Ceratina of Eastern Canada 



JESO Volume 139, 2008 



genetically as well as morphologically distinct. Although hybridization is thought to be 

 possible in artificial environments such as greenhouses and flight cages (Hung & Norden 

 1987), the fact that these sympatric species are genetically distinct suggests differences in 

 life history and behaviour are possible. 



Limited research has been done on the life history and behaviour of natural 

 populations of Ceratina in North America. Grothaus (1962) found that C. calcarata prefer 

 to nest in open areas, usually in older, drier stems, while C dupla prefer shaded areas 

 and recently dead stems. This life history difference between sister species parallels a 

 remarkably similar finding in two Asian species of the subgenus Ceratinidia, Ceratina 

 flavipes and C japonica, which are sympatric throughout Japan. Females of C japonica 

 prefer to nest in bushes or sparsely wooded areas, remaining shaded and humid, whereas 

 C. flavipes nest in comparatively open, dry areas (Sakagami & Maeta 1977). As with C. 

 calcarata and C. dupla, males of the two Japanese species are quite distinct, but females are 

 very difficult to distinguish (Shiokawa 1963; Yasumatsu & Hirashima 1969). 



Previous studies have shown COI to be a useful indicator gene to differentiate 

 even morphologically indistinguishable sister species. Halictus ligatus and H. poeyi are 

 sympatric, eusocial species with slightly different phenologies (Dunn et al. 1998). They 

 exhibit approximately 0.4% COI sequence variation within species and 4 to 5% between 

 species (Danforth et al. 1998). The degree of divergence between these two Halictus, 

 is comparable to that between the aforementioned C flavipes (Genbank accession no. 

 AY250190) and C japonica (AY250192) (Cronin 2004); comparison between these two 

 sequences reveals about 4.1% divergence. Both these species pairs are considerably more 

 divergent than C. calcarata and C. dupla appear to be. 



Morphologically similar females are found in various Old World subgenera of 

 Ceratina, including Ceratinidia (Shiokawa 1963; Yasumatsu & Hirashima 1969), Ceratina 

 sensu stricto and Neoceratina (Hirashima 1971), and numerous New World Zadontomerus 

 (Daly 1973). Although males of this genus have proven simple to distinguish based 

 on femoral tooth projections, tergal processes, elaborate genitalia and sternal suture 

 modifications, it seems that females across the genus Ceratina have more understated 

 distinctions. Eventually, closer examination for subtle differences among sympatric 

 species, perhaps aided by molecular systematics approaches, may reveal consistent female 

 key characters across the genus. 



Key to species 



Males 



1. Hind femur somewhat dilated toward base, but without a median projection, the 



greatest width near the base no more than a third its length (Figure 2a) 



C. dupla Say 



Hind femur with a median, triangular projection, femoral width at this point about equal 

 to half its length (Figure 2b) - 



2. Carina of tergum 7 very narrow, fully as long as broad, and not over a fourth as broad 



as the tergum (Figure 3a) C. stremia Smith 



Carina of tergum 7 at least twice as broad as long, fully half as broad as width of the 

 tergum (Figure 3b) & calcarata Robertson 



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