Effects of Ecological Fitting and Dispersal in a Generalist Stingless Bee: A Field Experiment

We tested the role of ecological fitting and dispersal in spreading a generalist stingless bee and its potential effects on forest bee assemblages. Phenotypic plasticity in two life history traits (colony reproductive rate and annual survival) together with colony density were used as measures of ‘ecological fitting’ of Tetragonisca angustula Latreille, 1811 (Ta) to three adjacent habitats: forest core (FC), forest edge (FE), and rubber tree matrix (RM). Swarms/ha were estimated six times over 12 months in four replicates/habitat types. Generalized Estimating Equations were used to analyze the relationship between habitat type and swarm occurrence. Colony density (colony/ha) and annual colony survival (a proxy for longevity) were compiled from our previous studies. A total of 329 swarms were captured across the three habitats during the sampling period. The colony reproductive rate (swarm/colony/year) of Ta was high (4 to 6) among the stingless bees and did not vary between the habitats, so it is configured as a conservative trait in this species. The swarming rate/ha was significantly lower in FC than in RM and FE, indicating spatially structured dispersion (SSD). The SSD and significantly lower colony density in FC supported the premise of mass effect on FC. Ta’s ecological fitting to FC involved increased colonial longevity and was successful. The ecological fitting of generalists and SSD is a process with rapid effects that probably drives the structuring of stingless bee assemblages in the Brazilian Atlantic Forest in a widespread deforestation and anthropization scenario.