Assessing genetic variation among Bombus Impatiens (Hymenoptera: Apidae) in two boroughs of New York City using mitochondrial DNA




Shannon U. Morath

Introduction

Bombus species (bumblebees) are important targets for conservation because many wild flowers and commercial crops depend on them for pollination. Urban habitats have been suggested as potentially important for conservation of bumblebees because of the increased diversity of flowering species in gardens and parks due to the addition of horticultural varieties and exotic species. Recent assessments of bee diversity in urban systems suggest that certain generalist species, such as bumblebees, have a greater abundance in urban areas, compared to surrounding natural habitats. Despite a possible abundance of bumblebees in urban habitats, little is known about the genetic variation of urban bees.

This study investigates the genetic diversity of Bombus impatiens worker bees sampled from four locations in New York City by sequencing a fragment of the mitochondrially encoded Cytochrome b gene. This approach was chosen because most species exhibit high levels of diversity in mtDNA, and intraspecific variation is expected in populations that are geographically separated. The objective of this study was to determine whether bees sampled in two boroughs of New York City were of the same population, or if there is a sufficient distance between the populations such that gene flow is prevented.

Figures


Figure 1-Successfully extracted bee mtDNA was amplified using PCR. Here PCR products of the mitochondrial gene Cytochrome b are visualized. The primers, designed to amplify a 434bp fragment based on Apis mellifera sequence data, had the following sequences: forward: 5’-TACTACCATGAGGACAAATATC-3’ and reverse: 5’-ATTACACCTCCTAATTTATTAG-3.’ Five B. impatiens sampled from four locations in New York City were analyzed. Locations of bees are shown above gel. (PV: Peaceful Valley, PA:Papo’s Garden, GH: Garden of Happiness, DR: Drew Garden.)


Figure 2-Sequences (360 bp) from the Cytochrome b gene for five B. impatiens specimens were obtained from purified PCR products and aligned using ClustalW.


Partial sequences of a mitochondrial gene of Bombus impatiens specimens were analyzed to determine the genetic heterogeneity of bees sampled in the Bronx and Manhattan, two boroughs of New York City. The minimal heterogeneity shown in the alignment of the Cytochrome b sequences indicates that there is some genetic variation in these populations. However, further analysis is required to clearly determine the genetic structure of B. impatiens populations in New York City.

The mitochondrial Cytb gene fragments sequenced in this study may not be the most appropriate method for assessing genetic heterogeneity across such a small geographic area. In future studies, microsatellite markers may provide more information about the genetic structure of Bombus impatiens in New York City.

Full Paper

Acknowledgments

I would like to thank Joe Frezzo and Leleesha Samaraweera for giving generously of their time and advice. I would also like to thank Dr. Berish Rubin for providing the impetus to learn the techniques used herein. I am grateful to Kevin C. Matteson for providing the specimens used in this study.


This document was last modified 05/09/2007.
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