DANIEL & TRIPP: LOUTERIDIUM : TAXONOMY, BIOLOGY, AND CONSERVATION 65 
extends along the trough formed by the lateral invaginations in the anterior portion of the throat 
(see Morphology above). Standing crop nectar volumes in three flowers of this plant of L. mexi- 
canum were 145.6 pi, 184.4 pi, and 197.6 pi (mean =175.9; SD = 27.0). These amounts are 
comparable to quantities present in other bat-adapted species of Acanthaceae, such as Ruellia 
malaca (up to 180 pi; Tripp and Lujan 2018), R. conzattii (432 pi; Daniel unpublished), and 
R. laslobasensis (168 pi; Daniel unpublished). 
Nectar quality for L. mexicanum and Table 4. Nectar sugar composition of samples from five 
L. parayi, expressed here by the ratios of flowers of Louteridium mexicanum (Breedlove & Daniel 
70879cv, grown from seed in a greenhouse) and three flow¬ 
ers of L. parayi (Daniel & Wendt 5805, from plants in then- 
native habitat). Percentages of the hexose sugars fructose (F) 
and glucose (G) are compared to the percent of sucrose (S). 
Sample means (ju) and sample standard deviations (s) for 
percentages and ratios are shown. Samples were analyzed by 
C.E. Freeman using High Performance Liquid Chromatogra¬ 
phy. 
the relative percentages of sucrose to 
hexose sugars (i.e., glucose + fructose), 
was determined by C.E. Freeman using 
high-performance liquid chromatogra¬ 
phy (HPLC), the methodology of which 
was outlined by Ellisens and Freeman 
(1988), with modifications noted in Free¬ 
man et al. (1991). The results of multiple 
samples of a single collection for each 
species are shown in Table 4. Baker and 
Baker (e.g., 1983, 1990) demonstrated 
correlations between sucrose:hexose 
ratios and pollinator types for numerous 
groups of plants. Nectar sugar ratios of 
Acanthaceae studied to date (e.g., Baker 
et al. 1998; Daniel 1986, 1990; 
Holmqvist et al. 2005; Freeman 1986; 
Freeman et al. 1991; Daniel and Free¬ 
man, unpublished data) generally con¬ 
form to these sugar preference correla¬ 
tions. Table 4 shows that sampled 
nectar profiles of L. mexicanum and 
L. parayi, species representative of two 
of the three sections of the genus, pertain to the “hexose-rich” category (i.e., S/G + F ranging from 
0.1 to 0.49; Baker and Baker 1983). Neotropical flowers visited/pollinated by bats are consistent¬ 
ly hexose-rich or hexose-dominant (Baker and Baker 1983). By contrast, hummingbird visited/pol¬ 
linated flowers generally offer sucrose-rich nectar (i.e., S/G + F ranging from 0.5 to 0.99; Baker 
and Baker 1983). Thus, based on our sampling, flowers of Louteridium have both floral morpho¬ 
logical traits and nectar sugar chemistry that strongly suggest adaptations for pollination by bats. 
Hummingbirds may be opportunistic visitors to these flowers during daylight hours, when bats are 
generally not present, and likely also serve as pollinators. 
Self-compatibility, Autonomous Agamospermy, and Vegetative Propagation.— 
Experiments and observations to determine self-compatibility and at least one form of asexual 
reproduction were undertaken on flowers of a greenhouse-cultivated plant of Louteridium 
mexicanum (Breedlove & Daniel 70879gh ) in March of 1990. Over several weeks, varying num¬ 
bers (n) of flowers were marked for each of the following treatments: control (n = 13, no treat¬ 
ment), emasculation (n = 10, anthers excised prior to dehiscence), and artificial self-pollination 
(n = 22, anthers excised prior to dehiscence and stigma manually dusted with pollen after 
dehiscence of anthers). Fruit-set was used as a measure of fertilization and self-compatibility. 
L. mexicanum samples 
%F 
%G 
%S 
S:F+G 
1 
32.4 
39.5 
28.1 
0.39 
2 
33.7 
44.3 
22.0 
0.28 
3 
34.4 
44.1 
21.5 
0.27 
4 
32.5 
39.7 
27.8 
0.39 
5 
32.2 
44.2 
23.6 
0.31 
V 
33.0 
42.4 
24.6 
0.33 
s 
1.0 
2.5 
3.2 
0.06 
L. parayi samples 
1 
34.4 
42.0 
23.6 
0.31 
2 
33.9 
42.9 
23.2 
0.30 
3 
34.4 
42.0 
23.6 
0.31 
V- 
34.2 
42.3 
23.5 
0.31 
s 
0.3 
0.5 
0.2 
0.00 
