See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/232669144 Honeydew Collecting in Malagasy Stingless Bees (Hymenoptera: Apidae: Meliponini) and Observations on Competition with Invasive Ants Article in African Entomology · April 2011 DOI: 10.4001/003.019.0111 CITATIONS READS 6 127 3 authors, including: Hauke Koch Marlotte Jonker University of Texas at Austin University of Freiburg 33 PUBLICATIONS 891 CITATIONS 3 PUBLICATIONS 15 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: TBA course View project ConFoBi - Conservation of Forest Biodiversity in Multiple-use Landscapes of Central Europe View project All content following this page was uploaded by Hauke Koch on 17 August 2014. The user has requested enhancement of the downloaded file. Honeydew collecting in Malagasy stingless bees (Hymenoptera: Apidae: Meliponini) and observations on competition with invasive ants H. Koch1*, C. Corcoran2 & M. Jonker3 1Experimental Ecology, Institute for Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092 Zurich, Switzerland 2Trinity College Dublin, Dublin 2, Ireland 3Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3a, 6708PB Wageningen, Netherlands We present the first record of honeydew feeding in Malagasy stingless bees. Two species of stingless bees, Liotrigona mahafalya and L. madecassa, collected honeydew produced by mealybugs on an Albizia perrieri (Fabaceae) tree in the dry deciduous forest of Kirindy, Madagascar. Honeydew might represent an important part of the diet of Malagasy stingless bees, especially in times of scarce floral resources in the highly seasonal environment of western Madagascar. The interaction between the bees and two species of invasive ants, Monomorium destructor and Paratrechina longicornis, in competition for the honeydew resource, was studied. Numbers of stingless bees and ants on the honeydew source were negatively correlated, with ants decreasing in density distally from the main trunk of the tree and bees showing the opposite trend. Invasive ants could therefore potentially threaten the native bees by displacing them from this resource. Key words: mealybugs, honeydew, Madagascar, Liotrigona, nonfloral resources, displace- ment. INTRODUCTION Honeydew produced by sap-sucking Homoptera dew from aphids tended by the ants. Honey bees is an important resource for a variety of organisms. avoided foraging at honeydew sources occupied by Ant-homopteran associations are often mutualistic ants (Zoebelein 1956b). Ant colonies often monop- and are especially well documented; in these rela- olize the honeydew resource on a particular plant tionships ants protect their homopteran partners and defend it against other inter- or intraspecific against predators and parasites (Schultz & competitors, but coexistence of several ant species McGlynn 2000) and often rely on honeydew as can also occur (Blüthgen et al. 2006). Stingless bees their most important food source (Davidson et al. of the genus Trigona can chemically deter ants 2003). from their nests, presumably with plant-derived Bees are also known to collect honeydew, in- terpenes, although it is not known if these deter- cluding honey bees (Apis spp.), bumble bees rents are also used in competition for resources (Bombus spp.) and several species from the family against other ants (Lehmberg et al. 2008). Andrenidae (Zoebelein 1956a). A few Neotropical The highly social stingless bees (Meliponini) are species of stingless bees have also been observed represented in Madagascar by eight species in the to collect honeydew from hemipterans (Roubik genus Liotrigona (Pauly et al. 2001; Koch 2010). 1989), and a species of Schwarzula even houses While several species inhabit the rainforests of the scale insects (Coccidae) inside their nest for this east (Michener 1990), they are most abundant in purpose (Camargo & Pedro 2002). Until now, how- the dry regions of the south and west, where the ever, there are to our knowledge no reports from local people also harvest honey from their nests the Afrotropical Region, including Madagascar, of (Brooks & Michener 1988). These bees appear to be stingless bees foraging for honeydew. polylectic foragers on pollen and nectar and nest Very few accounts exist on the interactions in tree cavities or bamboo stems (Pauly et al. 2001). between bees and ants, especially in competition In November 2009, we observed two species of for honeydew. Zoebelein (1956b), for example, Liotrigona, L. madecassa and L. mahafalya, collecting notes aggressive behaviour of Formica ants against honeydew from an unidentified species of mealy- honey bees (Apis mellifera) that try to collect honey- bug (Pseudococcidae) on a tree, Albizia perrieri *To whom correspondence should be addressed. (Fabaceae), in the dry deciduous forest of Kirindy, E-mail: [email protected] Madagascar. The same food source was also used African Entomology 19(1): 36–41 (2011) Koch et al.: Honeydew collecting in Malagasy stingless bees 37 by two species of invasive