Crataegus gaylussacia A. Heller, Bull. S. Calif. Acad. Sci.

Dickinson, Timothy A. & Han, Shery, 2023, What Is Suksdorf’S Hawthorn? Revision Of The Western North American 20 - Stamen Black-Fruited Hawthorns (Crataegus Series Douglasianae, Rosaceae Subtribe Malinae), Journal of the Botanical Research Institute of Texas 17 (1), pp. 151-189 : 175

Crataegus gaylussacia A. Heller, Bull. S. Calif. Acad. Sci. 2:69. 1903 ( Fig. 8B ). TYPE: U.S.A. CALIFORNIA. Sonoma Co.: Lagoon at Sebastopol , 20 Aug 1900, A. A. Heller 6052 (HOLOTYPE: NYBG00435881 (photo 00435881.jpg,http://sweetgum.nybg. org/science/vh/specimen-details/?irn=660541); ISOTYPES: HUH!, JEPS!, RM!, US!) .

Crataegus gaylussacia has the following heterotypic synonyms sensu J.B. Phipps (2013, 2015): Crataegus douglasii var. suksdorfii Sarg. Bot. Gaz. 44:65. 1907, C. punctata var. brevispina Douglas ex Hook., Fl. Bor.-Amer. (Hooker) 1(4):201. 1832, C. suksdorfii (Sarg.) Kruschke,Milwaukee Public Mus. Publ. Bot. 3:163 (1965).

Description.— Trees or shrubs to 7(–10) m, bark orange-brown on young twigs, becoming gray with age, smooth, but on trunks and large branches flaking irregularly. Thorns 9–14(–17) mm long, more or less straight, 3–4 mm in diameter at the base. Leaves microphylls, unlobed (occasionally pinnately lobed), singly to doubly serrate, 7–10 teeth per cm adjacent leaf apex, leaf base angles acute, bases cuneate or decurrent, apex angles acute, apices mostly convex or straight, surfaces pubescent, glabrescent, or glabrous, petioles 1–2(–5) mm long. Flowers with calyx lobes 1–2 mm long, not toothed, stamens 15–20, free, undehisced anthers pink at anthesis, 4–5 styles. Dried fruits 4–5 mm in diameter, purple-black at maturity, with persistent calyx lobes (often regardless of the number of pyrenes a fruit may contain only a single seed). For exemplars, see https://morphobank.org/permalink/?F1093.

Distribution.— Apparently restricted to Marin and Sonoma counties in California ( Fig. 3 ; 20–130 m ASL; California interior chaparral and woodlands ecoregion, NA1202).

Remarks.— In contrast to the recent Jepson Manual and Flora North America treatments ( Phipps 2013; Phipps 2015) the name Crataegus gaylussacia is here restricted to the California autotriploids because of their unique combination of cytotype, ecology ( Coughlan 2012; Coughlan et al. 2017b), morphology ( Fig. 1 , 2 ), and macrosatellite genotype ( Fig. 5 ). Heller (1903) observed that, prior to being recognized as a new species, the Sonoma County plants were referred to C. rivularis Nutt. , a taxon now known to differ markedly from C. gaylussacia in leaf shape, thorn size, and stamen number per flower ( Dickinson et al. 2008; Phipps 1999; Phipps 2015). Greene, in his Flora Franciscana (1891), followed Brewer and Watson (1880) in noting that C. gaylussacia (as his C. rivularis ) occurred in Sierra and Plumas counties, between Modoc Co. and Alpine Co. Greene contrasted C.douglasii as having longer thorns than C.gaylussacia (as C. rivularis ), and suggested that C. douglasii might not occur within the limits of his flora (“middle California ”).The stamen number data from an Alpine Co.specimen (D.W.Taylor5115, 9-Sep-1975 (UC1561066!headwaters of Forestdale Creek) suggests that more collecting in the Sierra Nevada, from Kern Co. north, with careful attention to variation in stamen numbers per flower, would repay the effort. Similarly, new collections from California north of the San Francisco Bay area and west of the Central Valley. Parallel collections of leaf tissue on desiccating silica gel could provide material for flow cytometric and molecular studies that could further illuminate the distributions of C. gaylussacia and C. douglasii , to say nothing of the correct application of these names in accounts of the California flora.

Ploidy level.— Autotriploids, 2n = 51, based on flow cytometric determinations of nuclear DNA content (N. Talent unpubl. data; Coughlan et al. 2014) and analyses of ITS2 ribotype diversity ( Zarrei et al. 2014).

