LES, DONALD H.1*, MICHAEL L. MOODY1, SURREY W. L. JACOBS2, and RANDALL J. BAYER3. 1Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut USA; 2Royal Botanic Garden, Sydney, Australia; 3Division of Plant Industry, CSIRO, Canberra, Australia. - Systematics and taxonomy of Australian seagrasses (family Zosteraceae).
The family Zosteraceae in Australia and New Zealand currently
comprises the monotypic Heterozostera (H. tasmanica) and
four Zostera species (Z. capricorni, Z. muelleri,
Z. mucronata, Z. novazealandica) all in subgenus
Zosterella. Species recognition in Zostera has always
been difficult in this region due to the use of taxonomic characters
that exhibit extensive intraspecific variability. Recent anatomical,
developmental and molecular evidence raises further questions on
generic delimitation (notably the distinctness of
Heterozostera) and subgeneric limits. To clarify the taxonomy
of Zosteraceae, we have undertaken an interspecific phylogenetic
investigation that focusus on Australian species of subgenus
Zosterella. We have examined material (including multiple
accessions of many taxa) comprising all Zosteraceae genera
(Heterozostera, Phyllospadix, Zostera), 6/7
species of Zostera subgenus Zosterella (including all
Australian/New Zealand species), and one of four species of
Zostera subgenus Zostera. Analyses of morphological
characters and DNA sequences from nuclear (ITS) and plastid
(trnK) genomes were used to construct phylogenetic trees of the
Zosteraceae, from which taxonomic relationships might better be
ascertained. Our results conclusively show 1) the nesting of
"Heterozostera" within the genus Zostera; 2)
the lack of molecular divergence among Australian/New Zealand
Zostera collections formerly segregated as four distinct
species; and 3) the lack of reliable morphological characters to
separate these four species. We recommend the abandonment of the genus
Heterozostera (while reinstating Zostera tasmanica), and
the taxonomic merger of remaining Australian/New Zealand
Zostera within a single species Z. capricorni which has
priority of publication.
Key words: Heterozostera tasmanica, Zostera capricorni, Zostera mucronata, Zostera muelleri, Zostera novazealandica, Zosteraceae