Shell-shape variation along the latitudinal range of the Chilean blue mussel Mytilus chilensis (Hupe 1854)

Abstract

Abs tra ctShell -sh ap e variation in th e C h ilean blue m u sselMyt ilu s chi len sis w as exam ined in eight popu la-tions coverin g th e tota lity of its distribu tion ran ge,which repr esen ts ov er 1800 km of la titu din al gradi-en t in the sou thea ste rn Paci¢c . The sh ell ou tlinesh ap es w ere assessed us in g elliptic Fou rier an alysisfollow ed by can on ica l variates an a lysis. Fou riercoeU cien ts show ed a h igh ly sign i¢ca n t m orpholo gi-cal variation be tw een the popu lations stud ied.Ca n on ica lva riates an alysis show ed a visu alassocia-tion of th e First ca n on ica l w ith con vexity of ven traledge an d u mbo sh ap e,w h ile the second axis w as as-sociated w ith sh ell elon gation . P reviously describe dge net ic pa tterns were m argin ally con gru en t w ithou r m orphomet ric pattern , thou gh ge o graph ic dis-ta n ce h ad a stron ge r eAect on m orphol ogy . Sh apech an ge (elon gation ) w as correlated w ith latitu din alclin alvariation .The m orphomet rica lan alysis provedto be an im portan t to ol for ev alu atin g th e com po -ne n ts of shell -sh ape va riation in m u ssels and todocu me n t association pa tterns w ith ge ogr aph ica lan d ecolo gica lva riables. Such pa tterns a re u sefu ltoestablish a w ide ¢eld ofw ork ,in clu d in g sexin g,sto ckrec og n ition , traceab ility stu dies an d prod uc tivem an age me n t in ge ner al.K e y w ord s: in ter-grou p d iscrim in ation , im agea n a lysis, ou tlin es, elliptic Fou rier a n a lysis, ca n on i-cal va riates an alysis, biog eogr aph y, M ytilus chilen-sis,blu e muss elsIntroductionThe C h ilean blue m u ssel Myt ilu s chilensis (H u pe185 4) is w idely distribu ted on h ard subs trates fromth e low er in tertida lzone to depth s o f25 m alon g theC h il ea nco s(Br rþm & Joh 1983). Ir ang e the S E P c i¢c vrs 4 0 1 f l ude ,f rom A ica ( 18 S)to Cape H n56 (La cellott iV et l .6 ) The if-f e rnt iaion pa tte ws c orel ted ith aph -cal d ista n ce, su gges tin g a steppin g-stone m odel ofth e pop u lation stru ctu re. Th is m odel w a s exp ecteddue to th e large dispersalability o flon g-lived plan kto -troph ic la rvae a n d th e pattern o f ocean cu rren tsalon g the C h i le nco s (Toro et .200 4, 0 6) I ad-d ition , a nly sof hell mrphol gy u lnea or -phomet ic v ab l es on three po u ions w nsou ther nC hile ar g how d oupopu lation (P u n ta A ren a s) w as th e m os t d iverge n t(Toro et al.200 4).In th e presen t study w e exam in ed shell m orphol -ogy variation to see if it follow ed th e sa m e pattern ofge net ic m ark ers alon g the 18 00 -k m grad ien t.To da te,m ost m orpholo gica l an alyses of Myti lus sp. shel lsh ave be en ba sed on she ll linea r m orphomet ric