ArticlePDF Available

Echeveria rosea Lindley (Crassulaceae): a Hummingbirddependent Succulent Epiphyte

Authors:

Figures

No caption available
… 
Content may be subject to copyright.
23 CACTUS AND SUCCULENT JOURNAL
H. DAVID JIMENO SEVILLA1,2, ANGÉLICA M. HERNÁNDEZ RAMÍREZ1,3 & THORSTEN KRÖMER1,4
Echeveria rosea Lindley
(Crassulaceae): a hummingbird-
dependent succulent epiphyte
The stonecrop family Crassulace-
ae has a worldwide distribution
with exception of Australia and
the Polynesian area. There are
about 1,500 species of Crassu-
laceae distributed in 33 genera,
which are characterized by their
rosetted succulent leaves. The family is often viewed
as a typical northern temperate element, although its
highest species richness is concentrated in Mexico
(about 325 species) and South Africa (about 250 spe-
cies). Most species grow saxicolous and/or terrestri-
al in dry areas and show Crassulacean Acid Metabo-
lism (CAM) as photosynthetic pathway, which is an
adaptation to arid conditions. In contrast, only seven
species in three genera (Echeveria, Kalanchoe, Sedum)
have been reported to grow mainly epiphytic (Kress
1989). Furthermore, Crassulaceae species are known
for a variable floral morphology, which is attractive for
a diverse spectrum of pollinators.1
A general approach to specify the pollination biol-
ogy of the Crassulaceae family includes the establish-
ment of five major pollination syndromes based on
floral types,
1. Melittophily or bee pollination is assumed for
species with short tubular corollas, which is
the most frequent and least specialized floral
characteristic in Crassulaceae (Figs. 1 & 2),
2. Psychophily or pollination by butterflies is
associated with long-tubed salver-shaped
flowers or flowers with petals forming a tube-
like structure, which have an intensive color-
ation (red, yellow) and a perfume-like scent
production over day (Fig. 3),
3. Sphingophily or pollination by hawkmoths
corresponds to long, whitish corolla tubes and
nocturnal strong sweet scent,
1Centro de Investigaciones Tropicales, Universidad
Veracruzana, Xalapa, Veracruz, México.
2bpdjimeno@yahoo.com.mx;3hernanra03@yahoo.com.mx;
4tkromer@uv.mx
1. Sedum praealtum and Bombus sp. Tlacolulan,
Veracruz, México.
2. Villadia elongata and Apis melifera. Huayacocotla,
Veracruz, México.
2013 VOLUME 85 NUMBER 3 24
4. Ornithophily or bird pollination is assumed to
red, long-tube corollas, abundant nectar pro-
duction and exserted anthers, and
5. Myophily or pollination by flies corresponds to
open flowers with darkish colors, freely acces-
sible nectar produced by large nectary scales
and foetid flowers (Thiede & Eggli 2006),
Fig. 4.
Nonetheless, studies on the pollination biology of
Crassulaceae family members are scarce, and only a
few species of the genera Aeonium (Esfeld et al. 2009,
Nelson 2010), Crassula ( Johnson et al. 1993), Diamor-
pha (Wyatt 1997, 1981), Dudleya (Aigner 2005, Jones
et al. 2010), Echeveria (Parra et al. 1993, 1998, Vargas
& Parra-Tabla 2002), and Sedum (Shahani 2007) have
been investigated in detail. Thus, for the great major-
ity of the species, there is no information on this sub-
ject available.
Mexico as a biodiversity
center of Echeveria
Echeveria is represented by about 140 species dis-
tributed from southwest Texas to Central and South
America. Of these, about 110 species occur in Mexico
and 107 species (97.2%) are endemic to the country
(Pérez-Calix & Franco-Martínez 2004). Furthermore,
Echeveria is the most speciose genus of the Crassu-
laceae family in Mexico. The name of the genus was
honored to the Mexican illustrator and botanist Ata-
nasio Echeverría y Godoy, who made several scientific
illustrations for the Flora of Mexico in collaboration
with the Spanish botanist Martín de Sessé y Lacas-
tra and the Mexican naturalist José Mariano Moci-
ño during the “Real Expedición Botánica a la Nueva
España” in the XVIII century.
