Diospyros egrettarum is a species of tree endemic to Mauritius and was once a dominant species throughout dry and coastal forests. Due to harvests for timber and firewood in the past the species was reduced to fewer than 10 individuals on the main land. The only viable population remained on Île aux Aigrettes,[2] a coral island off the east coast, where it was able to survive thanks to protective measures, such as the eradication of exotic plants and rats. The tree is named after this Island.
Most characteristic feature of the tree is the white bark of the often multistemmed trees. They form rectangular leathery leaves of dark colour with thick waxy cuticles. This species closest relative is Diospyros leucomelas (and less so Diospyros revaughanii), and it shares with these species a leathery leaf surface, a rounded leaf-base, very short petiole, and short fruits. The forest reaches an average canopy height around 5–8 metres, likely the height is restricted by the shallow depth of soil (seldom>15 cm), the floor is covered by native monarch fern. If undisturbed, the forest is quite resilient to invasive plants.
Detail of the dark, leathery, rectangular leaves
Pale colour of the trunks
The short, compact fruit and seeds
Dissection of Diospyros egrettarum trunk showing the valuable hard, black core.
Large rats predate on fruits and seedlings and might have reduced regeneration in the past. The fruits of the tree are eaten by numerous native and invasive species, such as the Telfair's skink,[3] pink pigeon and Aldabra giant tortoise, all of which benefit the tree by dispersing and enhancing seed growth. New introduced Aldabra giant tortoise[4] help to disperse the seeds [5]
Media related to Diospyros egrettarum at Wikimedia CommonsDiospyros egrettarum is a species of tree endemic to Mauritius and was once a dominant species throughout dry and coastal forests. Due to harvests for timber and firewood in the past the species was reduced to fewer than 10 individuals on the main land. The only viable population remained on Île aux Aigrettes, a coral island off the east coast, where it was able to survive thanks to protective measures, such as the eradication of exotic plants and rats. The tree is named after this Island.
Diospyros egrettarum I.Richardson, 1980 è una pianta della famiglia delle Ebenacee, endemica di Mauritius.[2]
Un tempo molto diffusa sull'isola di Mauritius, questa specie è stata, al pari di molte altre specie di ebano, intensamente sfruttata per la produzione di legname pregiato, e ciò ha fatto sì che la sua presenza sull'isola madre sia riducesse ad una decina di esemplari. L'unica popolazione cospicua si trova sull'Île aux Aigrettes, un isolotto corallino che sorge nei pressi della costa sud-orientale.[1]
Diospyros egrettarum è un arbusto o piccolo albero che può raggiungere i 3–5 m di altezza.[3]
I frutti sono ovali, lunghi circa 3 cm, contenenti otto grandi semi, immersi in una polpa appiccicosa, e racchiusi in un duro esocarpo.[4]
Fusti
Foglie
Frutti
Frutti e semi
Sezione del tronco
La dispersione dei semi di questa specie era un tempo affidata a due rettili frugivori di grossa taglia, entrambi estinti: lo scinco gigante di Mauritius (Leiolopisma mauritiana) e le tartarughe giganti del genere Cylindraspis, che si nutrivano dei suoi frutti. La loro estinzione ha creato seri problemi alla sopravvivenza di Diospyros egrettarum. Al fine di favorire la rigenerazione della popolazione presente sull'Île aux Aigrettes, è stato introdotto sull'isola un gruppo di tartarughe giganti di Aldabra (Aldabrachelys gigantea) che si sono rivelate efficaci nel favorire la dispersione dei semi; il passaggio dei semi attraverso l'intestino della tartaruga ne aumenta infatti la germinabilità.[4]
Per la ristrettezza del suo areale la IUCN Red List classifica Diospyros egrettarum come specie in pericolo critico di estinzione (Critically Endangered).[1]
Esemplari di questa specie si trovano nel mondo solo in cinque orti botanici.[3] Tra di essi merita di essere menzionato l'Orto botanico di Pamplemousses ove esiste un esemplare messo a dimora dal leader sudafricano Nelson Mandela.[5]
Diospyros egrettarum I.Richardson, 1980 è una pianta della famiglia delle Ebenacee, endemica di Mauritius.
Egretas melnkoks (Diospyros egrettarum), arī Egretas ebenkoks ir melnkoku dzimtas suga, kas endēma Maurīcijai. Tas ir reti sastopams melnkoks, kas Sarkanajā grāmatā ierindots kritiski apdraudēto sugu sarakstā.[1]
Sasniedz 3—5 m augstumu. Lapas veselas, kātainas, ar gludu malu un skaidri redzamu plūksnainu dzīslojumu, uz zariem pamīšus. Ziedi skarās lapu žāklēs.
Līdzīgi citiem melnkokiem, tā kodolkoksne ir ārkārtīgi cieta un smaga.[2]
Sastopams tikai Maurīcijā, kur cietzemē saglabājušies mazāk kā desmit īpatņu. Taču blakus esošajā Egretas saliņā sugas populācija 2007. gadā veidoja 3518 pieaugušus kokus.[2][3] Aug arī vairākos botāniskos dārzos gan Maurīcijā, gan citviet pasaulē.
Egretas melnkoks bija izturīgs pret invazīvo sugu ievešanu, taču tā izplatību stipri samazināja izciršana un ainavas izmaiņas, kā arī Maskarēnu milzu bruņurupuču un Maurīcijas milzu scinka iznīcināšana, kuri izplatīja melnkoka sēklas. Mazāku izmēru augļēdāji nespēja šīs sēklas norīt. Maurīcijas savvaļas fonda vadībā veiktā Egretas atbrīvošana no žurkām un svešzemju augiem labvēlīgi ietekmēja arī melnkoka populāciju.
2000. gadā Egretā tika atvesti pirmie četri Aldabras milzu bruņurupuči, kas aizņēma pagātnē izmedīto bruņurupuču ekoloģisko nišu. 2009. gadā to skaits bija pieaudzis līdz 19 pieaugušiem īpatņiem. Bruņurupuči lielā skaitā patērē nobirušos un nobriedušos melnkoku augļus, izvadot un izkaisot sēklas un radot simtiem jaunu asniņu lauciņus.[3][4]
Egretas melnkoks Pamplemuses botāniskajā dārzā
Melnkoka stumbri, Egreta
Bruņurupuču radīts melnkoku asniņu lauciņš Egretā
Egretas melnkoks (Diospyros egrettarum), arī Egretas ebenkoks ir melnkoku dzimtas suga, kas endēma Maurīcijai. Tas ir reti sastopams melnkoks, kas Sarkanajā grāmatā ierindots kritiski apdraudēto sugu sarakstā.
Diospyros egrettarum là một loài thực vật có hoa trong họ Thị. Loài này được I.Richardson mô tả khoa học đầu tiên năm 1980.[1]
Diospyros egrettarum là một loài thực vật có hoa trong họ Thị. Loài này được I.Richardson mô tả khoa học đầu tiên năm 1980.
