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AN EXAMINATION OF POLYPLOIDY AND PUTATIVE INTROGRESSION IN CALOCHORTUS SUBSECTION NUDI (LILIACEAE)
Author(s) -
Ness Bryan D.,
Soltis Douglas E.,
Soltis Pamela S.
Publication year - 1990
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1990.tb11393.x
Subject(s) - biology , introgression , ploidy , botany , hybrid , reproductive isolation , pollen , zoology , evolutionary biology , genetics , population , gene , demography , sociology
Calochortus subsection Nudi (section Calochortus ) comprises four extant species distributed from central California to southern Oregon. To elucidate relationships within this group, morphological, cytological, and electrophoretic investigations were undertaken. Allozyme data revealed two distinct groups in subsection Nudi: a coastal group, comprising C. uniflorus and C. umbellatus; and a Sierran group, comprising C. minimus and C. nudus. Calochortus uniflorus consists of diploids ( n = 10) and tetraploids ( n = 20). Several lines of evidence suggest that tetraploid C. uniflorus may be an autotetraploid: 1) quadrivalents were observed during meiosis in tetraploid C. uniflorus; 2) the mean genetic identity between the diploid and tetraploid cytotypes was much higher ( Ī = 0.963) than between either cytotype and C. umbellatus ( Ī = 0.903 and 0.904 for 2 x and 4 x, respectively); 3) diploid and tetraploid individuals of C. uniflorus were indistinguishable morphologically; and 4) both cytotypes of C. uniflorus occupy vernal meadows, whereas C. umbellatus occupies exposed serpentine ridges. Data from morphology and enzyme electrophoresis suggest that introgression, or at least extensive hybridization, has occurred between C. minimus and C. nudus. Principal coordinate analysis showed that pure C. minimus and C. nudus are morphologically distinct and that putatively introgressive populations are morphologically intermediate. Most putatively introgressive populations displayed reduced pollen viability relative to pure C. minimus and C. nudus. Allozyme data are consistent with the concept that hybridization and possibly introgression may have occurred between C. minimus and C. nudus. When allozyme data were analyzed by the unweighted pair‐group method of cluster analysis using arithmetic means, most putatively introgressive populations were placed between the C. minimus and C. nudus populations.