3. Crassula coccinea and butterfly. Drawing by H. David Jimeno Sevilla.
25 CACTUS AND SUCCULENT JOURNAL
The Echeveria genus seems to include a small spe-
cialized group of epiphytic succulent plants, which is
an exception in the Crassulaceae family. At least in
this genus, the epiphytic habit appears to be associat-
ed with humid montane forest, whereas most species
grow saxicolous in zonal arid habitats such as rocky
slopes and rock fissures under otherwise more humid
climatic conditions, or in mountain regions of moder-
ately arid areas.
Echeveria rosea an endemic
plant of Mexico
Echeveria rosea Lindley is a succulent epiphyte that
occurs in cloud and pine-oak forests from Tamauli-
pas to Chiapas, with a disjunct distribution in Guer-
rero. The species usually flowers from November to
February and has showy inflorescences with terminal
and lax racemes. The length of the inflorescences is
between 21-40 cm, each bearing 12-41 flowers, with
one to four open flowers per day. The yellow flower is
hermaphroditic and subtended by a red colored flo-
ral bract. The petals are fused at the base, providing
a receptacle for nectar. The flowers of E. rosea have
attributes that are related to hummingbird-pollination
(ornithophily), i.e., long-tubed corollas, lack of odour,
abundant nectar production and exserted anthers
(Parra et al. 1993).
Pollinators and floral visitors
Nectar is the most common form of floral reward
provided by animal-pollinated plants to their mutual-
istic partners. The preliminary results of our research
on the pollination biology of Echeveria rosea realized
in a pine-oak forest at “Cerro de la Magdalena”, cen-
tral Veracruz, indicate that Garnet-Troated Hum-
mingbird (Lamprolaima rhami) is the most frequent
floral visitor (Fig. 5), followed by White-Eared
Hummingbird (Basilinna leucotis = Hylocharis leu-
cotis), whereas Magnificent (Rivoli’s) hummingbird
(Eugenes fulgens) only occasionally visits E. rosea. Al l
mentioned hummingbirds forage for nectar and con-
tact the anthers and/or stigmas of the flowers, sug-
gesting that these are the main pollinators of E. rosea.
Interestingly, the geographic distributions of E.
rosea and Garnet-Troated Hummingbird in Mexico
are coincident. Moreover, the breeding season of Gar-
net-Troated Hummingbird in Mexico occurs when
E. rosea blooms. In this scenario, the relation between
Echeveria rosea and Lamprolaima rhami seems to be a
keystone mutualistic interaction with potential eco-
logical and evolutionary processes involved.
Other floral visitors are mites, however, flower
mites are considered as nectar robbers, because they
live and reproduce in flowers of the plant species, and
feed on their nectar and pollen without a pollinator
service for the plant.
Conservation
The cloud forest habitat of both species is threat-
ened, because it is strongly disturbed by illegal defor-
estation and agropecuary activities. As Echeveria rosea
is an epiphyte and thus dependent on the availabil-
ity of adequate host trees, it is very susceptible to dis-
appear by immoderate land use changes. Furthermore,
the Garnet-Troated Hummingbird is included in the
IUCN Red List of threatened species (BirdLife Inter-
national, 2009) and protected under Mexican law
(SEMARNAT, 2010). Thus, it is important to get a
better knowledge about the relationship of E. rosea
and their pollinators to devise adequate conservation
strategies in the future.
Acknowledgments
This study was funded by the Consejo Nacional
de Ciencia y Tecnología (CONACyT, grant number
376753).
RefeRences
Aigner PA. 2005. Variation in pollination performance
gradients in a Dudleya species complex: can general-
ization promote floral divergence? Functional Ecology
19: 681-689.
BirdLife International 2009. Lamprolaima rhami. In:
IUCN 2011. IUCN Red List of Threatened Species.
Version 2011.2. www.iucnredlist.org. Downloaded on
29 February 2012.
4. Sedum cf. hemsleyanum and diptera. Cerro Gordo,
Veracruz, México.
2013 VOLUME 85 NUMBER 3 26
Esfeld K, Koch MA, van der Niet T, Seifan M, Thiv M.
