The fidius group constitutes the basal clade in a phylogeny of the Afrotropical members of the ge... more The fidius group constitutes the basal clade in a phylogeny of the Afrotropical members of the genus, Copris Müller, 1764. In this paper we describe Copris crassus Deschodt and Davis as a new species in this group. We also demonstrate that the distributional function between two body dimensions (lateral horn length and mid-line elytron length) differs between Copris fidius (Olivier 1789) and C. crassus. Copris bihamatus Balthasar, 1965 is also a member of the fidius group. Nguyen-Phung (1988) suspected that it was a synonym of C. fidius (Olivier) so we compare specimens of similar body size and use the distributional function between body dimensions to demonstrate that C. bihamatus is indeed a synonym of C. fidius. We provide a key for all known valid species in the fidius group, except C. serius Nguyen-Phung, 1987.
Trogidae constitute a monophyletic and biologically unique family within Scarabaeoidea, being the... more Trogidae constitute a monophyletic and biologically unique family within Scarabaeoidea, being the only keratinophagous group in the superfamily. Traditionally, the family has been divided into three distinctive genera, Polynoncus Burmeister, Omorgus Erichson and Trox Fabricius. Although the taxonomy of the group is relatively well studied, changes to the existing classification have recently been proposed and the family as currently constituted has not been subjected to phylogenetic analyses. Here we present a molecular phylogeny for this cosmopolitan family based on three partially sequenced gene regions: 16S rRNA, 18S rRNA and 28S rRNA (domain 2). Included in the analyses are representatives belonging to four of the five extant genera (and three of the four subgenera) from all major zoogeographic regions, representing about 20%of the known trogid species diversity in the family. Phylogenetic analyses performed included parsimony and Bayesian inference. We deduce their historical biogeography by using trogid fossils as calibration points for divergence estimates. Our analyses resolved relationships between and within genera and subgenera that are largely congruent with existing phylogeny hypotheses based on morphological data. We recovered four well-supported radiations: Polynoncus, Omorgus, Holarctic Trox and African Phoberus MacLeay. On the basis of this study, it is proposed that taxonomic changes to the generic classification of the family be made. The subgenera Trox and Phoberus should be elevated to genera to include the Holarctic and all the Afrotropical species, respectively, and Afromorgus returned to subgeneric rank. Estimates of divergence time are consistent with a Pangaean origin of the family in the Early Jurassic. The subsequent diversification of the major lineages is largely attributed to the break-up of Pangaea and Gondwana in the Middle Jurassic and early Late Cretaceous, respectively.
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 1998
Desiccation resistance and water balance were examined in the adults of seven trogid species, whi... more Desiccation resistance and water balance were examined in the adults of seven trogid species, which differed both in body size and in the habitats from which they were collected. Body water contents (51–58% fresh mass) and desiccation rates at 27 °C (0.00026–0.00093 g h−1) in these species were very similar to those of unrelated, similar-sized beetles from arid habitats. The keratin beetles
A phylogenetic analysis of the Scarabaeini, based on 244 morphological characters, including 154 ... more A phylogenetic analysis of the Scarabaeini, based on 244 morphological characters, including 154 multistate, and 3 biological characters, is given. Tree topologies generated from unweighted data and some weighted algorithms are similar and support only two genera in the tribe; Scarabaeus L. and Pachylomerus Bertoloni. The basal clade is Pachylomerus and sister to Scarabaeus. Kheper Kirby stat. nov., Pachysoma MacLeay, Scarabaeolus Balthasar and Sceliages Westwood stat. nov are the only supported subgenera. The genus Drepanopodus Janssens syn. nov. is synonymised with Scarabaeus and six additional names, Madateuchus Paulian, Mnematidium Ritsema, Mnematium M'Leay, Neateilchus Gillet, Neomnematium Janssens and Neopachysoma Ferreira remain synonyms. A monophyletic origin of flightlessness is generally supported with the subgenus Pachysoma the most derived group in this clade. Rolling dung balls backwards is the ancestral behaviour and predominant mode of food relocation in Scarabaeini although tunnelling, forward pushing, and can'ying are also utilised by some lineages. Pushing food has evolved independently in Sceliages species and S. galen us (Westwood) and a novel mode of forward food relocation evolved in the subgenus Pachysoma. Feeding on wet dung is the plesiomorphic condition and maintained by the majority of species in the tribe. The most unusual feeding behaviours in the tribe are represented by the obligate millipede-feeding species of Sceliages and the dry dung pellets and/or detritus used by members of the subgenus Pachysoma.
Larvae of the scarabaeoid genera Germarostes Paulian, Cyphopisthes Gestro, Paulianostes Ballerio,... more Larvae of the scarabaeoid genera Germarostes Paulian, Cyphopisthes Gestro, Paulianostes Ballerio, Ceratocanthus White, Pterorthochaetes Gestro, Madrasostes Paulian, Astaenomoechus Martínez & Pereira (Ceratocanthidae) and Hybosorus Macleay, Phaeochrous Castelnau, and Anaides Westwood (Hybosoridae) are described, keyed and illustrated with fifty-seven drawings. A phylogenetic analysis of these two families based on larval morphology is presented. Fifty-four larval morphological and three biological characters from twenty-seven taxa revealed nineteen equally parsimonious cladograms. The monophyly of (Ceratocanthidae + Hybosoridae) is supported by four unambiguous unique synapomorphies: dorsal medial endocarina on cranium extended anteriorly into frontal sclerite; presence of large membranous spot on apical antennomere; labium dorsally with four pores in center (secondarily reduced to two pores in some groups); and presence of stridulatory organ on fore-and middle legs (secondarily reduced in some groups). Our analysis suggests that the family Hybosoridae is paraphyletic with respect to Ceratocanthidae. The clade comprising the hybosorid genera Hybosorus and Phaeochrous is the sister group of the remaining Hybosoridae plus Ceratocanthidae. It is supported by two unambiguous synapomorphies: two apical antennomeres completely joined and the stridulatory organ represented by seven to nine large teeth anteriorly on the middle leg. The hybosorid genus Anaides is a sister group to the remaining Hybosoridae plus Ceratocanthidae (without Hybosorus and Phaeochrous) and the ceratocanthid genus Germarostes is a sister group to the remaining Hybosoridae plus Ceratocanthidae (without Hybosorus, Phaeochrous and Anaides). The ceratocanthid genera Cyphopisthes, Astaenomoechus, Paulianostes, Pterorthochaetes, and Madrasostes constitute a sister group to the hybosorid genus Cryptogenius and are supported by the presence of two reversions: two dorsal pores on labium and completely reduced stridulatory organs on fore-and middle legs.
