A revision of the Argentinean endemic genus Eucranium Brullé (Coleoptera: Scarabaeidae: Scarabaeinae) with description of one new species and new synonymies

The evolution of Bolbites onitoides (Coleoptera: Scarabaeidae: Phanaeini): its phylogenetic significance, geographical polychromatism and the subspecies problem

The distribution of the iridescent dung beetle Bolbites onitoides can be divided, based on dorsal colouration, into a blue western-half and a red eastern-half. This has raised the question, in 1959, of whether the two colour variants could represent distinct subspecies. Having examined ~1200 specimens and evaluated the proposal under both an ontological and an operational subspecies concept, we conclude that B. onitoides should continue to be treated as a single monotypic species because: (1) two kinds of colour intermediates were found living among populations of the two main variants; (2) the distribution of the variants overlaps; (3) no other characters were seen to vary consistently in accordance with the colour variants; (4) the overall geographical pattern can be explained by phenomena other than (incipient) speciation, such as phenotypic plasticity and distinct selective regimes; and (5) colour has been extensively shown not to be a reliable indicator of speciation processes among dung beetles. By comparing our findings with other cases of polychromatism among scarabaeines, we discuss publications proposing subspecies taxa relying uniquely upon colour variants. We contend that, due to the often continuous, populational, polytopic and, several times, clinal nature of the intraspecific geographical variation, subspecies classification schemes should not be established simply to classify variation across a species range without a commitment to the reality as evolutionary entities of the taxa being proposed. The alternative stance championed by many contemporary authors to give trinomina to conspecific (meta)population lineages, in turn, may eventually prove to be adequate, but we express some of our concerns as to the feasibility of this practice. Whether these intraspecific taxa should be ranked in a Linnaean hierarchy – e.g. as subspecies – is equally an open question. We also elaborate on an evolutionary scenario where the role of the iridescence in sexual selection, as hypothesized in a previous work, may be an exaptation, not an adaptation, among the horned Phanaeina.

Male Horn Lack of Allometry May be Tied to Food Relocation Behaviour in Lifting Dung Beetles (Coleoptera, Scarabaeidae, Eucraniini)

The small dung beetle tribe Eucraniini includes extremely specialized species that have been defined as "lifters" according to their food relocation behaviour. They are characterized by the presence of well-developed expansions on the head and pronotum, which can be included in the large and varied group of horns, whose presence is usually related to complex reproductive tactics. In this study, two closely related species, Anomiopsoides cavifrons and A. heteroclyta, were examined employing traditional and geometric morphometrics to test whether the Eucraniini has polymorphic males that might exhibit different reproductive tactics, as in the sister tribe Phanaeini, for which a male trimorphism was demonstrated. If also present in Eucraniini polyphenism could be considered a plesiomorphy common to the two clades. The inter- and intraspecific shape variation and object symmetry of the head and the scaling relationships between body size and traits were evaluated. Marked interspecific and small intraspecific differences in shape variation, high symmetry, and similar isometric growth patterns were shown in both species. The hypothesis of male polymorphism in Anomiopsoides was thus rejected. Instead, the results supported the alternative hypothesis that Eucraniini lacks male polymorphism, perhaps due to functional constraints affecting the shape of the structures involved in their peculiar food relocating behaviour.

Scarabaeinae dung beetles from Ecuador: a catalog, nomenclatural acts, and distribution records

The Ecuadorian territory is divided into four natural regions: the coastal lowlands, the Andean highlands, the Amazon basin, and the Galapagos Islands. Each of these regions has its own ecosystems and specific vegetation. The purpose of this work is to compile an updated catalog of the Scarabaeinae (Coleoptera: Scarabaeidae) of Ecuador that includes distributional data and several nomenclatural acts. We compiled data from 25 scientific collections, with the examination of 13,550 scarabaeines; additionally, 390 bibliographic references were reviewed for their taxonomic histories. The Scarabaeinae fauna from Ecuador is represented by 33 genera and 223 species, with 45 range-restricted species; 27 species were erroneously recorded from the country. The following nomenclatural acts are made: (A) two new status as valid species: Canthon (Glaphyrocanthon) ohausi Balthasar, 1939, stat. n., and Deltochilum (Calhyboma) arrowi Paulian, 1939 stat. n.; (B) one new synonym: Uroxysmagnus Balthasar, 1940 = Uroxyslatesulcatus Bates, 1891, syn. n.; (C) two revalidated names: Canthidium (Canthidium) orbiculatum (Lucas, 1857) and Dichotomius (Luederwaldtinia) fortepunctatus (Luederwaldt, 1923); and (D) ten lectotypes designated for: Choeridiumorbiculatum Lucas, 1857; Choeridiumcupreum Blanchard, 1846; Canthidiumcoerulescens Balthasar, 1939; Canthonangustatus Harold, 1867; Canthonangustatusohausi Balthasar, 1939; Deltochilumtessellatum Bates, 1870; Pinotusfortepunctatus Luederwaldt, 1923; Pinotusglobulus Felsche, 1901; Uroxyslatesulcatus Bates, 1891; and Uroxysmagnus Balthasar, 1940. The type specimens related to the new nomenclatural acts are illustrated and the maps of the geographical distribution of all species are provided.

Daily Activity Patterns and Thermal Tolerance of Three Sympatric Dung Beetle Species (Scarabaeidae: Scarabaeinae: Eucraniini) from the Monte Desert, Argentina

Tolerance to extreme temperatures, thermal limits, and the mechanisms of thermoregulation are related to internal functions of insects and partly define their ecological niche. We study the association between daily activity of dung beetles from the Monte Desert in Argentina and their tolerance to high temperatures. Results indicate that for all three sympatric species studied, Eucranium belenae Ocampo, Anomiopsoides cavifrons (Burmeister), and Anomiopsoides fedemariai Ocampo, daily activity is associated to ground temperature. Eucranium belenae is active when ground temperature is relatively low and it is less tolerant to long periods of activity at high temperatures in the lab, while A. cavifrons and A. fedemariai are active when ground temperatures are higher, and they tolerate high temperatures for longer periods of time than E. belenae in the lab. These species coexist and use similar food sources, and this eco-physiological study may help to explain how they differentiate under the same environmental conditions. The Monte Desert is considered an extreme environment, and studies on thermal tolerance offer testable predictions to understand how species would respond to climate change.

Re-establishment of biting mouthparts in desert-living dung beetles (Scarabaeidae: Scarabaeinae) feeding on plant litter-Old structures reacquired or new ones evolved?

Evolution of mouthparts in adult dung beetles (Scarabaeidae: Scarabaeinae) for eating moist, fresh dung was linked with a loss of the ability to chew. However, the desert-living genus Pachysoma, probably evolved from a wet-dung feeding, Scarabaeus-like ancestor, has switched to a diet of dry fecal pellets (of rodents or small ruminants) and plant litter that requires re-establishment of chewing. Indeed, gut contents of a litter-feeding Pachysoma species indicate efficient food comminution. Based on scanning electron microscopy, cutting and grinding mouthpart structures in six Pachysoma species, of two lineages and with different food preferences, are described and compared with homologous structures in wet-dung feeding Scarabaeus species. In Pachysoma, cutting and breaking of large food items is probably performed by a clypeal scraper, a prominent epipharyngeal tooth and large maxillary galeal hooks. Further comminution is achieved by a large, grinding area evolved on the mandibular molae. Interspecific differences and the probable function and evolution of these structures are discussed. Particularly, the unique tools for cutting/breaking are completely novel structures and not results of some reacquisition of normal biting mouthparts.