2009. Little interspecific pollen transfer despite
overlap in pollinators between sympatric Aeonium
(Crassulaceae) species pairs. Flora 204: 709-717.
Jones CE, Shropshire FM, Allen RL, Atallah YC. 2010.
Pollination and reproduction in natural and mitiga-
tion populations of the many-stemmed Dudleya,
Dudleya multicaulis (Crassulaceae). Madroño 57:
42-53.
Johnson SD, Ellis A., Carrick P., Swift A., Horner N., Janse
Van Rensburg S., Bond W.J. 1993. Moth pollina-
tion and rhythms of advertisement and reward in
Crassula fascicularis (Crassulaceae). South African
Journal of Botany 59: 511-513.
Kress WJ. 1989. The systematic distribution of vascular
epiphytes. Pp.234-261. In: Lüttge, U. (ed.), Vascular
Plants as epiphytes, Evolution and Ecophysiology.
Ecological Studies 76, Springer-Verlag, Berlin-New
Yor k.
Nelson EC. 2010. Lizards on Aeonium lancerottense in
Lanzarote, Canary Islands: a new example of pollina-
tion by reptiles? Bradleya 28:15-18.
Parra V, Vargas CF, Eguiarte LE. 1993. Reproductive
biology, pollen and seed dispersal, and neighbor-
hood size in the hummingbird-pollinated Echeveria
gibbiflora (Crassulaceae). American Journal of Botany
80: 153-159.
Parra-Tabla V, Vargas C F, Eguiarte LE. 1998. Is Echeveria
gibbiflora (Crassulaceae) fecundity limited by pol-
len availability? An experimental study. Functional
Ecology 12: 591-595.
Pérez-Calix E, Franco-Martínez IS. 2004. Crasuláceas. In:
García-Mendoza AJ, Ordónez MJ, Briones-Salas M.
(eds), Biodiversidad de Oaxaca. Instituto de Biología,
UNAM-Fondo Oaxaqueño para la Conservación de la
Naturaleza-World Wildlife Fund, México, pp. 209-217.
SEMARNAT. 2010. NORMA Oficial Mexicana NOM-059-
SEMARNAT-2010, Protección ambiental-Especies nati-
vas de México de flora y fauna silvestres-Categorías
de riesgo y especificaciones para su inclusión, exclu-
sión o cambio-Lista de especies en riesgo. Jueves 30
de diciembre de 2010.
Shahani P. 2007. Demography and native bee pollina-
tion of Sedum laxum (Crassulaceae), an endemic,
clonal plant in a managed forest matrix landscape
of the Siskiyou Mountains. (Ph.D.), University of
California, Santa Cruz, United States, California.
Thiede J, Eggli U. 2006. Crassulaceae. In: K. Kubitzki (ed.),
The families and genera of vascular plants. Springer,
Hamburg, 9: 83-118.
Vargas CF, Parra-Tabla V. 2002. Floral abundance, terri-
toriality, and the importance of Echeveria gibbiflora to
Cynanthus latirostris (Apodiformes: Trochilidae) during
winter. Southwestern Naturalist, 47(4), 623-626.
Wyatt R. 1997. Reproductive ecology of granite out-
crop plants from the south-eastern United States.
Journal of the Royal Society of Western Australia 80:
123-129.
5. Echeveria rosea and Garnet-Throated Hummingbird (Lamprolarima rhami), Veracruz, México.
... Species of the stonecrop family Crassulaceae (ca. 1500 succulent species; Thiede & Eggli 2006) are known for their varied floral morphology, which potentially attract a diverse spectrum of pollinators (Jimeno et al. 2013). Nonetheless, the floral biology of the family is poorly studied and largely restricted to the establishment of floral types and pollination syndromes (Thiede & Eggli 2006). ...
... 145 species. Out of these, 81% are located in Mexico (Parra et al. 1993;Jimeno 2008), and most have restricted geographical distribution, resulting in high levels of endemism of Echeveria in Mexico (Parra et al. 1993;Jimeno 2008). The long and deep flowers of Echeveria species correspond to the typical hummingbirdpollination syndrome (Thiede & Eggli 2006;Parra et al. 1993Parra et al. , 1998Jimeno 2008;Jimeno et al. 2013). ...
... 145 species. Out of these, 81% are located in Mexico (Parra et al. 1993;Jimeno 2008), and most have restricted geographical distribution, resulting in high levels of endemism of Echeveria in Mexico (Parra et al. 1993;Jimeno 2008). The long and deep flowers of Echeveria species correspond to the typical hummingbirdpollination syndrome (Thiede & Eggli 2006;Parra et al. 1993Parra et al. , 1998Jimeno 2008;Jimeno et al. 2013). ...
Article
Full-text available
Flowers have evolved suites of traits that are associated with the attraction, reward and utilization of particular pollinator types. Specialization on particular pollinator functional group results in a particular combination of floral traits with consequences on plant fitness through efficient pollen delivery and pollen receipt at the population and species level. The aim of this study was to describe the floral morphology, nectar production patterns, floral visitors and natural fruit set in a population of Echeveria rosea Lindley (Crassulaceae) in central Veracruz, Mexico. The floral traits of Echeveria rosea correspond to the typical hummingbird pollination syndrome. The diurnal pattern of accumulated nectar (volume and amount of sugar) produced by the species corresponds to values reported for other hummingbird-pollinated species. Based on observations of foraging behavior, the Garnet-throated Hummingbird (Lamprolaima rhami) seems to be a more effective pollinator than the White-eared Hummingbird (Hylocharis leucotis). Fruit set per plant was high under natural conditions in the studied population of E. rosea. These results corroborate the hypothesis that E. rosea has a specialized hummingbird-pollination system that results in high fruit set under natural conditions.
... The amount of viable seeds was low possibly because the amount of pollen deposited on stigmas was insufficient. These species are likely to generate more offspring if grown in an open area for pollinators, as Charlesworth and Charlesworth (1987), Cruden (1976), Carque et al. (1996), Izco et al. (1998) and Jimeno-Sevilla et al. (2013), pollination of Crassulaceae occurs by insects, birds, wind, and water; the amount of pollen available would be greater. Aunque se reporta que puede haber autopolinización (Charlesworth y Charlesworth, 1987y Cruden, 1976, los resultados obtenidos indican que la polinización en Echeveria fue cruzada, lo cual concuerda con Izco et al. (1998) También Rojas-Aréchiga y Batis (2001) mencionan que la baja viabilidad de semillas se puede deber a que el embrión no se encuentra totalmente desarrollado al momento de su dispersión, por lo que se necesita de un periodo de tiempo para completar su maduración; cabe señalar que en la presente investigación, la semilla fue cosechada cuando los folículos estaban abriendo y las semillas habían madurado. ...
Article
Full-text available
Echeveria, género representativo de Crassulaceae por representar 97% de especies endémicas; sus plantas tienen características morfológicas atractivas para la horticultura ornamental. El conocimiento de las características reproductivas es útil para el mejoramiento genético, necesario para ser utilizado en las polinizaciones y aumentar la posibilidad de éxito de la fecundación. El objetivo fue conocer la viabilidad de polen, receptividad del estigma y tipo de polinización de cinco especies de Echeveria, con fines de mejoramiento genético. El trabajo se realizó de 2011 a 2013, en Cuernavaca, Morelos. Se usaron cinco especies E. agavoides, E. elegans, E. runyonii, E. pumila, E. perle. La viabilidad de polen se determinó mediante el método de tinción con ácido ácetico-carmín. La receptividad del estigma se evaluó con el método de Osborn; la evaluación fue a las 8:00, 10:00, 12:00, 14:00, 16:00, y 18:00 h. Para tipo de polinización se realizaron cuatro modalidades: 1) autopolinización; 2) emascular y cubrir flores; 3) polinización cruzada intra específica; y 4) polinización cruzada inter específica; se evaluo amarre de fruto y viabilidad de semillas. E. agavoides tuvo mayor porcentaje de polen viable (72.7%). La mayor receptividad se tuvo de 12:00 a 14:00 h (94.6 a 98%). En las cuatro modalidades de polinización se obtuvó 100% de amarre de fruto; solo hubo semilla viable en los frutos de polinización cruzada intra-específica (12.3%) y polinización cruzada inter-específica (11.3 a 12.3%). La polinización de las especies estudiadas fue cruzada. E. perle y E. runyonii no pueden fungir como hembras por no formar semillas viables.