containing 2.5 ϫ 10 5 PBMCs was added to each well after counting in the presence of trypan blue.... more containing 2.5 ϫ 10 5 PBMCs was added to each well after counting in the presence of trypan blue. The plates were incubated at 37°C for 4 hours before harvesting 20 l of supernatant. Percentage lysis was estimated as [(experimental counts Ϫ media control) ϫ 100]/(detergent counts Ϫ media control). Lysis of non-peptide controls was subtracted to give peptide-specific lysis. Media controls were between 10 to 15% of detergent controls. 22. One tetramer-positive CD8 ϩ cell was cloned directly into each well of a 96-well flat-bottomed plate (Nunc) in the presence of 10 6 irradiated PBMCs from at least three donors, together with phytohemagglutinin (5 g/ ml, Wellcome) in RPMI 1640 (Gibco) supplemented with glutamine, penicillin, streptomycin, and 5% human serum. After 4 days, Lymphocult-T (Biotest) was added to a final concentration of 10%. After 3 weeks the cultures were expanded into 24-well plates.
In Maputaland, South Africa vegetative and microclimatic changes on mined dunes drive the composi... more In Maputaland, South Africa vegetative and microclimatic changes on mined dunes drive the composition of the dung beetle fauna toward convergence with that in natural dune forest on unmined dunes. We assessed the pattern of these changes using a 23-year vegetational chronosequence on mined dunes, which passes from grassland (approximately 1 year) to open Acacia shrubland thicket to Acacia karroodominated woodland (approximately 9 years). Across this sequence, which represents successional stages in the restoration of dune forest, there was a sequential trend toward convergence in dung beetle species composition in both the entire species complement and, particularly, in shade specialist species. However, species abundance patterns showed a trend toward convergence only in early chronosequence Acacia woodland, followed by a decline in similarity between dung beetle assemblages of older Acacia woodland and unmined natural forest. This trend toward divergence was common both to the entire species complement, which includes widespread taxa, and to species endemic to Maputaland or the east coast. These trends in similarity and dissimilarity between dung beetle assemblages closely parallel the greater physiognomic and microclimatic similarity between early Acacia woodland and natural forest and the relative dissimilarity of older Acacia woodland. In conclusion, although percentage similarities between dung beetle assemblages of approximately 12-year woodland and natural forests were comparable with those between each natural forest stand, decline in similarity in older woodland stands suggests that lasting convergence in dung beetle species abundance will only be attained once the Acacia woodland is replaced by secondary natural forest.
Discontinuous gas exchange cycles are demonstrated in Omorgus radula (Erichson) (Coleoptera, Trog... more Discontinuous gas exchange cycles are demonstrated in Omorgus radula (Erichson) (Coleoptera, Trogidae) for the ®rst time, thus extending evidence for such cycles to another family of beetles. The closed,¯utter and open phases of the cycle were clearly distinguishable in this species, and the duration of these phases was 221 T 28, 1403 T 148 and 755 T 43 s (mean T SE), respectively. No evidence for signi®cant intraspeci®c mass scaling of VCO 2 or any of the components of the cycle was found. Although the prolonged F-phase recorded here is unusual for many insects, it has previously been found in other scarabaeoid beetles, especially those from xeric environments. It has been suggested that such modulation of the discontinuous gas exchange cycle may result in a reduced VCO 2 and, consequently, reduced water loss. In O. radula VCO 2 (15.25 T 1.49 ml/h) was considerably lower than that predicted from its body mass (0.207 T 0.006 g). However, the small relative contribution of respiratory transpiration (6.5%) to total water loss indicated that reduced VCO 2 has little to do with water economy. Rather, it may be a consequence of generally low activity levels of these beetles. The low respiratory water loss, but distinct subterranean component in the adult life of O. radula, lend some credence to the hypothesis suggesting that regular use of subterranean habitats might have been responsible for the evolution of discontinuous gas exchange cycles. However, non-adaptive hypotheses can still not be discounted.
Although discontinuous gas exchange cycles (DGC) are known from many insects, the effects of body... more Although discontinuous gas exchange cycles (DGC) are known from many insects, the effects of body size and temperature on DGC have not been widely examined. Here, these effects are investigated in five Scarabaeus dung beetle species from mesic and xeric habitats. The investigation tests two hypotheses: that previous estimates of the scaling exponents for the DGC and its characteristics are more broadly applicable to insects, and that, in response to temperature, both DGC frequency and the quantity of CO 2 emitted during the open (O) phase (Ophase emission volume) are modulated. Like previous workers, we find that scaled as mass 0.968 and that O-phase emissioṅ Vco 2 volume scaled as mass 0.833. However, temperature-associated increases in (Q 10 's of 2.19-2.65) were modulated mostly bẏ Vco 2 increases in DGC frequency since O-phase volumes remained constant across temperature. Flutter (F)-phase and O-phase durations were closely coupled to DGC duration, although the relationship between closed (C)-phase duration and DGC duration was less pronounced. We show that ventilation phase coefficients, previously considered a measure of the proportional duration of each phase of the DGC, calculated from the slopes of these relationships are a measure of change in phase duration with change in DGC duration and not a measure of the way in which total DGC duration is apportioned among phases. We suggest that proportions be used to estimate the contribution of each of the phases to the total duration of the DGC.
