Dwarf olive tree
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Dwarf olive tree ( Cneorum tricoccon ) |
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The dwarf olive tree ( Cneorum tricoccon ), also Dreibeeriger Zeiland called, is a plant belonging to the family of Rutaceae (Rutaceae). In older literature (e.g. Engler 1912), however , the genus Cneorum is listed as a separate family of dwarf olives (Cneoraceae).
distribution
Cneorum tricoccon is common in the western Mediterranean . In addition to being distributed on all the Balearic Islands , the plant is also found in the east and south of the Iberian Peninsula as well as in south-east France, Sardinia, Liguria and Tuscany (Straka et al. 1976; Traveset 1995b). A typical location is the maquis near the coast , in which the plant usually occurs from 50–500 m above sea level, up to a maximum of 1000 m above sea level (Traveset 2002, Tébar & Llorens 1997).
designation
The species is mentioned for the first time in Tournefort (1700), who coined the generic name Chamaelea ( Chamaelea tricoccos ) Tournefort, which was later changed to Cneorum L. by Carl von Linné (1753) .
Urban (1918) describes a plant species that he calls Cubincola trimera Urban and incorrectly classifies it as Euphorbiaceae . This species, renamed Cneorum trimerum (Urban) Chodat by Chodat (1921) and assigned to the Cneoraceae, grows endemically in the Sierra Maestra in the east of the island of Cuba (Lobreau-Callen et al. 1978, Lobreau-Callen & Jérémie 1986) . However, this seems to be an ecotype of Cneorum tricoccon (Lobreau-Callen & Jérémie 1986), although, according to Carlquist (1988), there are significant differences in the wood structure of Cneorum tricoccon and Cneorum trimenum , which he attributes not only to location adaptations .
If Cneorum trimenum is not a separate species, the range of Cneorum tricoccon would have to be expanded to include Cuba. In any case, both species are closely related and their peculiar disjunction is astonishing, because Cneorum tricoccon is considered a Mediterranean relic shrub that is said to have developed under tropical conditions during the early Tertiary (Traveset 1995a), at a time when North America and Eurasia were already were separated. Since the seeds of Cneorum tricoccon are not spread by birds but by lizards (Traveset 1995a, 1995b, Riera et al. 2002), long-distance transport of the diaspores is difficult to imagine.
Lobreau-Callen & Jérémie (1986) describe the locations of Cneorum ( Cneorum tricoccon or Cneorum trimerum ) in Cuba as undisturbed, difficult to reach and rich in endemics . Therefore, they assume an autochthonous species and reject the alternative explanation that the plant was introduced into Cuba in the course of the introduction of sheep in the 18th century. The only explanation that would remain is an origin of the species before the separation of the continents .
Another species of the genus Cneorum , originally described under the name Cneorum pulverulentum Vent. , was later transferred to its own genus Neochamaelea (Engl.) Erdtman as Neochamaelea pulverulenta (Vent.) Erdtman . It only occurs in the Canary Islands . It differs from the more widespread species Cneorum tricoccon in particular due to pollen characteristics .
description
Habit and leaf
Cneorum tricoccon is an almost hairless, evergreen shrub that rarely reaches heights of more than 1 m, but in exceptional cases it can also reach heights of around 2 m (Riera et al. 2002). The alternate leaves are sessile, entire, narrowly lanceolate. There are no stipules (Van Tieghem 1899, Straka et al. 1976). The leathery texture of the leaves and their somewhat rolled-up leaf blades can be seen as a xeromorphic adaptation.
