A new fossil species of Polypodium (Polypodiaceae) from the Oligocene of northern Bohemia (Czech Republic)

Phylogeny, Divergence Time Estimates, and Phylogeography of the Diploid Species of the <I>Polypodium vulgare</I> Complex (Polypodiaceae)

“…Mean divergence time estimates incorporating a fossil age constraint for that node ranged from 27.64-27.80 mya (analyses 1 and 3, respectively), whereas those not incorporating the fossil age constraint ranged between 24.65 and 24.77 mya (analyses 2 and 4). Thus, it appears that the older estimated divergence times for analyses 1 and 3 reflect the minimum age constraint imposed on that node by the Oligocene fossil dated at 26.80 ± 1.2 mya (Kvaček 2001). Nevertheless, all analyses indicate a mean divergence for node 7 in the late Oligocene, with substantial overlap in the 95% HPD estimates among all four analyses.…”

“…To compensate for uncertainty surrounding these estimates, each calibration point was assigned a normal distribution, with a mean equal to the best-age estimate and one standard deviation equal to ten percent of the best-age estimate (Rothfels et al 2012). Two of the four analyses included an additional age constraint from a Polypodiaceae fossil from the Oligocene (Kvaček 2001), with a minimum age of 26.8 ± 1.2 million years ago (mya; calibration point E). Kvaček (2001) presents strong, but inconclusive, evidence that the fossilized frond fragment with visible venation, intact sporangia, and observable spores belongs to the genus Polypodium.…”

“…Two of the four analyses included an additional age constraint from a Polypodiaceae fossil from the Oligocene (Kvaček 2001), with a minimum age of 26.8 ± 1.2 million years ago (mya; calibration point E). Kvaček (2001) presents strong, but inconclusive, evidence that the fossilized frond fragment with visible venation, intact sporangia, and observable spores belongs to the genus Polypodium. This calibration point was assigned an exponential distribution with a mean of 5 and an offset of 25.6 mya, resulting in a 95% confidence interval between 25.73 and 44.03 mya.…”

“…In addition, we use established calibrated divergence dates for the Polypodiaceae (Schuettpelz and Pryer 2009), together with a recently described Polypodium fossil (Kvaček 2001), to date the divergence of Polypodium s. s. and the P. vulgare complex. Our goals are to: 1) assess the monophyly of the P. vulgare complex and its hypothesized sister relationship with the P. plesiosorum group; 2) infer evolutionary relationships among the diploid taxa of the P. vulgare complex; 3) provide temporal and biogeographic context for the origin of the diploid species; and 4) lay the foundation for ongoing studies detailing the reticulate history and timing of allopolyploid formation within the P. vulgare complex.…”

“…2. Black circles with letters indicate the six calibration points using in this study: points A-D and F were obtained from Schuettpelz and Pryer (2009) and point E refers to a fossil reported by Kvaček (2001; Appendix 2). Small numbers above nodes indicate mean node age estimates from oldest (node 1) to youngest (node 41).…”