The Scarabaeini is an old world tribe of ball-rolling dung beetles that have origins dating back ... more The Scarabaeini is an old world tribe of ball-rolling dung beetles that have origins dating back to at least the mid-upper Miocene (19-8 million years ago). The tribe has received little to no attention in morphological or molecular phylogenetics. We obtained sequence data from the mitochondrial cytochrome oxidase subunit I (1197 bp) and 16S ribosomal RNA (461 bp) genes for 25 species of the Scarabaeini in an attempt to further resolve broad phylogenetic relationships within this tribe. Sequence data from both markers along with 216 morphological and 3 biological characters were analysed separately and combined. Independent analyses showed poorly resolved trees with many of the intermediate and basal nodes collapsed by low bootstrap values. Many sites in both genes exhibited strong A + T nucleotide bias and high interlineage divergences. The combined analysis revealed a number of well supported relationships such as the monophyly of the nocturnal species Scarabaeus satyrus, S.
By virtue of their low vagility, ightless insects are useful indicators of biogeographical histor... more By virtue of their low vagility, ightless insects are useful indicators of biogeographical history. R elationships of the ightless dung beetle genus, Gyronotus, are of particular interest due to its G ondwanaland ancestry, distinctive relict distribution along the south-eastern seaboard of Africa, and its restriction to forests which are seriously threatened by exploitation. Because of the limited number of diagnostic morphological characters, it was necessary to code morphometric data in order to conduct distance and cladistic parsimony analysis of interspeci c relationships in Gyronotus. There was a good correlation between relationships indicated by the dendrograms/cladograms and those determined by an examination of aedeagus character states both of which indicate a disjunction between south and east African species and a broad separation between northern and southern South African species. Comparison of the bilaterally asymmetrical aedeagi of Gyronotus with the symmetrical aedeagi of the sister genus, Anachalcos H ope, suggests geographical polarization of character states from greater plesiomorphy in east African Gyronotus to greater apomorphy in South African species, particularly in the southernmost element in which the aedeagus shows extreme asymmetry. F urthermore, body shape follows a similar geographical gradient in that the three Gyronotus species of tropical east Africa are signi cantly more elongate than the three ovoid, lowland/afromontane species of South Africa. An examination of historical factors suggests that this spatially-restricted distribution is the relict of a very old tropical lowland pattern. In extant taxa, the phylogenetic polarization is towards one of ve main centres of afrotropical forest biodiversity in the geologically old Eastern Arc and the adjoining lowland forest (Swahili centre of endemism). Survivors from old lineages may be one reason for such centres of high biodiversity.
Alterations in VO 2 or VCO 2 are amongst the more polemical physiological adaptations ascribed to... more Alterations in VO 2 or VCO 2 are amongst the more polemical physiological adaptations ascribed to insects. Generally, metabolic rate is thought to be lowered in response to arid conditions, and elevated in species from cold environments compared to their more temperate relatives. However, most studies have rarely addressed the influence of both environmental factors in unison. To this end, standard metabolic rate and its temperature dependence were measured (at 4°C intervals from 16 to 32°C) in six Scarabaeus dung beetle species (three flightless, three volant) from a variety of habitats (warm, arid to cool, mesic) in southern Africa using flow-through respirometry. Mass specific VCO 2 varied from 0.0158 ml g Ϫ1 h Ϫ1 at 16°C to 0.1839 ml g Ϫ1 h Ϫ1 at 32°C. The slopes of the rate temperature curves were similar for all species (Q 10 s of 2.14-2.84), although the intercepts differed significantly in the direction (warm arid to cool mesic): S. gariepinusϽS. hippocratesϽS. striatumϽS. galenusϽS. rusticusϽS. westwoodi. General linear models were fitted to the VCO 2 data with treatment temperature, wing status, mean annual rainfall and mean annual temperature as the independent variables. For all six species, the best fit model included treatment temperature and wing status only. Flightless species had significantly lower VCO 2 s than did winged ones. Amongst the flightless species, S. gariepinus, from the driest area, had the lowest VCO 2. Among the winged species it was impossible to determine whether environmental temperature or water availability were most important in influencing VCO 2 ; both were significant. We conclude that investigations of metabolic rate modulation, and especially metabolic cold adaptation, in insects must take both temperature and water availability into account.
We propose a model for earthquake afterslip based on rate and state variable friction laws. In th... more We propose a model for earthquake afterslip based on rate and state variable friction laws. In the model, afterslip is attributed to the interaction of a velocity-weakening region at depth (within which earthquakes nucleate) with an upper region of velocity-strengthening frictional behavior. The existence of this upper region is supported by independent seismologic observations and the results of laboratory friction experiments. In our model, afterslip is the result of relaxation of a stress perturbation within the velocitystrengthening region, which arises when an earthquake propagates into that region from below. We derive the stress perturbation and its decay from the friction constitutive law using a simple, 1 degree-of-freedom approximation for the elastic interaction between the fault and its surroundings. This approximation is based on thickness-averaged displacements and slip velocities within the velocity-strengthening region, which is assumed to slip as a rigid block. Coseismic and postseismic slip are coupled through the thickness-averaged stiffness k of the velocity-strengthening region. We assume k to be inversely proportional to the thickness of this region, which means that thicker velocity strengthening regions have a greater tendency to arrest coseismic slip. We model the afterslip-time histories of the 1966 Parkfield and 1987 Superstition Hills earthquakes and relate the model parameters to physical parameters which may govern the rheologic behavior of the faults. In accord with field observations, our model predicts (1) that afterslip on some faults scales with the thickness of the (unconsolidated) sedimentary cover and (2) that proportionally more afterslip occurs for earthquakes in which coseismic surface slip is small compared with coseismic slip at depth. Velocity-strengthening frictional behavior is to be expected for faults within poorly consolidated sediments and for those that contain significant gouge zones (about >500 m) within their shallow regions (<3-5 km). Combining our results with those of recent laboratory friction studies indicates that relatively young faults with little accumulated fault gouge should exhibit little afterslip.
Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 2003
Ball rolling by dung beetles is considered to be a derived behaviour that evolved under pressure ... more Ball rolling by dung beetles is considered to be a derived behaviour that evolved under pressure for space, and from competitors at the dung pat. Straight-line orientation away from the pat using a celestial cue should be the most successful rolling strategy to move dung to an unknown burial site. We tested this hypothesis in the field and the laboratory by presenting five species of ball-rolling beetles with different orientation tasks, involving reaction to obstacles as well as to reflected sunlight and artificial light sources. Beetles were found to consistently orientate along a chosen route, usually in the direction of the sun. Beetles rolling dung balls successfully negotiated barriers and returned to the original path as did beetles falling from ramps, or rotated about a fixed point while rolling a ball. The sun was found to be the main orientation cue, which could be substituted by reflected or artificial light. However, beetles reoriented themselves less accurately in response to lights in the laboratory, than they did to the reflected sun in the field. It is probable that phototactic orientation using the sun, which is widespread amongst arthropods, has been incorporated in the straight-line foraging behaviour that has evolved in ballrolling dung beetles.
Aim (1) To review briefly global biogeographical patterns in dung beetles (Coleoptera: Scarabaeid... more Aim (1) To review briefly global biogeographical patterns in dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae), a group whose evolutionary history has been dominated by ecological specialization to vertebrate dung in warmer climates. (2) To develop hypotheses accounting for the evolution of these patterns.
Page 1. Journal of Biogeography, 26, 1039-1055 Species turnover, community boundaries and biogeog... more Page 1. Journal of Biogeography, 26, 1039-1055 Species turnover, community boundaries and biogeographical composition of dung beetle assemblages across an altitudinal gradient in South Africa Adrian LV Davis, Clarke ...
Aim Changing conditions across spatial gradients are primary determinants of biotic regions, loca... more Aim Changing conditions across spatial gradients are primary determinants of biotic regions, local habitats, and distributional edges. We investigate how a climatic gradient and edaphic mosaic interact as multi-scale drivers of spatial patterns in scarabaeine dung beetles. The patterns are tested for congruency with ecoregion and floral boundaries over the same gradient, as responses to physical factors often differ among higher taxa. Location Southern Africa and the Nama Karoo-Kalahari ecotone, Northern Cape, South Africa. Methods Data consisted of the climatic distributions of 104 species and their abundances at 223 sites in two ecoregions/floral biomes, four bioregions, and 13 vegetation units. Factor analyses determined the biogeographical composition of the species, and regional-to local-scale patterns in species abundance structure. Hierarchical analysis of oblique factors determined the proportional contribution of spatial variance to patterns. One-way anova was used to test for significant separation of patterns along factor axes. Stepwise multiple regression was used to determine correlations of five physical attributes with species richness, Shannon-Wiener diversity, and factor loadings for the study sites. Results Four biogeographical influences overlap in the study region, although rank contribution declines from southwest arid through northeast savanna to widespread and southeast highland taxa. Species abundance structure comprises five subregional patterns, two centred to the northeast (Kalahari, Isolated Kalahari Dune) dominated by Kalahari influence, and three to the southwest (Nama Karoo subdivisions: Bushmanland, 'Upper', 'Stony Prieska') dominated by southwest arid influence. Kalahari deep sands are characterized especially by a warmer, moister climate, whereas the Nama Karoo mosaic of deep or stony soils is characterized especially by northwest aridity (Bushmanland), southeast cooler temperatures ('Upper'), or excessively stony soils ('Stony Prieska'). Four of the subregional patterns each comprised three localized patterns related primarily to relative stoniness, edge effects from geographical position, or incidence of rainfall. Species richness and diversity declined with decreasing rainfall and increasing stoniness. Main conclusions Climatic and edaphic factors are important multi-scale determinants of spatial patterns in dung beetle assemblage structure, with edaphic factors becoming more important at local spatial scales. The patterns are roughly congruent with the Kalahari Savanna-Nama Karoo ecotone at the floral biome or ecoregion scale, but show limited coincidence with finer-scale floral classification.
Dry conditions limit microbial decomposition of plant litter in deserts, which leaves a primary r... more Dry conditions limit microbial decomposition of plant litter in deserts, which leaves a primary role to detritivorous macroarthropods. In the sandy arid strip along the west coast of South Africa, such detritivores include the large scarabaeid dung beetle Pachysoma glentoni. Highly unusual among dung beetles, this species collects surface litter and drags it into an underground storage and feeding chamber which is abandoned after 6-7 days. Fresh stores for single beetles and for breeding pairs (mean depths: 30 and 39 cm) contained about 1.1 and 2.9 g organic matter, respectively. Using ergosterol as a biomarker for fungal biomass, we tested the hypotheses that (1) the dry detritus takes up water underground; (2) this promotes fungal growth on the detritus, and (3) fungi are the main food of the beetles. These hypotheses were disproved, but the stored litter, including floral remains, was shown to have relatively high quality (mean atomic C:N ratio: 35) and the beetles assimilated about 60% of it. Estimated weekly water gain per beetle, supplied entirely by the food, was about 0.6 g. Our results highlight unique nutritional adaptations to survival in deserts without the usual dung beetle food: wet dung of large herbivores.
The phylogeny of the Scarabaeinae, the largest and most important group of dung feeding beetles, ... more The phylogeny of the Scarabaeinae, the largest and most important group of dung feeding beetles, is hypothesised based on 200 morphological characters of 50 taxa, representing nearly one quarter of the known genera. We present a drastically different picture of evolution of this highly successful group of beetles than those previously proposed. It is apparent that gross morphology is correlated with either rolling or tunnelling but does not accurately reflect evolutionary history. Results indicate that there are not two separate clades of dung beetles, the rollers and tunnellers, but that rolling behaviour has evolved several times from ancestral tunnellers. The Dichotomiini, Canthonini, and Coprini are poly- or paraphyletic, whereas each of the remaining nine tribes appear as well supported monophyletic clades (the monophyly of the Gymnopleurini was not tested). The genera traditionally included in the Dichotomiini are the oldest and most basal lineages and all other clades, includ...
