Hightemperatureandburialinhibitseedgermination oftwoperennialMediterranean Euphorbia species Eduardo Narbona 1 , Montserrat Arista 2 and Pedro L. Ortiz 2 1 DepartamentodeBiologíaMoleculareIngenieríaBioquímica,UniversidadPablode Olavide,Ctra.UtreraKm1,41013Sevilla,Spain;e-mail:enarfer@upo.es 2 DepartamentodeBiologíaVegetalyEcología,UniversidaddeSevilla,Apdo.1095,41080 Sevilla,Spain Manuscriptaccepted5September2007 Abstract NarbonaE.,AristaM.andOrtizP.L.2007.Hightemperatureandburialinhibitseed germinationoftwoperennialMediterranean Euphorbia species.Bot.Helv.117:169– 180. SeedsoftheMediterranean Euphorbiaboetica and E.nicaeensis areproducedin summerbutgerminateonlyinautumn;theyareactivelydispersedbyants,whichmay causethemtobeburied.Herewetestedwhetherthedelayingerminationiscausedby thermodormancy,andwhetherseedlingsareabletoemergeafterburial.Seedsofthe perennial spurges Euphorbia boetica and E. nicaeensis were collected in four populations of southern Spain and were incubated at differing temperatures or after burial at differing soil depths. Most seeds germinated at 18–21 8C, but germination percentageswerereducedat25 8Candnearlyzeroat30 8C.In E.boetica,thelackof germinationat30 8Cwasduetothermoinhibition,asallseedsthathadnotgerminated at 30 8C did germinate when they were subsequently incubated at 18–21 8C. In contrast,about15%oftheviableseedsof E.nicaeensis didnotgerminateunderthese conditions,meaningthattheyhadenteredsecondarydormancy.Allviableseedsof E. boetica buriedat1and5cmemerged,butat10cmemergencewassignificantlylower. In contrast, very few buried seeds of E.nicaeensis emerged at all burial depths, and someburiedseedsenteredsecondarydormancy.Thedifferentgerminationstrategiesof the two species may reflect their different habitats and dispersal modes: E. boetica growsinthelowlandsonsandysoils,anditsseedsarealwaysburiedafterantdispersal, whereas E.nicaeensis livesinmontaneregionsonstonyandcompactsoils,anditsseeds maybefrequentlydispersedatsoilsurface,reducingtheselectivepressureforseedsto germinateafterburial. Bot.Helv.117(2007):169–180 0253-1453/07/020169-12 DOI10.1007/s00035-007-0816-9 #BirkhäuserVerlag,Basel,2007 Botanica Helvetica