Threatened Plants of Palau
Authors: Craig Costion
Citation: Costion, C. 2013. Threatened Endemic Plants of Palau. Conservation International. Apia, Samoa. 40 p.
Locality: Republic of Palau
Abstract:

The Pacific is the largest biodiversity hotspot region on earth and is arguably the most vulnerable to extinctions. Islands have historically been exceptionally vulnerable to extinctions. In 2004 the IUCN determined that out of all known recorded extinctions from mammals, birds, amphibians, reptiles, and molluscs; 72% were island species. Although the abundance of endemic and rare plants with restricted distributions in the Pacific is widely acknowledged, little is known about them. Palau, at the western most edge of this region has approximately 130-135 endemic plant species confined to only 453 km². Previous estimates of plant endemism rates for this region have proven to be overestimated by far (Costion & Lorence 2012). Many of these plants are rare, restricted in distribution, and/or very poorly known. Approximately 15% of these are only known from the type collections. A preliminary IUCN red-list assessment of all endemic plant species for Palau (Costion et al. 2009) found that for over 60% of them data was insufficient for establishing a red-list category.

Progress towards a complete IUCN Red Listing of endemic plants in this region is imperative, as threats to the island from development and invasive species are increasing. The lack of a complete understanding of which plant taxa are threatened, and to what degree, remains a significant barrier to effective biodiversity conservation in Micronesia’s most diverse flora. This challenge was addressed in this CEPF project by targeting specific taxa for further collection and population inventory while progressing knowledge on the threatened status of the entire flora by investigating human impact through time on the Palau islands.


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Families: 11
Genera: 12
Species: 15
Total Taxa: 15

Page 1 of 1: 1

endemic, tree, volcanic lowland forest. Fairly common, small to medium sized tree, occurring throughout the limestone Rock Islands; inland forest, not adjacent coast. Prior to this project, this species was only known from the type collection and had not been photographed before.
endemic, tree, volcanic lowland forest. A new record of this rare species was discovered in one of the last remaining forested areas of Koror
endemic, tree, volcanic lowland forest, limestone forests, atolls and strand vegetation along the coast. Very small range of occurrence with a rare and scattered distribution within this area. During the project we were able to photograph active pollinators on the flowers, an unidentified bee or wasp. Further work is required to identify the pollinator to species. However, loss of pollinators or lack of cross pollination does not appear to be a problem for this threatened palm.
endemic, tree, volcanic lowland forest. This species occurs throughout the limestone islands of Palau but not in high numbers. It has been observed in the limestone islands of Airai down to the southern most Rock Islands, suggesting it is well distributed across the limestone islands. The trees can form medium to large sized buttresses.
endemic, tree, volcanic lowland forest, limestone forests, atolls and strand vegetation along the coast. This medium to large tree species was photographed for the first time during the project, and is now represented in the BNM herbarium collection. Data is still lacking to determine its abundance but it is known to occur on both volcanic and limestone substrates in Palau so it may require a lower priority for conservation.
endemic, tree, volcanic lowland forest and savannah grassland. This species is now believed to be a synonym of the Palau endemic Pandanus aimiriikensis, which may be restricted to volcanic islands, and is in line for subsequent revision.
endemic, tree, limestone forests, atolls and strand vegetation along the coast. This species was previously thought to be endemic to Peleliu but recent genetic work (now in progress) suggests it may be the same species as Pandanus aimiriikensis. Since it is morphologically distinct from the volcanic island populations of Pandanus amiriikensis it is under current investigation. This species was widespread and abundant on the island of Peleliu and throughout the limestone islands.
endemic, herb-shrub, volcanic lowland forest, limestone forests, atolls and strand vegetation along the coast. This species occurs commonly throughout the limestone islands and in wet areas of Babeldaob. It is a small semi-woody herb or small understory shrub.
endemic, tree, volcanic lowland forest. This species occurs commonly throughout the limestone islands, particularly on the high inland karst ridges, but also occasionally along the coast.
endemic, tree, volcanic lowland forest. This species is common throughout Babeldaob occurring in both forest and open savanna areas. It can occur as a short shrub in open savanna or a tall, medium sized tree in closed forest. It is often confused with the closely related Timonius subauritus but can be distinguished by its much longer persistent calyx and often (though not consistent) more pubescent growth.
endemic, tree, volcanic lowland forest. This species is now moved from
endemic, tree, volcanic lowland forest, limestone forests, atolls and strand vegetation along the coast. This species occurs along the limestone bluffs throughout the rock islands and can be confused with the closely related Pouteria obovata. It is known only from few collections but appears to occur throughout the limestone islands.
endemic, herb, volcanic lowland forest. This is a rare inconspicuous plant, known only from one mountain top locality on a moist basalt outcrop. We recently distinguished this plant from two other recognized endemic Selaginella species in Palau by studying the type and comparing existing collections at BNM. The other two species of Palau endemic Selaginella, Selaginella dorsicola and Selaginella pseudo-volkensii, may actually be only one valid species represented by two names. This will require follow up study by an expert in the genus.
endemic, tree, volcanic lowland forest, limestone forests, atolls and strand vegetation along the coast. There has been previous uncertainty regarding whether this species is a Palau endemic under the name Medusanthera caroliensis or if it is synonymous with the more widespread species Medusanthera laxiflora. Recent collections and photographs were made and sent away for expert identification and confirmed it to be the nonendemic M. laxiflora.
endemic, vine, volcanic lowland forest. Collections of a Cayratia species matching the type of Cayratia palauana were made during the project. This species was previously only known to us from the type collection. It was only found at two sites in the Rock Islands, both disturbed sites, one an exposed site adjacent to a radio tower, the other an exposed area adjacent a tree-fall and cliff. It was also observed on Peleliu, which is all secondary recovering limestone forest with many breaks in the canopy. It is currently recognized as endemic species to the limestone islands of Palau, but due to its preference for disturbed sites (often an indicator of a recently introduced taxon) its taxonomic status is worthy of further investigation.