The fidius group constitutes the basal clade in a phylogeny of the Afrotropical members of the ge... more The fidius group constitutes the basal clade in a phylogeny of the Afrotropical members of the genus, Copris Müller, 1764. In this paper we describe Copris crassus Deschodt and Davis as a new species in this group. We also demonstrate that the distributional function between two body dimensions (lateral horn length and mid-line elytron length) differs between Copris fidius (Olivier 1789) and C. crassus. Copris bihamatus Balthasar, 1965 is also a member of the fidius group. Nguyen-Phung (1988) suspected that it was a synonym of C. fidius (Olivier) so we compare specimens of similar body size and use the distributional function between body dimensions to demonstrate that C. bihamatus is indeed a synonym of C. fidius. We provide a key for all known valid species in the fidius group, except C. serius Nguyen-Phung, 1987.
Trogidae constitute a monophyletic and biologically unique family within Scarabaeoidea, being the... more Trogidae constitute a monophyletic and biologically unique family within Scarabaeoidea, being the only keratinophagous group in the superfamily. Traditionally, the family has been divided into three distinctive genera, Polynoncus Burmeister, Omorgus Erichson and Trox Fabricius. Although the taxonomy of the group is relatively well studied, changes to the existing classification have recently been proposed and the family as currently constituted has not been subjected to phylogenetic analyses. Here we present a molecular phylogeny for this cosmopolitan family based on three partially sequenced gene regions: 16S rRNA, 18S rRNA and 28S rRNA (domain 2). Included in the analyses are representatives belonging to four of the five extant genera (and three of the four subgenera) from all major zoogeographic regions, representing about 20%of the known trogid species diversity in the family. Phylogenetic analyses performed included parsimony and Bayesian inference. We deduce their historical biogeography by using trogid fossils as calibration points for divergence estimates. Our analyses resolved relationships between and within genera and subgenera that are largely congruent with existing phylogeny hypotheses based on morphological data. We recovered four well-supported radiations: Polynoncus, Omorgus, Holarctic Trox and African Phoberus MacLeay. On the basis of this study, it is proposed that taxonomic changes to the generic classification of the family be made. The subgenera Trox and Phoberus should be elevated to genera to include the Holarctic and all the Afrotropical species, respectively, and Afromorgus returned to subgeneric rank. Estimates of divergence time are consistent with a Pangaean origin of the family in the Early Jurassic. The subsequent diversification of the major lineages is largely attributed to the break-up of Pangaea and Gondwana in the Middle Jurassic and early Late Cretaceous, respectively.
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 1998
Desiccation resistance and water balance were examined in the adults of seven trogid species, whi... more Desiccation resistance and water balance were examined in the adults of seven trogid species, which differed both in body size and in the habitats from which they were collected. Body water contents (51–58% fresh mass) and desiccation rates at 27 °C (0.00026–0.00093 g h−1) in these species were very similar to those of unrelated, similar-sized beetles from arid habitats. The keratin beetles
A phylogenetic analysis of the Scarabaeini, based on 244 morphological characters, including 154 ... more A phylogenetic analysis of the Scarabaeini, based on 244 morphological characters, including 154 multistate, and 3 biological characters, is given. Tree topologies generated from unweighted data and some weighted algorithms are similar and support only two genera in the tribe; Scarabaeus L. and Pachylomerus Bertoloni. The basal clade is Pachylomerus and sister to Scarabaeus. Kheper Kirby stat. nov., Pachysoma MacLeay, Scarabaeolus Balthasar and Sceliages Westwood stat. nov are the only supported subgenera. The genus Drepanopodus Janssens syn. nov. is synonymised with Scarabaeus and six additional names, Madateuchus Paulian, Mnematidium Ritsema, Mnematium M'Leay, Neateilchus Gillet, Neomnematium Janssens and Neopachysoma Ferreira remain synonyms. A monophyletic origin of flightlessness is generally supported with the subgenus Pachysoma the most derived group in this clade. Rolling dung balls backwards is the ancestral behaviour and predominant mode of food relocation in Scarabaeini although tunnelling, forward pushing, and can'ying are also utilised by some lineages. Pushing food has evolved independently in Sceliages species and S. galen us (Westwood) and a novel mode of forward food relocation evolved in the subgenus Pachysoma. Feeding on wet dung is the plesiomorphic condition and maintained by the majority of species in the tribe. The most unusual feeding behaviours in the tribe are represented by the obligate millipede-feeding species of Sceliages and the dry dung pellets and/or detritus used by members of the subgenus Pachysoma.
Larvae of the scarabaeoid genera Germarostes Paulian, Cyphopisthes Gestro, Paulianostes Ballerio,... more Larvae of the scarabaeoid genera Germarostes Paulian, Cyphopisthes Gestro, Paulianostes Ballerio, Ceratocanthus White, Pterorthochaetes Gestro, Madrasostes Paulian, Astaenomoechus Martínez & Pereira (Ceratocanthidae) and Hybosorus Macleay, Phaeochrous Castelnau, and Anaides Westwood (Hybosoridae) are described, keyed and illustrated with fifty-seven drawings. A phylogenetic analysis of these two families based on larval morphology is presented. Fifty-four larval morphological and three biological characters from twenty-seven taxa revealed nineteen equally parsimonious cladograms. The monophyly of (Ceratocanthidae + Hybosoridae) is supported by four unambiguous unique synapomorphies: dorsal medial endocarina on cranium extended anteriorly into frontal sclerite; presence of large membranous spot on apical antennomere; labium dorsally with four pores in center (secondarily reduced to two pores in some groups); and presence of stridulatory organ on fore-and middle legs (secondarily reduced in some groups). Our analysis suggests that the family Hybosoridae is paraphyletic with respect to Ceratocanthidae. The clade comprising the hybosorid genera Hybosorus and Phaeochrous is the sister group of the remaining Hybosoridae plus Ceratocanthidae. It is supported by two unambiguous synapomorphies: two apical antennomeres completely joined and the stridulatory organ represented by seven to nine large teeth anteriorly on the middle leg. The hybosorid genus Anaides is a sister group to the remaining Hybosoridae plus Ceratocanthidae (without Hybosorus and Phaeochrous) and the ceratocanthid genus Germarostes is a sister group to the remaining Hybosoridae plus Ceratocanthidae (without Hybosorus, Phaeochrous and Anaides). The ceratocanthid genera Cyphopisthes, Astaenomoechus, Paulianostes, Pterorthochaetes, and Madrasostes constitute a sister group to the hybosorid genus Cryptogenius and are supported by the presence of two reversions: two dorsal pores on labium and completely reduced stridulatory organs on fore-and middle legs.
