BR. J. ENT. NAT. HIST., 7: l<W4 



SHORT DISTANCE FORM FREQUENCY DIFFERENT Efi 

 IN MELANIC LEPIDOPTERA ACROSS HABITAT BOUNDARD 8 



Tamsin Fraiers 



Downing College, Cambridge University, Regent Street, Cambridge CB2 IDQ 



Tom Boyles 

 Emmanuel College, Cambridge University, St Andrew's Street, Cambridge CB2 3AI J . 



Carys Jones and Michael Majerus* 

 Department of Genetics, Cambridge University, Downing Street, Cambridge CB2 3 EH. 



The evolution of industrial melanism in the peppered moth, Bistort betularia (L.), 

 is considered to be a classic example of evolution in action. The primary selective 

 agent involved has been shown to be differential bird predation, the melanic morph 

 f. carbonaria being more cryptic in heavily polluted regions, but less cryptic than 

 the typical form in relatively unpolluted areas (Kettlewell, 1955a, 1956). Mani 

 (1990) has successfully shown by computer simulation that fitness differences 

 between the forms estimated from bird predation experiments provide good agreement 

 with geographic differences in the frequencies of the forms, at least on a coarse 

 scale. 



Recent work on melanic polymorphism in other species of Lepidoptera has 

 shown that the frequencies of melanic forms may change abruptly and significantly 

 over very short distances across habitat boundaries. Kearns and Majerus (1987) 

 showed that the frequencies of melanic forms of Aids repandata (L.) and Semiothisa 

 liturata (Clerck), taken in a moth trap under a close plantation conifer canop> . 

 in Dyfed, Wales, were significantly higher than in a moth trap some 50 yards 

 away in open deciduous woodland. Similar results have subsequently been obtained 

 for Agriopis marginaria (F.) (Majerus, 1989) in Hampshire, A. repandata, Peribatodes 

 rhomboidaria (D. & S.) and Idaea aversata (L.), in Surrey (Jones et al., in prcsv). 

 and Chloroclysta truncata (Hufn.), Thera obeliscata (Hiibn.), Thera firmata 

 (Hiibn.) and Noctua pronuba L., in Gloucestershire (Aldridge et al., 1993). 



We here provide data from a short period of moth trapping at Box Hill, Surrex 

 showing that morph specific frequency differences over short distances oocui 

 in many, but not all, species of moth with melanic forms. In so doing we extend 

 the list of species in which significant habitat-related frequency differences have 

 been recorded, and provide the first data showing species in which such differences 

 do not occur. 



Methods 



Trapping was carried out from 22.vi to 2.vii. 1992, between approximately 2 1 .30 p.m. 

 and 1.00 a.m., in Juniper Bottom, Box Hill, Surrey. 



Juniper Bottom is an east-west running valley with mature yew woodland 

 along its sides. The canopy of the wood is extremely dense leading to a very dark. 

 under-canopy with virtually no ground cover, except under occasional broad-leaf 

 trees, such as whitebeam, and below breaks in the canopy caused by the blow downs 

 of October 1987. This sparse ground cover consists mainly of dog's mercury. 



*Author for correspondence. 



