PHALAENOPSIS MYSORENSIS SALDANHA (ORCHIDACEAE): NOTE ON DISTRIBUTION AND ECOLOGY

Phalaenopsis mysorensis Saldanha, an orchid species endemic to South India has recently been recorded in Sri Lanka from a few isolated hill forests in the northern and eastern dry lowlands. The minute habit, small white flowers and short unbranched peduncle distinguishes P. mysorensis from its congener P. deliciosa, the only recorded Phalaenopsis in Sri Lanka. The habit and habitat of the species are described based on recent observations and collections.


INTRODUCTION
Phalaenopsis Blume, represented by about 40 species, is a tropical Asiatic genus mainly distributed in Indonesia and the Philippines (Seidenfaden and Wood, 1992). All species are small to medium sized epiphytes with flattened roots, which are sometimes photosynthetic. A few leaves are clustered together on a reduced stem. The inflorescence is either short or long and sometimes rather flattened. Flowers are small to medium in size (Seidenfaden and Wood, 1992;Dressler, 1993). Phalaenopsis deliciosa Reiehb. (Kingidium deliciosum (Reiehb.) Sweet), the only other species previously recorded from Sri Lanka belongs to this genus (Jayaweera, 1981). Although Christenson (2006) has mentioned that this species occurs in Sri Lanka, information on it's distribution and ecology has not been recorded.

Phalaenopsis mysorensis
Disc with two pairs of asymmetrical antennae that cover the narrow groove of the mid lobe. Column 2 mm long slightly winged with a 2 mm long foot. Operculum 2 celled. Pollinia 0.8 x 0.4 mm, 4 in 2 unequal pairs on a stipes, attached to a triangular viscidium. Capsule 1.3 x 0.4 cm long, oblong (Fig. 1). So far, this species has not been recorded from the mid or high elevation Wet zone forests in Sri Lanka, which also have wet, misty, windswept microhabitats similar to those in the Dry and Intermediate zone hill tops.
In India, it is distributed in Kerala state in the districts of Trivandrum, Palghat, Thrissur and Wayanand; and in Karnataka state in the districts of Hassan and Trichur (Saldanha, 1974;1976;Sathish Kumar and Manilal, 1994;Sathish Kumar and Manilal, 2004).
In Sri Lanka, flowering and fruiting have been recorded from October to March coinciding with the North-East monsoon. In the dry season (April to September), leaves dry out, become paler and are shed, when only the flat roots and tiny stem are visible. Roots remain green and photosynthetic. In the next rainy season, new leaf shoots appear. During the dry period the plants can be misidentified as some other leafless orchid species such as Taeniophyllum sp. or Cheiloschista sp. This unique phenological condition is characteristic for some Himalayan subgenera such as Aphyllae, Parishianae and Proboscidioides, which are subjected to extreme wet and dry conditions annually. As a water conservation measure, they shed their leaves during the drought period (Christenson, 2001). However, P. mysorensis along with its other Sri Lankan congener, P. deliciosa belong to the subgenus Phalanopsis. Such phenological conditions have not been recorded in the above subgenus. In these hill tops, cool but extreme desiccating conditions prevail during the dry period of the South-West monsoon. However, in the North-East monsoon it is exposed to very much wetter conditions.
In Sri Lanka this species has an unusually fragmented distribution pattern restricted to a few isolated hill tops. The major threat to the species is death resulting from felling of host trees.