Abstract
This study investigated the effects of ant attendance on the parasitoid community and parasitism of lac insect Kerria yunnanensis aggregations in Yunnan province, China. We manipulated ant attendance to establish three treatments: (1) ant exclusion; (2) low ant attendance by several ant species; and (3) high ant attendance by Crematogaster macaoensis. Five parasitoid species were collected, with two species contributing 82.7 and 13.2% of total abundance respectively. Total parasitoid abundance was lowest in the February sample when K. yunnanensis was in its younger life stage, being significantly lower in the ant exclusion treatment. In April, all three treatments had significantly different parasitoid abundances, being highest in the ant exclusion treatment and the lowest in the high ant attendance treatment. When ants were present, there were strong negative relationships between total parasitoid abundance and ant abundance, with the relationships being dependent upon the ant species composition and abundance. The patterns of total parasitoid abundance were driven by the two most abundant parasitoid species. Parasitoid species richness did not differ among treatments or between sample times, however, multivariate analysis confirmed that overall parasitoid community structure differed significantly among treatments and between sample times, with the high ant attendance treatment differing most from the other two treatments. Interestingly the absence of ants did not result in increased parasitism from four of the five parasitoids. Ants in lac insect farming systems have a clear role for agricultural pest management. A full understanding of the asymmetric abilities of ants to influence parasitoid communities, and affect parasitism of hosts will require further experimental manipulation to assess the relative roles of 1) the abundance of each individual ant species on parasitoid access to hosts, 2) competition among parasitoids, and 3) the interaction between the first two factors.
Highlights
Honeydew-producing insects and ants have many mutualistic associations, in which ants obtain honeydew that phytophagous insects exude [1], and in return, the ants protect the symbionts from their natural enemies [2,3,4,5]
This is largely due to the February sample having approximately half (5) the number of ants per crust compared to the April sample (10), and the greater presence of the two most common ants, C. ferrari and C. macaoensis in April compared to February
Total parasitoid abundance was lowest in the February sample when K. yunnanensis was in its younger life stage, and interestingly was significantly lower in the ant exclusion treatment and high ant attendance treatments sampled in February and April
Summary
Honeydew-producing insects and ants have many mutualistic associations, in which ants obtain honeydew that phytophagous insects exude [1], and in return, the ants protect the symbionts from their natural enemies [2,3,4,5]. The strength of associations between ant and honeydew-producing insects, as well as the ability for ants to protect their symbionts from predators and parasites, vary greatly, even for the same pair of species among habitats [6] Factors influencing these partnerships include the species of tending ants [7,8,9,10], the aggregation size of the honeydewproducing insects [11,12], temperature [13], the developmental stage of the honeydew-producing insects [12,14], as well as competition among honeydew-producing insect aggregations for the services of ant mutualists [12,15,16,17]. In China, lac production is worth US$92 million annually, and the lac insect most commonly cultivated is K. yunnanensis [20]
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