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Abstract Detail



Polyploidy, microevolution and species level systematics

Doucette, EricThomas [1], Cushman, Kevin [2], Burgess, Michael B. [3], Campbell, Christopher [4].

Semi-cryptic ploidy variation in Amelanchier pallida (Rosaceae) Authors: E.T. Doucette, K.R. Cushman, M.B. Burgess, and C.S. Campbell.

Amelanchier pallida was described in 1891 by E. L. Greene who considered this species to be limited to northern California. Jones’ 1946 monograph of the genus expanded this species’ distribution to most of California, southern Oregon, and western Nevada. Subsequent floras used Jones’ distribution of A. pallida or lumped it into A. utahensis. We discovered diploids and tetraploids fitting Greene’s description of A. pallida from northern California, southern Oregon, and western Nevada, but not elsewhere. Diploids are known only from a small region in north-central California and adjacent Oregon. This area is rich in endemics, and the diploids may be paleoendemics. Tetraploids grow in the same area and also a little farther south and into western Nevada. Tetraploids mostly have larger flowers and hairier twigs and leaves than diploids. We observed tetraploids growing near diploids without evidence of hybridization. Apomixis, which has been documented in all Amelanchier polyploids that have been studied, may facilitate reproductive isolation of polyploids. DNA sequences from a LEAFY gene and ETS, however, suggest that tetraploids from California and Nevada are allopolyploids. Identity of the other parental species is uncertain. These plants have a predominance of diploid A. pallida alleles, presumably from backcrossing or segregation. In Yreka, California, the type locality, we found only tetraploids that are morphologically indistinguishable from the type. The name A. pallida therefore should be applied to the tetraploid. The diploid is morphologically distinct and geographically distant from all other known Amelanchier diploids, and its alleles coalesce in gene trees. There is some hybridization with A. alnifolia, but not enough to outweigh morphological and genetic support for species status of the diploid. Because ploidy levels can be difficult to distinguish, we propose an informal group, the pallida complex, to accommodate uncertainty in identification. Semi-cryptic ploidy variation is common in Amelanchier.

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1 - University of Maine, School of Biology and Ecology, 5735 Hitchner Hall, Orono, ME, 04469-5735, USA
2 - P.O. Box 143, Levant, ME, 04456, USA
3 - University of Pennsylvania, 16 W Highland Ave, Apt. 2, Philadelphia, PA, 19118, USA
4 - University of Maine, Department of Biological Sciences, 261 HITCHNER HALL, ORONO, ME, 04469-5735, USA

Keywords:
apomixis
endemism
Polyploidy
species
species complex.

Presentation Type: Symposium or Colloquium Presentation
Session: C9
Location: Belle-Chasse/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 4:30 PM
Number: C9008
Abstract ID:337
Candidate for Awards:None


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