58 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, 28 Sept. 2018, No. 2 
Table 2. Approximate meiotic chromosome counts of some Trichantherinae ( Bravaisia, Louteridium, 
and Sanchezia ). Herbarium vouchers are at CAS. See text for discussion. 
Taxon 
n 
Location 
Collector & Number 
Bravaisia berlandieriana 
32 
BELIZE: Orange Walk 
Daniel 8263 
Bravaisia berlandieriana 
29 
BELIZE: Orange Walk 
Daniel 8263 
Bravaisia berlandieriana 
ca. 26 
BELIZE: Corozal 
Daniel 8265 
Bravaisia grandiflora 
ca. 44-47 
MEXICO: Chiapas 
Daniel & Bartholomew 4998 
Louteridium chartaceum 
ca. 24 (-26) 
BELIZE: Belize 
Daniel & Butterwick 5905 
Louteridium donnell-smithii 
ca. 30 
MEXICO: Chiapas 
Breedlove & Daniel 71197 
Louteridium mexicanum 
ca. 30 
MEXICO: Chiapas 
Breedlove & Daniel 70879 
Louteridium mexicanum 
ca. 28 (-30) 
MEXICO: Chiapas 
Daniel & Ton 6182 
Sanchezia parvibractetata 
ca. 36-40 
MEXICO: Chiapas 
Breedlove & Daniel 71315 
conflicting numbers of chromosomes in different cells of the same collection; dark staining cyto¬ 
plasm; dark staining particles in cytoplasm that do not appear to be either chromosomes or B-chro- 
mosomes; and meiotic irregularities (e.g., bivalents aligned in the middle region of a cell and with 
scattered univalents elsewhere or different numbers of chromosomes per pole in a cell at telophase 
I). Most counts were made at metaphase I. Like the previously published counts for Sanchezia, 
haploid numbers obtained for Bravaisia are relatively high (Table 2). Approximate counts obtained 
for Louteridium (Table 2) are lower numbers (n = ca. 24 to 30), but still somewhat high for Acan- 
thaceae (e.g., Daniel et al. 1984). Using a probable ancestral basic number ofx = 7 for the family, 
Daniel (2000) suggested that n = 68 for Sanchezia oblonga represents cytological evolution to the 
decaploid level. Although definitive counts for all Trichantherinae and knowledge of chromosome 
numbers in its sister group(s) will be necessary to propose an ancestral basic number for the sub¬ 
tribe, it appears that included taxa exhibit high chromosome numbers, and that polyploidy and 
probably also dysploidy were significant in the evolution of taxa in this subtribe. 
Distribution, Endemism, and Habitats 
The geographic distribution of Louteridium occurs entirely in the northern hemisphere of the 
Neotropics. Its northern limit (i.e., L. tamaulipense in Tamaulipas, Mexico) is 23°07’37.45”N; its 
southernmost extent (i.e., L. costaricense in Chiriqui, Panama) is 08°41’25.09”N; its westernmost 
occurrence (i.e., L. koelzii in Jalisco, Mexico) is 103°28’18.42”W; and its eastern limit (i.e., 
L. costaricense in Guna Yala, Panama) is 078°49’40.88”W. The greatest linear extent of the genus 
is 2,866 km from west-central Mexico to southeastern Panama. As currently known, the distribu¬ 
tion of Louteridium is not continuous in Central America. Louteridium donnell-smithii occurs as 
far southeast as western Honduras, and the geographic range of Louteridium costaricense, the 
southernmost-occurring species, occurs from northern Costa Rica to eastern Panama, leaving a gap 
of approximately 570 km in eastern Honduras and Nicaragua from which no Louteridium has been 
collected. It is possible that L. costaricense occurs in southeastern Nicaragua near occurrences in 
northeastern Costa Rica, but the species has yet to be collected from the former country. 
Eight species occur in Mexico, with six of them endemic to that country (Fig. 8). Four of these 
endemics (L. brevicalyx, L. dendropilosum, L. koelzii, and L. rzedowskianum ) occur in dry forests 
of western and southern Mexico on the Pacific versant. The other two Mexican endemics occur in 