Flowers and inflorescence
The small, yellow, andromonözisch distributed flowers are either individually axillary or, more rarely, in three-flowered axillary cones (Straka et al. 1976, Tébar & Llorens 1997, Caris et al. 2006). The flower formula is K3 C3 A3 (G3). Occasionally, however, tetrameric flowers or those with only one or two stamens and carpels appear . Trimere flowers are an exception in the Rutaceae, and since the sister species Cneorum pulverulentum forms four-fold flowers, the trimery is probably a reduction. However, there is no evidence of a fusion of leaf primordia during flower ontogenesis (Caris et al. 2006). Another derived feature in the flower area is the reduction to a stamen circle. The sepals , the longer, lanceolate petals as well as the episepal, dithecal and tetrasporangiate stamens stand free, the latter being inserted in three dimples of a massive disc bulge ( androgynophore ) (Daumann 1974, Caris et al. 2006). The gynoceum consists of a post-genital syncarpic, triple and superior ovary with a central-angled placentation , which ends in a straight, long, ontogenetically late-developing style with three flat oblong-egg-shaped scars (Straka et al. 1976, Caris et al. 2006). The carpels are divided into two compartments by a false, often incomplete septum, each with a crassinucellate, anatropic and bitegmic ovule (Engler 1912, Straka et al. 1976, Boesewinkel 1984). As the seeds ripen, the shape changes from anatropic to strongly kampylotropic (Boesewinkel 1984). In addition to the already mentioned disc nectarium, in which the nectar is continuously excreted via stomata which are distributed over the entire surface of the androgynophore, Van Tieghem (1899) suspects a septal nectarium in the flower of Cneorum tricoccon . Within the ovary there are three septal cleft spaces that open outwards in the base of the style. Van Tieghem calls these crevices septal nectaries and he describes nectar secretion from the epidermal cells lining the crevices (Van Tieghem 1899). Such a secretion could not be confirmed by experiments by Daumann (1974), who could only prove an intensive nectar excretion of the disc nectarium. Caris et al. (2006) assume that the clefts are the result of incomplete syncarpy. There are similar septal fissures in Ruta chalepensis L. (as Ruta bracteosa DC. Prodr .; Schmid 1985) and Koelreuteria paniculata Laxm. from the closely related Sapindaceae (Ronse de Craene et al. 2000, Caris et al. 2006). Furthermore, typical of the flower of tricoccon Cneorum three lobed projections, which in the transition region between ovary and stylus are formed and are equipped with the Androgynophor stomata (Caris et al. 2006).
fruit
When the fruit ripens from December to July (flowering between November and June), a reddish-colored fleshy fruit develops, which breaks down into three drupe-like partial fruits (Straka et al. 1976, Traveset 1995b, Caris et al. 2006). According to Caris et al. (2006) the septal columns play a role.
pollination
The pollination takes place by different Hymenoptera . In particular, Daumann (1974) mentions Apis mellifera L. ( honey bee ), Ceratina cucurbitina ROSSI., Ceratina cyanea K., Halictus gemmens DOURS., Halictus smeathmanellus K. and Xylocopa violacea L. as pollinators in France. On Cabrera , where Apis mellifera does not occur, Plagiolepis pygmaea occurs as an additional pollinator (Traveset 2002).
Pollen and chromosome number
The pollen is tricolorate and 35 × 29 µm in size (Erdtman 1952) and the number of chromosomes is 2n = 36 according to Goldblatt (1976).
Seed dispersal
Cneorum tricoccon is saurochoric and the two lizards Podarcis lilfordi and Podarcis pityusensis (Lacertidae) are known to spread. The fruits are eaten by the lizards. After the intestinal passage, the seeds germinate, so that one has to speak of an endozoochory or endosaurochory (Traveset 1995a, 1995b, Riera et al. 2002). Since around 250 AD, i.e. after humans introduced weasels and snakes to the Balearic Islands, the lizard species mentioned are considered to be extinct on Mallorca and Menorca, so that other distribution options must exist. According to Traveset (1995b), the pine marten ( Martes martes ) and gorse cat ( Genetta genetta ), later introduced as weasels and snakes, are responsible for the distribution. In contrast to the lizards, however, the spreading by the carnivorous mammals does not seem to be very effective because the mammals, unlike the lizards, do not take all the fruit from the plant. In Menorca there is only a small population of about 50 specimens of Cneorum tricoccon . Fossil finds, however, indicate a greater distribution in earlier times. In the course of switching to other distributors, the locations of the plants have apparently also shifted. In contrast to the fossil evidence (lizard as a diffuser), which suggests that the plants spread to the area between sea level up to 500 m above sea level, today the plants can be found at up to 1000 m above sea level (Riera et al. 2002). The reason for this is again given in this context to the martens and gorse cats, which mainly live in higher altitudes.
literature
- FD Boesewinkel: Development of ovule and seed coat in Cneorum tricoccon L. (Cneoraceae). In: Acta Bot. Neerl. Volume 33, No. 1, 1984, pp. 61-70.
