Jonathan F. Colville

Species turnover of monkey beetles (Scarabaeidae: Hopliini) along environmental and disturbance gradients in the Namaqualand region of the succulent Karoo, South Africa

Species turnover of monkey beetle (Scarabaeidae: Hopliini) assemblages along disturbance and environmental gradients was examined at three sites within the arid, winter rainfall Namaqualand region of the succulent Karoo, South Africa. At each site two study plots with comparable vegetation and soils but contrasting management (grazing) histories were chosen, the disturbed sites having fewer perennial shrubs and generally more annuals and bare ground. Beetles collected using coloured pan-traps showed a consistently higher abundance in disturbed sites. Lepithrix, Denticnema and Heterochelus had higher numbers in disturbed plots, while Peritrichia numbers were lower in disturbed areas. Measures of species richness and diversity were consistently higher in the undisturbed sites. Distinctive assemblages of monkey beetles and plants occurred at each site. A high compositional turnover (β diversity) was recorded for both monkey beetles and plants along a rainfall gradient; between-site β diversity values ranged from 0.7 to 0.8 (out of a maximum of 1.0). Species turnover of beetles was higher between the disturbed sites along the environmental gradient than the corresponding undisturbed sites. The high monkey beetle species turnover is probably linked to the high plant species turnover, a distinctive feature of succulent Karoo landscapes. Monkey beetles are useful indicators of overgrazing disturbance in Namaqualand, as their pollinator guilds are apparently disrupted by overgrazing. A shift away from perennial and bulb pollinator guilds towards those favouring weedy annuals was observed in disturbed areas. The consequences to ecosystem processes due to the effects of disturbance on monkey beetle communities and the role of monkey beetles as indicators of disturbance is discussed, as well as the implications of disturbance on monkey beetle pollination guilds.

Pollinator shifts as triggers of speciation in painted petal irises (Lapeirousia: Iridaceae)

BACKGROUND AND AIMS Adaptation to different pollinators has been hypothesized as one of the main factors promoting the formation of new species in the Cape region of South Africa. Other researchers favour alternative causes such as shifts in edaphic preferences. Using a phylogenetic framework and taking into consideration the biogeographical scenario explaining the distribution of the group as well as the distribution of pollinators, this study compares pollination strategies with substrate adaptations to develop hypotheses of the primary factors leading to speciation in Lapeirousia (Iridaceae), a genus of corm-bearing geophytes well represented in the Cape and presenting an important diversity of pollination syndromes and edaphic preferences. METHODS Phylogenetic relationships are reconstructed within Lapeirousia using nuclear and plastid DNA sequence data. State-of-the-art methods in biogeography, divergence time estimation, character optimization and diversification rate assessments are used to examine the evolution of pollination syndromes and substrate shifts in the history of the group. Based on the phylogenetic results, ecological factors are compared for nine sister species pairs in Lapeirousia. KEY RESULTS Seventeen pollinator shifts and ten changes in substrate types were inferred during the evolution of the genus Lapeirousia. Of the nine species pairs examined, all show divergence in pollination syndromes, while only four pairs present different substrate types. CONCLUSIONS The available evidence points to a predominant influence of pollinator shifts over substrate types on the speciation process within Lapeirousia, contrary to previous studies that favoured a more important role for edaphic factors in these processes. This work also highlights the importance of biogeographical patterns in the study of pollination syndromes.

One proboscis, two tasks: Adaptations to blood-feeding and nectar-extracting in long-proboscid horse flies (Tabanidae, Philoliche)

Female Pangoniinae in the tabanid fly genus Philoliche can display remarkably elongated proboscis lengths, which are adapted for both blood- and nectar-feeding. Apart from their role as blood-sucking pests, they represent important pollinators of the South African flora. This study examines the morphology of the feeding apparatus of two species of long-proboscid Tabanidae: Philoliche rostrata and Philoliche gulosa – both species display adaptations for feeding from a diverse guild of long-tubed flowers, and on vertebrate blood. The heavily sclerotised proboscis can be divided into two functional units. The short, proximal piercing part is composed of the labrum-epipharynx unit, the hypopharynx and paired mandible and maxilla. The foldable distal part is composed of the prementum of the labium which solely forms the food canal and is responsible for nectar uptake via the apical labella. The proboscis works as a drinking straw, relying on a pressure gradient provided by a two-part suction pump in the head. Both proboscis and body lengths and suction pump dimensions show a significantly correlated allometric relationship with each other. This study provides detailed insights into the adaptations for a dual diet using an elongated sucking proboscis, and considers these adaptations in the context of the evolution of nectar feeding in Brachycera.

