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A botanical oasis rather than a biological desert: Rediscoveries, new species and new records in a tropical city

Wiley
Plants, People, Planet
Authors:

Abstract

Societal Impact Statement Cities present a unique challenge for conservation. While overall native biodiversity is reduced, remnant habitats in the urban matrix can be important refugia for native and endemic species. This study reviews the rediscovery of 173 presumed nationally extinct plant taxa and discovery of 155 new native plant records, including 22 new to science and five endemics, in the botanically densely‐collected tropical city‐state of Singapore. The findings of this study indicate that plant rediscoveries and new discoveries are still possible in cities and urban areas with remaining fragments of original forest reserved for species protection, and investment in comprehensive botanical surveys and taxonomic research. Summary The conservation of native species‐dominated forest fragments and investment into botanical surveys and taxonomic research have enabled the rediscovery of presumed nationally extinct plant taxa and discovery of new native plant records in the tropical city‐state of Singapore. We compared national plant checklists of 2009, 2022, and the national Red Data Book (third edition in press) to enumerate rediscovered and newly discovered native vascular plant taxa in the last 14 years. We examined if these were from taxonomic specialist redetermination of only pre‐existing specimens or newly collected from field surveys, and if they were from particular sites and vegetation types, disproportionately represented by certain life forms and families, and predominantly threatened. We documented 173 rediscoveries and 155 new records after 2009, including 22 new to science and five endemics. Most rediscoveries were newly collected from field surveys, but most new records resulted from redetermination of pre‐existing specimens. Native species‐dominated forest fragments were the most important sites for the first collection of new records or first re‐collection of rediscoveries. Trees and climbers were well‐represented among the rediscoveries and new records. Epiphytes were significantly under‐represented compared to their proportion in the presumed nationally extinct flora. Most rediscoveries and new records are nationally Critically Endangered but regionally and globally not assessed. Our findings indicate hope for the persistence of rare native plant species and opportunities for conservation in cities.
RESEARCH ARTICLE
A botanical oasis rather than a biological desert: Rediscoveries,
new species and new records in a tropical city
Louise Neo
1
| Kwek Yan Chong
1
| Stuart Lindsay
1,2
|
David J. Middleton
1,2
| Puay Yok Tan
1
| Kenneth Boon Hwee Er
1
1
National Parks Board, Singapore Botanic
Gardens, Singapore, Republic of Singapore
2
Royal Botanic Garden Edinburgh, Edinburgh,
Scotland, UK
Correspondence
Louise Neo, National Parks Board, Singapore
Botanic Gardens, 1 Cluny Road, Singapore
259569, Republic of Singapore.
Email: neolouise@gmail.com;louise_neo@
nparks.gov.sg
Societal Impact Statement
Cities present a unique challenge for conservation. While overall native biodiversity
is reduced, remnant habitats in the urban matrix can be important refugia for native
and endemic species. This study reviews the rediscovery of 173 presumed nationally
extinct plant taxa and discovery of 155 new native plant records, including 22 new to
science and five endemics, in the botanically densely-collected tropical city-state of
Singapore. The findings of this study indicate that plant rediscoveries and new dis-
coveries are still possible in cities and urban areas with remaining fragments of origi-
nal forest reserved for species protection, and investment in comprehensive
botanical surveys and taxonomic research.
Summary
The conservation of native species-dominated forest fragments and investment
into botanical surveys and taxonomic research have enabled the rediscovery of
presumed nationally extinct plant taxa and discovery of new native plant records
in the tropical city-state of Singapore.
We compared national plant checklists of 2009, 2022, and the national Red Data
Book (third edition in press) to enumerate rediscovered and newly discovered
native vascular plant taxa in the last 14 years. We examined if these were from
taxonomic specialist redetermination of only pre-existing specimens or newly col-
lected from field surveys, and if they were from particular sites and vegetation
types, disproportionately represented by certain life forms and families, and pre-
dominantly threatened.
