in the form of small cells; eyes medium in size (Fig. 6, HW/EW = 1.5-1.6). Pronotal surface similar to that of head; with posterior angles obtuse; lateral bead narrow, of even width throughout; pronotal striae finely incised, extending nearly 1/2 distance across pronotum (Fig. 6). Elytron with anterolateral angle obtuse, not extended anteriorly (Fig. 6); surface similar to pronotum but with fine microsculpture cells more distinct. Prosternal process moderately broad, lateral margins slightly angulate, apex of process narrowly rounded (Fig. 14); metacoxae impunctate, but with distinct microreticulation; metacoxal process with lateral lobe minute. Pro-and mesotarsi broader in male than female. Metatrochanter very large relative to metafemur (Fig. 21).
Variation. No significant variation was identified in the single series of this species.
Etymology. This species is named after the second author's mother, Christine Anne Montano, who taught her to work hard and seek to achieve.
Coloration. Head yellow brown, darker in region near medial margins of eyes; pronotum yellow brown, diffusely brown medially along posterior margin and in narrow band along anterior margin; elytron brown with diffuse yellow pattern, yellow basally, laterally along about ¾ length of elytra and in subtriangular subapical area (Fig. 8).
Variation. This species exhibits considerable variation in color between the two main regions in which it has been collected (Surinam/Guyana and Venezuela). The eastern specimens are noticeably darker in overall coloration (Fig. 7) than those from Venezuela which are more distinctly marked with yellow maculae on the elytra and lighter in color on the pronotum and head (Fig. 8). The distinctive male genitalia (Fig. 29) are similar in each of the two populations, though, and so this color variation is regarded as intraspecific.
Distribution and habitat. Fontidessus ornatus is more widespread and common than other species in the genus. It ranges from the western margin of the Guiana Shield through northeastern Venezuela to central and southern Suriname (Fig. 33). It is found in hygropetric habitats.
Comments. The original description of F. ornatus included 15 specimens. This type series was mixed together with specimens of F. toboganensis and F. wheeleri. The holotype of F. ornatus had already been dissected, but based on considerable new material, it appears that the genitalia had been damaged somewhat and, worse yet, exchanged with the genitalia of what became the holotype of F. wheeleri. The genitalia are redescribed and reillustrated here based on newly dissected specimens with greater precision and in correct association with the species to which they belong.  Miller, 2008 Figs 9, 16, 23, 30, 31 Fontidessus wheeleri Miller, 2008 in Miller andSpangler 2008: 50. Type locality. Venezuela, Territorio Federal Amazonas, 40km S Puerto Ayacucho, at El Tobogan, Coromoto.
Coloration. Head yellow brown, brown along posterior margins and medial margins of eyes; pronotum broadly brown along posterior margin, narrowly dark brown along anterior margin; elytron brown with the following yellow maculae: 1) a basal macula in an irregular band extending posteriorly along suture at medial margin, 2) a lateral longitudinal macula posterior to humeral angle, broader anteriorly and extending posteriorly in narrow band to near apex, 3) a subtriangular subapical macula (Fig.  9). Ventral surfaces of thorax and abdomen dark brown except prosternum, prosternal process, propleuron and pronotal epipleuron yellow-brown; appendages yellow to yellow-brown.
Variation. The extent of the dorsal maculae varies among specimens with some having the maculae reduced, but most with extensive maculae that are well-defined.
Distribution and habitat. This species is known only from a few localities along the far western margin of the Guiana Shield around Puerto Ayacucho (Fig. 31). Specimens have been found in hygropetric situations.
Comments. This species was originally based on two specimens (the holotype and a paratype) that were originally collected together with the type series of F. ornatus and F. toboganensis, which were described at the same time (Miller and Spangler 2008). The holotype of F. wheeleri had been dissected some time prior to the original description, but, based on a few additional specimens examined for this paper, the male genitalia were apparently somewhat damaged (torn and crushed somewhat), and also switched with those of the holotype of F. ornatus, which had also been dissected previously. For that reason, the male genitalia are redescribed and reillustrated here based on newly dissected specimens in association with the correct species based on examination on a few additional specimens. This species has been only rarely collected.