Table 2. Thermal effects on the phenotypes of natural reproductive parasites of insects.
| Host | Symbiont | Nature of symbiosis | Assay type | Impact of temperature on phenotype | Source |
|---|---|---|---|---|---|
| Aedes polynesiensis | Wolbachia | CI | Phenotype, cytology | CI eliminated by 32–33 °C exposure as larvae for 5–7 days. 30–32 °C did not eliminate CI. Larva dies above 33 °C. | Wright and Wang (1980) |
| Drosophila equinoxalis | ESRO Spiroplasma | MK | Phenotype | MK reduced by embryonic heat treatment with various temperatures and durations between 34 and 40 °C. | Malogolowkin (1959) |
| D. nebulosa | NSRO Spiroplasma | MK | Phenotype, qPCR | Highly penetrant MK at 25 °C. At 18 °C, there is loss of fully female broods at generation 2. At 28 °C, gradual loss occurs until at generation 8, 1/8 strains show strong female bias. | Anbutsu et al. (2008) |
| D. willistoni | WSRO Spiroplasma | MK | Phenotype | No effect of embryonic heat treatment at various temperatures and durations between 34 and 40 °C. | Malogolowkin (1959) |
| D. bifasciata | A-group Wolbachia | MK | Phenotype, cytology | Phenotype lost between 23.5 and 25 °C. | Hurst et al. (2000, 2001) |
| D. melanogaster | wMelPop Wolbachia (may not exist in wild) | Premature host death | Phenotype | No mortality effect at 19 °C. At 25 °C, wMelPop induces early mortality, with effect increasing at 29 °C. | Min and Benzer (1997); Reynolds et al. (2003) |
| D. simulans | wRi Wolbachia | CI | Phenotype, cytology | Ageing and rearing males at elevated temperature (27 °C) reduces incompatibility; larval thermal environment critical. | Clancy and Hoffmann (1998) |
| D. simulans | Wolbachia | CI | Phenotype | CI suppressed in crosses between two unidirectionally incompatible fly strains exposed to 28 °C in early life. | Hoffmann et al. (1986) |
| D. simulans | Wolbachia | CI | Phenotype | Larval heat shock at 36 °C (1 h) reduced CI in adult male flies. Egg mortality was 90% rather than 45%. Heat shock did not influence survival or fertility. | Feder et al. (1999) |
| Nasonia vitripennis | Wolbachia strain A | CI | Phenotype, qPCR | Positive correlation between density and CI penetrance within temperature groups. However, density and CI were decoupled between groups. Temperature may change the density threshold required for CI. | Bordenstein and Bordenstein (2011) |
| Ostrinia scapulalis | Wolbachia | MK | Phenotype, PCR | Exposing larval female moths to 63 °C for 20–30 min suppresses phenotype. 40 min has a greater effect but causes high lethality. 53 °C not efficient at nonlethal exposure times. 34–38 °C for long periods does not fully suppress MK. | Sakamoto et al. (2008); Sugimoto et al. (2015) |
| Tribolium confusum | Wolbachia | CI | Phenotype | Suppression of CI with exposure to 37 °C for 12 days in larval stage. Number of individuals lacking the phenotype increases with exposure time. | Stevens (1989) |
| Trichogramma cordubensis | Wolbachia | Induces thelytoky | Phenotype with ‘permissive passage' | Thelytoky reduced over 4 generations at 30 °C, significant during generations 2–4. Recovery with 4 generations of passage at 23 °C. | Girin and Boulétreau (1995); Pintureau et al. (1999) |
| Tetranychus urticae | Wolbachia | CI | Phenotype, PCR with ‘permissive passage' | High loss of phenotype after 4 generations at 32 °C (threshold at 31–32 °C). Development time was reduced, and many heat-cured lines died out. | van Opijnen and Breeuwer (1999) |
Abbreviations: CI, cytoplasmic incompatibility; MK, male killing; qPCR, quantitative PCR.
In ‘Assay type' details, Phenotype is strength of phenotype measured; qPCR, PCR, cytology and Southern hybridization are means by which symbiont presence was confirmed; and permissive passage is test for symbiont presence conducted after recovering the lineage to standard thermal environment.