Lacandonia
Encyclopedia
Lacandonia schismatica is the sole species of the genus Lacandonia and is endemic to the Lacandon Jungle
in the Mexican
state of Chiapas
. It is known from very few populations and is considered endangered by the researchers who investigate this species. L. schismatica is a saprophytic species that contains no chlorophyll
and has the unique characteristic of inverted positions of the male (androecium) and female (gynoecium
) floral parts, something that had not been seen in any other plants with the occasional exception of some individuals of the related Triuris brevistylis.
, mycotroph
ic habit. This species exhibits racemous
inflorescence
s and bract
-like leaves. The flowers are actinomorphic and are considered "inverted" from the typical flower arrangement–usually 3 (but sometimes two to four) stamen
s are in the center of the flower surrounded by 60 to 80 pistils. This characteristic where the position of the androecium and the gynoecium
are inverted is unique in the known and described taxa of flowering plant
s.
Flowers of L. schismatica are bisexual
and self-pollinate and fertilize before the flower opens (preanthesis cleistogamy
). They are true flowers as opposed to pseudanthia as had been suggested earlier in the literature. The three-celled pollen
grains germinate within the anthers and the pollen tube
grows through the receptacle to reach the ovaries
. L. schismatica can be found flowering year-round when its environment is moist enough, with a particularly active flowering period in November and December. Owing to the prenathesis cleistogamy, a form of autogamy (self-pollination), the known population of L. schismatica lacks genetic variability and has a high instance of homozygosity. The haploid chromosome number of this species is n = 9.
. In 1991, Traudel Rübsamen-Weustenfeld suggested that L. schismatica be included in the family Triuridaceae
within the genus Sciaphila
, Peltophyllum, or its own genus. Another study in 1998 presented data that supports the separation of L. schismatica into its own, monotypic
family. The APG II system
transferred the genus to the Triuridaceae
and placed that family in the Pandanales
.
's "hopeful monsters", meaning that the inverted floral morphology could have arisen from a macromutation in the genes that control floral development. It is also possible that chromosomal repatterning, also known as chromosomal rearrangement, was the origin of this species.
Since the original description and early work on this species in the 1990s, other field work has revealed some instances of L. schismatica flowers that were unisexual. The closely related species Triuris brevistylis was discovered to be mostly dioecious
but a few individuals were located that had bisexual flowers with the flower arrangement inverted, just like that of the normal L. schismatica flowers. This discovery led the authors of the study to conclude that the inverted floral morphology evolved before L. schismatica and T. brevistylis diverged. Isolated populations during the Quaternary Period (around five million years ago) when temperatures in the Lacandon lowland rainforest were six to eight °C
(10.8 to 14.4 °F
) cooler than today. This hypothesis is supported by the geographic distribution where L. schismatica is restricted to the warmer lowlands and T. brevistylis has a distribution in the cooler highlands.
Lacandon Jungle
The Lacandon Jungle is an area of rainforest which stretches from Chiapas, Mexico into Guatemala and into the southern part of the Yucatán Peninsula. The heart of this rainforest is located in the Montes Azules Biosphere Reserve in Chiapas near the border with Guatemala in the Montañas del Oriente...
in the Mexican
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
state of Chiapas
Chiapas
Chiapas officially Estado Libre y Soberano de Chiapas is one of the 31 states that, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 118 municipalities and its capital city is Tuxtla Gutierrez. Other important cites in Chiapas include San Cristóbal de las...
. It is known from very few populations and is considered endangered by the researchers who investigate this species. L. schismatica is a saprophytic species that contains no chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
and has the unique characteristic of inverted positions of the male (androecium) and female (gynoecium
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
) floral parts, something that had not been seen in any other plants with the occasional exception of some individuals of the related Triuris brevistylis.
Description
L. schismatica is a small saprophytic plant that lacks chlorophyll and has a rhizomatousRhizome
In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...
, mycotroph
Mycotroph
A mycotroph is a plant that gets all or part of its carbon, water, or nutrient supply through symbiotic association with fungi. The term can refer to plants that engage in either of two distinct symbioses with fungi:...
ic habit. This species exhibits racemous
Raceme
A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
s and bract
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
-like leaves. The flowers are actinomorphic and are considered "inverted" from the typical flower arrangement–usually 3 (but sometimes two to four) stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s are in the center of the flower surrounded by 60 to 80 pistils. This characteristic where the position of the androecium and the gynoecium
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
are inverted is unique in the known and described taxa of flowering plant
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
s.
