Influence of Temperature on Intra- and Interspecific Resource Utilization within a Community of Lepidopteran Maize Stemborers

Abstract

Competition or facilitation characterises intra- and interspecific interactions within communities of species that utilize the same resources. Temperature is an important factor influencing those interactions and eventual outcomes. The noctuid stemborers, Busseola fusca and Sesamia calamistis and the crambid Chilo partellus attack maize in sub-Saharan Africa. They often occur as a community of interacting species in the same field and plant at all elevations. The influence of temperature on the intra- and interspecific interactions among larvae of these species, was studied using potted maize plants exposed to varying temperatures in a greenhouse and artificial stems kept at different constant temperatures (15°C, 20°C, 25°C and 30°C) in an incubator. The experiments involved single- and multi-species infestation treatments. Survival and relative growth rates of each species were assessed. Both intra- and interspecific competitions were observed among all three species. Interspecific competition was stronger between the noctuids and the crambid than between the two noctuids. Temperature affected both survival and relative growth rates of the three species. Particularly at high temperatures, C. partellus was superior in interspecific interactions shown by higher larval survival and relative growth rates. In contrast, low temperatures favoured survival of B. fusca and S. calamistis but affected the relative growth rates of all three species. Survival and relative growth rates of B. fusca and S. calamistis in interspecific interactions did not differ significantly across temperatures. Temperature increase caused by future climate change is likely to confer an advantage on C. partellus over the noctuids in the utilization of resources (crops).

Fig 1. PVC surrogate stem for rearing stemborer larvae on artificial diet.

(a) halves of pipe before they are joined, (b) full pipe after halves have been joined.

Fig 2

Survival (a) and relative growth rates (b) of Chilo partellus (Cp), Busseola fusca (Bf) and Sesamia calamistis (Sc) larvae on maize and surrogate stems under varying temperatures. Means (± SE) with different letters are significantly different at 5% level according to the GLM for survival and the Student-Newman-Keuls test for relative growth rates.

Fig 3

Survival (a) and relative growth rates (b) of Chilo partellus (Cp), Busseola fusca (Bf) and Sesamia calamistis (Sc) at low density (6L) and high density (12L) infestation at 25°C. Means (± SE) with different letters are significantly different at 5% level according to the GLM for survival and the Student-Newman-Keuls test for relative growth rates.

Fig 4

Comparison of survival of Chilo partellus (Cp), Busseola fusca (Bf) and Sesamia calamistis (Sc) larvae as single-species (a) and between borer species in multi-species communities at different constant temperatures (b-e). Means (± SE) with different letters are significantly different at 5% level. GLM (binomial).

Fig 5

Comparison of the relative growth rates (RGR) of Chilo partellus (Cp), Busseola fusca (Bf) and Sesamia calamistis (Sc) larvae as single-species (a) and between borer species in multi-species communities at different constant temperatures (b-e). Means (± SE) with different letters are significantly different at 5% level according to the Student-Newman-Keuls test.

Fig 6

Comparative survival (a) and RGR (b) between single-species and multi-species communities of Chilo partellus (Cp), Busseola fusca (Bf) and Sesamia calamistis (Sc) under different constant temperatures. Statistical comparisons were only made between single- and the corresponding multi-species pairings (see Tables 5 and 6).