A cockroach that jumps

We report on a newly discovered cockroach (Saltoblattella montistabularis) from South Africa, which jumps and therefore differs from all other extant cockroaches that have a scuttling locomotion. In its natural shrubland habitat, jumping and hopping accounted for 71 per cent of locomotory activity. Jumps are powered by rapid and synchronous extension of the hind legs that are twice the length of the other legs and make up 10 per cent of the body weight. In high-speed images of the best jumps the body was accelerated in 10 ms to a take-off velocity of 2.1 m s−1 so that the cockroach experienced the equivalent of 23 times gravity while leaping a forward distance of 48 times its body length. Such jumps required 38 µJ of energy, a power output of 3.4 mW and exerted a ground reaction force through both hind legs of 4 mN. The large hind legs have grooved femora into which the tibiae engage fully in advance of a jump, and have resilin, an elastic protein, at the femoro-tibial joint. The extensor tibiae muscles contracted for 224 ms before the hind legs moved, indicating that energy must be stored and then released suddenly in a catapult action to propel a jump. Overall, the jumping mechanisms and anatomical features show remarkable convergence with those of grasshoppers with whom they share their habitat and which they rival in jumping performance.

Time management and nectar flow: flower handling and suction feeding in long-proboscid flies (Nemestrinidae: Prosoeca)

A well-developed suction pump in the head represents an important adaptation for nectar-feeding insects, such as Hymenoptera, Lepidoptera and Diptera. This pumping organ creates a pressure gradient along the proboscis, which is responsible for nectar uptake. The extremely elongated proboscis of the genus Prosoeca (Nemestrinidae) evolved as an adaptation to feeding from long, tubular flowers. According to the functional constraint hypothesis, nectar uptake through a disproportionately elongated, straw-like proboscis increases flower handling time and consequently lowers the energy intake rate. Due to the conspicuous length variation of the proboscis of Prosoeca, individuals with longer proboscides are hypothesised to have longer handling times. To test this hypothesis, we used field video analyses of flower-visiting behaviour, detailed examinations of the suction pump morphology and correlations of proboscis length with body length and suction pump dimensions. Using a biomechanical framework described for nectar-feeding Lepidoptera in relation to proboscis length and suction pump musculature, we describe and contrast the system in long-proboscid flies. Flies with longer proboscides spent significantly more time drinking from flowers. In addition, proboscis length and body length showed a positive allometric relationship. Furthermore, adaptations of the suction pump included an allometric relationship between proboscis length and suction pump muscle volume and a combination of two pumping organs. Overall, the study gives detailed insight into the adaptations required for long-proboscid nectar feeding, and comparisons with other nectar-sucking insects allow further considerations of the evolution of the suction pump in insects with sucking mouthparts.

Optimising Regionalisation Techniques: Identifying Centres of Endemism in the Extraordinarily Endemic-Rich Cape Floristic Region.

We used a very large dataset (>40% of all species) from the endemic-rich Cape Floristic Region (CFR) to explore the impact of different weighting techniques, coefficients to calculate similarity among the cells, and clustering approaches on biogeographical regionalisation. The results were used to revise the biogeographical subdivision of the CFR. We show that weighted data (down-weighting widespread species), similarity calculated using Kulczinsky’s second measure, and clustering using UPGMA resulted in the optimal classification. This maximized the number of endemic species, the number of centres recognized, and operational geographic units assigned to centres of endemism (CoEs). We developed a dendrogram branch order cut-off (BOC) method to locate the optimal cut-off points on the dendrogram to define candidate clusters. Kulczinsky’s second measure dendrograms were combined using consensus, identifying areas of conflict which could be due to biotic element overlap or transitional areas. Post-clustering GIS manipulation substantially enhanced the endemic composition and geographic size of candidate CoEs. Although there was broad spatial congruence with previous phytogeographic studies, our techniques allowed for the recovery of additional phytogeographic detail not previously described for the CFR.

Levyns’ Law: explaining the evolution of a remarkable longitudinal gradient in Cape plant diversity

It has been known for many decades that the diversity of clades endemic to the Greater Cape Floristic Region (GCFR) declines along a longitudinal (west-east) gradient, in concert with a reduction in the proportion of winter rainfall. In honour of the pioneering work by Margaret Levyns, we recognise this pattern as Levyns’ Law, and illustrate it with distribution data for 23 speciose endemic clades. All patterns were consistent with Levyns’ Law. Here we assess explanations for Levyns’ Law in terms of theories invoked to explain the evolution of diversity patterns along other diversity macro-gradients. Neither the metabolic nor the ecological opportunity hypotheses convincingly explain Levyns’ Law. Surprisingly, almost no research has been done on the evolutionary opportunities associated with the Mid Miocene onset of a winter-rainfall regime in the western GCFR, despite this phenomenon being frequently invoked to explain the diversification of many GCFR clades. In all other respects, niche space both now and historically shows no major differences between the western, winter rainfall, and the eastern, year-round rainfall regions of the GCFR. We suggest that higher Pleistocene climatic and biome stability in the western GCFR – the age and area hypothesis – best explains Levyns’ Law. Pronounced instability in the east reduced diversification rates via increased rates of extinction of lineages. Testing the age and area hypotheses will require, inter alia, proxy data for Pleistocene environmental and biotic dynamics, an analysis of diversification rates in relation to rainfall seasonality, and an assessment of the patterns of phylogenetic diversity in the GCFR.

