Laurence D. M. Packer:
PhD (Toronto)
Professor of Biology and Environmental Studies

Research Interests:
 

There are four main areas of research going on in my lab. at present. (1) Bee systematics and taxonomy, (2) bee conservation genetics, (3) sociobiology, and (4) biodiversity. I do occasionally accept students who want to do something completely different. For example, Hume Douglas is currently revising the Eastern North American click beetles of the genus Cardiophorus.

1) SYSTEMATICS and TAXONOMY. There are about 20,000 species of bee worldwide, divided into approximately 7 families. My main research activity at the moment concerns performing taxonomic revisionary and phylogenetic studies of the bee subfamily Xeromelissinae.  There are approximately 60 new species requiring description, but each field trip I take to South America yields more.  Erin Willis is contributing to this work through a revision of the xeromelissine subgenus Chilioediscelis.

In addition to these revisional studies, I am involved in producing keys for the identification of Canadian bees to the level of genus and postdoctoral fellow Julio Genaro is compiling catalogues of bees of the Caribbean region.

An additional part of our taxonomic work is the use of DNA barcoding for the identification of bees.  PhD student Jason Gibbs is studying taxonomic problems in Lasioglossum (Dialictus) using this technology (http://www.barcodeoflife.org/index.php).

2) CONSERVATION GENETICS. Bees are more prone to extinction than are almost all other organisms because of the genetic load that results from their sex determining mechanism.  Single locus sex determination in haplodiploid insects causes haploids to be males, heterozygotes at the sex locus to be females and homozygotes at the sex locus to be diploid males.  Recent work by Amro Zayed (please see our PNAS paper) has shown that this effect alone makes bees almost an order of magnitude more prone to extinction than are other organisms.  Particularly at risk are specialist bees, those that collect pollen from only one, or a few closely related, species of plant.  In collaboration with researchers in Chile, work in my laboratory has shown that levels of genetic variation are substantially reduced in specialists in comparison to generalists and that levels of gene flow among populations are also lower.

Bumble bees seem particularly prone to extinction and there are several species that have recently suffered catastrophic population declines.  While they are expected to be more sensitive to the effects of small population size even than most other bees (because the amount of resources required by single breeding units – the colony, are so large that the number of colonies in an area is likely to be small relative to the number of nests of solitary bees), it seems likely that introduced bee diseases have something to do with this.  Sheila Colla is investigating the causes of population decline in Canadian bumble bee species.

Further studies of genetic variation, gene flow and the impact of diploid males upon the persistence of bee populations are badly needed and will be one future focus of research in my laboratory.

3) SOCIOBIOLOGY. How can one explain the evolution of a sterile worker caste in social insects? Most research on this question has dealt with taxa such as ants, honeybees and yellowjackets. But all of these have been social for at least 100 million generations and it is too late to find out what factors contributed to social evolution in these insects. Consequently, my research looks at groups of species which contain both solitary and social species or species which are polymorphic with a mixture of social and solitary individuals in different populations or even within the same population.  Exactly this kind of variation is found within the bee subfamily Halictinae in which eusociality has arisen at least 4 times but has been lost even more often.

Future work in this area will involve using microsatellite markers (developed originally as part of the conservation genetics work noted above) to establish genealogies within nests.

4). BIODIVERSITY. Jennifer Grixti recently repeated a historical study of bee biodiversity 30 years after the original study.  We found that the number of bee species had increased at the site, and the most likely explanation is that there had been an increase in habitat complexity over the intervening time. 

Current projects involve performing bee biodiversity studies associated with different coffee growing practices in Costa Rica (Hien Ngo), a bee biodiversity study in Patagonia (Anne-Isabelle Gravel) and the use of bees as indicators of oak savannah restoration (Alana Taylor). 

What factors determine the level of diversity of bee faunas is a topic of considerable economic importance as it is known that increased bee diversity results in increased crop pollination.  Future research on this topic in my laboratory will be guided by findings of an NCEAS (National Center for Ecological Analysis and Synthesis) workshop, of which I am a participant.

Journal Papers

Papers Published in Books: