New Zealand phylogeography: evolution on a small continent

Abstract

New Zealand has long been a conundrum to biogeographers, possessing as it does geophysical and biotic features characteristic of both an island and a continent. This schism is reflected in provocative debate among dispersalist, vicariance biogeographic and panbiogeographic schools. A strong history in biogeography has spawned many hypotheses, which have begun to be addressed by a flood of molecular analyses. The time is now ripe to synthesize these findings on a background of geological and ecological knowledge. It has become increasingly apparent that most of the biota of New Zealand has links with other southern lands (particularly Australia) that are much more recent than the breakup of Gondwana. A compilation of molecular phylogenetic analyses of ca 100 plant and animal groups reveals that only 10% of these are even plausibly of archaic origin dating to the vicariant splitting of Zealandia from Gondwana. Effects of lineage extinction and lack of good calibrations in many cases strongly suggest that the actual proportion is even lower, in keeping with extensive Oligocene inundation of Zealandia. A wide compilation of papers covering phylogeographic structuring of terrestrial, freshwater and marine species shows some patterns emerging. These include: east-west splits across the Southern Alps, eastwest splits across North Island, north-south splits across South Island, star phylogenies of southern mountain isolates, spread from northern, central and southern areas of high endemism, and recent recolonization (postvolcanic and anthropogenic). Excepting the last of these, most of these patterns seem to date to late Pliocene, coinciding with the rapid uplift of the Southern Alps. The diversity of New Zealand geological processes (sinking, uplift, tilting, sea level change, erosion, volcanism, glaciation) has produced numerous patterns, making generalizations difficult. Many species maintain pre-Pleistocene lineages, with phylogeographic structuring more similar to the Mediterranean region than northern Europe. This structure reflects the fact that glaciation was far from ubiquitous, despite the topography. Intriguingly, then, origins of the flora and fauna are island-like, whereas phylogeographic structure often reflects continental geological processes.

The repeated evolution of large seeds on islands

“…The three main islands (North, South and Stewart Islands) are encircled by numerous smaller islands [15], the flora of which consists mainly of taxa that have dispersed overwater from New Zealand. Although many of these islands were once connected by land bridges, we focused on four island groups that remained isolated from the main islands during the Pleistocene (Kermadec, Three Kings, Chatham and sub-Antarctic Islands; see [16]). In particular, we focused on the Chatham group (1768 W, 448 S), situated 850 km east of the main islands (figure 1).…”

'Moa's Ark' or 'Goodbye Gondwana': is the origin of New Zealand's terrestrial invertebrate fauna ancient, recent or both?

“…More broadly, a recent compilation of molecular phylogenetic analyses of~100 plant and animal groups suggests that only 10% of these are even plausibly of archaic origin predating the vicariant split of Zealandia from Gondwana (Wallis and Trewick 2009). They summarise current opinion on the extent of the Oligocene drowning episode thusly: 'If further paleontological data reveal evidence of uninterrupted fossil records through the Oligocene, complete inundation is made less likely (Winkworth et al 1999;Lee et al 2009).…”

“…Cooper and Cooper 1995), more recently Waters and Craw (2006) suggested that there is no strong evidence for continuously emergent land through the period (see also Landis et al 2008). Trewick et al (2007) and Wallis and Trewick (2009) asserted that the preponderance of biogeographical evidence favours a scenario of complete submergence during the Oligocene, and some authors have suggested that the entire terrestrial biota arrived via dispersal during the last 22 million years (Landis et al 2008).…”

Did postglacial sea-level changes initiate the evolutionary divergence of a Tasmanian endemic raptor from its mainland relative?

“…A close phylogenetic relationship is observed between A. audax and Aquila gurneyi from New Guinea and adjacent islands [70,71], and if this represents a proxy for the existence of A. audax in Australia, then the amount of cytochrome b sequence divergence between these lineages (average p distance 3.7%; [70]) rejects the possibility that A. audax is too young to have colonized Tasmania before the LGM. Whereas changes in climate across the LGM have been implicated for extirpation and recolonization of mid-latitude populations in the Northern Hemisphere [72], they appear to have been less influential on species distributions at similar latitudes in the Southern Hemisphere [73,74]. Other animals presently distributed in Tasmania and mainland Australia, including prey species of A. audax, exhibit genetic divergences compatible with occupation of Tasmania during glacial periods [24,[75][76][77].…”