ants, Monomorium availability for mealybugs, we counted the number destructor and Paratrechina longicornis. Since the of leaves for each branch segment. tree was standing freely and both ant species were To assess the temporal variation of ant activity of nesting either in the base of the trunk or in the the different ant species on the tree, the number of ground nearby, the ants had to travel along the ants crossing a line around the trunk of the tree at trunk and main branches to reach the honeydew 1.5 m height was counted for 5 minutes every hour resource. Therefore, we expected the density of starting at 4:25 until 19:25 and again at 22:05 on ants to decrease with increased pathway length four consecutive days. Since no ants were observed (i.e. to honeydew resources distal from the trunk). nesting in the tree itself, this provided an estimate Bees on the other hand are not constrained in this of the relative numbers of ants foraging for honey- way, since they can fly to the best available resource dew at different times during the day. The ambient site in the tree. We therefore hypothesized that the temperature was recorded using a digital thermo- mealybugs that are further away from the trunk meter within a shaded crevice of the tree. would be visited mainly by bees and less visited by ants. We sampled units of mealybug assemblages Statistical analysis across the tree at different distances from the Relationships between the different variables trunk to test this predicted association. were assessed with Spearman rank correlations calculated using Minitab® (Release 13.32) statisti- MATERIAL AND METHODS cal software. A scatter plot of the density of ant and stingless bee individuals against the pathway Ant/stingless bee comparison distance was produced and trendlines were fitted Observations were made on four consecutive to the data points via a nonlinear regression days at the end of the dry season in November assuming a logistic population growth model 2009 on a freestanding Albizia perrieri on the (b1/1 + exp(b2+b3×x) in IBM SPSS Statistics 19 grounds of the Centre National de Formation, (2010). d’Études et de Recherche en Environement et Forestière (CNFEREF) field station (20°03’S RESULTS 44°39’E), approximately 60 km northeast of the city of Morondava in the Menabe region of west- General observations central Madagascar. Liotrigona madecassa and L. mahafalya were In order to test for different spatial distributions observed landing on mealybug assemblages on of ants and bees on the study tree we observed the study tree and ingesting excess honeydew. No 15 cm segments of different randomly selected specific behaviour by the bees to stimulate honey- branches (n = 18), which were evenly distributed dew production by mealybugs was observed. Bees along the accessible parts of the tree. The number were most abundant in the morning and late after- of ants, stingless bees and mealybugs present in noon with more than one hundred individuals each segment were recorded twice daily, between visiting the tree simultaneously during observa- 8:00–9:00 and 17:00–18:00, coinciding with the tion times. Bee activity ceased completely towards peak activity of the bees (H. Koch, C. Corcoran, M. midday and at night. Two ant species, Monomorium Jonker, pers. obs.), for two days. The numbers of destructor and Paratrechina longicornis, were observed bees, ants and mealybugs were averaged over all foraging on honeydew at the same time as the four of these observations per segment. The exact bees. M. destructor was the most abundant of these number of mealybugs present was difficult to ants on the observed mealybug units with assess, therefore only the number of adult females 708 individuals out of 734 ants counted in total visible with the aid of a hand lens, was counted (96%). Figure 1 shows the activity of M. destructor as an estimate. The length of the pathway was and P. longicornis during the course of the day on measured as the shortest distance along branches the study tree. P.longicornis appeared to be crepus- from the ground to a particular mealybug assem- cular, with highest activities during dusk and blage. Mealybugs were mostly clustered around dawn and no activity from 10:00 to 15:00. By the bases of both existing and newly emerging contrast, M. destructor was more active towards leaves, where they gained access to the phloem midday and showed reduced activity during the with their proboscis. To approximate resource night. Accordingly, the activity of M. destructor was 38 African Entomology Vol. 19, No. 1, 2011 Fig. 1. Diel activity of Paratrechina longicornis and Monomorium destructor on the studied tree as measured by number of individuals crossing a line around the tree trunk in five-minute intervals, counted on four consecutive days. positively correlated with temperature (Spearman presence of mealybugs or pathway distance. rank correlation, r = 0.569, P < 0.001, n = 44), while An exponential decrease of ant abundance per P.