Zeuxine Lindley

Ariyarathne, W. A. M. P., Yakandawala, Deepthi, Samuel, Rosabelle & Wijesundara, Siril, 2017, Evaluating the occurrence and conservation statuses of Sri Lankan Orchids (Orchidaceae): Observations on newly recorded species and undocumented regions, Phytotaxa 308 (1), pp. 37-53 : 51-52

Zeuxine Lindley

There are five species belong to this genus including two endemics. Zeuxine reginasilvae [Syn: Zeuxine regia non (Lindl.) Trimen] is the only observed endemic and it is an EN species ( MOE, 2012). According to Jayaweera (1981), this species was observed in submontane or mid-country tropical wet evergreen forests, Fernando & Ormerod (2008) have recorded it in lowland wet zone. During the present study period, this species was observed from the sites in lowland wet zone and the sub montane zone. Our observation conflicts the available data.

Orchids have a sensitive and complex biological relationship with the surrounding habitat, such as mycorrhizal association for the germination and specific pollinators. According to the observations made during the field studies, almost all the visited sites are under human influence presently. Adam’s Peak is a site with highest species richness but some of the observed species survives in very small populations. Habenaria dolichostachya , H. pterocarpa and Arundina minor are few of the species observed in the Adam’s Peak in small populations and all these species were found close to foot paths and were getting disturbed due to man made constructions. Most of the forest reserves are undergoing certain level of human disturbance and wild plants are removed from the natural habitats for different reasons like medicinal use and collected by flower enthusiasts and growers. Disturbances by different wild animals such as elephants in Adam’s Peak, wild boars in Hantane, Kalupahana, Kanneliya and Riverstan and as well as humans are responsible for the destruction of natural habitats. However the species existing outside of the protected areas are more vulnerable compared to the species surviving in the conserved regions. Access to the protected areas and removal of either fauna or flora are prohibited by law inside the protected areas. However due to lack of knowledge regarding these laws, illegal exploitation of protected species inside and outside of protected areas are still going on in a higher rate.

According to Jayaweera (1981) and Jayasuriya (1984), there were 29 species of orchids recorded from the Ritigala SNR. However, only three species were encountered during this investigation of which only two species were identified. The third species belongs to the genus Eulophia but could not be identified to the species level due to insufficient morphological characters. Gastrochilus acaulis is a new record for Ritigala SNR. During this study 13 species were recorded from Horton Plains NP. In 1981, Jayaweera recorded 11 species and Ranawana and Jayarathne (2016) mentioned seven species including three additional species from Horton Plains NP. This study has recorded 19 species in 17 genera including 5 endemics from the Knuckles region including Riverston, Deanston, Corbet’s Gap and Kalupahana. Orchids occurring in the Riverston and Deanston have not been documented upto now. Seventeen species from Rangala- Corbet gap, and three species from Kalupahana forest have been recorded ( Jayaweera, 1981). In 2003, Bambaradeniya and Ekanayake have documented seven species from the Knuckles region and in the present study we too recorded the occurrence of same species excluding Vanda tessallata . In 1981, Jayaweera recorded 8 species from Sinharaja Forest but we have recorded only 6 species. However, Arundina graminifolia , Bulbophyllum thwaitesii , Diploprora championi , Phalaenopsis deliciosa , and Zeuxine reginasilvae are new records for Sinharaja FR during the present study. There were 21 species recorded from Adam’s Peak FS ( Jayaweera, 1981)., but the present study records only 16 species of which Bulbophyllum elegans , Habenaria acuminata , Habenaria dolichostachya , Habenaria pterocarpa , Liparis elliptica are new records. In 1981, even though Jayaweera recorded 20 species from Hakgala SNR, during the present study only 4 species were encountered and among them Phaius wallichii Lindl. is a new record. From Kanneliya Forest Reserve, only one species was recorded by Jayaweera in 1981, but this study records 13 species in 12 genera including 1 endemic species which is a very good record. However, Jayaweera (1981) mentioned 24 species from Hantane FR but the present study records only 10 species.

Different reasons could be attributed for not recording all the previously cited orchids in the visited sites; extracting plants in large scale for various reasons or natural disasters, some orchids are not visible unless they are in bloom (eg.; I. speciosa , and D. pallens ), disappearance of vegetative parts above the soil surface during the dormancy period in the dry season (eg.; A. regalis , Habenaria species, D. neilgherrensis ) and deviations among recorded and visited sites and trails. The actual number of orchids observed during the present study would have been increased if all the plants could have been identified down to the species level.

One of the drawbacks in conserving natural resources is the lack of the knowledge on what we actually have. In the present study also only 42.4% of the documented orchid species in Sri Lanka were recorded. Therefore continuous taxonomic surveys are required to monitor the conservation status, knowledge on each species and discovering new species with in-situ and ex-situ conservation measures.