Lacandonia

Last updated

Lacandonia
Lacandonia.PNG
Flower of Lacandonia schismatica
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Pandanales
Family: Triuridaceae
Genus: Lacandonia
E.Martínez & Ramos

Lacandonia is a mycoheterotrophic plant that contains no chlorophyll and has the unusual 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 exceptions of Trithuria and on occasion the related Triuris brevistylis . [1]

Contents

Description

Lacandonia is a small, mycoheterotrophic plant that lacks chlorophyll and has a rhizomatous growth pattern. This genus exhibits racemous inflorescences and small, bract-like leaves. The flowers are actinomorphic and are considered "inverted" from the typical flower arrangementusually 3 (but sometimes two to four) malestamens are in the center of the flower, surrounded by 60 to 80 female pistils. This characteristic, where the positions of the androecium and the gynoecium are reversed, is unique in the known and described taxa of the flowering plants. [2] [3] [4]

Flowers of Lacandonia are bisexual; they 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. [5] 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. [3] Owing to the preathesis cleistogamy, a form of autogamy (self-pollination), the known population of L. schismatica lacks genetic variability and has a high incidence of homozygosity. [6] The haploid chromosome number of this species is n = 9. [4]

Taxonomy and botanical history

Lacandonia is a genus of mycoheterotrophic plants in the Triuridaceae, with very unusual inverted floral morphology. It has two known species: [7] [8]

Lacandonia 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 Triuridales. [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 family. [2] The APG II system transferred the genus to the Triuridaceae and placed that family in the Pandanales. [10] Lacandonia was long considered monotypic, until the discovery of a second species, Lacandonia brasiliana, in Guaribas Biological Reserve in Brazil in 2012. [11]

Evolution

The difficulty expressed in 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 Goldschmidt'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 was the origin of this species. [4]

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, in the same way as that of 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, in which L. schismatica is restricted to the warmer lowlands and T. brevistylis has a distribution in the cooler highlands.[ how? ]

Related Research Articles

<span class="mw-page-title-main">Stamen</span> Male organ of a flower

The stamen is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium.

<span class="mw-page-title-main">Pandanales</span> Order of monocot flowering plants

Pandanales, the pandans or screw-pines, is an order of flowering plants placed in the monocot clade in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web systems. Within the monocots Pandanales are grouped in the lilioid monocots where they are in a sister group relationship with the Dioscoreales. Historically the order has consisted of a number of different families in different systems but modern classification of the order is based primarily on molecular phylogenetics despite diverse morphology which previously placed many of the families in other groupings based on apparent similarity. Members of the order have a subtropical distribution and includes trees, shrubs, and vines as well as herbaceous plants. The order consists of 5 families, 36 genera and about 1,610 species.

<span class="mw-page-title-main">Plant reproductive morphology</span> Parts of plant enabling sexual reproduction

Plant reproductive morphology is the study of the physical form and structure of those parts of plants directly or indirectly concerned with sexual reproduction.

<span class="mw-page-title-main">Gynoecium</span> Female organs of a flower

Gynoecium is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of pistils and is typically surrounded by the pollen-producing reproductive organs, the stamens, collectively called the androecium. The gynoecium is often referred to as the "female" portion of the flower, although rather than directly producing female gametes, the gynoecium produces megaspores, each of which develops into a female gametophyte which then produces egg cells.

<span class="mw-page-title-main">Hernandiaceae</span> Family of flowering plants

The Hernandiaceae are a family of flowering plants (angiosperms) in the order Laurales. Consisting of five genera with about 58 known species, they are distributed over the world's tropical areas, some of them widely distributed in coastal areas, but they occur from sea level to over 2000 m.

<span class="mw-page-title-main">Sabiaceae</span> Family of flowering plants

Sabiaceae is a family of flowering plants that were placed in the order Proteales according to the APG IV system. It comprises three genera, Meliosma, Ophiocaryon and Sabia, with 66 known species, native to tropical to warm temperate regions of southern Asia and the Americas. The family has also been called Meliosmaceae Endl., 1841, nom. rej.

