Fig. 1: Reproduced pictures of Exallage auricularia (Eared Starviolet) showed in the 2017 post

I just realised that I had mixed up the identity of Exallage auricularia (Eared Starviolet) and Spermacoce ocymifolia (Slender Buttonweed) in a post in June 2017 (Fig. 1). That plant spotted back then should be Exallage auricularia, known in the 2022 Singapore flora checklist as Hedyotis auricularia. Hedyotis auricularia is a synonym of Exallage auricularia according to the Plants of the World Online (POWO) website.

The error was uncovered when I was updating the botanical name table in another old post in June 2018. With the availability of new version of Singapore flora checklist in 2022, I have constructed a table to consolidate the names (if any) of the 13 species in the Hedyotis-Oldenlandia complex listed in my post in June 2018 (Table 1) with that from the older flora checklist and from the POWO website. I have adopted the naming convention from the POWO website. The observations count on iNaturalist website viewed on 19 January 2025 was included in the table as a rough guage of the prevalence of the species in Singapore.

While the variances seen in the names used among checklist versions and websites are more due to preference of botanists, the one that stands out is Hedyotis prostrata, previosuly named as Oldenlandia cristata. The 2022 flora checklist indicated that Oldenlandia cristata has been misapplied (auct. non) to this plant. Nevertheless, the name Hedyotis prostrata was not found in the iNaturalist website. Instead, the images of the plant are still being consolidated under the name Oldenlandia cristata in that website.

As for the observations count in the iNaturalist website, the one that surprises me initially was Exallage auricularia (locally known as Hedyotis auricularia). There was no obervation from Singapore when I did the check on 19 January 2025. This was not the case back on 12 November 2022 when the observations count was 10. The search for the answer evetually led me to a note in iNaturalist website by Ethan.

Soon after, I noted that Exallage auricularia was nationally extinct according to the 2022 flora checklist and the Rubiaceae edition of the Flora of Singapore published in 2019. These all then make sense as the correct Exallage auricularia is indeed very rare and I have only spotted it once.

This week, I revisited the location in the nearby park where I initially observed Exallage auricularia to assess its current status. The population is no longer present at that site. However, I discovered a larger population along the edge of the park, growing adjacent to a drain. Due to the presence of a metal barrier at waist height, likely installed to prevent individuals from falling into the drain, I opted to take a few photographs from a distance rather than attempting to climb over the barrier to access the plant.