- P. Caris, E. Smets, K. De Coster, LP Ronse De Craene: Floral ontogeny of Cneorum tricoccon L. (Rutaceae). In: Plant Systematics and Evolution. Volume 257, 2006, pp. 223-232.
- S. Carlquist: Wood anatomy of Cneoraceae: Ecology, relationships, and generic definition. In: Aliso. Vol. 12, no. 1, 1988, pp. 7-16.
- R. Chodat: Sur un nouveau Cneorum. Le Cneorum trimerum (Urb.) Chodat. In: Bulletin de la Société Botanique, Genéve. ser. 2, Vol. 124, 1921, pp. 23-24.
- E. Daumann: On the question of the occurrence of a septal nectarium in dicotyledons. At the same time a contribution to the flower morphology and pollination ecology of Buxus L. and Cneorum L. In: Preslia. Volume 42, 1974, pp. 97-109.
- Adolf Engler : Syllabus of the plant families. Borntraeger brothers, Berlin 1912, OCLC 465393449 .
- G. Erdtman: Pollen morphology and plant taxonomy - Angiosperms. Almquist and Wiksell, Stockholm 1952, OCLC 1131199960 .
- P. Goldblatt: New or Noteworthy Chromosome Records in the Angiosperms. In: Annals of the Missouri Botanical Garden. Vol. 63, no. 4, 1976, pp. 889-895.
- C. Linnaeus : Species plantarum. 1st edition. Stockholm 1753.
- D. Lobreau-Callen, J. Jérémie: L'espéce Cneorum tricoccon (Cneoraceae, Rutales) représentée á Cuba. Grana 25, 1986, pp. 155-158.
- D. Lobreau-Callen, S. Nilsson, F. Albers, H. Straka: Les Cneoraceae (Rutales): étude taxonomique, palynologique et systématique. Grana 17, 1978, pp. 125-139.
- N. Riera, A. Traveset, O. Garcia: Breakage of mutualisms by exotic species: the case of Cneorum tricoccon L. in the Balearic Islands (Western Mediterranean Sea). In: Journal of Biogeography. Volume 29, 2002, pp. 713-719.
- Ronse de Craene, LP, Smets, E., Clinckemaillie, D .: Floral ontogeny and anatomy in Koelreuteria with special emphasis on monosymmetry and septal cavities. In: Plant Systematics and Evolution. Volume 223, 2000, pp. 91-107.
- R. Schmid: Functional interpretations of the morphology and anatomy of septal nectaries. In: Acta Bot. Neerl. Volume 34, No. 1, 1985, pp. 125-128.
- H. Straka, F. Albers, A. Mondon: The position and structure of the family Cneoraceae (Rutales). In: Contributions to the biology of plants. Volume 52, 1976, pp. 267-310.
- FJ Tébar, L. Llorens: Floral biology of Cneorum tricoccon L. (Cneoraceae): an unknown case of andromonoecy. In: Collect. Bot. Vol. 23, 1997, pp. 105-113.
- JP Tournefort : Institutiones rei Herbariæ. Tomus Primus. Parisiis e typographia regia 1700. (697 pages)
- A. Traveset: Reproductive ecology of Cneorum tricoccon L. (Cneoraceae) in the Balearic Islands. In: Botanical Journal of the Linnean Society. Vol. 117, No. 3, 1995, pp. 221-232.
- A. Traveset: Seed dispersal of Cneorum tricoccon L. (Cneoraceae) by lizards and mammals in the Balearic Islands. In: Acta Oecologica. Volume 16, No. 2, 1995, pp. 171-178.
- A. Traveset: Consequencias de la ruptura de mutualismos planta-animal para la distribución de especies vegetales en las Islas Baleares. In: Revista Chilena de Historia Natural. Volume 75, 2002, pp. 117-126.
- I. Urban : About two Euphorbiaceen genera. In: Reports of the German Botanical Society. Volume 36, 1918, pp. 501-507, panel XVI.
- MP Van Tieghem: Sur les Cnéoracées. In: Annales des Sciences Naturelles Botanique. Ser. 8, No. 9, 1899, pp. 363-369.
Individual evidence
- ^ Cneorum tricoccon at Tropicos.org. In: IPCN Chromosome Reports . Missouri Botanical Garden, St. Louis
Web links
- Entry in Plants for a Future. (engl.)