<span class="mw-page-title-main">Trochodendraceae</span> Family of flowering plants

Trochodendraceae is the only family of flowering plants in the order Trochodendrales. It comprises two extant genera, each with a single species along with up to five additional extinct genera and a number of extinct species. The living species are native to south east Asia. The two living species both have secondary xylem without vessel elements, which is quite rare in angiosperms. As the vessel-free wood suggests primitiveness, these two species have attracted much taxonomic attention.

<i>Degeneria</i> Genus of flowering plants

Degeneria is a genus of flowering plants endemic to Fiji. It is the only genus in the family Degeneriaceae. The APG IV system of 2016, recognizes this family, and assigns it to the order Magnoliales in the clade magnoliids.

<span class="mw-page-title-main">Triuridaceae</span> Family of flowering plants

Triuridaceae are a family of tropical and subtropical flowering plants, including nine genera with a total of approximately 55 known species. All members lack chlorophyll and are mycoheterotrophic. The heterotrophic lifestyle of these plants has resulted in a loss of xylem vessels and stomata, and a reduction of leaves to scales.

<span class="mw-page-title-main">Pseudanthium</span> Type of inflorescence, clusters of flowers

A pseudanthium is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, composite flowers, or capitula, which are special types of inflorescences in which anything from a small cluster to hundreds or sometimes thousands of flowers are grouped together to form a single flower-like structure. Pseudanthia take various forms. The real flowers are generally small and often greatly reduced, but the pseudanthium itself can sometimes be quite large.

<i>Trithuria</i> Genus of aquatic plants

Trithuria is a genus of small ephemeral aquatic herb that represent the only members of the family Hydatellaceae found in India, Australia, and New Zealand. All of the 13 formally characterized species of Trithuria are found in Australia, with the exception of T. inconspicua and T. konkanensis, which are found in New Zealand and India, respectively. Until DNA sequence data and a reinterpretation of morphology proved otherwise, these plants were believed to be monocots related to the grasses (Poaceae). They are unique in being the only plants besides two members of Triuridaceae in which the stamens are in the center of the flower while the pistils surround them; in Hydatellaceae the resulting 'flowers' may instead represent condensed inflorescences or non-flowers.

Triuris is a genus in the family Triuridaceae. It consists of species that are small and achlorophyllous, occurring in tropical Mexico, Guatemala, and northern South America.

<i>Lacandonia schismatica</i> Species of flowering plant

Lacandonia schismatica is a species of mycoheterotrophic plant in the Triuridaceae. It is endemic to Lacandon Jungle in the State of Chiapas in southern Mexico. It is known from very few populations and is considered endangered by the researchers who investigate this species. It, and its recently discovered relation Lacandonia braziliana, are the only known flowering plants which in its natural population has a spatial inversion of the reproductive floral whorls : the 2 to 4 stamens are positioned centrally within the flower, and the 60 to 80 carpels arranged in a ring around them. Perhaps even more remarkable than the reversed positions of male and female parts is the unique mode of pollination. The pollen grain never leaves the anther, but sends the pollen tube backwards through the length of the stamen, across the receptacle and then into the pistil from below.

<span class="mw-page-title-main">Whorl (botany)</span> Arrangement of plant parts around the stem

In botany, a whorl or verticil is a whorled arrangement of leaves, sepals, petals, stamens, or carpels that radiate from a single point and surround or wrap around the stem or stalk. A leaf whorl consists of at least three elements; a pair of opposite leaves is not called a whorl.

<span class="mw-page-title-main">Monotropoideae</span> Subfamily of flowering plants in the heather family Ericaceae

Monotropoideae, sometimes referred to as monotropes, are a flowering plant subfamily in the family Ericaceae. Members of this subfamily are notable for their mycoheterotrophic and non-photosynthesizing or achlorophyllous characteristics.

<span class="mw-page-title-main">Solanaceae</span> Family of flowering plants that includes tomatoes, potatoes and tobacco

The Solanaceae, or the nightshades, are a family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spices, weeds, and ornamentals. Many members of the family contain potent alkaloids, and some are highly toxic, but many—including tomatoes, potatoes, eggplant, bell and chili peppers—are used as food. The family belongs to the order Solanales, in the asterid group and class Magnoliopsida (dicotyledons). The Solanaceae consists of about 98 genera and some 2,700 species, with a great diversity of habitats, morphology and ecology.

