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Croton Chromosome counts
The following table shows that chromosome numbers are variable in Croton and may be phylogenetically very informative. We made a comprehensive survey of chromosome number reports in the genus, finding over 70 individual counts (summarized in the table below). The most widely reported number is n = 10 (22 species in 10 sections), followed by n = 14 or 28 (4 spp. in one section), n = 8 (3 spp. in 2 sections), n = 32 or 64 (3 spp. in one section), n = 9 (one sp.), and n = 16 or 32 (one sp.).

Based on these data, we are very eager to obtain chromosome counts from additional taxa, particularly in section Astraea, to see if other members share n = 9 as in C. lobatus. No member of the very distinctive section Eluteria has so far been counted, and section Crotonopsis should similarly be targeted for chromosome counts.

Very few native Old World taxa have been counted, so a better representation of chromosome counts is needed for them.

If anybody could provide us with viable seeds from vouchered collections of Croton, we will attempt to grow them to obtain root tip counts.

Gam = gametophytic, Spor.= sporophytic, Ref.= reference
Species Gam. Spor. Section Ref. Location and Comments
C. ciliato-glanduliferus Ortega 10 - Adenophyllum Seavey 1975 -
C. humilis L. 10 - Adenophyllum Urbatsch et al. 1975 Mexico (Nuevo Leon)
C. joufra Roxb. 10 - Argyrocroton Mehra 1976 as "jaufre" in IPCN; India
C. joufra Roxb. 10 - Argyrocroton Mehra & Hans 1969 India: Khasia & Jaintia hills, Shillong
C. laevigatus Vahl 11 - Argyrocroton Sarkar et al. 1972 reported as C. oblongifolius Roxb.
C. laevigatus Vahl 10 - Argyrocroton Gill et al. 1981 reported as C. oblongifolius Roxb.
C. laevigatus Vahl 10 - Argyrocroton Bedi et al. 1980 reported as C. oblongifolius Roxb.; India (Uttar Pradesh)
C. roxburghii Vahl 10 - Argyrocroton Mehra & Hans 1969 reported as C. roxburghianus Bal.; India (Assam)
C. roxburghii Vahl 10 - Argyrocroton Mehra 1976 reported as C. roxburghianus Bal.
C. lobatus L. 9 - Astraea Brunel & Laplace 1977 -
C. lobatus L. 9 - Astraea Miller & Webster 1966 Nicaragua (near Managua)
C. caudatus Giesel. 10 - Cascarilla Mehra & Hans 1969 India (East Himalayas, Darjeeling)
C. caudatus Giesel. 10 - Cascarilla Mehra 1976 -
C. lorentzii Mull. Arg. 10 - Cascarilla Bernardello et al. 1990 Argentina (Córdoba)
C. bonplandianus Baill. 10 - Cascarilla? Choda & Mehra 1972 India
C. bonplandianus Baill. 10 - Cascarilla? Hans 1973 India (Assam)
C. bonplandianus Baill. - 20 Cascarilla? Sidhu & Bir 1983 -
C. bonplandianus Baill. - 20 Cascarilla? Sharma 1970 -
C. bonplandianus Baill. 10 - Cascarilla? Koul et al. 1976 -
C. bonplandianus Baill. 10 20 Cascarilla? Bir & Sidhu 1979 -
C. bonplandianus Baill. - 20 Cascarilla? Bir & Sidhu 1980 -
C. bonplandianus Baill. 10 - Cascarilla? Datta 1967 India (West Bengal); Datta 9637 - CBLH
C. bonplandianus Baill. 10 - Cascarilla? Sidhu 1979 -
C. bonplandianus Baill. 10 - Cascarilla? Patil 1985 India
C. bonplandianus Baill. 10 - Cascarilla? Gajapathy 1962 India
C. bonplandianus Baill. 10 - Cascarilla? Pal 1964 India
C. bonplandianus Baill. 10 - Cascarilla? Trivedi et al. 1982 Reported as C. sparsiflorus Morong
C. bonplandianus Baill. 8 - Cascarilla? Sanjappa 1979 Reported as C. sparsiflorus Morong; India: Karnataka, Bangalore
C. bonplandianus Baill. 8 - Cascarilla? Baquar 1967 Reported as C. sparsiflorus Morong - Hans (1973) says this report "seems dubious." Pakistan (Bangladesh)