Figures

FIG. 8. Western North American 20-Stamen Black-Fruited Hawthorns (Crataegus Section Douglasianae). A. Crataegus ×suksdorfii (Sarg.) Kruschke; TRT00014409, Heckel,M.& Talent N.NT565, 15 May 2010, triploid,Castlegar,British Columbia.Photo: N.Talent; used with permission.B. Crataegus gaylussacia A.Heller;TRT00002016,Shiller,J., Tusha,J.,Dickinson,T.A.& Heckel, M.PORE-509-1, 26 Apr 2010,triploid,Point Reyes National Seashore, California. Collected under National Park Service permit PORE-2010-SCI-0010. Photo: T.A. Dickinson. C. Crataegus rhodamae-loveae sp. nov. Photo © Keir Morse 2008, Deer Creek Center, Selma, Oregon; used with permission (https://calphotos.berkeley.edu/cgi/img_query?enlar ge=0000+0000+0208+0944).

FIG. 3. Map of western North America showing the locations at which 233 Crataegus individuals were sampled for DNA extraction and amplification microsatellite loci (Appendix 2; Coughlan et al. 2017b; Han 2013; Han et al. 2013).Taxa sampled at each site indicated by symbol shape and color. Figure produced using R package ggmap (Kahle & Wickham 2013) and Google Maps (Map data © Google).

FIG. 1. PrincipalComponents (PCA;A–C) andCanonical Discriminant (CA;D)Analyses of a Crataegus morphology dataset (N = 246;Appendix 1) with six descriptors (used earlier in Dickinson et al.2008) transformed by ranging to a (0,1) interval:THNL,Thorn length (mm);THND,Thorn diameter at base (mm);relX,Leaf blade length above the widest point divided by leafwidth at the widest point;relZ,Leaf blade lengthbelow the widest point divided by leaf width at the widest point;STAM,Number of stamens per flower (fruit);STYL,Number of styles per flower (fruit).A. PCA biplot showing the component-descriptorcorrelations as vectors.Convexhulls enclosepoints representing specimens of C.suksdorfii sensu lato (suk)with 20 stamens per flower,specimens of C.gaylussacia (gay) with 20 stamens per flower fromMarin and Sonoma countiesin California,and specimens ofC.douglasii(dou) with 10 stamens per flower (Appendix 1). B.Cytotype differentiation of the sample as givenin the inset key.Convexhulls enclose points representing specimens of the different cytotypes.C.Positions of type specimens included in the sample:C.suksdorfii sensu stricto,W.N.Suksdorf numbers 4034, 4419,5026,5031,and5040(holotype andisosyntypes);Br,C.punctatabrevispinacollected byDavidDouglas;G,C.gaylussacia;D,C.douglasii specimens and specimens grown from seed collected by David Douglas;Ba, C.douglasii forma badia; and T,C. tennoWana (the latter two synonymized with C. douglasii. In C,the convex hulls enclose points representing specimens of C.gaylussacia, C.douglasii, and the diploid and polyploid components of C. suksdorfii sensu lato.Specimensrepresenting W.N.Suksdorf4419, theholotype of C.suksdorfii proposed below,are also enclosedwithin a convex hull. D. Canonical Discriminant Analysis of five 20-stamen groups of specimens in our sample:gay,C.gaylussacia; iso4419,W.N.Suksorf 4419, C.suksdorfii sensu lato isosyntype collected in 1905 in ‘Falcon Valley,’Klickitat Co.WA (Love 1998);isoBingen,W.N. Suksorf isosyntypes (4034, 5026, 5031, 5040) collected in1905along theColumbia RiverinBingenWA;suk,allopolyploidC.suksdorfii sensulato;andsuk2x,diploidC.suksdorfiisensu lato.Asterisks indicate that the ordination axis corresponds to a significant eigenvalue according to the broken-stick criterion (PCA) or other criterion (likelihood ratio for canonical axes;Friendly & Fox 2017); axes not associated with eigenvalues judged to be significant in these ways should be compared with the equidistribution among all axes of the total sample variance.

FIG.2.Boxplots contrastingthorn andpetioledimensionsbetween Crataegus gaylussaciaand Crataegussuksdorfii sensulato (andC.douglasii;compare Fig.1; Appendix 1). A,width of thorn at its base inmm.B, lengthof thorn in mm;C,petiole length in mm;note difference inscales between A,B,and C.Data are mean dimensions for samples of five thorns per each of 198 specimens,or a similar number of petioles for 38 specimens.

FIG. 5.Boxplots contrasting the density of leaf teeth between diploid and autopolyploid,andallopolyploid,Crataegus suksdorfii sensu lato.Data from isosyntypes (Bingen,Falcon Valley)of C.douglasiivar.suksdorfii Sarg.demonstrate their similarity to theallopolyploids (Appendix 3).Theisosyntypes were collected byW.N.Suksdorf at Bingen,Washington along theColumbia River(WNS4034,5026,5031,and 5040),and at his farm in“Falcon Valley” (WNS4419).Data are mean densities for five leaves for each of the numbers of specimens shown.