containing 2.5 ϫ 10 5 PBMCs was added to each well after counting in the presence of trypan blue.... more containing 2.5 ϫ 10 5 PBMCs was added to each well after counting in the presence of trypan blue. The plates were incubated at 37°C for 4 hours before harvesting 20 l of supernatant. Percentage lysis was estimated as [(experimental counts Ϫ media control) ϫ 100]/(detergent counts Ϫ media control). Lysis of non-peptide controls was subtracted to give peptide-specific lysis. Media controls were between 10 to 15% of detergent controls. 22. One tetramer-positive CD8 ϩ cell was cloned directly into each well of a 96-well flat-bottomed plate (Nunc) in the presence of 10 6 irradiated PBMCs from at least three donors, together with phytohemagglutinin (5 g/ ml, Wellcome) in RPMI 1640 (Gibco) supplemented with glutamine, penicillin, streptomycin, and 5% human serum. After 4 days, Lymphocult-T (Biotest) was added to a final concentration of 10%. After 3 weeks the cultures were expanded into 24-well plates.
In Maputaland, South Africa vegetative and microclimatic changes on mined dunes drive the composi... more In Maputaland, South Africa vegetative and microclimatic changes on mined dunes drive the composition of the dung beetle fauna toward convergence with that in natural dune forest on unmined dunes. We assessed the pattern of these changes using a 23-year vegetational chronosequence on mined dunes, which passes from grassland (approximately 1 year) to open Acacia shrubland thicket to Acacia karroodominated woodland (approximately 9 years). Across this sequence, which represents successional stages in the restoration of dune forest, there was a sequential trend toward convergence in dung beetle species composition in both the entire species complement and, particularly, in shade specialist species. However, species abundance patterns showed a trend toward convergence only in early chronosequence Acacia woodland, followed by a decline in similarity between dung beetle assemblages of older Acacia woodland and unmined natural forest. This trend toward divergence was common both to the entire species complement, which includes widespread taxa, and to species endemic to Maputaland or the east coast. These trends in similarity and dissimilarity between dung beetle assemblages closely parallel the greater physiognomic and microclimatic similarity between early Acacia woodland and natural forest and the relative dissimilarity of older Acacia woodland. In conclusion, although percentage similarities between dung beetle assemblages of approximately 12-year woodland and natural forests were comparable with those between each natural forest stand, decline in similarity in older woodland stands suggests that lasting convergence in dung beetle species abundance will only be attained once the Acacia woodland is replaced by secondary natural forest.
Discontinuous gas exchange cycles are demonstrated in Omorgus radula (Erichson) (Coleoptera, Trog... more Discontinuous gas exchange cycles are demonstrated in Omorgus radula (Erichson) (Coleoptera, Trogidae) for the ®rst time, thus extending evidence for such cycles to another family of beetles. The closed,¯utter and open phases of the cycle were clearly distinguishable in this species, and the duration of these phases was 221 T 28, 1403 T 148 and 755 T 43 s (mean T SE), respectively. No evidence for signi®cant intraspeci®c mass scaling of VCO 2 or any of the components of the cycle was found. Although the prolonged F-phase recorded here is unusual for many insects, it has previously been found in other scarabaeoid beetles, especially those from xeric environments. It has been suggested that such modulation of the discontinuous gas exchange cycle may result in a reduced VCO 2 and, consequently, reduced water loss. In O. radula VCO 2 (15.25 T 1.49 ml/h) was considerably lower than that predicted from its body mass (0.207 T 0.006 g). However, the small relative contribution of respiratory transpiration (6.5%) to total water loss indicated that reduced VCO 2 has little to do with water economy. Rather, it may be a consequence of generally low activity levels of these beetles. The low respiratory water loss, but distinct subterranean component in the adult life of O. radula, lend some credence to the hypothesis suggesting that regular use of subterranean habitats might have been responsible for the evolution of discontinuous gas exchange cycles. However, non-adaptive hypotheses can still not be discounted.
Although discontinuous gas exchange cycles (DGC) are known from many insects, the effects of body... more Although discontinuous gas exchange cycles (DGC) are known from many insects, the effects of body size and temperature on DGC have not been widely examined. Here, these effects are investigated in five Scarabaeus dung beetle species from mesic and xeric habitats. The investigation tests two hypotheses: that previous estimates of the scaling exponents for the DGC and its characteristics are more broadly applicable to insects, and that, in response to temperature, both DGC frequency and the quantity of CO 2 emitted during the open (O) phase (Ophase emission volume) are modulated. Like previous workers, we find that scaled as mass 0.968 and that O-phase emissioṅ Vco 2 volume scaled as mass 0.833. However, temperature-associated increases in (Q 10 's of 2.19-2.65) were modulated mostly bẏ Vco 2 increases in DGC frequency since O-phase volumes remained constant across temperature. Flutter (F)-phase and O-phase durations were closely coupled to DGC duration, although the relationship between closed (C)-phase duration and DGC duration was less pronounced. We show that ventilation phase coefficients, previously considered a measure of the proportional duration of each phase of the DGC, calculated from the slopes of these relationships are a measure of change in phase duration with change in DGC duration and not a measure of the way in which total DGC duration is apportioned among phases. We suggest that proportions be used to estimate the contribution of each of the phases to the total duration of the DGC.
