Marc A. Baker

A Cytological and Morphometric Analysis of a Triploid Apomict, Opuntia xKelvinensis (Subgenus Cylindropuntia, Cactaceae)

A morphometric analysis ofOpuntia spinosior, O. fulgida, and their putative hybrid,O. × kelvinensis was supplemented with cytogenetic data and pollen stainability for all OTUs. The morphometric analysis supported the hypothesis for the hybrid origin ofO.×kelvinensis and indicated that limited backcrossing has occurred betweenO.×kelvinensis andO. spinosior. Almost all individuals investigated ofO.×kelvinensis are triploid, with 33 chromosomes, those ofOpuntia fulgida are mostly diploid, but in part triploid, and all ofO. spinosior investigated are diploid. The very high percentage of sterile seed produced by triploidO.×kelvinensis is almost certainly a consequence of unequal segregation of chromosomes in pollen mother cells during anaphase I. The ability ofO.×kelvinensis to reproduce vegetatively is attributable to itsO. fulgida parentage. It is hypothesized that the success ofO.×kelvinensis is a result of its particularly preadaptive genome isolated from infrequent backcrossing via meiotic irregularities of odd-polyploidy and its ability to reproduce vegetatively.

Chromosome numbers in some cacti of western North America-VIII.

Abstract: Chromosome numbers are determined for 514 individuals belonging to 119 taxa within Cactaceae. Nineteen taxa have chromosome numbers reported for the first time. Based on geographic, morphological, and cytological data, three new nomenclatural combinations are made: Cylindropuntia ×cardenche (GRIFFITHS) PINKAVA & M. A. BAKER, Cylindropuntia imbricata (HAWORTH) F.M.KNUTH var spinitecta (GRIFFITHS) M.A.BAKER, and Echinocereus bonkerae THORNBER & BONKER ssp apachensis (W.BLUM & RUTOW) A.D.ZIMMERMAN. Four species are here newly published as interspecific hybrids based, in part, on several character states intermediate of their respective sympatric putative parents: Cylindropuntia ×cardenche (GRIFFITHS) PINKAVA & M.A.BAKER (pro. sp) comb. nov., Cylindropuntia ×pallida (ROSE) F.M.KNUTH (pro. sp), Opuntia ×charlestonensis CLOKEY (pro. sp), and Opuntia streptacantha LEMAIRE × O. tomentosa SALM-DYCK.

Morphometric Analysis of Escobaria sneedii var. sneedii, E. sneedii var. leei, and E. guadalupensis (Cactaceae)

Abstract We used discriminant analysis to assess taxonomic status of three closely related, rare taxa within the cactus genus Escobaria (E. guadalupensis, E. sneedii var. sneedii, and E. sneedii var. leei). These three taxa consist of nine isolated populations; six of these populations consist of morphologically typical specimens (i.e., similar to the type specimen), while three populations are of questionable taxonomic status. We used the six morphologically typical populations (referred to as assigned populations) to derive predictive discriminant functions for each taxon. These discriminant functions were then applied to assigned populations to determine the status and taxonomic boundaries of each taxon, and to the three questionable populations (referred to as unassigned populations) to interpret their taxonomic status. Our model included four predictor variables: number of immature stems, mature stem diameter, number of radial spines, and length of the innermost central spines. Discriminant analysis correctly classified >93% of 186 individuals from the six assigned populations, suggesting a distinct status for each taxon. Applying the predictive discriminant functions to unassigned populations resulted in classifying a large percentage of individuals from each unassigned population into each of two taxa. This suggests that the unassigned populations consist of morphological intermediates, possibly as the result of hybridization. Meiotic chromosome numbers of n = 11 were determined for E. guadalupensis, E. sneedii var. leei, and the three unassigned populations. Communicating Editor: Richard Jensen

Chromosome numbers of American Acanthaceae

A total of 72 meiotic chromosome numbers were determined for 58 taxa representing 23 genera of Acanthaceae from the United States, Mexico, Panama, and Peru. Chromosome numbers of 41 of these taxa are reported for the first time. Chromosome numbers obtained in Aphanosperma (n = 18), Chalarothyrsus (n = 18), Gypsacanthus (n = 18), Ixtlania (n = 14), Razisea (n = 18), and Teliostachya (n = 9) are the first for these genera. Our counts for Dicliptera resupinata (n = 40), Elytraria imbricata (n = 12), Justicia pectoralis (n = 11), and Yeatesia mabryi (n = 18) differ from previously published numbers for these species. Constancy of chromosome number appears to be characteristic of certain genera of Acanthaceae whereas variation due to polyploidy and aneuploidy occurs in others. Various generic relationships are discussed with respect to the chromosome numbers now known for neotropical Acanthaceae.

