Abstract
Morphometrics and meristics are measurable and countable traits, respectively, that are under simultaneous control by genetic and/or environmental factors. Resolving morphometric and meristic spatial variation can be a useful technique for identifying population structure and connectivity. The present study investigated morphometric and meristic character variation within three flounder species, sand flounder (Rhombosolea plebeia), greenback flounder (R. tapirina), and yellowbelly flounder (R. leporina) in New Zealand, predominantly in the South Island. Four morphometric measurements and two meristic characters were obtained from 857 juvenile flounder, standardised, and analysed. Consistent with a previous genetic analysis, the differentiation of morphometric and meristic characters supported the idea that sand flounder populations north and south of 42o S were reproductively isolated, and although statistically non-significant, there was an indication that yellowbelly flounder collected from Lake Ellesmere and Orowaiti Lagoon may have been reproductively isolated. Only juvenile sand flounder and greenback flounder were collected in the tidal reaches of estuaries throughout east Otago and the populations are considered undifferentiated based on intra-species morphometric and meristic characters. Our results demonstrated that the influence of environmental variation and adaptive physiology of juvenile flounder likely contributed to the morphometric and meristic variation of individuals among estuaries and years.