Podocarpus pallidus

N.E. Gray 1959

Common names

Uhiuhi [Tongan] (Farjon 2010).

Taxonomic notes

Type: Tonga, Tongatapu group, 'Eua, 'Ohonua, western side of plateau region, H.E. Parks 16212 (lecto F). No synonyms. P. pallidus was included in study of the rbcL sequence data for 144 Podocarpaceae taxa by Knopf et al. (2012). P. pallidus was not clearly resolved, but was placed within a large clade with 25 other Malesian taxa, including all of those native to Pacific oceanic islands as well as other Malesian and Indochinese species.

Description

Shrubs or trees to 10 m tall and 25 cm dbh, usually with a single, sometimes low-branching trunk. Bark light brown weathering gray, inner bark reddish brown. Twigs round, finely grooved. Foliage buds ovoid-conical, 2-6 mm long, with spreading or recurving, acuminate outer scales. Leaves dimorphic, petiolate, linear-lanceolate, straight or slightly falcate; lustrous light green above, pale below; 40-120 × 5-11 mm (up to 150 × 17 mm on saplings); margins flat to slightly revolute; upper midrib narrow, acute, sometimes fading distally; lower midrib wider, obtuse or flattened; apex acute or acuminate, sometimes mucronate. Pollen cones axillary, solitary, sessile, subtended by triangular bud scales, 25-40 × 3-4 mm wide when active, yellowish white. Seed cones axillary, solitary, on stout 5-15 mm peduncles, receptacles subtended by 2 foliola 2 mm long; ripe receptacle succulent, red to blackish red, 10-13 × 10 mm. Seeds solitary, ovoid to globose, within epimatium 10-13 × 8-10 mm, blue to brown with glaucous bloom, crest absent or minute (Farjon 2010).

Distribution and Ecology

Tonga: 'Eua and 'Uta Vava'u. These two islands are about 325 km apart. Grows at elevations of 50-300 m, scattered in Calophyllum- and Garcinia-dominated montane forestforest patches along the limestone plateau escarpment and in ravines or gullies (Farjon 2010, Enright and Jaffré 2011).

The IUCN reports that this species is "Vulnerable" to extinction due to a small extent of occurrence (17.5 km²) and a very small area of occupancy (2.25 km²); the total reproductive population is almost certainly less than 1000 plants. There is also virtually no undisturbed natural vegetation remaining within its habitat. Although this tiny population size warrants a "Critically Endangered" designation, there is no evidence that the population is currently in decline. Potential threats include agricultural land clearing, but the greatest threat may be stochastic; such a small population could be wiped out by a single extreme event, such as an especially severe hurricane or fire (Thomas 2013).

Seed dispersal is a challenge for plants on isolated oceanic islands. For P. pallidus only the Pacific imperial pigeon (Ducula pacifica) and "flying fox" bats (Pteropus tonganus) are known to disperse its seeds (McConkey and Drake). It is interesting to reflect that the Tongan giant pigeon, Tongoenas burleyi, was formerly known from 'Eua, but was extirpated shortly after human colonization of the islands about 2,850 years ago (Steadman and Takano 2020). How did the loss of this disperser affect Podocarpus pallidus?

Remarkable Specimens

No data as of 2023.02.08.

Ethnobotany

There are no recorded uses (Farjon 2010).

Observations

See the collection records on GBIF (accessed 2023.02.08).

Remarks

The epithet pallidus means pale, probably referring to the pale green leaves.

Citations

Enright, Neal J., and Tanguy Jaffré. 2011. Ecology and Distribution of the Malesian Podocarps. Pp. 57-77 in Turner, Benjamin L. and Cernusak, Lucas A. (eds.), Ecology of the Podocarpaceae in Tropical Forests. Smithsonian Contributions to Botany. https://doi.org/10.5479/si.0081024X.95.viii, accessed 2023.02.07.

Gray, N.E. 1959. Bishop Museum Bulletin 220:46.

McConkey, Kim R., and Donald R. Drake. 2015. Low redundancy in seed dispersal within an island frugivore community. AoB Plants 7. https://doi.org/10.1093/aobpla/plv088.

Steadman, D. W. and O. M. Takano. 2020. A new genus and species of pigeon (Aves, Columbidae) from the Kingdom of Tonga, with an evaluation of hindlimb osteology of columbids from Oceania. Zootaxa 4810(3). https://doi.org/10.11646/zootaxa.4810.3.1.

Thomas, P. 2013. Podocarpus pallidus. The IUCN Red List of Threatened Species 2013: e.T34092A2845063. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T34092A2845063.en, accessed 2023.02.08.

See also

An Assessment of Critically Endangered Plant Species of the Kingdom of Tonga (accessed 2023.02.08).

The species account at Threatened Conifers of the World.