<span class="mw-page-title-main">Pentapetalae</span> Group of eudicots known as core eudicots

In phylogenetic nomenclature, the Pentapetalae are a large group of eudicots that were informally referred to as the "core eudicots" in some papers on angiosperm phylogenetics. They comprise an extremely large and diverse group that accounting about 65% of the species richness of the angiosperms, with wide variability in habit, morphology, chemistry, geographic distribution, and other attributes. Classical systematics, based solely on morphological information, was not able to recognize this group. In fact, the circumscription of the Pentapetalae as a clade is based on strong evidence obtained from DNA molecular analysis data.

Sexual selection is described as natural selection arising through preference by one sex for certain characteristics in individuals of the other sex. Sexual selection is a common concept in animal evolution but, with plants, it is oftentimes overlooked because many plants are hermaphrodites. Flowering plants show many characteristics that are often sexually selected for. For example, flower symmetry, nectar production, floral structure, and inflorescences are just a few of the many secondary sex characteristics acted upon by sexual selection. Sexual dimorphisms and reproductive organs can also be affected by sexual selection in flowering plants.

Barbara Ambrose is a botanist working in the field of Plant Evolutionary Developmental Biology (Evo-Devo). As the Director of Laboratory Research at the New York Botanical Garden, Ambrose is a prolific scholar and leader and mentor in her field who is interested in patterns in plant diversity on macro and micro scales.

<span class="mw-page-title-main">Floral morphology</span>

In botany, floral morphology is the study of the diversity of forms and structures presented by the flower, which, by definition, is a branch of limited growth that bears the modified leaves responsible for reproduction and protection of the gametes, called floral pieces.

References

  1. Esteban Martinez and Clara Hilda Ramos Lacandoniaceae (Triuridales): Una Nueva Familia de Mexico. Ann. of the Missouri Botanical Garden, Vol. 76, No. 1 (1989), pp. 128-135
  2. 1 2 Vázquez-Santana, S., Engleman, E. M., Martínez-Mena, A., and Márquez-Guzmán, J. (1998). Ovule and seed development of Lacandonia schismatica (Lacandoniaceae). American Journal of Botany, 85(3): 299-304.
  3. 1 2 Márquez-Guzmán, J., Vázquez-Santana, S., Engleman, E. M., Martínez-Mena, A., and Martínez, E. (1993). Pollen development and fertilization in Lacandonia schismatica (Lacandoniaceae). Annals of the Missouri Botanical Garden , 80(4): 891-897.
  4. 1 2 3 Davidse, G. and Martínez, E. (1990). The chromosome number of Lacandonia schismatica (Lacandoniaceae). Systematic Botany, 15(4): 635-637.
  5. Barbara A. Ambrose, Silvia Espinosa-Matías, Sonia Vázquez-Santana, Francisco Vergara-Silva, Esteban Martínez, Judith Márquez-Guzmán and Elena R. Alvarez-Buylla. (2006). Comparative developmental series of the Mexican triurids support a euanthial interpretation for the unusual reproductive axes of Lacandonia schismatica (Triuridaceae). American Journal of Botany, 93(1): 15-35.
  6. Coello, G., Escalante, A., and Soberon, J. (1993). Lack of genetic variation in Lacandonia schismatica in its only known locality. Annals of the Missouri Botanical Garden, 80(4): 898-901.
  7. Kew World Checklist of Selected Plant Families
  8. Davidse, G. & al. (eds.) (1994). Flora Mesoamericana 6: 1-543. Universidad Nacional Autónoma de México, México, D.F.
  9. Martínez, E. and Ramos, C. H. (1989). Lacandoniaceae (Triuridales): Una neuva familia de Mexico. Annals of the Missouri Botanical Garden, 76(1): 128-135.
  10. The Angiosperm Phylogeny Group. (2003). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society, 141(4): 399-436.
  11. Melo, Aline; Alves, Marccus Vinicius da Silva (2012). "The discovery of Lacandonia (Triuridaceae) in Brazil". Phytotaxa. 40: 22–24, f. 1–2. doi:10.11646/phytotaxa.40.1.3.