Acoustic behaviour was studied in the four species of Alebra Fieber leafhoppers found in Britain, which are morphologically the closest in the genus: A . wahlbergi (Boheman), A . coryli Le Quesne, A . albostriella (FallCn) and A . uiridis Rey. One male call, of a diagnostic structure and produced in all behavioural contexts observed, was recorded for each species. No female acoustic signals were identified. Using male call pattern the three species of Alebra coexisting on Castanea saliva Miller in Kastanitsa, southern Greece, were identified as A . wahlbergi, A . albostriella and A . uiridis. Individuals of A . uiridis from Kastanitsa had more pronounced external pigmentation than those from Cardiff, South Wales. Discriminant and principal component analysis on variables of the male call of A . uiridis distinguished the populations from Cardiff and Kastanitsa, but could not differentiate populations from the two British host plants, Quercuspetraea and Q. cenis, in Cardiff. The British and Greek populations differed in the covariation as well as the duration of call components.Castanea saliva was also recognized as a host plant of A . uiridis in Cardiff. Individuals collected from C. saliva had external patterning in the same range of variation as that found for individuals from species of Quercus.Present evidence strongly suggests that divergencc in the acoustic species recognition signals of Alebra is occurring among geographic rather than sympatric host plant-associated populations.

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Populations n l the four species of (Xloiiona commonly found i n thr Netherlands (:, dorsnta. (.:,q/aucrJrunr. C. J?izai&i/a and C. i'asroriircr -\vere cultured in thc laboratory nn t'tiqmit~.! aiotmlis, their exclusive host p l a n t in thc field. The low frequency substratr-transmitted signals produced during the calling phase of mating hchaviour \vcre digitally analyscd for the ni;iles and lemalcs of each species. Variables s r l e r t e d to cover most aspcrts nf tlic rall \+err measured, and variatinn was q i~~i~i t i f c d \vithin species and statistically tested uniiing species iising univariatca and multivariate techniques. Tlic calls of the nidcs \\ere inore complex in structure than thosc of the f;*rnalea, with two dilIerent phase patterns recognizcd, and wcrc species-specific. C. glaumrms and C: iotrmirn wrre also separated on variables o l the kmalc call, I)ut C. dorsnta and C. unarngdtiln cumplctcly ~~vcrlappcd. No sigiitic;int diftercnccs were h i n d bet\veen the c:ills of the long-\\inged and . h r twinged feinalc moi-phs of C. siiiarqdii/a. pnasible rolv for v;iriatiiin in calling signals. and [responses to thcm, in the evolution and maintcnancc of rcproductivc isolation in C%liii7uiin is discussed.

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