Another Northern North Island To Chatham Islands Disjunction
Senecio marotiri C.Webb. was described as a Hauraki Gulf endemic by Dr Colin Webb in 1988. Prior to 1988 the species had been considered a form of the S. lautus “lautusoid” (sensu Ornduff) complex. Webb distinguished it from that species by its taller, narrowly erect habit, lanceolate to linear-lanceolate leaves, narrower and longer capitula, shorter ray florets, larger seeds (cypsela) and by its chromosome number (2n = 80 in S. marotiri, 2n = 40 in S. lautus Wild. ). Although S. marotiri has a superficial resemblance to S. lautus, nrDNA Internal Transcribed Spacer Sequences (ITS) place it as sister species to S. quadridentatus Labill., a species which on further investigation it has a remarkable morphological resemblance to (P. J. de Lange pers. comm.). Webb recognised S. marotiri from the Bay of Islands, the Chicken Islands group and several near shore western Coromandel islands. Subsequently Department of Conservation Threatened Plant Scientist Peter de Lange recorded it from Great Barrier, the Mokohinau and Poor Knights Islands.Last week as part of an investigation into the status of Chatham island forms of Lepidium oleraceum Sparrm. and Phormium tenax J.R.Forst. et G.Forst., a party lead by de Lange and including Landcare Research biosystematists Peter Heenan and Rob Smissen discovered Senecio marotiri growing amongst the Chatham Islands endemic S. radiolatus F.Muell. subsp. radiolatus. Only a few plants were seen, and the species was not noted in similar sites on the main Chatham (Rekohu) Island, Pitt, Mangere, Rabbit Islands or the Murumuru Rock Stacks.
This discovery adds to the growing number of species either shared with, or apparently having a northern New Zealand origin.
The same field team also discovered c.500 plants of the Poor Knights spleenwort, north of Point Somes, at the north western extremity of Chatham (Rekohu) Island.
Posted: 18/02/2006