C. bonplandianus Baill. - 20, 40, 50 Cascarilla? Kothari et al. 1980 Reported as C. sparsiflorus Morong; India (Kerala, Trivandrum, Pettah)
C. bonplandianus Baill. 10 - Cascarilla? Miller & Webster 1966 India
C. persicaria Baill. 10 - Cascarilla? Mehra 1976 Brazil; for section see Adansonia 4: 342. 1864.
C. aromaticus L. 10 - Croton Kothari et al. 1981 India (Tamil Nadu, Tinnaveli, Courtallum)
C. ruizianus (vel aff.) Mull. Arg. 32 64 Cyclostigma Diers 1961 Peru
C. sarcopetalus Mull. Arg. 32 - Cyclostigma Bernardello et al. 1990 Argentina (Córdoba)
C. xalapensis Kunth ca. 60 - Cyclostigma Miller & Webster 1966 Honduras (Morazan)
C. californicus Mull. Arg. 14 - Drepadenium Urbatsch et al. 1975 Mexico (Baja California)
C. californicus var. tenuis (Wats.) Ferg. 14 - Drepadenium Szweykowski 1965 California (Los Angeles Co., Point Dume); complex structural heterozygotes!
C. dioicus Cav. 14 - Drepadenium Ward 1984 -
C. dioicus Cav. 14 - Drepadenium Urbatsch et al. 1975 Mexico (Coahuila)
C. dioicus Cav. 28 - Drepadenium Urbatsch et al. 1975 Texas (El Paso)
C. punctatus Jacq. 14 - Drepadenium Bell 1965 North Carolina (Onslow Co.), Bell 17063 - NCU
C. texensis (Kl.) Mull. Arg. 14 - Drepadenium Urbatsch et al. 1975 New Mexico (Eddy Co.)
C. texensis (Kl.) Mull. Arg. 28 - Drepadenium Urbatsch et al. 1975 Texas (Randall Co.)
C. wigginsii L. C. Wheeler 14 - Drepadenium Spellenberg 1986 Mexico (Sonora, S of Puerto Libertad)
C. setigerus Hook. 10 - Eremocarpus Miller & Webster 1966 California (Los Angeles Co.)
C. setigerus Hook. - 20 Eremocarpus Heiser & Whitaker 1948 -
C. klotzschianus Thwaites 11 - Furcaria Sharma 1970 -
C. klotzschianus Thwaites 10 - Furcaria Datta 1967 India (West Bengal); Datta 4272 - CBLH
C. klotzschianus Thwaites - 20 Furcaria Kothari et al. 1980 India (Kerala, Kottayam, Kallarkutty)
C. glandulosus L. - 16 Geiseleria Perry 1943 grown by Croizat at Arnold Arboretum, MA
C. palmeri S. Wats. - 16 Geiseleria Perry 1943 grown by Croizat at Arnold Arboretum, MA
C. monanthogynus Michx. - 16 Gynamblosis Perry 1943 grown by Croizat at Arnold Arboretum, MA
C. monanthogynus Michx. 10 - Gynamblosis Urbatsch et al. 1975 Texas (Travis Co.)
C. subpannosus Mull. Arg. 10 - Julocroton Di Fulvio 1973 Argentina (Córdoba); Hunziker 18569 (CORD)
C. alabamensis E.A.Smith ex Chapman 32 - Lamprocroton Farmer 1962 Warrior River plants (Tuscaloosa Co., AL)
C. alabamensis E.A.Smith ex Chapman 16 32 Lamprocroton Farmer 1962 Cahaba plants (Bibb Co., AL)
C. alabamensis E.A.Smith ex Chapman 32 - Lamprocroton (see also Eluteria) Farmer & Thomas 1969 Alabama (Tuscaloosa Co.); counts from 33 individuals in 2 populations
C. argentinus Mull. Arg. 10 - Lamprocroton?? Di Fulvio 1973 Argentina (Córdoba); Di Fulvio 177 (CORD)
C. capitatus var. capitatus Michx. 10 - Pilinophytum Urbatsch et al. 1975 Texas (Johnston Co.)
C. capitatus var. lindheimeri Michaux (Engelm. et A. Gray) Muell. Arg. - 20 Pilinophytum Lewis et al. 1962 USA
C. tiglium L. 10 - Tiglium Mehra & Hans1969 India (Khasia and Jaintia hills, Mawsmai)
C. tiglium L. 10 - Tiglium Mehra 1976 India
C. cortesianus Kunth 10 - Velamea Miller & Webster 1966 Mexico: Tamaulipas
C. fruticulosus Torr. ca. 24 - Velamea Urbatsch et al. 1975 Texas (Travis Co.)
C. pottsii (Kl.) Mull. Arg. 9 - Velamea Urbatsch et al. 1975 Texas (Presidio Co.)
C. pottsii var. pottsii (Kl.) Mull. Arg. 20 - Velamea Ward 1983 -
C. torreyanus Mull. Arg. 10 - Velamea Urbatsch et al. 1975 Mexico (Coahuila)
C. magdalenae Millsp. 10 - Velamea? Urbatsch et al. 1975 Mexico (Baja California Sur)

 

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