We documented 173 rediscoveries and 155 new records after 2009, including
22 new to science and five endemics. Most rediscoveries were newly collected
from field surveys, but most new records resulted from redetermination of pre-
existing specimens. Native species-dominated forest fragments were the most
important sites for the first collection of new records or first re-collection of redis-
coveries. Trees and climbers were well-represented among the rediscoveries and
new records. Epiphytes were significantly under-represented compared to their
Received: 31 July 2023 Revised: 16 November 2023 Accepted: 4 December 2023
DOI: 10.1002/ppp3.10482
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any
medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
© 2024 The Authors. Plants, People, Planet published by John Wiley & Sons Ltd on behalf of New Phytologist Foundation.
Plants People Planet. 2024;113. wileyonlinelibrary.com/journal/ppp3 1
proportion in the presumed nationally extinct flora. Most rediscoveries and new
records are nationally Critically Endangered but regionally and globally not
assessed.
Our findings indicate hope for the persistence of rare native plant species and
opportunities for conservation in cities.
KEYWORDS
checklist, endemism, extinction, flora, Flora of Singapore, plant conservation, Red Data Book,
urban environments
1|INTRODUCTION
Cities are commonly perceived to be biological deserts(Spotswood
et al., 2021). They present challenges for conservation and are viewed
as novel ecosystems (Hobbs et al., 2006), comprising a landscape
matrix of small vegetation fragments amidst ornamental green spaces
and urban infrastructure (Grimm et al., 2008). Cities potentially carry a
large extinction debt (i.e., species may take time to go extinct even
after much of their natural habitat has been lost, and may be persist-
ing in low numbers with reduced fitness), depending on the land use
history and ecological traits of species (Planchuelo et al., 2020). While
the density of native biodiversity is substantially lower in cities due to
habitat loss and fragmentation, the fragments of natural habitats that
persist can still be important refugia for native plants and animals
(Soanes & Lentini, 2019; Spotswood et al., 2021), including endemics
(i.e., known only from a particular territory and nowhere else). The
conservation value of small habitat remnants dominated by native
species has been demonstrated in human-modified landscapes, show-
ing that these remaining habitats may be more resilient than we think,
and that not all small populations may be predisposed to rapid extinc-
tion (Riva & Fahrig, 2022; Volenec & Dobson, 2020; Wintle
et al., 2019). All these points suggest opportunities for conservation
action to mitigate the loss of species in cities, such as conserving and
restoring native species-dominated habitat remnants, reconnecting
habitat fragments, establishing urban green spaces as supplementary
novel habitats, and developing species recovery programmes
(Aronson et al., 2017; Soanes & Lentini, 2019; Wang et al., 2022). To
underpin this work, there is an urgent need to invest in taxonomic
research and intensify biodiversity surveys in the field, without which
the fundamental questions of which species are extant and how best
to conserve them cannot be addressed (Pimm, 2020; Wilson, 2017).
There are examples of cities that have actively incorporated such
actions. Singapore is a city-state that has experienced much ecological
transformation since its founding as a British colony in 1819 and sub-
sequent agricultural expansion and urbanisation (Corlett, 1992).
Today, tropical lowland primary and secondary rain forests remain on
only 21.5% of the land area, and mangrove and coastal forests on
0.91% of the land area (Yee et al., 2011). Most of these forests exist
as fragments across the main and offshore islands (Yee et al., 2011).
Native species-dominated forests are most extensive in the Bukit
Timah and Central Catchment Nature Reserves (BTNR and CCNR),
totalling 2018 ha on the main island. To increase habitat availability
and counter edge effects, buffer parks comprising secondary forests
regenerating from abandoned orchards and plantations have been
established over the last decade (Er, 2018). Nature corridors compris-
ing multi-tiered plantings along roads have also been established to
ensure ecological connectivity between forest remnants across the
island (Figure 1), as part of the vision of transforming Singapore into a
City in Nature (Er, 2021).
