How old is the Hawaiian biota? Geology and phylogeny suggest recent divergence

Abstract

This study quantifies long-term landscape changes in the Hawaiian archipelago relating to dispersal, speciation and extinction. Accounting for volcano growth, subsidence and erosion, we modelled the elevations of islands at time intervals of 0.5 Myr for the last 32 Myr; we also assessed the variation in the spacing of volcanoes during this period. The size, spacing and total number of volcanic islands have varied greatly over time, with the current landscape of large, closely spaced islands preceded by a period with smaller, more distantly spaced islands. Considering associated changes in rates of dispersal and speciation, much of the present species pool is probably the result of recent colonization from outside the archipelago and divergence within contemporary islands, with limited dispersal from older islands. This view is in accordance with abundant phylogenetic studies of Hawaiian organisms that estimate the timing of colonization and divergence within the archipelago. Twelve out of 15 multi-species lineages have diverged within the lifetime of the current high islands (last 5 Myr). Three of these, and an additional seven (mostly singlespecies) lineages, have colonized the archipelago within this period. The timing of colonization of other lineages remains uncertain.

A well-sampled phylogenetic analysis of the polystichoid ferns (Dryopteridaceae) suggests a complex biogeographical history involving both boreotropical migrations and recent transoceanic dispersals

“…The first peak period is between 18 and 8 Ma and corresponds to the formation of large and substantial islands such as Gardner (ca 15.8 Ma) and Necker (ca. 11.8 Ma) that were comparable to the present island of Hawaii (Price and Clague, 2002). The second peak period (ca.…”

“…These divergence time estimates indicate that both subclades have diverged before the emergence of the extant islands of the Hawaii archipelago (0.5-5 million years old; Price and Clague, 2002). Specifically, the stem age of subclade A 1 (20 (11-31) Ma) is comparable to what Schneider et al (2005) and Sundue et al (2014) estimated for Asplenium and Adenophorus, i.e.…”

“…24.3 (27.0-21.5) Ma and 22.5 (29.0-14.1) Ma respectively. Therefore, our dating estimates suggest that the P. hillebrandii lineage together with above two, were among first plants to colonize Hawaii (Clague, 1996;Price and Clague, 2002;Schneider et al, 2005;Sundue et al, 2014).…”

“…For Hawaii, two periods (named as ''peak periods") have been identified as offering the best opportunities for colonisation (Price and Clague, 2002). The first peak period is between 18 and 8 Ma and corresponds to the formation of large and substantial islands such as Gardner (ca 15.8 Ma) and Necker (ca.…”

High gene flow due to pelagic larval dispersal among South Pacific archipelagos in two amphidromous gastropods (Neritomorpha: Neritidae)

“…Climactic fluctuations over the past several million years (Hope, 1996) and the rapid erosion and eventual subsidence of individual islands (Whittaker et al, 2008) ensure that populations in oceanic island streams will be subject to local extinction and re-colonization over evolutionary timescales (Covich, 2006). These processes can be expected to leave a molecular signature in the form of shallow, star-like genealogies (Slatkin and Hudson, 1991), and estimates for colonization events that greatly post-date the formation of each archipelago (Price and Clague, 2002).…”