Presentation Title

Interacting impacts of drought and habitat fragmentation on San Diego's native bees

Start Date

November 2016

End Date

November 2016

Location

HUB 302-120

Type of Presentation

Poster

Abstract

Declines in pollinator populations as a result of environmental changes associated with human activity have been reported across the world recently. While many studies have focused on single causes of pollinator declines, such as habitat loss, climate warming, or the spread of pathogens, few studies investigate how multiple sources of environmental change may jointly impact pollinator populations. Here, we examine how an extreme drought event interacts with habitat fragmentation to alter the composition of a diverse assemblage of native bees, which are the most important pollinators in many ecosystems. Collecting native bees, using permutational multivariate analysis of variance (PERMANOVA), as well as using a linear mixed-effects model allowed us to identify differences in bee assemblage composition between reserves and fragments and between pre-drought and post-drought years. The magnitude of assemblage shifts associated with drought appears similar between fragments and reserves, suggesting that drought and fragmentation have distinct effects on bee assemblages in our region. Linear mixed-effects models revealed that fragmentation, drought, and their interactions influenced a higher proportion of specialist than generalist bee species, with certain species appearing to benefit from one or both forms of environmental change. Our results suggest that drought and habitat fragmentation may interact to yield complex, profound shifts in bee assemblages and that disentangling these complex effects may require longer-term studies.

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Nov 12th, 1:00 PM Nov 12th, 2:00 PM

Interacting impacts of drought and habitat fragmentation on San Diego's native bees

HUB 302-120

Declines in pollinator populations as a result of environmental changes associated with human activity have been reported across the world recently. While many studies have focused on single causes of pollinator declines, such as habitat loss, climate warming, or the spread of pathogens, few studies investigate how multiple sources of environmental change may jointly impact pollinator populations. Here, we examine how an extreme drought event interacts with habitat fragmentation to alter the composition of a diverse assemblage of native bees, which are the most important pollinators in many ecosystems. Collecting native bees, using permutational multivariate analysis of variance (PERMANOVA), as well as using a linear mixed-effects model allowed us to identify differences in bee assemblage composition between reserves and fragments and between pre-drought and post-drought years. The magnitude of assemblage shifts associated with drought appears similar between fragments and reserves, suggesting that drought and fragmentation have distinct effects on bee assemblages in our region. Linear mixed-effects models revealed that fragmentation, drought, and their interactions influenced a higher proportion of specialist than generalist bee species, with certain species appearing to benefit from one or both forms of environmental change. Our results suggest that drought and habitat fragmentation may interact to yield complex, profound shifts in bee assemblages and that disentangling these complex effects may require longer-term studies.