Flowers of L. schismatica are bisexual
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
and self-pollinate and fertilize before the flower opens (preanthesis cleistogamy
Cleistogamy
Cleistogamy or automatic self-pollination describes the trait of certain plants to propagate by using non-opening, self-pollinating flowers...
). They are true flowers as opposed to pseudanthia as had been suggested earlier in the literature. The three-celled pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
grains germinate within the anthers and the pollen tube
Pollen tube
The pollen tubes is the male gametophyte of seed plants that acts as a conduit to transport the male sperm cells from the pollen grain, either from the stigma to the ovules at the base of the pistil, or directly through ovule tissue in some gymnosperms .After pollination, the pollen tube...
grows through the receptacle to reach the ovaries
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
. L. schismatica can be found flowering year-round when its environment is moist enough, with a particularly active flowering period in November and December. Owing to the prenathesis cleistogamy, a form of autogamy (self-pollination), the known population of L. schismatica lacks genetic variability and has a high instance of homozygosity. The haploid chromosome number of this species is n = 9.
Distribution and habitat
L. schismatica is known from several small populations at altitudes around 200 m (656 ft) in the Lacandon Jungle, a rainforest in southeastern Mexico. It grows in shady sites within this rainforest. Gerrit Davidse and Esteban Martínez noted in 1990 how the plants are "extremely localized and highly endangered" due to encroaching habitat conversion to cattle pasture. They also explain that the species is difficult to cultivate and thus encourage other scientists to study this unique organism's biology before it can no longer be found in the wild.Taxonomy and botanical history
L. schismatica was first described by Martínez and Clara Hilda Ramos in 1989, who placed the species in its own family, Lacandoniaceae, which itself was placed in the TriuridalesTriuridales
Triuridales was an order of flower plants that was used in the well-known Cronquist system, in the subclass Alismatidae, with this circumscription:* order Triuridales*: family Petrosaviaceae*: family Triuridaceae...
. In 1991, Traudel Rübsamen-Weustenfeld suggested that L. schismatica be included in the family Triuridaceae
Triuridaceae
Triuridaceae is a family of flowering plants. Such a family has been recognized by relatively few taxonomists.The APG II system, of 2003, does recognize such a family and places it in the order Pandanales, in the clade monocots...
within the genus Sciaphila
Sciaphila
Sciaphila is a genus of flowering plants in the family Triuridaceae....
, Peltophyllum, or its own genus. Another study in 1998 presented data that supports the separation of L. schismatica into its own, monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
family. The APG II system
APG II system
The APG II system of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Group. It was a revision of the first APG system, published in 1998, and was superseded in 2009...
transferred the genus to the Triuridaceae
Triuridaceae
Triuridaceae is a family of flowering plants. Such a family has been recognized by relatively few taxonomists.The APG II system, of 2003, does recognize such a family and places it in the order Pandanales, in the clade monocots...
and placed that family in the Pandanales
Pandanales
Pandanales is an order of flowering plants, with a pantropical distribution.The APG III system places the Pandanales in the monocots. Both the APG III and APG II systems include five families in this order:* Cyclanthaceae* Pandanaceae* Stemonaceae...
.
Evolution
The difficulty expressed in correctly placing the species in the proper family is due to the unique floral morphology. How this inverted position of the androecium and gynoecium evolved is unknown, but some studies have posed hypotheses. Davidse and Martínez suggested that L. schismatica could be one of Richard GoldschmidtRichard Goldschmidt
Richard Benedict Goldschmidt was a German-born American geneticist. He is considered the first to integrate genetics, development, and evolution. He pioneered understanding of reaction norms, genetic assimilation, dynamical genetics, sex determination, and heterochrony...
's "hopeful monsters", meaning that the inverted floral morphology could have arisen from a macromutation in the genes that control floral development. It is also possible that chromosomal repatterning, also known as chromosomal rearrangement, was the origin of this species.
Since the original description and early work on this species in the 1990s, other field work has revealed some instances of L. schismatica flowers that were unisexual. The closely related species Triuris brevistylis was discovered to be mostly dioecious
Dioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...
but a few individuals were located that had bisexual flowers with the flower arrangement inverted, just like that of the normal L. schismatica flowers. This discovery led the authors of the study to conclude that the inverted floral morphology evolved before L. schismatica and T. brevistylis diverged. Isolated populations during the Quaternary Period (around five million years ago) when temperatures in the Lacandon lowland rainforest were six to eight °C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(10.8 to 14.4 °F
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
) cooler than today. This hypothesis is supported by the geographic distribution where L. schismatica is restricted to the warmer lowlands and T. brevistylis has a distribution in the cooler highlands.