Genome Size Evolution in Ephedra
The Gnetalean gymnosperm genus Ephedra is chromosomally highly variable. In contrast to the relatively small genomes of most angiosperms (mean 1C = 5.6 pg), gymnosperm genomes are typically large (mean 1C = 18.1 pg), exhibit relatively low chromosome numbers (range 2n = 14 – 66), and show a remarkable consistency of number and karyotype within genera and generally few polyploids are found. In contrast to this uniformity, Ephedra, a genus with ca. 50 species, is chromosomally highly variable – with numbers spanning nearly the whole range encountered in gymnosperms as a whole (i.e. 2n = 14 – 56) and 69% of the 52 species being polyploid (Ickert-Bond et al., 2015, Ickert-Bond & Renner 2016). In collaborating with Aretuza Sousa (Munich University), Ilia Leitch and Jaume Pellicer (Kew Gardens) funded by a DAAD visiting faculty research fellowship.
Inferring Phylogenetic Relationships using Chloroplast Genomes
We used multiplex sequencing-by-synthesis (MSBS) of multiple plastid genomes on the Illumina Genome Analyzer to resolve phylogenetic relationships in Ephedra and Gnetum and the Gnetales as a whole. First, we PCR-amplified the plastid genomes using 25 primer pairs. Tagged microreads from each species were then assembled with a combination of de novo (YASRA) and reference-guided (RGA) assembly (RGA) using previously published plastid genomes as references. We have amplified and obtained sequences using this method for over 30 gnetalean species (from Gnetum and Ephedra) NSF AToL: Gymnosperms on the Tree of Life: Resolving the Phylogeny of Seed Plants (NSF-0629657).
Dispersal syndromes and niche evolution in NW Ephedra
Ephedra dispersal involves wind, birds, or terrestrial animals. Wind-dispersed seeds have dry, winged bracts of the strobili; bird- and lizard-dispersed seeds are enclosed in fleshy, brightly colored bracts and seeds dispersed by seed-caching rodents are large and enclosed in dry, membranous bracts. Dispersal by wind and frugivores occurs in Old and the New World species, while rodent dispersal is only known from New World species. Together with Israel Loera and Victoria Soza (INECOL), we investigate the ecological consequences the three different dispersal syndromes have. Species dispersed by birds have higher phylogenetic niche divergence for mean annual temperature (and to a lesser extent mean annual precipitation) and occupy a broader set of temperature regimes than rodent-dispersed species, which has been attributed to the higher dispersal ability of birds compared to scatter-hoarding rodents. The short-distance movement of seeds from the mother plant due to rodents may be especially beneficial in arid conditions (Loera et al. 2015).
Taxonomic Revision of New World Ephedra
A long-standing goal of mine has been a taxonomic revision of the New World Ephedra. Extensive field work throughout the distributional range of New World Ephedra, including trips to Mexico, Ecuador, Chile, Argentina and throughout the SW United States have greatly improved my understanding of the morphological variability of the genus, including observation of habitats, associated species and soils. All type specimens and over 4,000 herbarium vouchers in many herbaria (ARIZ, ASC, ASU, CIIDIR, CONC, DES, E, F, GH, JEPS, LE, MERL, MCNS, MO, NY, QCA, QCNE, RM, RSA, SGO, SI, SRSU, UC, UNM, and US. ) have been examined and annotated to form the basis of my taxonomic revision. The New World species of Ephedra are here revised and shown to comprise 22 species, two infraspecific taxa, and three hybrid taxa. A full taxonomic account of New World Ephedra is presented, including pen and ink plates for each species; and their distribution is mapped (to be submitted to Systematic Botany Monographs).
Ickert-Bond, S.M., Renner, S.S. 2016. The Gnetales: Recent insights on their morphology, reproductive biology, chromosome numbers, biogeography, and divergence times. Journal of Systematics and Evolution 54(1): 1-16 (Featured on the cover). [Link]
Bolinder, K., A.M. Humphreys, J. Ehrlen, R. Alexandersson, S.M. Ickert-Bond, C. Rydin. 2016. From near extinction to diversification by means of a shift in pollination mechanism in the gymnosperm relict Ephedra (Ephedraceae, Gnetales). Botanical Journal of the Linnean Society 180: 461-477. [Link] [Link to Wiley]
Bolinder, K., L. Norbäck Ivarsson, A. Humphreys, S.M. Ickert-Bond, F. Han, C. Hoorn, C. Rydin, Catarina. 2015. Pollen morphology in Ephedra (Gnetales) and its evolutionary implications. Grana, DOI:10.1080/00173134.2015.1066424 [Link]
Loera, I., S.M. Ickert-Bond, and V. Sosa. 2015. Ecological consequences of contrasting dispersal syndromes in New World Ephedra: higher rates of niche evolution related to dispersal ability. Ecography 38: 1187–1199. [Link]
Loera, I., V. Sosa, and S.M. Ickert-Bond. 2012. Diversification in North America arid lands: niche conservatism, divergence and expansion of habitat explain speciation in the genus Ephedra. Molecular Phylogenetics and Evolution 65: 437-450. [Link]
Ickert-Bond, S.M. 2012. Ephedraceae. In Baldwin, B.G., D.H. Goldman, D.J. Keil, R. Patterson and T.J. Rosatti (eds.), Second Edition of The Jepson Manual: Vascular Plants of California. Berkeley: University of California Press. Pp: 140-142, 147. [Link to eFlora treatment]
Kakiuchi, N., M. Mikage, S.M. Ickert-Bond, M. Maier-Stolte, and H. Freitag. 2011. A molecular phylogenetic study of the Ephedra distachya / E. sinica complex in Eurasia. Willdenowia 41 (2): 203-215 (Featured on the cover). [Link]
Ickert-Bond, S.M., and C. Rydin. 2011. Micromorphology of the seed envelope of Ephedra L. (Gnetales) and its relevance for the timing of evolutionary events. International Journal of Plant Sciences 172:36-48 (Featured on the cover). [Link]
Ickert-Bond, S.M., C. Rydin, and S.S. Renner. 2009. A fossil-calibrated relaxed clock for Ephedra indicates an Oligocene age for the divergence of Asian and New World clades and Miocene entry into South America. Journal of Systematics and Evolution 47: 444-456. [Link]
Ickert-Bond, S.M. 2005. Ephedraceae. In G. Harling and L. Andersson (eds.), Flora of Ecuador, no. 75: 3-10. Botanical Institute, Göteburg University, Göteburg, Sweden.
Ickert-Bond, S.M., and M. F. Wojciechowski. 2004. Phylogenetic relationships in Ephedra (Gnetales): Evidence from nuclear and chloroplast DNA sequence data. Systematic Botany 29 (4): 834-849. [Link]
Ickert-Bond, S.M., J.J. Skvarla, and W.F. Chissoe. 2003. Pollen dimorphism in Ephedra L. (Ephedraceae). Review of Palaeobotany and Palynology 124: 325-334. [Link]
Ickert-Bond, S.M. 2002. Ephedra L. (Ephedraceae) in Ecuador, contributions from micromorphology and anatomy, pp. 2-19 in Freire-Fierro, A. & D. A. Neill (eds.) 2002. La Botánica en el Nuevo Milenio, Memorias del III Congreso Ecuatoriano de Botánica. Publicaciones de la Fundación Ecuatoriana para la Investigación y Desarrollo de la Botánica FUNBOTANICA 4. Quito, 260 p.