Do high soil temperatures on Namibian fairy circle discs explain the absence of vegetation?

Evenly-dispersed enigmatic bare discs known as 'fairy circles' occur within grasslands of the pro-Namib Desert. In spite of their conspicuous appearance, their nature and origin is still debated. The possible inhibitory effects of high surface and sub-surface soil temperatures on grass germination and seedling development on fairy circles have not yet been investigated. We measured maximum, mean daily (24 hour) and mean daytime (sunrise to sunset) temperatures of fairy circles and matrices in the NamibRand Nature Reserve (southwest Namibia). Optimum germination and growing temperatures, and thermal maxima of Stipagrostis ciliata, a grass commonly associated with fairy circle grasslands, were determined experimentally in growth trials. Seeds and seedlings were exposed to temperatures of 35 °C, 37 °C, 41 °C, 44 °C and 47 °C for 10 days. The optimum growth temperature range of S. ciliata seedlings was determined to be 35 °C to 37 °C, with depressed growth above 47 °C. Seed germination was also depressed at 47 °C, and optimal germination occurred between 35 °C to 37 °C. Circle soils were consistently 2 °C cooler than matrix soils at both surface and 15 cm depths, and though the soil surface achieved daily temperatures of 45 °C and 47 °C for the circle and matrix respectively, mean daily temperatures at 15 cm depth were 36 °C and 38 °C respectively, coinciding with the optimum germination and growing temperature of S. ciliata. Circle soil temperature is thus unlikely to limit S. ciliata germination and seedling growth and contribute to the maintenance of a bare disc, as both thermal conditions and the presence of higher soil moisture on circles provide a more favourable growing environment than the matrix

Limited dispersal and local adaptation promote allopatric speciation in a biodiversity hotspot

International audienceRecently diverged or diverging populations can offer unobstructed insights into early barriers to gene flow during the initial stages of speciation. The current study utilised a novel insect system (order Mantophasmatodea) to shed light on the early drivers of speciation. The members of this group have limited dispersal abilities, small allopatric distributions and strong habitat associations in the Cape Floristic Region biodiversity hotspot in South Africa. Sister taxa from the diverse family Austrophasmatidae were chosen as focal species (Karoophasma biedouwense, K. botterkloofense). Population genetics and Generalized Dissimilarity Modelling (GDM) were used to characterise spatial patterns of genetic variation and evaluate the contribution of environmental factors to population divergence and speciation. Extensive sampling confirmed the suspected allopatry of these taxa. However, hybrids were identified in a narrow region occurring between the species' distributions. Strong population structure was found over short geographic distances; particularly in K. biedouwense in which geographic distance accounted for 32% of genetic variation over a scale of 50 km (r = .56, p < .001). GDM explained 42%-78% of the deviance in observed genetic dissimilarities. Geographic distance was consistently indicated to be important for between species and within population differentiation, suggesting that limited dispersal ability may be an important neutral driver of divergence. Temperature, altitude, precipitation and vegetation were also indicated as important factors, suggesting the possible role of adaptation to local environmental conditions for species divergence. The discovery of the hybrid-zone, and the multiple allopatric species pairs in Austrophasmatidae support the idea that this could be a promising group to further our understanding of speciation modes

The importance of monkey beetle (Scarabaeidae: Hopliini) pollination for Aizoaceae and Asteraceae in grazed and ungrazed areas at Paulshoek, Succulent Karoo, South Africa

The relative importance of monkey beetles (Hopliini, Scarabeidae) as pollinators of Asteraceae and Aizoaceae in the Succulent Karoo as well as the influence of livestock grazing on their abundance and diversity was investigated. Hopliine beetles proved to be the, or among the, most abundant flower visitors of 12 investigated plant species. However, during single flower observations at three Aizoaceae species, bees (Apoidea), bee flies (Bombyliidae) and pollen wasps (Masaridae) were the most frequent flower visitors. However, monkey beetles carried the highest Asteraceae and Aizoaceae pollen loads, and are therefore considered to play a vital role in the pollination of these two families. Abundance, species richness and diversity of Hopliini did not appear to be heavily affected by livestock grazing. Annual variation in the composition of monkey beetle populations was more dramatic. Still, some species showed higher abundances on heavily grazed rangeland while others only occurred under low grazing pressure. It is presumed that changes in the composition of the vegetation, especially the observed decrease of perennial plants in favour of annuals and geophytes (Todd and Hoffman 1999) could in turn affect the composition of monkey beetle assemblages

A jumping cockroach from South Africa, Saltoblattella montistabularis, gen. nov., spec. nov. (Blattodea: Blattellidae)

A jumping cockroach (Saltoblattella montistabularis) from Table Mountain, Cape Town, South Africa, is described. The new genus is defined, the characteristics of the species are thoroughly described with particular emphasis on unusual morphological adaptations for jumping. These include dramatic elongation of hind femur and tibia and enlargement of hind femur. The femur ventrally has a longitudinal groove for reception of the tibia during extreme fl exure prior to a jump. The euplantulae have unusual surface papillae which may assist landing after a jump. Further modifi cations from the standard cockroach design probably related to jumping locomotion are hemispherically-protruding compound eyes and a second point of articulation for the fi rst antennal segment. The hook of the male phallomeres is on the left, and the female does not rotate the ootheca prior to deposition. The exact position of the genus within the family Blattellidae is not clear; it is preliminarily placed in Blattellinae. The species and its jumping adaptations are compared with another recently discovered, but extinct jumping ‘cockroach’

Postembryonic development of the unique antenna of Mantophasmatodea (Insecta)

The postembryonic antennal development and life cycle of a member of the insect order Mantophasmatodea (Lobatophasma redelinghuysense) was investigated using a series of annulus counts and a time sequence of head capsule measurements. The life cycle comprised six instars. Females achieved significantly larger head capsules from instar 2 onwards, resulting in adult females having a larger mean head capsule diameter (2.58 mm) than males (2.27 mm). Antennae of first instar larvae comprised a smooth four-segmented basiflagellum and a seven-segmented, sensilla-rich distiflagellum. Lengthening of the basiflagellum was achieved by the addition of two annuli per moult, generated by division of the basal annulus (meriston). Annulus number and the unique annulation pattern of the distiflagellum remained constant until adulthood. The segmentation pattern of adult antennae (comprising a basiflagellum and a distiflagellum of 14 and seven annuli respectively) and mode of antennal longation was consistent for all 11 species examined. Subdivisions in basiflagellar annuli were observed in adults of all species examined, although they are not considered to be true annular divisions. The structure of the mantophasmatodean antenna appears to be autapomorphic within Insecta, bearing little resemblance to that of Grylloblattodea, Dictyoptera or Phasmatodea, all putative sister groups of the antophasmatodea. However, the mode of flagellar elongation most closely resembles that of Isoptera, Blattaria and Dermaptera

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Microsatellite Sequences_KB1_KB50

Microsatellite Sequences_KB1_KB5