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).
Highlights
Maize (Zea mays L.) is one of the most important cereal crops worldwide, utilized as human food, animal feed and industrial raw materials [1, 2]
In developing countries such as in Africa, 95% of total maize production, mostly by small scale farms, is used for human food. Maize production in this region is fraught with a myriad of challenges including pests, diseases, drought and nutrient deficiency [1]. Lepidopteran stemborers such as the indigenous noctuids Busseola fusca (Fuller) and Sesamia calamistis (Hampson) and the exotic crambid Chilo partellus (Swinhoe) attack the maize crop in East and southern Africa [3, 4]
This paper reports on the kind of intra- and interspecific interactions that characterise resource utilization by communities of B. fusca, S. calamistis and
Summary
Maize (Zea mays L.) is one of the most important cereal crops worldwide, utilized as human food, animal feed and industrial raw materials [1, 2]. Maize production in this region is fraught with a myriad of challenges including pests, diseases, drought and nutrient deficiency [1] Lepidopteran stemborers such as the indigenous noctuids Busseola fusca (Fuller) and Sesamia calamistis (Hampson) and the exotic crambid Chilo partellus (Swinhoe) attack the maize crop in East and southern Africa [3, 4]. S. calamistis is present in low numbers at all elevations It is only at the mid-elevations do the three species occur as a mixed community, but the predominance of a species may vary with location and season [7, 9, 10]
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