Phacelia stebbinsii Constance & Heckerd, P. marcescens Eastw. ex J.F.Macbr., and P. quickii J.T.Howell are morphologically similar annual taxa endemic to the west side of the Sierra Nevada in California. Experimental crosses show P. quickii is reproductively isolated from the other two species, and that P. marcescens and P. stebbinsii readily produce fully fertile F1 and S2 hybrid progeny, but typically only when P. marcescens is the carpellate parent. The presence of geographic separation, habitat differences, unilateral crossability, pollen certation, and problems with cotyledon emergence in hybrid seedlings provide evidence P. stebbinsii is distinct from P. marcescens and they are maintained as separate species. Flower and fruit characters used to distinguish these three species from each other appear to be related to differences in seed dispersal and seedling establishment in different habitats.
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21 April 2022
COMPARATIVE MORPHOLOGY, BIOSYSTEMATICS, AND REPRODUCTIVE ECOLOGY OF PHACELIA STEBBINSII, P. MARCESCENS, AND P. QUICKII
Gregory J. Lee
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Madroño
Vol. 69 • No. 1
January–March 2022
Vol. 69 • No. 1
January–March 2022
Biosystematics
Humiles
Phacelia marcescens
Phacelia quickii
Phacelia stebbinsii
reproductive isolation
transfer of function