Concomitant with this vision is the investment into taxonomic
research on the plant diversity of Singapore and the region, including
the initiation of the Flora of Singapore project (Middleton, 2019).
Comprehensive botanical surveys of forest remnants have also been
commissioned. As a result, a number of plant species presumed
nationally extinct have been rediscovered in the last decade or so,
while new plant records for Singapore have been discovered and sev-
eral endemic species newly described (Er et al., 2022). This is unex-
pected considering that Singapore is probably the most botanically
densely-collected tropical country in the world (Middleton
et al., 2019). With the recent rediscoveries, the proportion of native
vascular plant species presumed to be extinct in Singapore has been
revised downwards from 31.1% (Tan et al., 2008) to 24.1%
(Middleton et al., in press).
This paper reviews the rediscovery of native (vascular) plant taxa
presumed nationally extinct and the discovery of new native records,
including new endemics, that have arisen from taxonomic research
and botanical surveys in the forest fragments of Singapore over the
last 14 years (from November 2009 to July 2023). We examine this
(re)discovered flora to provide insights on the following questions: (a)
Were these predominantly from taxonomic specialist redetermination
of only pre-existing unidentified or misidentified specimens, or from
new collections from field surveys? (b) Were these published in cer-
tain years as a result of collated field survey results? (c) Were these
recorded from certain sites and vegetation types that could indicate
where future surveys should be targeted? (d) Were these dispropor-
tionately represented by certain life forms and plant families?
(e) Were there factors that could predict the rediscoveries in particu-
lar? (f) Were the rediscoveries and new records predominantly rare
and threatened taxa, as indicated by their national, regional and global
conservation statuses?
2NEO ET AL.
2|METHODS
2.1 |Data collection
Through the Flora of Singapore project (Middleton, 2019) and the
work required for a third edition of the Singapore Red Data Book
(Middleton et al., in press), an updated national checklist and bibliogra-
phy of all native, naturalised, and casual bryophytes and vascular
plants and their conservation statuses was compiled and published by
Lindsay et al. (2022; see definitions of native and non-native status
categories therein). This enumerated 2388 native (including
11 endemic), 476 naturalised or casual, and 101 cryptogenic vascular
plant taxa for Singapore. Prior to this, the last vascular plant checklist
for Singapore was published by Chong et al. (2009), following the sec-
ond edition of the Singapore Red Data Book (Davison et al., 2008).
Since the work of Lindsay et al. (2022), additional rediscoveries and
new records have been documented (e.g., Ng, Yong, & Lim, 2022;
Niissalo et al., 2023; Thomas et al., 2023) and incorporated into the
Singapore Red Data Book (third edition) to update the conservation
statuses of all native plant species in Singapore (Middleton et al., in
press).
1
We compared the statuses of vascular plant taxa (including infra-
specific ranks) listed in Chong et al. (2009) with Lindsay et al. (2022)
and Singapore Red Data Book (third edition; Middleton et al., in press).
We defined rediscoveries as native taxa presumed nationally extinct
in 2009 (or, in a few cases, erroneously considered to be extant in
Chong et al., 2009, or missing from Chong et al., 2009 but otherwise
known from other literature to have been nationally extinct in 2009)
that have been re-encountered since then, either from a new field
collection (after 2009) or the recent redetermination of pre-existing
unidentified or misidentified specimens collected within the last
30 years. Any native plant species is considered nationally extinct in
Singapore if it has not been collected within the last 30 years (Davison
et al., 2008). Taxa considered in Chong et al. (2012) to have been
erroneously listedas extinct in Chong et al. (2009) were excluded as
clerical errors rather than genuine rediscoveries. New native records
are defined as taxa not previously recognised in Singapore in 2009 but
which all evidence suggests would have occurred in the original vege-
tation of the country, now added either from a new field collection
(after 2009) or the recent redetermination of pre-existing unidentified
or misidentified specimens, including the correction of previously mis-
applied names. New native records which result from the redetermi-
nation of pre-existing specimens may include taxa that are already
nationally or globally extinct. New records of cryptogenic taxa were
also compiled because there is currently insufficient evidence to
exclude these taxa from being native, but these were not included in
the quantitative analyses (10 taxa only, see Data S1).
