Caladenia citrina

The native vegetation of the Leeuwin-Naturaliste Ridge - one of the highest population growth areas in Australia - has been severely fragmented and degraded, by clearance. The main ongoing threats to Caladenia spp. of the Leeuwin ridge are further habitat degradation, and weed infestation, other threats to Caladenia species include spread of Phytophthora cinnamoni, Phytophthora cryptogea; grazing, most notably by kangaroos (Macropus fuliginosus) but also rabbit and stock and potentially insects. Digging by small mammals including rabbits and Quendas (Isoodon obesulus), are a potential threat as they dig burrows or seek orchid tubers as a food source; prescribed burning undertaken when the orchid is most vulnerable (between April to early November); and accidental damage from firebreak maintenance and other infrastructure maintenance. Recreational impacts such as trampling, picking of orchid flowers, soil compaction, rubbish dumping and habitat fragmentation by establishment of paths by visitors may exert further pressure on populations. Threats to roadside subpopulations include grading, chemical spraying, construction of drainage channels and the mowing of roadside vegetation.

Poor recruitment threatens other Caladenia spp. of the region with few plants developing seed without artificial assistance. It is suspected that low orchid recruitment rates from seed dispersed in their natural environment may in part be due to the patchy distribution of mycorrhiza . Natural recruitment of terrestrial orchids may only occur in years when a longer growing season results from above average spring rainfall prior to the onset of summer dormancy. Climatic conditions during this time are more conducive to the formation of tubers.

Caladenia citrina is a distinctive, attractive and unusually-coloured member of the C. longicauda complex (Hopper and Brown 2001). Illegal collection may also threaten this species.

The Leeuwin-Naturaliste ridge is a key area for biodiversity conservation. Habitat conservation measures are in place within the Leeuwin-Naturaliste National Park. Additionally, recovery plans for threatened Caladenia spp. which have similar distributions are also in place. They include fencing against grazing, deep-ripping, rubbish removal and spot spraying of weeds. Caladenia citrina is considered restricted but not threatened in Western Australia (A. Brown pers. comm. 2009). The taxon is listed as a species of local significance, with disjunct outlying populations within the park (Frewer et al. 1999).

The response of this species to fire should be investigated. Suitable fire management strategies are being developed for other threatened Caladenia of the region. Adverse impacts from land use should be minimized. Seeds should be collected and stored for germplasm conservation. Although recent surveys of orchids have been conducted within the park, field surveys in historical sites of collection, in suitable habitat and potential habitat, should be undertaken to locate any additional subpopulations, occurrences, remnants and determine whether local extinction has occurred. Detection of the species is optimum during the flowering period from late September to November.

It is currently listed on Appendix II of the Convention on International Trade in Endangered Species (CITES). The taxon is grown in botanical institutions and by hobbyists.