... Echeveria species are succulent species that belong to the Crassulaceae family which has a worldwide distribution with over 1,500 species with 33 genera and has been characterized due to its rosette succulent leaves (Jimeno et al. 2013). Because of its easy propagation and beauty of its leaf rosettes and colorful flowers, this genus has been growing in popularity among houseplant and botanical collectors. ...
... The amount of viable seeds was low possibly because the amount of pollen deposited on stigmas was insufficient. These species are likely to generate more offspring if grown in an open area for pollinators, as Charlesworth and Charlesworth (1987), Cruden (1976), Carque et al. (1996), Izco et al. (1998) and Jimeno-Sevilla et al. (2013), pollination of Crassulaceae occurs by insects, birds, wind, and water; the amount of pollen available would be greater. Aunque se reporta que puede haber autopolinización (Charlesworth y Charlesworth, 1987y Cruden, 1976, los resultados obtenidos indican que la polinización en Echeveria fue cruzada, lo cual concuerda con Izco et al. (1998) También Rojas-Aréchiga y Batis (2001) mencionan que la baja viabilidad de semillas se puede deber a que el embrión no se encuentra totalmente desarrollado al momento de su dispersión, por lo que se necesita de un periodo de tiempo para completar su maduración; cabe señalar que en la presente investigación, la semilla fue cosechada cuando los folículos estaban abriendo y las semillas habían madurado. ...
Article
Full-text available
Echeveria, is a representative genus from Crassulaceae to represent 97% of endemic genus; its plants have attractive morphological characteristics for ornamental horticulture. Knowledge of reproductive characteristics are useful for genetic improvement, necessary to be used in pollination and increase the chance of successful fertilization. The objective was to determine pollen viability, stigma receptivity and pollination type of five species of Echeveria, for breeding purposes. The work was done from 2011 to 2013, in Cuernavaca, Morelos. Five species E. agavoides, E. elegans, E. runyonii, E. pumila, E. perle were used. Pollen viability was determined by staining with carmine acetic acid. Stigma receptivity was assessed with the Osborn method; assessment was at 8:00, 10:00, 12:00, 14:00, 16:00, and 18:00 h. For pollination type four modes were performed: 1) self-pollination; 2) emasculating and cover flowers; 3) intra-specific cross-pollination; and 4) inter-specific cross-pollination; fruit set and seed viability was evaluated. E. agavoides had higher percentage of viable pollen (72.7%). Greater receptivity was from 12:00 to 14:00 hrs (94.6 to 98%). In the four modes of pollination 100% of fruit set was obtained; there was only viable seeds in fruits of intra-specific cross pollination (12.3%) and inter-specific cross pollination (11.3 to 12.3%). The pollination of the species studied were crossed E. perle and E. runyonii can not serve as females by not forming viable seeds.
Article
The Crassulaceae family is the most representative of Mexico due to the high endemism of most of its species and to its historical-cultural significance. They are prized and valued on the international market, causing an intense and illegal harvest and sacking of plants, fruits and seeds, with the purpose of selling and recording them in other countries. Morphological characteristics are used to study genetic diversity, to identify cultivated plants and the method of molecular characterization measures genetic variability and diversity with the purpose of conservation and protection of genetic resources. On that basis, the objective of this research work was the morphological and molecular characterization by RAPD (Random Amplified Polymorphic DNA) of twelve species of the Crassulaceae family. Twelve species of the family Crassulaceae were studied: Echeveria runyonii, E. perle, E. agavoides, E. pumila var. glauca x E. Walther., E. elegans, E. pulvinata, E. derembergii, E. setosa, Pachyphytum oviferum, Sedum clavatum, S. nussbaumerianum, and S. palmeri, which are endemic species. For morphological characterization, some characteristics used for plant description of some species from the Crassulaceae family were employed. Molecular characterization was performed by RAPD. Data were processed using the Numerical Taxonomic and Multivariate Analysis System (NTSYSpc 2.1). Quantitative characters separated the twelve species into five groups according to the cluster analysis. Six groups were obtained with the RAPD analysis. The most genetically similar species were: E. runyonii and E. derembergii, indicating more genetic crossing possibilities for interspecific hybridization.