The Scarabaeini is an old world tribe of ball-rolling dung beetles that have origins dating back ... more The Scarabaeini is an old world tribe of ball-rolling dung beetles that have origins dating back to at least the mid-upper Miocene (19-8 million years ago). The tribe has received little to no attention in morphological or molecular phylogenetics. We obtained sequence data from the mitochondrial cytochrome oxidase subunit I (1197 bp) and 16S ribosomal RNA (461 bp) genes for 25 species of the Scarabaeini in an attempt to further resolve broad phylogenetic relationships within this tribe. Sequence data from both markers along with 216 morphological and 3 biological characters were analysed separately and combined. Independent analyses showed poorly resolved trees with many of the intermediate and basal nodes collapsed by low bootstrap values. Many sites in both genes exhibited strong A + T nucleotide bias and high interlineage divergences. The combined analysis revealed a number of well supported relationships such as the monophyly of the nocturnal species Scarabaeus satyrus, S.
By virtue of their low vagility, ightless insects are useful indicators of biogeographical histor... more By virtue of their low vagility, ightless insects are useful indicators of biogeographical history. R elationships of the ightless dung beetle genus, Gyronotus, are of particular interest due to its G ondwanaland ancestry, distinctive relict distribution along the south-eastern seaboard of Africa, and its restriction to forests which are seriously threatened by exploitation. Because of the limited number of diagnostic morphological characters, it was necessary to code morphometric data in order to conduct distance and cladistic parsimony analysis of interspeci c relationships in Gyronotus. There was a good correlation between relationships indicated by the dendrograms/cladograms and those determined by an examination of aedeagus character states both of which indicate a disjunction between south and east African species and a broad separation between northern and southern South African species. Comparison of the bilaterally asymmetrical aedeagi of Gyronotus with the symmetrical aedeagi of the sister genus, Anachalcos H ope, suggests geographical polarization of character states from greater plesiomorphy in east African Gyronotus to greater apomorphy in South African species, particularly in the southernmost element in which the aedeagus shows extreme asymmetry. F urthermore, body shape follows a similar geographical gradient in that the three Gyronotus species of tropical east Africa are signi cantly more elongate than the three ovoid, lowland/afromontane species of South Africa. An examination of historical factors suggests that this spatially-restricted distribution is the relict of a very old tropical lowland pattern. In extant taxa, the phylogenetic polarization is towards one of ve main centres of afrotropical forest biodiversity in the geologically old Eastern Arc and the adjoining lowland forest (Swahili centre of endemism). Survivors from old lineages may be one reason for such centres of high biodiversity.
Alterations in VO 2 or VCO 2 are amongst the more polemical physiological adaptations ascribed to... more Alterations in VO 2 or VCO 2 are amongst the more polemical physiological adaptations ascribed to insects. Generally, metabolic rate is thought to be lowered in response to arid conditions, and elevated in species from cold environments compared to their more temperate relatives. However, most studies have rarely addressed the influence of both environmental factors in unison. To this end, standard metabolic rate and its temperature dependence were measured (at 4°C intervals from 16 to 32°C) in six Scarabaeus dung beetle species (three flightless, three volant) from a variety of habitats (warm, arid to cool, mesic) in southern Africa using flow-through respirometry. Mass specific VCO 2 varied from 0.0158 ml g Ϫ1 h Ϫ1 at 16°C to 0.1839 ml g Ϫ1 h Ϫ1 at 32°C. The slopes of the rate temperature curves were similar for all species (Q 10 s of 2.14-2.84), although the intercepts differed significantly in the direction (warm arid to cool mesic): S. gariepinusϽS. hippocratesϽS. striatumϽS. galenusϽS. rusticusϽS. westwoodi. General linear models were fitted to the VCO 2 data with treatment temperature, wing status, mean annual rainfall and mean annual temperature as the independent variables. For all six species, the best fit model included treatment temperature and wing status only. Flightless species had significantly lower VCO 2 s than did winged ones. Amongst the flightless species, S. gariepinus, from the driest area, had the lowest VCO 2. Among the winged species it was impossible to determine whether environmental temperature or water availability were most important in influencing VCO 2 ; both were significant. We conclude that investigations of metabolic rate modulation, and especially metabolic cold adaptation, in insects must take both temperature and water availability into account.
We propose a model for earthquake afterslip based on rate and state variable friction laws. In th... more We propose a model for earthquake afterslip based on rate and state variable friction laws. In the model, afterslip is attributed to the interaction of a velocity-weakening region at depth (within which earthquakes nucleate) with an upper region of velocity-strengthening frictional behavior. The existence of this upper region is supported by independent seismologic observations and the results of laboratory friction experiments. In our model, afterslip is the result of relaxation of a stress perturbation within the velocitystrengthening region, which arises when an earthquake propagates into that region from below. We derive the stress perturbation and its decay from the friction constitutive law using a simple, 1 degree-of-freedom approximation for the elastic interaction between the fault and its surroundings. This approximation is based on thickness-averaged displacements and slip velocities within the velocity-strengthening region, which is assumed to slip as a rigid block. Coseismic and postseismic slip are coupled through the thickness-averaged stiffness k of the velocity-strengthening region. We assume k to be inversely proportional to the thickness of this region, which means that thicker velocity strengthening regions have a greater tendency to arrest coseismic slip. We model the afterslip-time histories of the 1966 Parkfield and 1987 Superstition Hills earthquakes and relate the model parameters to physical parameters which may govern the rheologic behavior of the faults. In accord with field observations, our model predicts (1) that afterslip on some faults scales with the thickness of the (unconsolidated) sedimentary cover and (2) that proportionally more afterslip occurs for earthquakes in which coseismic surface slip is small compared with coseismic slip at depth. Velocity-strengthening frictional behavior is to be expected for faults within poorly consolidated sediments and for those that contain significant gouge zones (about >500 m) within their shallow regions (<3-5 km). Combining our results with those of recent laboratory friction studies indicates that relatively young faults with little accumulated fault gouge should exhibit little afterslip.
