Phylogenetic divergence of island biotas: Molecular dates, extinction, and “relict” lineages

Abstract

Island formation is a key driver of biological evolution, and several studies have used geological ages of islands to calibrate rates of DNA change. However, many islands are home to “relict” lineages whose divergence apparently pre‐dates island age. The geologically dynamic New Zealand (NZ) archipelago sits upon the ancient, largely submerged continent Zealandia, and the origin and age of its distinctive biota have long been contentious. While some researchers have interpreted NZ's biota as equivalent to that of a post‐Oligocene island, a recent review of genetic studies identified a sizeable proportion of pre‐Oligocene “relict” lineages, concluding that much of the biota survived an incomplete drowning event. Here, we assemble comparable genetic divergence data sets for two recently formed South Pacific archipelagos (Lord Howe; Chatham Islands) and demonstrate similarly substantial proportions of relict lineages. Similar to the NZ biota, our island reviews provide surprisingly little evidence for major genetic divergence “pulses” associated with island emergence. The dominance of Quaternary divergence estimates in all three biotas may highlight the importance of rapid biological turnover and new arrivals in response to recent climatic and/or geological disturbance and change. We provide a schematic model to help account for discrepancies between expected versus observed divergence‐date distributions for island biotas, incorporating the effects of both molecular dating error and lineage extinction. We conclude that oceanic islands can represent both evolutionary “cradles” and “museums” and that the presence of apparently archaic island lineages does not preclude dispersal origins.

Multiple lineages of hyper‐diverse Zopheridae beetles survived the New Zealand Oligocene Drowning

“…Although our analyses have recovered orphan lineages with divergence times stretching back to the Cretaceous (e.g. Rytinotus and Tarphionivea ), the biogeographic significance of such lineages has been previously questioned (Grandcolas, Nattier, & Trewick, ; McCulloch & Waters, ; Sharma & Wheeler, ; Waters & Craw, ). It is often argued that extinction of sister taxa inhabiting neighbouring areas yields long orphan branches that erroneously appear to have exclusively existed in an area, such as New Zealand.…”

“…The emerging biogeographic consensus supports a complex colonization history for the formation of the New Zealand biota, including autochthonous elements representing Gondwanan lineages. Although the hypothesis of a mass extinction or bottlenecking of lineages during the Oligocene has been examined by analysing the distributions of divergence times across taxa (Heenan & McGlone, ; McCulloch & Waters, ; Wallis & Jorge, ), it has not been tested using explicit models of diversification (May, Hohna, & Moore, ; Pybus & Harvey, ). These models enable the detection of an increase in the extinction rate and/or a decrease in speciation rate, which we can predict to have occurred during the Oligocene Drowning.…”

Ancient DNA from the extinct Haitian cave-rail (Nesotrochis steganinos) suggests a biogeographic connection between the Caribbean and Old World

“…[4]). Because of this delay, islands acted as refugia of diversity in the recent past [4,5]. Still, we have a limited understanding of the phylogenetic affinities of species lost after human contact, thereby limiting what we know about the evolutionary and biogeographic mechanisms underpinning these communities.…”

Comparative phylogeography of two Agarophyton species in the New Zealand archipelago

“…Key index words: biogeographic and oceanographic barriers; demography; glacial-interglacial cycles; Gracilariales; ITS2; parapatric genetic clusters; species co-occurrence; species diagnostic molecular tool Abbreviations: AMOVA, analysis of molecular variance; BSP, Bayesian skyline plots; LGM, last glacial maximum; MCMC, Markov Chain Monte Carlo; SAMOVA, spatial analysis of molecular variance; SSD, sum squared deviations A large proportion of marine algae in New Zealand are endemic (e.g., up to 40% of Rhodophyceae; Nelson 2012), which is considered to be a consequence of in situ radiations of ancient Gondwanan lineages after the separation of Zealandia from Australasia, and from taxa that colonized New Zealand after the Oligocene marine transgression, during which most of the archipelago was submerged (McDowall 2008, Neall and Trewick 2008, Sharma and Wheeler 2013, Wallis and Jorge 2018, McCulloch and Waters 2019. However, a number of marine species present in New Zealand also inhabit other regions of the southern hemisphere, such as Australia, sub-Antarctic islands, and South America (Waters 2008, Fraser et al 2009b, Guillemin et al 2014.…”

“…A large proportion of marine algae in New Zealand are endemic (e.g., up to 40% of Rhodophyceae; Nelson 2012), which is considered to be a consequence of in situ radiations of ancient Gondwanan lineages after the separation of Zealandia from Australasia, and from taxa that colonized New Zealand after the Oligocene marine transgression, during which most of the archipelago was submerged (McDowall 2008, Neall and Trewick 2008, Sharma and Wheeler 2013, Wallis and Jorge 2018, McCulloch and Waters 2019). However, a number of marine species present in New Zealand also inhabit other regions of the southern hemisphere, such as Australia, sub‐Antarctic islands, and South America (Waters 2008, Fraser et al.…”