Article
Full-text available
The pollination biology ofCrassula fascicularisLam. (Crassulaceae) was studied at Bain’s Kloof, South Africa. No diurnal visitors to the flowers were observed, but geometrid moths carryingC. fascicularis pollen on their proboscides were caught in a light trap between 20:30 and 04:00. Nectar is secreted in the afternoon and evening, reaching a maximum volume when the moths are active. Scent production almost ceases at midday and then gradually reaches peak intensity around midnight. The floral features of C. fascicularis are compared with those of the related speciesCrassula coccinea L. which is pollinated by butterflies.
Article
Full-text available
During the ongoing studies of the Crassulaceae family for the Flora of Veracruz (Mexico), we found two new species of Crassulaceae (Echeveria uxorium and Sedum jarocho), and eight new records for the state: Crassula connata var. connata, Echeveria bifida, E. coccinea, E. halbingeri, Sedum corynephyllum, S. ebracteatum, S. guatemalense, and Villadia patula. Data on the distribution and habitat of each species are given.
Article
Full-text available
We investigated the reproductive biology of the rare and endangered plant, Dudleya multicaulis at five separate sites, three natural and two mitigation sites. We employed dawn to dusk observations to determine the spectrum of pollinators visiting D. multicaulis, took pollen samples from visitors to determine floral constancy, sampled nectar to determine volume produced per flower, examined the number of flowers per inflorescence, the number of those flowers that produced seed, and total seed set to determine reproductive output, completed seed germination tests to determine viability, and transplanted germinated seedlings from Petri dishes to soil to determine how well seedlings survive transplanting. Dudleya multicaulis was visited by flower beetles, native and European honey bees, flies, and a variety of other insects. Nectar production per flower averaged 0.12 µl. Bees averaged 99% floral constancy to D. multicaulis. Reproductive output measured by flower production and fruit/seed set were not significantly different among sites. Among all populations, the average fruit set ranged from 86.9 to 94.4%. The large fruit set coupled with the diversity of floral visitors suggests that D. multicaaulis is not pollinator limited. Data suggest that D. multicaulis is capable of self-pollination in absence of vectors. Seed germination and transplanted seedling survival did not differ significantly among sites. Results suggest that sowing seed may be better for plant establishment rather than transplanting when mitigation is necessitated.
Article
Full-text available
Most of the Piedmont Physiographic Province of the southeastern United States is covered with mixed mesophytic forest of oaks, hickories, and pines. Within this "sea", however, are "islands" of exposed granite and gneiss. A characteristic, and largely endemic, assemblage of plants has adapted to the environmental extremes that bare rock provides by strongly altering their morphology, physiology, and life history. With respect to their reproductive ecology, however, these plants appear very similar to their congeners and to the Piedmont flora as a whole. Except for ant-pollinated Diamorpha smallii, most species show the expected range of pollen vectors, including wind, bees, flies, butterflies, moths and one species of hummingbird. Fruit and/or seed dispersal appears to be highly localised and effected primarily by wind and water. If anything, most species appear to possess adaptations against long-distance dispersal, which would carry propagules into the inhospitable matrix of oak-hickory-pine forest. Mating systems are variable, including examples of both self-compatible and self-incompatible taxa. Consistent with the expectation of low gene flow between populations on isolated outcrops, genetic data show strong differentiation and suggest the potential for genetic drift and/or natural selection to result in divergence. Some of the endemic species on granite outcrops have originated by allopolyploidy, whereas others appear to represent products of more gradual divergence in geographical isolation. There is reason to believe that some weedy species of early successful sites were originally restricted to granite outcrops and spread more recently to sites disturbed by human activities.
Article
Observations made in a garden in Lanzarote, Canary Islands, in June 2009 of Atlantic lizards (Gallotia atlantica atlantica) on the inflorescences of Aeonium lancerottense (Crassulaceae) are reported. These reptiles may be acting as pollinators of this endemic plant.
