The New Zealand endemicPlagiochila caducifoliais a disjunct population ofPlagiochila spinulosa(Plagiochilaceae: Jungermanniopsida)

Abstract

We present molecular data demonstrating that the New Zealand endemic Plagiochila caducifolia represents an isolated population of Plagiochila (sect. Arrectae) spinulosa, a species previously thought confined to the eastern Holarctic but which also occurs in Lesotho, southern Africa. In New Zealand, the wide distribution of P. spinulosa in undisturbed and relatively isolated habitats throughout the South Island is consistent with an indigenous, rather than adventive, species. Plagiochila spinulosa is the first reported bipolar disjunct species within the Plagiochilaceae. Although other bipolar disjunctions are known in vascular and non-vascular plants, they usually involve species with wider circumboreal or circumarctic distributions, presumably indicating an origin in the Northern Hemisphere. Most species of Plagiochila sect. Arrectae reproduce asexually by caducous leaves and have disjunct distributions; the significance of this correlation and biogeographic patterns in this lineage both require testing against additional data.