Rehan and Richards 



JESO Volume 139, 2008 



eastern Canada, Ceratina calcarata and C. dupla are sympatric. 



Morphologically, C. strenua is easily distinguishable from C. dupla and C. 

 calcarata, most notably by its smaller size. However, separating C dupla and C calcarata 

 is problematic: although there are recognizable differences among males, females are 

 remarkably similar. As a result, many entomologists have given up trying to differentiate 

 female C. calcarata and C. dupla in their samples and instead combine both taxa into one 

 category for their species lists (Clinebell 2002; Mitchell 2002; Reed 1995). Although 

 it is likely that both species occur in sympatry throughout much or all of their range, it 

 is difficult to discern whether one species may predominate in an area as floral records 

 and geographic distributions rely on males of each species (Daly 1973). The inability to 

 differentiate females of these problematic species has also negatively affected studies on 

 their life history. For example, Johnson's (1988) study on Ceratina calcarata sex ratios in 

 Indiana, omitted all-female broods because he was only confident in identifying males of 

 the species. 



Currently, eastern North American Ceratina are identified using Mitchell (1962). 

 In this key, females of C. dupla and C. calcarata are distinguished by comparison of the 

 number of punctures in the area of the scutum between the notaulices: C. dupla have 

 numerous punctures whereas C. calcarata have few, if any. The problem is that this 

 character description is easily misinterpreted, and there is disagreement about whether the 

 distinguishing character works. However, this taxonomic problem is difficult to resolve 

 without independent evidence that the specimens being examined are indeed correctly 

 identified members of the two species. 



In this paper, we propose a simpler description of the traditional character used 

 to distinguish female C. calcarata and C. dupla. Following thorough examination and 

 description of the character based on scanning electron microscopy (SEM), we test this 

 character's reliability by assessing non-entomologists' ability to use it to identify the two 

 species. In addition, we provide genetic evidence that C. calcarata and C. dupla are indeed 

 separate species based on comparisons of their DNA sequences for the cytochrome oxidase 

 subunit 1 gene for the two species, allowing us to independently distinguish the species 

 identities of specimens used to validate our proposed taxonomic character. 



Methods 



Sampling and Identification 



Specimens were collected in pan traps during the summers of 2005 and 2006 from 

 St. Catharines, Ontario. Pan traps used were blue, white and yellow plastic bowls (6 oz; 

 SOLO PS6-0099) filled with soapy water and spaced ten metres apart in transects. Insects 

 land on the water surface and drown, as the soap in the water acts as a surfactant. All 

 specimens were subsequently preserved in 70% ethanol. Ceratina specimens were initially 

 identified using Mitchell (1962). Following identification, most samples were returned to 

 70% ethanol for storage, but 24 specimens (12 females from each species) were dissected 

 for SEM imaging and DNA extraction (see below). With legs and wings removed, the 

 thoraces of these specimens were used for SEM imagery of the dorsal side, the heads and 

 abdomens being reserved for DNA. 



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