Limits...
Divergent thermal specialisation of two South African entomopathogenic nematodes.

Hill MP, Malan AP, Terblanche JS - PeerJ (2015)

Bottom Line: Acclimation had both negative and positive effects on temperature stress survival of both species, although the overall variation meant that many of these effects were non-significant.There was no indication of a consistent loss of plasticity with improved basal thermal tolerance for either species at upper lethal temperatures.At lower temperatures measured for H. zealandica, the 5 °C acclimation lowered survival until below -12.5 °C, where after it increased survival.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre of Excellence for Invasion Biology, Department of Conservation Ecology and Entomology, Faculty of AgriSciences, Stellenbosch University , South Africa.

ABSTRACT
Thermal physiology of entomopathogenic nematodes (EPN) is a critical aspect of field performance and fitness. Thermal limits for survival and activity, and the ability of these limits to adjust (i.e., show phenotypic flexibility) depending on recent thermal history, are generally poorly established, especially for non-model nematode species. Here we report the acute thermal limits for survival, and the thermal acclimation-related plasticity thereof for two key endemic South African EPN species, Steinernema yirgalemense and Heterorhabditis zealandica. Results including LT50 indicate S. yirgalemense (LT50 = 40.8 ± 0.3 °C) has greater high temperature tolerance than H. zealandica (LT50 = 36.7 ± 0.2 °C), but S. yirgalemense (LT50 = -2.4 ± 0 °C) has poorer low temperature tolerance in comparison to H. zealandica (LT50 = -9.7 ± 0.3 °C), suggesting these two EPN species occupy divergent thermal niches to one another. Acclimation had both negative and positive effects on temperature stress survival of both species, although the overall variation meant that many of these effects were non-significant. There was no indication of a consistent loss of plasticity with improved basal thermal tolerance for either species at upper lethal temperatures. At lower temperatures measured for H. zealandica, the 5 °C acclimation lowered survival until below -12.5 °C, where after it increased survival. Such results indicate that the thermal niche breadth of EPN species can differ significantly depending on recent thermal conditions, and should be characterized across a broad range of species to understand the evolution of thermal limits to performance and survival in this group.

No MeSH data available.


Related in: MedlinePlus

Thermal performance curves for two entomopathogenic nematodes.(A) Lower lethal temperatures (LLTs) as a function of percentage survival (0–1). Curves glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. (B) Upper lethal temperatures (ULTs) as a function of percentage survival(/10). Curves represent glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. See Table 1 for model summaries.
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fig-1: Thermal performance curves for two entomopathogenic nematodes.(A) Lower lethal temperatures (LLTs) as a function of percentage survival (0–1). Curves glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. (B) Upper lethal temperatures (ULTs) as a function of percentage survival(/10). Curves represent glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. See Table 1 for model summaries.

Mentions: Heterorhabditis zealandica and S. yirgalemense displayed contrasting lethal temperature responses (Fig. 1). Overall, S. yirgalemense displayed greater survival at higher temperatures than H. zealandica (simplified Wald z = − 4.48, p < 0.001) (Table 1). For lower lethal temperatures, this pattern was reversed: H. zealandica had higher survival at low temperatures than S. yirgalemense (simplified Wald z = 7.99, p < 0.001) (Table 1). These differences are also reflected in the lethal temperature values predicted by the generalized linear models (Table 2). The predicted curves for survival of the two species show distinct and contrasting responses to upper and lower lethal temperatures (Fig. 1).


Divergent thermal specialisation of two South African entomopathogenic nematodes.

Hill MP, Malan AP, Terblanche JS - PeerJ (2015)

Thermal performance curves for two entomopathogenic nematodes.(A) Lower lethal temperatures (LLTs) as a function of percentage survival (0–1). Curves glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. (B) Upper lethal temperatures (ULTs) as a function of percentage survival(/10). Curves represent glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. See Table 1 for model summaries.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493674&req=5

fig-1: Thermal performance curves for two entomopathogenic nematodes.(A) Lower lethal temperatures (LLTs) as a function of percentage survival (0–1). Curves glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. (B) Upper lethal temperatures (ULTs) as a function of percentage survival(/10). Curves represent glm logit model fits. Green is Heterorhabditis zealandica, orange is Steinernema yirgalemense. See Table 1 for model summaries.
Mentions: Heterorhabditis zealandica and S. yirgalemense displayed contrasting lethal temperature responses (Fig. 1). Overall, S. yirgalemense displayed greater survival at higher temperatures than H. zealandica (simplified Wald z = − 4.48, p < 0.001) (Table 1). For lower lethal temperatures, this pattern was reversed: H. zealandica had higher survival at low temperatures than S. yirgalemense (simplified Wald z = 7.99, p < 0.001) (Table 1). These differences are also reflected in the lethal temperature values predicted by the generalized linear models (Table 2). The predicted curves for survival of the two species show distinct and contrasting responses to upper and lower lethal temperatures (Fig. 1).

Bottom Line: Acclimation had both negative and positive effects on temperature stress survival of both species, although the overall variation meant that many of these effects were non-significant.There was no indication of a consistent loss of plasticity with improved basal thermal tolerance for either species at upper lethal temperatures.At lower temperatures measured for H. zealandica, the 5 °C acclimation lowered survival until below -12.5 °C, where after it increased survival.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre of Excellence for Invasion Biology, Department of Conservation Ecology and Entomology, Faculty of AgriSciences, Stellenbosch University , South Africa.

ABSTRACT
Thermal physiology of entomopathogenic nematodes (EPN) is a critical aspect of field performance and fitness. Thermal limits for survival and activity, and the ability of these limits to adjust (i.e., show phenotypic flexibility) depending on recent thermal history, are generally poorly established, especially for non-model nematode species. Here we report the acute thermal limits for survival, and the thermal acclimation-related plasticity thereof for two key endemic South African EPN species, Steinernema yirgalemense and Heterorhabditis zealandica. Results including LT50 indicate S. yirgalemense (LT50 = 40.8 ± 0.3 °C) has greater high temperature tolerance than H. zealandica (LT50 = 36.7 ± 0.2 °C), but S. yirgalemense (LT50 = -2.4 ± 0 °C) has poorer low temperature tolerance in comparison to H. zealandica (LT50 = -9.7 ± 0.3 °C), suggesting these two EPN species occupy divergent thermal niches to one another. Acclimation had both negative and positive effects on temperature stress survival of both species, although the overall variation meant that many of these effects were non-significant. There was no indication of a consistent loss of plasticity with improved basal thermal tolerance for either species at upper lethal temperatures. At lower temperatures measured for H. zealandica, the 5 °C acclimation lowered survival until below -12.5 °C, where after it increased survival. Such results indicate that the thermal niche breadth of EPN species can differ significantly depending on recent thermal conditions, and should be characterized across a broad range of species to understand the evolution of thermal limits to performance and survival in this group.

No MeSH data available.


Related in: MedlinePlus