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Benjamin Bomfleur

Publications and source records attributed to Benjamin Bomfleur.

2 recordsLinked to original sources
bioRxiv2014

Using more than the oldest fossils: Dating Osmundaceae by three Bayesian clock approaches

A major concern in molecular clock dating is how to use information from the fossil record to calibrate genetic distances from DNA sequences. Here we apply three Bayesian dating methods that differ in how calibration is achieved-- node dating(ND) in BEAST, total evidence(TE) dating in MrBayes, and the fossilised birth-death(FBD) in FDPPDiv--to infer divergence times in the Osmundaceae or royal ferns. Osmundaceae have 13 species in four genera, two mainly in the Northern Hemisphere and two in South Africa and Australasia; they are the sister clade to the remaining leptosporangiate ferns. Their fossil record consists of at least 150 species in [~]17 genera and three extinct families. For ND, we used the five oldest fossils, while for TE and FBD dating, which do not require forcing fossils to nodes and thus can use more fossils, we included up to 36 rhizome and frond compression/impression fossils, which for TE dating were scored for 33 morphological characters. We also subsampled 10%, 25%, and 50% of the 36 fossils to assess model sensitivity. FBD-derived divergence dates were generally greater than ages inferred from ND dating; two of seven TE-derived ages agreed with FBD-obtained ages, the others were much younger or much older than ND or FBD ages. We favour the FBD-derived ages because they best match the Osmundales fossil record (including Triassic fossils not used in our study). Under the preferred model, the clade encompassing extant Osmundaceae (and many fossils) dates to the latest Palaeozoic to Early Triassic; divergences of the extant species occurred during the Neogene. Under the assumption of constant speciation and extinction rates, FBD yielded 0.0299 (0.0099-0.0549) and 0.0240 (0.0039-0.0495) for these rates, whereas neontological data yielded 0.0314 and 0.0339. However, FBD estimates of speciation and extinction are sensitive to violations in the assumption of continuous fossil sampling, therefore these estimates should be treated with caution.#

Plant Biology↗
bioRxiv2014

Osmunda pulchella sp. nov. from the Jurassic of Sweden—reconciling molecular and fossil evidence in the phylogeny of Osmundaceae

The systematic classification of Osmundaceae has long remained controversial. Recent molecular data indicate that Osmunda is paraphyletic, and needs to be separated into Osmundastrum and Osmunda s. str. Here we describe an exquisitely preserved Jurassic Osmunda rhizome (O. pulchella sp. nov.) that combines diagnostic features of Osmundastrum and Osmunda, calling molecular evidence for paraphyly into question. We assembled a new morphological matrix based on rhizome anatomy, and used network analyses to establish phylogenetic relationships between fossil and extant members of modern Osmundaceae. We re-analysed the original molecular data to evaluate root-placement support. Finally, we integrated morphological and molecular data-sets using the evolutionary placement algorithm. Osmunda pulchella and five additional, newly identified Jurassic Osmunda species show anatomical character suites intermediate between Osmundastrum and Osmunda. Molecular evidence for paraphyly is ambiguous: a previously unrecognized signal from spacer sequences favours an alternative root placement that would resolve Osmunda s.l. as monophyletic. Our evolutionary placement analysis identifies fossil species as ancestral members of modern genera and subgenera. Altogether, the seemingly conflicting evidence from morphological, anatomical, molecular, and palaeontological data can be elegantly reconciled under the assumption that Osmunda is indeed monophyletic; the recently proposed root-placement in Osmundaceae--based solely on molecular data--likely results from un- or misinformative out-group signals.

Paleontology↗