Cytogeography of the subalpine marsh marigold polyploid complex (Caltha leptosepalas.l., Ranunculaceae).
OBJECTIVE
Unrecognized variation in ploidy level can lead to an underestimation of species richness and a misleading delineation of geographic range.Caltha leptosepala(Ranunculaceae) comprises a complex of hexaploids (6x), rare nonaploids (9x), and dodecaploids (12x), all with unknown distributions. We delineate the geographic distribution and contact zones of the cytotypes, investigate morphologies of cytotypes and subspecies, and discuss the biogeography and evolutionary history of the polyploid complex.


METHODS
Using cytologically determined specimens as reference, propidium iodide flow cytometry was performed on silica-dried samples and herbarium specimens from across the range ofC. leptosepalas.l. Genome size estimates from flow cytometry were used to infer cytotypes. A key morphological character, leaf length-to-width ratio, was measured to evaluate whether these dimensions are informative for taxon and/or cytotype delimitation.


RESULTS
Dodecaploids were more northerly in distribution than hexaploids, and a single midlatitude population in the Northern Rockies yielded nonaploids. Genome size estimates were significantly different between all cytotypes and between hexaploid subspecies. Leaf length-to-width ratios were significantly different between subspecies and some cytotypes.


CONCLUSIONS
Caltha leptosepalapresents clear patterns of cytotype distribution at the large scale. Marked differences in morphology, range, and genome size were detected between the hexaploid subspecies,C. leptosepalasubsp.howelliiin the Cascade-Sierra axis andC. leptosepalasubsp.leptosepalain the Rockies. Sympatry between cytotypes in the Cascades and a parapatric distribution in the Northern Rockies suggest unique origins and separate lineages in the respective contact zones.
Department of Biological Sciences, PO Box 413, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201 USA keirwefferling@gmail.com.
Keir M
KM
Wefferling
Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal.|Botanic Garden, University of Coimbra, Calçada Martim de Freitas 3000-456 Coimbra, Portugal.
Sílvia
S
Castro
Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal.
João
J
Loureiro
Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal.
Mariana
M
Castro
Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal.
Daniela
D
Tavares
Department of Biological Sciences, PO Box 413, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201 USA.
Sara B
SB
Hoot
D032461:Chromosomes, Plant / Q000235:genetics; D059646:Genome Size / Q000235:genetics*; D018745:Genome, Plant / Q000235:genetics*; D005843:Geography; D011003:Ploidies; D011123:Polyploidy; D011156:Population Density; D011157:Population Dynamics; D029626:Ranunculaceae / Q000145:classification / Q000235:genetics* / Q000254:growth & development; D013045:Species Specificity; D053833:Wetlands
Caltha; Cascades; Pacific Northwest; Ranunculaceae; Rocky Mountains; contact zone; cryptic species; cytogeography; polyploid; refugia