For each rediscovery and new record, we considered the year of
first publication to be the first record of (re)discovery (this is because
FIGURE 1 Nature reserves, nature park networks (including nature areas, nature parks, and park connectors and trails) and nature corridors in
Singapore.
1
A table of native plant taxa and their conservation assessments in the Singapore Red Data
Book (third edition) can be accessed online at https://www.nparks.gov.sg/biodiversity/
wildlife-in-singapore/species-list/flora (National Parks Board, 2023).
NEO ET AL.3
the year of first collection can be difficult to use or interpret, especially
since some taxa were not correctly identified at the time of collection).
We compiled life forms according to Chong et al. (2009) and supple-
mented by personal observations, national conservation statuses
according to Middleton et al. (in press), and regional and global conser-
vation statuses according to the ThreatSearch database of the Botanic
Gardens Conservation International (BGCI, 2023). For taxa (re)discov-
ered from new field collections only, we noted the site of first (re)collec-
tion and the vegetation type according to Yee et al. (2016).
2.2 |Statistical analyses
We used Pearson's chi-square tests of association to compare the
proportions of rediscoveries and new records that resulted from new
field collections or from the taxonomic redetermination of only pre-
existing specimens. We also compared the proportions of rediscov-
eries and new records across life forms and plant families, and against
the presumed nationally extinct and the total native flora of
Singapore. In cases of small sample sizes (i.e., <10 taxa per cell in the
contingency table being analysed), we used Fisher's exact test.
We tested factors possibly associated with the rediscovered
taxa. Generalised linear models (GLMs) with binomial error distribu-
tions and a logit link function were fitted with rediscovery as a
binary response variable and predictors shown in Table 1. General-
ised linear mixed models (GLMMs) were additionally fitted with the
same predictors as fixed effects and plant family as a categorical
random effect to account for the statistical non-independence of
species, which are phylogenetic units with shared evolutionary
histories (Felsenstein, 1985). Models with phylogenetic tree-based
controls were also tested, but the improvement in fit was found to
be negligible compared to simply controlling for family as a random
effect. The analyses were conducted in the R statistical program-
ming environment (R Core Team, 2023) using the functions glm
and glmer. A global (full) model was built and the dredgefunction
was used to identify models with the most parsimonious combina-
tions of predictors. Models were assessed by the Akaike Information
Criterion corrected for small sample sizes (AICc) and the best-
supported models were considered to be those with ΔAICc < 2
(Burnham et al., 2011).
3|RESULTS
3.1 |Plant rediscovery and discovery in Singapore
There have been 173 rediscoveries and 155 new native records for
Singapore in the last 14 years (from November 2009 to July 2023;
Figure 2a and Data S1). The rediscoveries include 11 infraspecific
taxa, whereas the new records include 10 infraspecific taxa. Most
rediscoveries were from new collections through field surveys (90.8%)
rather than from the redetermination of only pre-existing unidentified
or misidentified specimens by taxonomic specialists; on the other
hand, more new records resulted from the redetermination of pre-
existing specimens (56.8%) rather than new field collections
(Figure 2a;χ
2
=85.3, df =1, p< .001).
Among the new native records, 22 taxa were new to science at
the time of discovery in Singapore (based on the date of publication
of the protologue; Data S1 and Figure 3). Sixteen of these were pri-
marily identified through redetermination of pre-existing specimens,
highlighting the critical role of taxonomic expertise in recognising and
describing new taxa. Fourteen of the 22 taxa were first described
from type material collected from Singapore. Five of the new native
records are endemic to Singapore based on current knowledge, and
one of these (Neonauclea kranjiensis) is already globally extinct. There
is no biogeographical pattern immediately apparent from the distribu-
tion ranges of the rediscovered and newly recorded taxa, which
extend from Singapore or Singapore and Peninsular Malaysia only, to
surrounding territories such as Sumatra and Borneo, throughout
TABLE 1 Possible predictors of whether plant taxa presumed
extinct in Singapore will be rediscovered, and their hypothesised
mechanisms. *The Floras considered were: Flora Malesiana, Tree
Flora of Malaya, Flora of Peninsular Malaysia, Flora of Singapore, and
Tree Flora of Sabah and Sarawak.
