VARIABILITY ON STABLE ISOTOPES (13C, 15N) OF CAMELIDS BONE COLLAGEN: IMPLICATION TO HOLOCENE HUMAN PALEOECOLOGY

ADOLFO GIL; GUSTAVO NEME; CINTIA ABBONA; ARMANDO DAUVERNÉ; GISELA A. QUIROGA; EVA PERALTA; CLARA OTAOLA

Viña del Mar

Conferencia; IsoECOL; 2018

Camelids,mostlyguanacos(Lamaguanicoe)arethemoreprominentbigsizedherbivorousinSouthAmericaandoneofthemostsignificantresourceinhumandietduringpre-industrialtime.Thestudyofcamelidsisotopicdietissignificantfordifferentaspects.First,becauseitwasacommonresourceforpasthumanpopulationsinsouthAmerica;second,itshighabundanceduringtheHolocenemakethisspecieaproxyforpaleoecologicalreconstruction.Finally,isotopicinformationinthisspecieisusefulforconservationbiologyascamelidarebeingdisplacedbyhumanactivitiesduringthelastcentury,todaytechnicaldecisionarebeingdeveloptoprotectandmanagethisspeciesbutlackingthegeneralinformationaboutcamelidsstrategiesanditsniche.Allofthisaspectscanbeconsideredbasedonstableisotopesignalfrombonecollagen.NorthwestPatagoniaisahighlyenvironmentalandclimaticvariableregion,withsignificantcamelidspopulationlivingtodayandarichHolocenerecordofthisspecie.Aspartofthegeographicvariation,theregionincludedifferentdesertscalledAltoandina,PatagoniaandMonte.WetestifthereissignificantvariationonguanacoisotopicsignalwithinthethreebiogeographicdesertsandweexploreiftheguanacoisotopicsignalshowstemporalvariationthroughtheHolocene.MonteandPatagoniacamelidsdifferinthemannerexpected,withMontesampleshavingmorepositiveaveragevaluesofẟ13Candẟ15N.TheAltoandinosamples,ontheotherhand,aresimilartoPatagoniabutstatisticallynotdifferentwithMonte.However,thesmallamountofsamplescanexplainthisstatisticaltrend.Thespatialpatterninẟ13CshowtheenrichedaveragelocalizedintheNortheastquarterbutasdiscontinuousareasinterceptwithamoredepletedẟ13Csamples.Atthesametime,ẟ15NshowamorevariableandcounterintuitivespatialpatternthatdonotfollowtheexpectationinFigure2.Ontheotherhand,thetemporaltrendsshowanewpatternpreviouslyignored.Thereissomevisualchangethroughtimethatrejecttheideaofstabletrends.Clearly,thehighpositivecorrelationbetweenẟ13Candẟ15Ncouldindicateanenvironmental/climaticvariableisexplainingthetemporaltrends.Ifso,itcanbeproposethisvariationthroughtimeisreflectingchangeintheecosystemsthatcouldimplychangeinC3/C4plantsfrequencyand/orchangeintheisotopicvalueonthevegetationincludingthesamephotosyntheticway.Theenrichesẟ13Cduringtheearly/middleHolocene,associatedwithaweakincreasein15NcouldconfirmtheincreaseinannualplantsproposedbyMarkgraff(1983)reflectingandincreasingofaridity.Clearly,anincreaseinthesamplesizeandanimproveinthestudyofrelationshipbetweenẟ13Cbonecollagencamelidsandenvironmentcouldconfirmorrejectthistrends.