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.