Predictor Hypothesis
Woody/non-woody (binary) Woody plants such as trees and
shrubs may be easier to
encounter, access and observe,
and are often better-studied
than herbaceous plants. These
are therefore less likely to have
been overlooked and more likely
to be genuinely nationally
extinct, reducing chances of
rediscovery.
Climbing or (hemi)epiphytic/
not climbing or (hemi)
epiphytic (binary)
Climbing or epiphytic plants may
be more difficult to encounter,
access and observe, thereby
reducing chances of rediscovery.
Woody climbing/(hemi)
epiphytic (interaction)
Compared to herbaceous climbers
which are mostly found in the
forest understorey, or woody
non-climbing/non-(hemi)
epiphytic plants which may be
easier to encounter, access and
observe, plants which are
climbing/(hemi)epiphytic and
woody often flower and fruit
high up in the forest canopy and
may be more difficult to
encounter, access and observe,
reducing chances of rediscovery.
Number of national or regional
Floras* in which the family
has been treated
(continuous)
This is a proxy for taxonomic effort
or interest, since taxa from
families which have been revised
more times for the region could
be better-known and therefore
may be genuinely nationally
extinct, reducing chances of
rediscovery.
4NEO ET AL.
Southeast Asia, and from Africa or India and South China to Australia
and the Pacific (see Data S1).
A study by Kristensen et al. (2020) predicted that the number of
native plant species discovered for Singapore has not yet levelled off.
Indeed, when we plotted the cumulative number of taxa added
between 2009 and July 2023 as compiled in the present study, we
found that this continues to increase steadily (Figure 2b). The average
rediscovery rate was about 12 species per year. Examining the num-
ber of rediscoveries and new records based on the year of first publi-
cation, peaks were observed in 2012, 2018 and 2022 (Figure 2c). The
2012 peak in rediscoveries is mostly due to the publication by Chong
et al. (2012) of rediscoveries based on specimens collected from 2009
to 2012. Peaks in both rediscoveries and new records were observed
in 2018, of which about half can be attributed to the publication of
collated results from comprehensive field surveys (e.g., Chong
et al., 2018; Ho et al., 2018; Khoo et al., 2018; Lim et al., 2018) and
the other half to precursor publications of the Flora of Singapore,
mainly resulting from the redetermination of pre-existing specimens
(e.g., Seah & Wong, 2018; Turner, 2018; Wong & Mahyuni, 2018).
The 2022 peak in rediscoveries mostly consists of those published in
Lindsay et al. (2022), which were based on even more recent speci-
mens such as those collected for a genome-sequencing project of the
native vascular plants of the BTNR (Niissalo & Choo, 2021), and also
those made by taxonomic specialists redetermining specimens for the
Flora of Singapore project.
Determining the site of the first collection of the rediscoveries
and new records can suggest where further surveys should be tar-
geted (Figure 2d). The same sites were important for the rediscoveries
and new records: the highest number of collections were from the
lowland primary rain forest fragment of the BTNR (44 rediscoveries,
22 new records), followed by the last substantial area of freshwater
swamp forest remaining in Singapore, the Nee Soon Swamp Forest
(NSSF; 43 rediscoveries, 17 new records), and the rest of the CCNR
(excluding the NSSF) that comprises a mixture of primary and native
FIGURE 2 Summary statistics of plant rediscoveries and new native records for Singapore in the last 14 years. (a) Rediscoveries and new
records for Singapore from November 2009 to July 2023, from new field collections compared to taxonomic work and redetermination of pre-
existing specimens. (b) The cumulative number of plant species recorded in Singapore since 1880. The black line is based on data from Kristensen
et al. (2020; see figure 2a in that paper) while the red line shows the newly recorded taxa after 2009 based on year of first publication compiled
in the present study. (c) The number of rediscoveries and new records published yearly after 2009. (d) Sites of first (re)discovery for taxa newly
recorded from field surveys. BTNR, Bukit Timah Nature Reserve; CCNR, Central Catchment Nature Reserve (excluding the NSSF); LNR, Labrador
Nature Reserve; NSSF, Nee Soon Swamp Forest; SBG rain forest, rain forest fragment in the Singapore Botanic Gardens; SBWR, Sungei Buloh
Wetland Reserve.