CIRCUMSCRIPTION OF ECHINOCEREUS ARIZONICUS SUBSP. ARIZONICUS: PHENETIC ANALYSIS OF MORPHOLOGICAL CHARACTERS IN SECTION TRIGLOCHIDIATUS (CACTACEAE), PART II

ABSTRACT A multivariate analysis was performed for populations of Echinocereus (section Triglochidiatus) to facilitate the taxonomic circumscription of E. arizonicus subsp. arizonicus. Twenty-one morphological characters for 16 populations evidenced the validity of at least two subspecific taxa within E. arizonicus: E. arizonicus subsp. arizonicus and E. arizonicus subsp. nigrihorridispinus. Principle components analysis indicated that stem characters were most diagnostic in defining two distinct groups of populations, each including the type locality of one of the two subspecies. Unweighted pair group method with arithmetic mean (UPGMA) clustered populations of the two subspecies apart from one another and from those of the outgroup, E. triglochidiatus subsp. mojavensis. For most measured characters, means differed significantly between the two subspecies. Discriminant analysis correctly classified 97.0% for individuals of E. arizonicus subsp. arizonicus and 94.7% for individuals of E. arizonicus subsp. nigrihorridispinus, compared to an overall 97.8% correct classification of individuals for all perfect-flowered taxa of section Triglochidiatus investigated.

Chromosome Numbers and Their Systematic Implications in Some North American Acanthaceae

Meiotic chromosome numbers are reported for 30 taxa representing 12 genera of Acanthaceae from Mexico and the southwestern United States. Chromosome numbers of 25 of these taxa are reported for the first time. Chromosome numbers obtained in Henrya (n = 18), Hol- ographis (n = 13, 26, 39), Mexacanthus (n = 18), Mirandea (n = 18), and Stenandrium (n = 26) are the first for these genera. A newly reported chromosome number in Justicia is n = 11. Polyploidy and aneuploidy appear to have been frequent events in the family and are especially evident in the large, polymorphic genus Justicia. Generic relationships are discussed with respect to the known chromosome numbers.

Geographic distribution and taxonomic circumscription of populations within Coryphantha section Robustispina (Cactaceae).

UNLABELLED PREMISE OF STUDY Taxonomic circumscription of subspecific taxa within Coryphantha robustispina was evaluated with morphological data and microsatellites. This study was the first to compare adequately sampled morphological and DNA analyses at the population level in the Cactaceae. This comparison was important to test reliability of both methods and to gain a better understanding of phytogeography, evolution, and systematics of the species, knowledge that could prove useful for other taxa as well. Populations of C. robustispina subsp. robustispina are listed as endangered by the U. S. Fish and Wildlife Service. Our primary goal was to explore correlations among geographical distribution, morphology, and genetics of selected populations throughout the range of the species and the outgroup, C. poselgeriana. • METHODS Stem characters were measured for 638 individuals among 16 populations. Flower characters were measured for 180 individuals among 12 populations. Ten microsatellite DNA loci were isolated and characterized for 204 individuals among 13 populations. Data were analyzed using various multivariate analyses. • RESULTS Our results indicated that, within Coryphantha robustispina, there were three morphologically, genetically, and geographically coherent groups represented by the names C. robustispina subsp. robustispina, C. robustispina subsp. uncinata, and C. robustispina subsp. scheeri. For most analyses, distinctions among the three groups were primarily not as great as those between any one of them and the outgroup. • CONCLUSIONS Results suggested that the three subspecific taxa within Coryphantha robustispina are good subspecies but should not be elevated to species rank. The closely aligned results between morphology and microsatellite data support the design and utility of both methods.

Cylindropuntia chuckwallensis (Cactaceae), a New Species from Riverside and Imperial Counties, California

Abstract A gynodioecious hexaploid (n  =  33), Cylindropuntia chuckwallensis M. A. Baker & M. A. Cloud-Hughes, is newly described. Populations of C. chuckwallensis extend from the Eagle Mountains of Joshua Tree National Park, through the Chuckwalla Mountains of Riverside County, to the north side of the Chocolate Mountains in Imperial County, California, USA, and occur on a variety of substrates primarily between 400–1600 m (1312–5250 ft) elevation. Of the flowering individuals studied, 38% produced only pollen-sterile flowers. Flower color in C. chuckwallensis ranges from dark red-purple (33%) through orange (54%) to yellow (13%). For most individuals (93%) the style and filaments are dark red to light pink. Morphological measurements were made for 15 populations of Cylindropuntia, including four of C. chuckwallensis, four of C. echinocarpa, three of C. multigeniculata, and four of C. acanthocarpa. Multivariate analyses indicated that C. chuckwallensis possesses a unique combination of characters. Fewer than 3% of the 121 C. chuckwallensis individuals sampled were misclassified by discriminate function analysis, one as C. echinocarpa, and three as C. multigeniculata.