Comparative morphology of the mouthparts of the megadiverse South African monkey beetles (Scarabaeidae: Hopliini): feeding adaptations and guild structure

Although anthophilous Coleoptera are regarded to be unspecialised flower-visiting insects, monkey beetles (Scarabaeidae: Hopliini) represent one of the most important groups of pollinating insects in South Africa’s floristic hotspot of the Greater Cape Region. South African monkey beetles are known to feed on floral tissue; however, some species seem to specialise on pollen and/or nectar. The present study examined the mouthpart morphology and gut content of various hopliine species to draw conclusions on their feeding preferences. According to the specialisations of their mouthparts, the investigated species were classified into different feeding groups. Adaptations to pollen-feeding included a well-developed, toothed molar and a lobe-like, setose lacinia mobilis on the mandible as well as curled hairs or sclerotized teeth on the galea of the maxillae. Furthermore, elongated mouthparts were interpreted as adaptations for nectar feeding. Floral- and folial-tissue feeding species showed sclerotized teeth on the maxilla, but the lacinia was mostly found to be reduced to a sclerotized ledge. While species could clearly be identified as floral or folial tissue feeding, several species showed intermediate traits suggesting both pollen and nectar feeding adaptations. Mismatches found between mouthpart morphology and previously reported flower visiting behaviours across different genera and species requires alternative explanations, not necessarily associated with feeding preferences. Although detailed examinations of the mouthparts allowed conclusions about the feeding preference and flower-visiting behaviour, additional morphological and behavioural investigations, combined with greater taxon sampling and phylogenetic data, are still necessary to fully understand hopliine host plant relationships, related to monkey beetle diversity.

Counting complete? Finalising the plant inventory of a global biodiversity hotspot

The Cape Floristic Region—the world’s smallest and third richest botanical hotspot—has benefited from sustained levels of taxonomic effort and exploration for almost three centuries, but how close is this to resulting in a near-complete plant species inventory? We analyse a core component of this flora over a 250-year period for trends in taxonomic effort and species discovery linked to ecological and conservation attributes. We show that >40% of the current total of species was described within the first 100 years of exploration, followed by a continued steady rate of description. We propose that <1% of the flora is still to be described. We document a relatively constant cohort of taxonomists, working over 250 years at what we interpret to be their ‘taxonomic maximum.’ Rates of description of new species were independent of plant growth-form but narrow-range taxa have constituted a significantly greater proportion of species discoveries since 1950. This suggests that the fraction of undiscovered species predominantly comprises localised endemics that are thus of high conservation concern. Our analysis provides important real-world insights for other hotspots in the context of global strategic plans for biodiversity in informing considerations of the likely effort required in attaining set targets of comprehensive plant inventories. In a time of unprecedented biodiversity loss, we argue for a focused research agenda across disciplines to increase the rate of species descriptions in global biodiversity hotspots.

A striking new species of Prosoeca Schiner, 1867 (Diptera: Nemestrinidae): An important pollinator from the Bokkeveld Plateau, Northern Cape Province, South Africa

For more than 20 years an undescribed species of Prosoeca has been referred to in numerous publications by pollination biologists, evolutionary biologists and ecologists, originally as being part of the Prosoeca peringueyi Lichtwardt, 1920, pollination guild. Ongoing research in these and related fields has necessitated the formal description of this large-bodied, striking new species, with a proboscis 1.5-2.3 x body length (mean proboscis length ± SD 36.25 ± 3.90 mm). Prosoeca marinusi Barraclough sp. nov. is described from a long series from the Hantam National Botanical Garden, Nieuwoudtville, Bokkeveld Plateau, Northern Cape Province, South Africa. The species is a narrow-range endemic and is restricted to the Nieuwoudtville area. Observations on the biology of the species are also presented. Prosoeca marinusi Barraclough sp. nov. is the only or main pollinator of at least four plant species (all regional endemics) in the family Iridaceae that flower from August to September. During August, Lapeirousia oreogena Goldblatt and Babiana vanzyliae L. Bolus are the main host flowers, while later in the spring season, Babiana framesii L. Bolus is most abundant in the Nieuwoudtville area.