The effect of habitat fragmentation on the bee visitor assemblages of three Australian tropical rainforest tree species.

Tobias J Smith,Margaret M Mayfield

doi:10.1002/ece3.4339

Abstract

Tropical forest loss and fragmentation can change bee community dynamics and potentially interrupt plant–pollinator relationships. While bee community responses to forest fragmentation have been investigated in a number of tropical regions, no studies have focused on this topic in Australia. In this study, we examine taxonomic and functional diversity of bees visiting flowers of three tree species across small and large rainforest fragments in Australian tropical landscapes. We found lower taxonomic diversity of bees visiting flowers of trees in small rainforest fragments compared with large forest fragments and show that bee species in small fragments were subsets of species in larger fragments. Bees visiting trees in small fragments also had higher mean body sizes than those in larger fragments, suggesting that small‐sized bees may be less likely to persist in small fragments. Lastly, we found reductions in the abundance of eusocial stingless bees visiting flowers in small fragments compared to large fragments. These results suggest that pollinator visits to native trees living in small tropical forest remnants may be reduced, which may in turn impact on a range of processes, potentially including forest regeneration and diversity maintenance in small forest remnants in Australian tropical countryside landscapes.

Highlights

The fragmentation of terrestrial ecosystems is one of the biggest contributors to biodiversity loss on the planet (Dirzo & Raven, 2003; Hanski, 1998; Harrison & Bruna, 1999; Millennium Ecosystem Assessment, 2005), and the negative consequences have been documented in numerous plant and animal groups (e.g., Arroyo-Rodriguez & Dias, 2010; Cushman, 2006; Didham, Ghazoul, Stork, & Davis, 1996; Turner, 1996)
As intertegular distance (ITD), and general body size, has been positively correlated with flight distance in bee species (Gathmann & Tscharntke, 2002; Greenleaf, Williams, Winfree, & Kremen, 2007; van Veen & Sommeijer, 2000), our results suggest that smaller-sized bees may be less capable of accessing, or residing in, small fragments than larger-bodied bees
Our results contribute to the growing body of evidence suggesting that habitat fragmentation can have significant negative effects on bee communities in tropical landscapes

Summary

| INTRODUCTION

The fragmentation of terrestrial ecosystems is one of the biggest contributors to biodiversity loss on the planet (Dirzo & Raven, 2003; Hanski, 1998; Harrison & Bruna, 1999; Millennium Ecosystem Assessment, 2005), and the negative consequences have been documented in numerous plant and animal groups (e.g., Arroyo-Rodriguez & Dias, 2010; Cushman, 2006; Didham, Ghazoul, Stork, & Davis, 1996; Turner, 1996). Empirical studies on the effects of habitat fragmentation on bees are historically uncommon (Cane, 2001), and even with a rise in interest in this topic over recent years, most studies that have been conducted focus on the neotropics (e.g., Aizen & Feinsinger, 1994; Brosi, 2009; Brosi, Daily, Shih, Oviedo, & Duran, 2008; Calvillo, Ramirez, Parra-Tabla, & Navarro, 2010; Ferreira et al, 2015; Powell & Powell, 1987; Tonhasca Jr, Blackmer, & Albuquerque, 2002) While these studies have had mixed results, including both negative (e.g., Aizen & Feinsinger, 1994; Calvillo et al, 2010) and neutral (e.g., Tonhasca Jr et al, 2002) effects of fragmentation on bee diversity, they all tend to show that different bee groups respond differently to fragmentation, probably as a result of distinct nesting and foraging traits among species (Brosi et al, 2008). We ask two questions: (a) Does the richness, abundance, and composition of bees visiting three common floral host trees differ between small and large forest fragments in fragmented Australian tropical landscapes? and (b) In addition to any taxonomic variation, are there detectable functional differences in the bee assemblages found in large and small forest fragments visiting the same host tree species?

| METHODOLOGY

| DISCUSSION

| CONCLUSIONS

Findings

CONFLICT OF INTEREST