NEO ET AL.5
species-dominated secondary forest (41 rediscoveries, 13 new
records). Other sites included offshore islands comprising fragments
of coastal and mangrove forests and native species-dominated sec-
ondary forest, and other secondary forest fragments including nature
parks and corridors.
Trees and climbers were almost equally the most well-
represented life forms among the rediscoveries, followed by ground
herbs and epiphytes; whereas trees were the most well-represented
among the new records, followed by climbers, ground herbs and
shrubs (Figure 4). The proportions of rediscoveries and new records
represented by each life form were significantly different (χ
2
=10.5,
df =4, p< .05), with epiphytes significantly more well-represented
among the rediscoveries (pairwise post hoc tests with Bonferroni cor-
rection, p< .05), and trees (including palms), ground herbs (including
seagrasses) and shrubs (including bamboos) more well-represented
among the new records but not significantly so.
The proportion of rediscoveries represented by each life form
was significantly different from that of the presumed nationally
extinct flora (χ
2
=61.0, df =4, p< .001; Figure 4), with climbers sig-
nificantly more well-represented among the rediscoveries (pairwise
FIGURE 3 Some of the plant taxa both new
to Singapore and new to science at the time of
discovery. (a) Canthiumera robusta, (b) Utania
nervosa, (c) Hanguana neglecta, (d) Hanguana
rubinea, (e) Nervilia singaporensis,(f)Ventilago
ferruginea, (g) Gynochthodes praetermissa,
(h) Zingiber singapurense. Photo credits: ab, eh:
X.Y. Ng; cd: R. Lim.
6NEO ET AL.
post hoc tests with Bonferroni correction, p< .001) and epiphytes sig-
nificantly under-represented (p< .001). The proportion of new
records represented by each life form was significantly different from
that of the total native flora (χ
2
=12.7, df =4, p< .05; Figure 4), with
climbers significantly more well-represented among the new records
(pairwise post hoc tests with Bonferroni correction, p< .05).
Among the rediscoveries, the two most well-represented families
(Figure 5) were the Orchidaceae (26 taxa of which 24 were from new
field collections) and Rubiaceae (13 taxa of which 10 were from new
field collections). The Orchidaceae were significantly under-repre-
sented in the rediscoveries compared to the presumed nationally
extinct flora (χ
2
=9.30, df =1, p< .01).
Among the new records, the most well-represented families
(Figure 5) were the Rubiaceae (18 taxa, all from redetermined pre-
existing specimens), Orchidaceae (eight taxa of which five were from
new field collections), Euphorbiaceae (eight taxa of which seven were
from redetermined pre-existing specimens) and Annonaceae (eight
taxa of which six were from new field collections). The Rubiaceae
(χ
2
=6.86, df =1, p< .01) and Euphorbiaceae (Fisher's exact test,
p< .05) were significantly over-represented in the new records com-
pared to the total native flora.
3.2 |Predictors of rediscovered plant taxa
Of the models tested to predict the rediscovered plant taxa, GLMMs
with family as a random effect were better supported (lower AICc
value) than GLMs without the random effect. There was only one
best-supported model and only the interaction term between woody
and climbing/(hemi)epiphytic habit had a significant effect, suggest-
ing that rediscovered taxa were more likely to be woody and slightly
more likely to be climbing/(hemi)epiphytic, but significantly more
likely to be both woody and climbing/(hemi)epiphytic (Figure 6).
