The influence of habitat and species attributes on the density and nest spacing of a stingless bee (Meliponini) in the Atlantic Rainforest.

Marília Dantas Silva,Mauro Ramalho

doi:10.13102/sociobiology.v63i3.1037

Abstract

T. spinipes lives in perennial eusocial colonies and builds nests exposed on tree branches. Why this habitat generalist with exposed nests cannot nest successfully in forest habitats is intriguing. This study explores the hypothesis this species reaches higher densities in vegetation with open canopies and the subsidiary shading hypothesis, assuming the failure of exposed nests in closed canopy rainforest. As this species shows the basic attributes of territorial foraging groups, the hypothesis of uniform nest spacing is also tested. Comparative field data on nest density and spacing in open canopy vegetation and adjacent closed canopy forest are used to test these hypotheses. In random 40 20x200m plots in rubber groves, 18 nests were recorded. This nest density for a single stingless bee was approximately 36 times higher than in the adjacent rainforest. The high density of nests in the rubber groves is also associated with a regular spatial distribution of nests. The ostensive patrolling distances from the colonies probably operates at short distances, which still corresponds to large territorial areas for such a small stingless bee.We conclude that: this species faces powerful nesting constraints in the ever green and closed canopy of rainforest habitats; as the nest density approaches the density threshold, the patrolling mechanism regulates access to prospective nest sites; the high availability of sunny sites for nesting within the deciduous and open canopy of rubber trees favours the high nest density of T. spinipes and its wide spread distribution where this agroforestry system dominates.

Highlights

The stingless bees occupy multiple habitat types but are diverse and abundant in tropical rainforests. They depend mainly on nest structure and building materials for thermoregulation, which likely constrains their distribution to the hot tropical-subtropical zone (Sakagami, 1982; Roubik, 1989). They live in sessile, perennial and eusocial colonies, most species depend on pre-existing cavities as nesting sites, and very few species build exposed nests (Hubbell & Johnson, 1977; Nogueira-Neto, 1997; Camargo, 2007)
The nests were sampled in two habitats that represents the two extremes of canopy exposure to sunlight: the more open deciduous rubber grove canopies that are exposed to direct sunlight for 1-2 months each year; and the dense closed evergreen canopies of the rainforest
18 nests of T. spinipes were recorded in the 16 hectare of rubber groves sampled, with a density of 1.1 nests/ha (Table 1)

Summary

Introduction

The stingless bees occupy multiple habitat types but are diverse and abundant in tropical rainforests. Some authors suggest that the density and spatial distribution of colonies should be influenced by the availability of nesting cavities, this hypothesis has been refuted by several studies in tropical forests (Hubbell & Johnson, 1977; Eltz et al, 2002; Silva et al, 2014).

Results

Conclusion