Trends in system atics
Hybrid origin of Cox's Sandpiper confirmed by molecular analysis The taxonom ic statu s of Cox's Sa ndpi per Ca lidris param elanotos has been co ntroversial ever si nce its fo rm al descripti on in 1982 (pa rker 1982). Parker's descr ipt io n was based o n two moul ting birds co ll ected by John B Cox in South Austra li a in the mid 19705 . Fi eld obse rvations and photographs (eg, Prin gle 1987) of simil ar birds in A ustrali a showed that it is interm edi ate in plu mage between Pectoral Sa ndpiper C melanotos and Curl ew Sa nd piper C fe rruginea (Cox 1989a, 1990a). However, in the absence of any indica t ions of the ex istence and locati on of a breed ing popu lat ion, the taxonom ic status of Cox's Sa ndpiper was d iffjcu lt to eva lu ate. Th e controversy has sw irl ed arou nd two questio ns: first, is Cox's Sandp iper a va lid spec ies or a hybrid?; second, if it is a hybrid , w hat are its pa rents? Th ere is no shortage of th eori es. Buckl ey (1988) predicted that Cox's Sandpi per would 'prove to be a va lid, overl ooked, Siberia n-breed ing Ca lidris, one of th ose re licts in th e sa me group as As iatic Dowitcher L[imnodromus] semipalmatus, Little Curlew N umenius minutus, Slender-bill ed Curlew N. tenuirostris, Spoon-billed Sa ndpiper [Euryno rh ynchus p ygm eusl and Nord man n's G reenshank Tringa guttifer'. O th ers we re less conv inced of its spec ific statu s. In recent yea rs, th e v iew has developed th at Cox's Sand piper represents a hybrid. Cox himse lf favo ured the hybrid theory and suggested that one of the pa rents is Pectora l Sa ndp iper and th e oth er pare nt either Curl ew Sa nd piper or Sharp-ta il ed Sa nd piper C acuminata (Cox 1989a, 1990a). Stepanya n (1990) postul ated th at Cox's Sa nd piper rep resents an intergeneri c hyb rid between a fe male Ruff Philom achus pugnax and a male of either Pectoral or Sharp-ta il ed Sa ndp iper. G iven all this unce rta inty, Vuilleum ier et al (1992), in th eir assess ment of newly desc ri bed b ird spec ies, concl uded that th e recognitio n of Cox's Sa ndp iper was premature and treated it as a 'spec ies inquirend a'. The inconclu sive ness of the morpho log ica l analyses on w hi ch all th ese op ini ons were ultimate ly based ca l led fo r an investigatio n using a d iffere nt approac h. Now we have o ne, an A ustra li an study based on two kin ds of mo lec ul ar data: Chri stidi s et al (1996) seq uenced 288 base pa irs of the mitochondri al cytoc hro me b gene of Pectoral, Curlew and Cox's Sandpipers to see w hether the m itocho ndri al DNA (mtDNA) of Cox's Sandp iper is d ifferent fro m th e other two spec ies. MtDNA is
passed on from th e mother to her offsprin g, 50 compa ri so n of mtDNA prov ides a means of identify ing the matern al parent of a putative hybri d . Th us, if Cox's Sa ndpi per rep resents a hybrid , its mtDNA seq uence shoul d be ident ica l o r almost identica l to th at of its matern al parent. If Cox's Sa ndp iper is a va li d species, one woul d expect th at some mtDNA d ifferences are revea led, beca use mtDNA seq uences of all Ca lidris spec ies analysed 50 fa r d iffe r at least 4% from eac h other. The mtD NA of Cox's Sandp iper proved to be identica l to th at of Curlew Sandp iper, w hi ch shows th at Cox's Sa ndpiper represents a hyb ri d, w ith Cur lew Sandp iper constitutin g th e matern al parent. Add it ional i nfo rm atio n about pa rentage was obtained from an all ozyme analys is, in w hi ch severa l poss ible parental spec ies were in cl uded. Thi s study rul ed out that Cox's Sandpiper co uld be th e result of hybridi zatio n w ith Sharp-ta il ed Sa ndpiper or Ruff. Both studi es, taken together, indicate th at Cox's Sa nd piper is th e prod uct of hyb ridi zat ion between a male Pectoral Sandp iper and a female Curlew Sa ndpiper. A lthough Cox's Sandpi pe r is by fa r the most freq uentl y record ed hyb rid sa nd piper, w ith fo ur o r fi ve seen each year in A ustrali a (Cox 1990b), several oth er putati ve hybri d sa ndpipers have been repo rted . Th e most famo us of th ese is Cooper's Sandpi per 'Ca lidris cooperi', of w hi ch onl y a single spec imen is known, co ll ected on Long Island, New Vork, U SA, in 1833. A simil ar bird captured in New South W ales, Australi a, in Ma rch 198 1, was identi fied by Cox (1989a, 1990b), w ho suggested th at Cooper's Sandp iper is a hybri d between Sharp-tail ed Sa ndpi per and Curl ew Sa ndpiper (Cox 1990a). A n unident ifi ed sand p iper at Sa ltho lme Poo ls, Cleve land, England, in September- Octobe r 1989 (Ga ntl ett & G rant 1989) may have been a hybr id between Pectora l Sandpiper and D unlin C alpina. Astrange Ca lidris at Cley, Norfo lk, England, in Jul y 1990, showed intermedi ate c haracters of Pectora l Sa ndp iper and Whi te-rum ped Sa nd piper C fuscicol/is, and could have been a hyb ri d. A nother strange sandp ipe r at Cley, in November 1993, was ident if ied as a poss ible hybri d between D unlin and Purple Sand pi per C maritima (M illi ngto n 1994). Jonsson (1996) recently determin ed th at an im mature stint at Groote Keeten, Noord-Ho lland, Neth erl ands, in September 1995, was the resu lt of hybri d izati o n between Li ttle Stint C m inuta and Temm inck's Stint C temminckii. An all eged intergeneri c hyb ri d between Ba i rd's Sa nd p iper C ba irdii and Buff-breasted Sa ndp iper 255