However, this model had low explanatory power, with low marginal
and conditional variances explained by the fixed effects (R
2m
=.035)
and combination of fixed and random effects (R
2c
=.097),
respectively.
3.3 |Conservation statuses of rediscoveries and
new records
Most of the rediscovered and newly recorded taxa (94.2% and 62.6%,
respectively) have been evaluated as nationally Critically Endangered
(Figure 7; Middleton et al., in press). However, when considering their
regional and global conservation statuses, most of these taxa have not
been assessed as they are probably still not sufficiently well-known
throughout their distribution ranges (Data S1).
4|DISCUSSION
Despite Singapore's highly urbanised environment and historically
well-documented flora, plant discovery has clearly not yet levelled off,
FIGURE 4 Proportions of rediscoveries and new records represented by life form compared to the presumed nationally extinct and the total
native flora of Singapore.
NEO ET AL.7
with 173 rediscoveries and 155 new native records in 14 years. Hum-
phreys et al. (2019) compiled rediscoveries of presumed globally
extinct species over three decades and estimated a rediscovery rate
of 16 species per year. Here, we report an average rediscovery rate of
12 per year for presumed nationally extinct taxa. The findings of our
study highlight the critical importance of comprehensive botanical
surveys and taxonomic research for plant (re)discovery, as has also
been noted by similar studies in Europe (e.g., Abeli et al., 2021) and
globally (Vorontsova et al., 2021).
4.1 |Plant rediscoveries and discoveries by life
form and family
That trees and climbers were so well-represented among both the
rediscoveries and new records was a surprising finding, especially
because trees are often assumed to be better-studied and less likely
to be overlooked (e.g., Humphreys et al., 2019). A possible reason for
this could be the previous mis-identification of some of these taxa
owing to the lack of good diagnostic features in pre-existing specimen
material (Goodwin et al., 2015). In Southeast Asia's aseasonal lowland
rain forests, many plants have supra-annual reproductive cycles, and
reproductive material for many large tree and canopy climber species
is often not easy to come by. This, coupled with their great height, can
make it difficult for representative specimens to be collected and
properly identified without taxonomic specialists' attention. Closely
related species are often difficult to tell apart from vegetative charac-
ters alone, and cryptic species are often overlooked until detailed
study is undertaken (Bacon et al., 2022). For example, closely related
tree species in the Euphorbiaceae were only recently recognised as
two new records of Blumeodendron and one new record of Endosper-
mum through painstaking taxonomic research (van Welzen
et al., 2020). Some tree species may also be extremely rare and thus
eluded detection, such as Margaritaria indica, first discovered in
Singapore in 2014 and known to occur in very low numbers through-
out its range (Low et al., 2014), and Neonauclea kranjiensis, first
described in 2018 from a single specimen collected in 1894 from
Singapore, now extinct and known from nowhere else in the world
(Seah & Wong, 2018).
Cryptic species have also been teased apart among herbaceous
plants in Singapore. In the genus Hanguana, seven species have been
distinguished from the species complex previously referred to as
Hanguana malayana, of which five are new native records for
Singapore and two are endemic (Leong-
ˇ
Skorniˇ
cková & Boyce, 2015;
Niissalo & Leong-
ˇ
Skorniˇ
cková, 2017). Molecular and morphological
evidence were used in combination to support the description of a
new species of terrestrial orchid, Nervilia singaporensis (Niissalo
et al., 2020), which had been recognised under a misapplied name for
a long time. Nevertheless, we found that herbaceous plants such as
ground herbs and epiphytes were under-represented among the redis-
coveries and new records, compared to their proportions in the total
native flora and the presumed nationally extinct flora. In particular,
FIGURE 5 Proportions of rediscoveries and new records in the topmost well-represented families compared to the presumed nationally
extinct and the total native flora of Singapore.