Journal of Comparative Physiology A: Sensory, Neural, and Behavioral Physiology, 2003
Ball rolling by dung beetles is considered to be a derived behaviour that evolved under pressure ... more Ball rolling by dung beetles is considered to be a derived behaviour that evolved under pressure for space, and from competitors at the dung pat. Straight-line orientation away from the pat using a celestial cue should be the most successful rolling strategy to move dung to an unknown burial site. We tested this hypothesis in the field and the laboratory by presenting five species of ball-rolling beetles with different orientation tasks, involving reaction to obstacles as well as to reflected sunlight and artificial light sources. Beetles were found to consistently orientate along a chosen route, usually in the direction of the sun. Beetles rolling dung balls successfully negotiated barriers and returned to the original path as did beetles falling from ramps, or rotated about a fixed point while rolling a ball. The sun was found to be the main orientation cue, which could be substituted by reflected or artificial light. However, beetles reoriented themselves less accurately in response to lights in the laboratory, than they did to the reflected sun in the field. It is probable that phototactic orientation using the sun, which is widespread amongst arthropods, has been incorporated in the straight-line foraging behaviour that has evolved in ballrolling dung beetles.
Aim (1) To review briefly global biogeographical patterns in dung beetles (Coleoptera: Scarabaeid... more Aim (1) To review briefly global biogeographical patterns in dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae), a group whose evolutionary history has been dominated by ecological specialization to vertebrate dung in warmer climates. (2) To develop hypotheses accounting for the evolution of these patterns.
Page 1. Journal of Biogeography, 26, 1039-1055 Species turnover, community boundaries and biogeog... more Page 1. Journal of Biogeography, 26, 1039-1055 Species turnover, community boundaries and biogeographical composition of dung beetle assemblages across an altitudinal gradient in South Africa Adrian LV Davis, Clarke ...
Aim Changing conditions across spatial gradients are primary determinants of biotic regions, loca... more Aim Changing conditions across spatial gradients are primary determinants of biotic regions, local habitats, and distributional edges. We investigate how a climatic gradient and edaphic mosaic interact as multi-scale drivers of spatial patterns in scarabaeine dung beetles. The patterns are tested for congruency with ecoregion and floral boundaries over the same gradient, as responses to physical factors often differ among higher taxa. Location Southern Africa and the Nama Karoo-Kalahari ecotone, Northern Cape, South Africa. Methods Data consisted of the climatic distributions of 104 species and their abundances at 223 sites in two ecoregions/floral biomes, four bioregions, and 13 vegetation units. Factor analyses determined the biogeographical composition of the species, and regional-to local-scale patterns in species abundance structure. Hierarchical analysis of oblique factors determined the proportional contribution of spatial variance to patterns. One-way anova was used to test for significant separation of patterns along factor axes. Stepwise multiple regression was used to determine correlations of five physical attributes with species richness, Shannon-Wiener diversity, and factor loadings for the study sites. Results Four biogeographical influences overlap in the study region, although rank contribution declines from southwest arid through northeast savanna to widespread and southeast highland taxa. Species abundance structure comprises five subregional patterns, two centred to the northeast (Kalahari, Isolated Kalahari Dune) dominated by Kalahari influence, and three to the southwest (Nama Karoo subdivisions: Bushmanland, 'Upper', 'Stony Prieska') dominated by southwest arid influence. Kalahari deep sands are characterized especially by a warmer, moister climate, whereas the Nama Karoo mosaic of deep or stony soils is characterized especially by northwest aridity (Bushmanland), southeast cooler temperatures ('Upper'), or excessively stony soils ('Stony Prieska'). Four of the subregional patterns each comprised three localized patterns related primarily to relative stoniness, edge effects from geographical position, or incidence of rainfall. Species richness and diversity declined with decreasing rainfall and increasing stoniness. Main conclusions Climatic and edaphic factors are important multi-scale determinants of spatial patterns in dung beetle assemblage structure, with edaphic factors becoming more important at local spatial scales. The patterns are roughly congruent with the Kalahari Savanna-Nama Karoo ecotone at the floral biome or ecoregion scale, but show limited coincidence with finer-scale floral classification.
Dry conditions limit microbial decomposition of plant litter in deserts, which leaves a primary r... more Dry conditions limit microbial decomposition of plant litter in deserts, which leaves a primary role to detritivorous macroarthropods. In the sandy arid strip along the west coast of South Africa, such detritivores include the large scarabaeid dung beetle Pachysoma glentoni. Highly unusual among dung beetles, this species collects surface litter and drags it into an underground storage and feeding chamber which is abandoned after 6-7 days. Fresh stores for single beetles and for breeding pairs (mean depths: 30 and 39 cm) contained about 1.1 and 2.9 g organic matter, respectively. Using ergosterol as a biomarker for fungal biomass, we tested the hypotheses that (1) the dry detritus takes up water underground; (2) this promotes fungal growth on the detritus, and (3) fungi are the main food of the beetles. These hypotheses were disproved, but the stored litter, including floral remains, was shown to have relatively high quality (mean atomic C:N ratio: 35) and the beetles assimilated about 60% of it. Estimated weekly water gain per beetle, supplied entirely by the food, was about 0.6 g. Our results highlight unique nutritional adaptations to survival in deserts without the usual dung beetle food: wet dung of large herbivores.
The phylogeny of the Scarabaeinae, the largest and most important group of dung feeding beetles, ... more The phylogeny of the Scarabaeinae, the largest and most important group of dung feeding beetles, is hypothesised based on 200 morphological characters of 50 taxa, representing nearly one quarter of the known genera. We present a drastically different picture of evolution of this highly successful group of beetles than those previously proposed. It is apparent that gross morphology is correlated with either rolling or tunnelling but does not accurately reflect evolutionary history. Results indicate that there are not two separate clades of dung beetles, the rollers and tunnellers, but that rolling behaviour has evolved several times from ancestral tunnellers. The Dichotomiini, Canthonini, and Coprini are poly- or paraphyletic, whereas each of the remaining nine tribes appear as well supported monophyletic clades (the monophyly of the Gymnopleurini was not tested). The genera traditionally included in the Dichotomiini are the oldest and most basal lineages and all other clades, includ...
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