Abstract
Ant-hemipteran mutualism has been well documented, and many studies have reported the interference competition between ant species for the mutualism. However, little is known on how this interference competition impacts the reciprocally beneficial association. Previous studies demonstrated that the invasive mealybug Phenacoccus solenopsis (Tinsley) has established close mutual relationship with the ghost ant Tapinoma melanocephalum (Fabricius). The sympatric ants, Paratrechina longicornis (Latreille) and Tetramorium bicarinatum (Nylander) were frequently observed to compete for nutrient honeydew produced by P. solenopsis with T. melanocephalum. Herein, we investigated the effects of interference competition between the ant species on the ant-mealybug interactions. Phenacoccus solenopsis benefited from the tending by T. melanocephalum and P. longicornis. Interference competition between T. melanocephalum and P. longicornis interrupted the mutualism, suppressed the trailing activity of both species, but negligibly influenced the parasitism of Aenasius bambawalei Hayat, a solitary endoparasitoid of P. solenopsis. Harmonia axyridis, a predator of P. solenopsis, showed a significant avoidance when encountering with T. melanocephalum or P. longicornis, but not T. bicarinatum. Ant workers showed higher aggressiveness and lower exploratory activity when T. melanocephalum encountered P. longicornis. However, competition between T. melanocephalum and T. bicarinatum seldom influenced the trailing and exploratory activity of T. melanocephalum. It is concluded that interference competition for mutualism between ant species can mediate ant-mealybug associations and the fitness of mealybug colony. Our results also demonstrate that the effects of interference competition between ant species on ant-mealybug mutualism are varied among ant species.
Highlights
Mutualism, which is defined as the reciprocally beneficial interaction between two species, is an important ecological interaction [1,2]
Our results demonstrate that the effects of interference competition between ant species on ant-mealybug mutualism are varied among ant species
Many studies have illustrated the interference competition between invasive and native ants for the limited carbohydrates produced by hemipterans, few studies have examined the competition between native ant species, and it remains unclear how this interference competition affects the outcome of ant-hemipteran mutualism
Summary
Mutualism, which is defined as the reciprocally beneficial interaction between two species, is an important ecological interaction [1,2]. Ants tend and protect honeydew-producing hemipterans from predators and parasitoids in a wide range of ecosystems [5]. Hemipterans provide ants with honeydew as a crucial food source [6,7]. The mutual relationship would be stable when the trade-off between the cost and benefit is in balance [12]. This mutual relationship can be strongly influenced by the local biotic neighborhoods in which it occurs [13]. The beneficial effects of mutualist species on each other can vary along with the changes in biotic factors, such as the density of associated species, seasonality, Insects 2020, 11, 91; doi:10.3390/insects11020091 www.mdpi.com/journal/insects
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