Rehan and Richards 



JESO Volume 139, 2008 



FIGURE 5. Thoracic puncture dimorphism of female Ceratina. a. C. dupla, more punctate 

 with two or more complete longitudinal rows of punctures inside the parapsidal lines and 

 around the medial line; central area between medial line and parapsidal lines always punc- 

 tate in posterior half of mesoscutum. b. C. calcarata, less punctate with one to two incom- 

 plete longitudinal rows of punctures inside the parapsidal lines and around the medial line; 

 areas between medial line and parapsidal lines usually impunctate with, at most, a couple of 

 central punctures in posterior half of mesoscutum. 



DNA Sequence Divergence Between Ceratina calcarata and Ceratina dupla 



We compared 774 base pairs of cytochrome oxidase one (COI) for 1 1 individuals of 

 C. calcarata and 9 of C. dupla that had been previously identified using the morphological 

 character described above. Sequences fell cleanly into two groups, distinguished by 7 fixed 

 differences between the two species, providing evidence that C. calcarata and C. dupla 

 are indeed genetically isolated in sympatry. Pair-wise comparisons among all individuals 

 revealed significantly greater sequence divergence between species (mean pairwise 

 difference, 1 .29%) than within species (C. calcarata, 0.46 %; C. dupla, 0.029 %; AMOVA: 

 F ST = 0.80993, df= 1,18, pO.OOOOl). 



Discussion 



The biological species concept defines species as groups of actually or potentially 

 interbreeding natural populations that are reproductively isolated from other such groups 

 (Mayr 1942). Previous studies have provided some evidence that C. calcarata and C. 

 dupla are separate species due to a lack of heterozygotes at multiple isozyme loci in natural 

 populations (Hung & Norden 1987). Our study confirms that the two species are indeed 



64 



