Two centuries of biodiversity discovery and loss in Singapore.

There is an urgent need for reliable data on the impacts of deforestation on tropical biodiversity. The city-state of Singapore has one of the most detailed biodiversity records in the tropics, dating back to the turn of the 19th century. In 1819, Singapore was almost entirely covered in primary forest, but this has since been largely cleared. We compiled more than 200 y of records for 10 major taxonomic groups in Singapore (>50,000 individual records; >3,000 species), and we estimated extinction rates using recently developed and novel statistical models that account for "dark extinctions," i.e., extinctions of undiscovered species. The estimated overall extinction rate was 37% (95% CI [31 to 42%]). Extrapolating our Singapore observations to a future business-as-usual deforestation scenario for Southeast Asia suggests that 18% (95% CI [16 to 22%]) of species will be lost regionally by 2100. Our extinction estimates for Singapore and Southeast Asia are a factor of two lower than previous estimates that also attempted to account for dark extinctions. However, we caution that particular groups such as large mammals, forest-dependent birds, orchids, and butterflies are disproportionately vulnerable.

Extinction rate of discovered and undiscovered plants in Singapore.

Extinction is a key issue in the assessment of global biodiversity. However, many extinction rate measures do not account for species that went extinct before they could be discovered. The highly developed island city-state of Singapore has one of the best-documented tropical floras in the world. This allowed us to estimate the total rate of floristic extinctions in Singapore since 1822 after accounting for sampling effort and crypto extinctions by collating herbaria records. Our database comprised 34,224 specimens from 2076 native species, of which 464 species (22%) were considered nationally extinct. We assumed that undiscovered species had the same annual per-species extinction rates as discovered species and that no undiscovered species remained extant. With classical and Bayesian algorithms, we estimated that 304 (95% confidence interval, 213-414) and 412 (95% credible interval, 313-534) additional species went extinct before they could be discovered, respectively; corresponding total extinction rate estimates were 32% and 35% (range 30-38%). We detected violations of our 2 assumptions that could cause our extinction estimates, particularly the absolute numbers, to be biased downward. Thus, our estimates should be treated as lower bounds. Our results illustrate the possible magnitudes of plant extirpations that can be expected in the tropics as development continues.

Tasa de Extinción de Plantas Descubiertas y No Descubiertas en Singapur Resumen La extinción es un tema importante para la valoración de la biodiversidad global. Sin embargo, muchas medidas de la tasa de extinción no consideran a las especies que se extinguieron antes de que pudieran ser descubiertas. Singapur, la ciudad-estado isleña altamente desarrollada, tiene una de las floras mejor documentadas del mundo. Esto nos permitió estimar la tasa total de las extinciones florísticas en Singapur desde 1822 después de considerar el esfuerzo de muestreo y las criptoextinciones cuando recopilamos los registros de herbarios. Nuestra base de datos incluyó 34,224 especímenes de unas 2,076 especies nativas, de las cuales 464 especies (22%) estaban consideradas como extintas a nivel nacional. Asumimos que las especies no descubiertas tuvieron la misma tasa anual de extinción por especie que las especies descubiertas y que ninguna especie no descubierta permanecía en existencia. Con algoritmos clásicos y bayesianos, respectivamente, estimamos que 304 (95% IC 213-414) y 412 (95% IC 313-534) especies adicionales se extinguieron antes de que fueran descubiertas; las estimaciones correspondientes de la tasa de extinción total fueron 32% y 35% (rango de 30-38%). Detectamos violaciones en nuestras dos suposiciones que podrían causar que nuestras estimaciones de extinción, particularmente los números absolutos, tuvieran un sesgo hacia abajo. Por lo tanto, nuestras estimaciones deberían ser tratadas como límites inferiores. Nuestros resultados ilustran las magnitudes posibles de las extirpaciones de plantas que pueden esperarse en los trópicos conforme el desarrollo continúa.

Species-area relationships and biodiversity loss in fragmented landscapes.

To estimate species loss from habitat destruction, ecologists typically use species-area relationships, but this approach neglects the spatial pattern of habitat fragmentation. Here, we provide new, easily applied, analytical methods that place upper and lower bounds on immediate species loss at any spatial scale and for any spatial pattern of habitat loss. Our formulas are expressed in terms of what we name the 'Preston function', which describes triphasic species-area relationships for contiguous regions. We apply our method to case studies of deforestation and tropical tree species loss at three different scales: a 50 ha forest plot in Panama, the tropical city-state of Singapore and the Brazilian Amazon. Our results show that immediate species loss is somewhat insensitive to fragmentation pattern at small scales but highly sensitive at larger scales: predicted species loss in the Amazon varies by a factor of 16 across different spatial structures of habitat loss.

Why do understorey Licuala palm fruits turn from red to white and then black when ripe?

Licuala ferruginea Becc., a tropical forest understorey palm, is observed to have fruits that appear red in colour when unripe, turning pink, then white, purple and finally black in colour as they ripen. We monitored 13 fruiting palms in rainforest fragments and recorded the consumption of fruits by animals via camera traps. We also documented the fruiting phenology of two palms in the nursery. In the rainforest fragments, a Cream-vented Bulbul (Pycnonotus simplex) was observed plucking a mature purple fruit from a L. ferruginea palm, before flying away with the fruit in its beak. This was the only bird that was observed feeding on the mature fruit. A range of mammals, dominated by edge species such as the Long-tailed Macaque and Wild Boar, were observed to consume L. ferruginea fruits indiscriminately across all five colour stages, thereby limiting the dispersal of the fruits. Forest bulbul gape sizes also matched the fruit size, suggesting that forest bulbuls are the likely dispersers of the palm in the original forest where edge species are not in high densities. We further posit that the initial phase of red fruits, with high contrasting red reflectance against a green foliage background, might be a form of early advertisement to birds. The fruit then turns pink and white, which have high green reflectance and is less contrasting, thereby reducing the conspicuity of the fruit. This allows the fruit to ripen with high fructose and glucose content, and turn purple and black, which are known visual cues for birds. This study provides indicative support for the dispersal syndrome hypothesis and highlights the potential effects of forest fragmentation on plant-frugivore interactions.