Article
It is still unknown what exact role interspecific gene flow and reticulate patterns of gene transfer may play in adaptive radiations. To contribute to a better understanding of gene flow in a morphologically diverse and species-rich lineage, we investigated pollen transfer in the adaptively radiated Macaronesian Crassulaceae-Sempervivoideae. We aimed at comparing pollinator spectra and pollen transfer rates among sympatric species of Aeonium. Field studies were conducted on Tenerife (Canary Islands) including pollinator observations and estimations of pollen transfer using fluorescent dye powder as pollen analogue. Our results indicate an overlap in visiting insects among four sympatric species pairs of Aeonium. However, our dye experiments indicate that on an average about 95% of the detected pollen transfer was infraspecific. Only a small proportion of interspecific pollen transfer could be recorded. We explain these outcomes by specific pollinator behaviour such as floral preference and constancy during a foraging bout. This may be linked to different reward regimes of the studied Aeonium species.
Article
Formica schaufussi, a medium-sized ant common throughout the Piedmont and Coastal Plain of the southeastern United States, has been observed in association with Diamorpha smallii, a self-incompatible annual endemic to granite outcrops in the Southeast, over a 6-yr period. Observations of ants collected on the flowers show large numbers of the sticky pollen grains adhering to hairs and indentations primarily on the thoraces of the ants. Though small native bees and flies are frequent and sometimes effective pollinators, it is highly unlikely that the monotypic genus Diamorpha coevolved with the introduced honeybee, as has been suggested. Characteristics indicative of an "ant-pollination syndrome" include occurrence in hot, dry habitats, a high density of very small plants bearing overlapping inflorescences at a uniform height, and low seed number, pollen volume, and nectar quantity.
Article
Little is known about the reproductive biology of the Crassulaceae. We studied a population of Echeveria gibbiflora in the Pedregal de San Angel ecological preserve in Mexico City, Mexico. Each flower is open and producing nectar 7 to 8 days. On the days of maximum nectar production (flowers 4-6 days old) an average of 14.5 mul accumulates in a flower per day. The maximum rate of nectar production is between 0700 and 0900 hours. The average sugar concentration in the nectar is 43.7%. In a given flower, pollen is exposed and the stigmas are receptive at the same time. The average natural fruit-set-and seed-set are 56.6% and 35.5%, respectively. The pollen-ovule ratio is 124, and the plants are fully self-compatible. The flowers are pollinated by only one species of hummingbird (Cynanthus latirostris) and are never visited by insects. Pollen movement is very limited (mean of pollinator flight distances = 0.72 m, mean distance fluorescent dyes = 0.92 m). Seed dispersion is by gravity and wind, and also is very limited (an average of 1.07 m). The total genetic neighborhood area is 15 m2 to 17 m2, producing a neighborhood effective population size (N(b)) of 5.01 to 39.7 individuals. This is a very small N(b), indicating that genetic drift may be a dominant force in the evolution of this species.
Article
1. An experimental approach, manually pollinating all the flowers of individual plants, was used to measure the effect of pollen limitation on female fecundity of the hummingbird-pollinated perennial shrub Echeveria gibbiflora in the ecological preserve of Pedregal de San Angel around México City, México. Eleven randomly selected plants were manually over-pollinated in all their flowers and another 11 were left to be freely visited by natural pollinators.2. Manually pollinated plants produced significantly more fruit and seeds than control plants (1·38 and 1·74 times, respectively). There was no change in average mass of fruits.3. Considering individual fruit production per plant sampled three times in one season, decreases in fruit mass and average seeds per fruit were observed within the same reproductive season for both treatments. For the manually pollinated plants, from the start to the end of the reproductive season, seed set decreased 55·9%; while in control plants seed set decreased 33·4% in the same period. For both treatments, average fruit mass decreased 26%.4. Vegetative growth was not significantly different between control and experimental plants but hand-pollinated plants showed a smaller reproduction probability for the following year.5. It is concluded that female fecundity in E. gibbiflora is limited by pollen early in the reproductive season and by resources in the middle and the end of the season.