The South African Pollen Monitoring Network: Insights from 2 years of national aerospora sampling (2019-2021).

BACKGROUND: Pollen monitoring has been discontinuously undertaken in South Africa, a country with high biodiversity, a seasonal rainfall gradient, and nine biomes from arid to subtropical. The South African Pollen Monitoring Network was set up in 2019 to conduct the first long-term national aerospora monitoring across multiple biomes, providing weekly reports to allergy sufferers and healthcare providers. METHODS: Daily airborne pollen concentrations were measured from August 2019 to August 2021 in seven cities across South Africa. Updated pollen calendars were created for the major pollen types (>3%), the average Annual Pollen Index over 12 months was calculated, and the results were compared to available historical data. RESULTS: The main pollen types were from exotic vegetation. The most abundant taxa were Poaceae, Cupressaceae, Moraceae and Buddleja. The pollen season start, peak and end varied widely according to the biome and suite of pollen taxa. The main tree season started in the last week of August, peaked in September and ended in early December. Grass seasons followed rainfall patterns: September-January and January-April for summer and winter rainfall areas, respectively. Major urban centres, for example, Johannesburg and Pretoria in the same biome with similar rainfall, showed substantive differences in pollen taxa and abundance. Some major differences in pollen spectra were detected compared with historical data. However, we are cognisant that we are describing only 2 years of data that may be skewed by short-term weather patterns. CONCLUSIONS: Differences in pollen spectra and concentrations were noted across biomes and between geographically close urban centres. Comparison with historical data suggests pollen spectra and seasons may be changing due to anthropogenic climate change and landscaping. These data stress the importance of regional and continuous pollen monitoring for informed care of pollinosis.

The metabolic costs of sexual signalling in the chirping katydid Plangia graminea (Serville) (Orthoptera: Tettigoniidae) are context dependent: cumulative costs add up fast.

Katydids produce acoustic signals via stridulation, which they use to attract conspecific females for mating. However, direct estimates of the metabolic costs of calling to date have produced diverse cost estimates and are limited to only a handful of insect species. Therefore, in this study, we investigated the metabolic cost of calling in an unstudied sub-Saharan katydid, Plangia graminea Using wild-caught animals, we measured katydid metabolic rate using standard flow-through respirometry while simultaneously recording the number of calls produced. Overall, the metabolic rate during calling in P. graminea males was 60% higher than the resting metabolic rate (0.443±0.056 versus 0.279±0.028 ml CO2 h-1 g-1), although this was highly variable among individuals. Although individual call costs were relatively inexpensive (ranging from 0.02 to 5.4% increase in metabolic rate per call), the individuals with cheaper calls called more often and for longer than those with expensive calls, resulting in the former group having significantly greater cumulative costs over a standard amount of time (9.5 h). However, the metabolic costs of calling are context dependent because the amount of time spent calling greatly influenced these costs in our trials. A power law function described this relationship between cumulative cost (y) and percentage increase per call (x) (y=130.21x-1.068, R2=0.858). The choice of metric employed for estimating energy costs (i.e. how costs are expressed) also affects the outcome and any interpretation of costs of sexual signalling. For example, the absolute, relative and cumulative metabolic costs of calling yielded strongly divergent estimates, and any fitness implications depend on the organism's energy budget and the potential trade-offs in allocation of resources that are made as a direct consequence of increased calling effort.

Juvenile hormone titers, ovarian status and epicuticular hydrocarbons in gynes and workers of the paper wasp Belonogaster longitarsus.

The prevailing paradigm for social wasp endocrinology is that of juvenile hormone (JH) functioning pleiotropically in potential and actual queens, where it fuels dominance behaviors, stimulates ovarian growth and/or affects the production of status-linked cuticular compounds. In colonies with annual cycles (e.g., temperate-zone species), female adults produced at the end of the summer (called gynes) are physiologically primed to hibernate. Despite the absence of egg-laying in the pre-overwintering phase, gynes engage in dominance interactions that may affect reproductive potential following hibernation. JH levels have long been inferred to be low in gynes but this has never been tested. In what is the first study to measure JH in gyne-containing colonies of a temperate paper wasp, and the first to incorporate hormone assays in Belonogaster, our results show that the JH titer positively correlates with gyne-specific traits (including oocyte length and a low frequency of foraging trips) in B. longitarsus, a South African paper wasp. Measures of dominance correlated with oocyte length, but not all dominant females possessed activated ovaries. The cuticular hydrocarbon profiles of gynes and workers were distinct, with oocyte length and JH titer showing a positive association with longer-chain methyl-branched alkanes. Nonetheless, evidence for a role of JH in dominance was inconclusive. Finally, the range of JH titers among gynes, and the positive association of JH titers with ovarian status and prospective fertility signals, makes it unlikely that the gyne phenotype is maintained by low JH levels.

Effects of within-generation thermal history on the flight performance of Ceratitis capitata: colder is better.

The influence of thermal history on temperature-dependent flight performance was investigated in an invasive agricultural pest insect, Ceratitis capitata (Diptera: Tephritidae). Flies were exposed to one of four developmental acclimation temperatures (Tacc: 15, 20, 25, 30°C) during their pupal stage and tested at these temperatures (Ttest) as adults using a full-factorial study design. Major factors influencing flight performance included sex, body mass, Ttest and the interaction between Ttest and Tacc. Successful flight performance increased with increasing Ttest across all acclimation groups (from 10% at 15°C to 77% at 30°C). Although Tacc did not affect flight performance independently, it did have a significant interaction effect with Ttest. Multiple comparisons showed that flies which had been acclimated to 15°C and 20°C performed better than those acclimated to 25°C and 30°C when tested at cold temperatures, but warm-acclimated flies did not outperform cold-acclimated flies at warmer temperatures. This provides partial support for the 'colder is better' hypothesis. To explain these results, several flight-related traits were examined to determine whether Tacc influenced flight performance as a consequence of changes in body or wing morphology, whole-animal metabolic rate or cytochrome c oxidase enzyme activity. Although significant effects of Tacc could be detected in several of the traits examined, with an emphasis on sex-related differences, increased flight performance could not be explained solely on the basis of changes in any of these traits. Overall, these results are important for understanding dispersal physiology despite the fact that the mechanisms of acclimation-related changes in flight performance remain unresolved.