8NEO ET AL.
the Orchidaceae, despite being the family with the most rediscovered
taxa, was still significantly under-represented in the rediscoveries
compared to its large proportion in the presumed nationally extinct
flora. Further field surveys and taxonomic work could allow for more
(re)discoveries of these groups of plants, although, in the case of the
Orchidaceae, it may also be possible that many orchids are genuinely
nationally extinct owing to habitat loss and overharvesting in the past
(Turner et al., 1994).
4.2 |Predictors of rediscovered plant taxa
Plants that are both woody and climbing/(hemi)epiphytic were
shown to be slightly more likely to be rediscovered than plants lack-
ing either of these characteristics. We hypothesised that woody
climbers or (hemi)epiphytes are typically inaccessible and not often
reproductive, but these factors may apparently have improved rather
than reduced chances of rediscovery because these plants could
have been overlooked and/or more specialist attention has been
paid to them recently. For example, Jasminanthes maingayi, a rare
woody climber, was rediscovered after 120 years when a treefall
lowered a plant from the forest canopy, allowing flowering material
to be collected and identified (Yeoh et al., 2013). Likewise, two
species of the woody liana genus Uncaria were rediscovered after
more than 130 years when they flowered and substantial effort was
made to collect material from more than 10 m above the ground
(Ng, Lua, et al., 2022).
Nevertheless, the statistical model we tested had very low
explanatory power in predicting the rediscovered taxa. This suggests
that differences in life form can only explain a small part of the proba-
bility of rediscovering an extinct species, and that rediscoveries are
driven by other factors we did not test, or may simply be largely
attributed to chance (e.g., as demonstrated by the discovery of Jasmi-
nanthes maingayi described above). Moreover, the number of national
or regional Floras in which the plant families have been treated did
not have a significant effect, but this could be because almost half of
the rediscovered taxa are from families not yet treated in any national
or regional Flora.
FIGURE 7 National conservation statuses (according to Middleton et al., in press) of rediscoveries and new records for Singapore in the last
14 years.
FIGURE 6 Predicted effects of woody and climbing/(hemi)
epiphytic habits and their interaction on the probability of
rediscovery. The vertical lines are confidence intervals.
NEO ET AL.9
4.3 |From plant (re)discovery to conservation
Our findings demonstrate the importance of continuing field surveys
for tropical plant discovery even in a small city-state that has already
been densely collected and explored. Our findings also emphasise the
value of remnant forest fragments within an urban matrix. Protected
primary forest sites were shown to be particularly important, with the
collated results of targeted comprehensive surveys of the BTNR and
the NSSF contributing to spikes in both rediscoveries and new
records. The small number of (re)discoveries in young regenerating
secondary forests and buffer parks shows how even such highly dis-
turbed fragments can support some rare native species (e.g., Neo
et al., 2014).
Taxonomic work resulting in the redetermination of pre-existing
specimens was even more important than new field collections for the
discovery of new native records. Of the 22 new records that were also
new to science, 16 were described from pre-existing specimens rather
than new field collections. These findings reinforce those of Bebber
et al. (2010), which demonstrated that an overwhelming 84% of new
species described between 1970 and 2010, out of a dataset of 3219
species, were based on pre-existing rather than new field collections.
The representation of plant families among the rediscoveries and new
records further indicates a positive relationship between taxonomic
work and plant discovery. Of the families most well-represented
among the rediscoveries and new records, the Rubiaceae was treated
in a published volume of the Flora of Singapore (Wong et al., 2019)
while the Euphorbiaceae and Annonaceae are among those being
actively prepared. This underscores the importance of investment in
taxonomic research and maintaining expertise in the local flora,
because having a high number of working specialists can be associated
with a high number of plant discoveries, that is, the botanist effect
(Moerman & Estabrook, 2006). Establishing and maintaining local
expertise is also important (Ahrends et al., 2011), with future species
discoveries and descriptions predicted to be more likely from resident
rather than non-resident taxonomists (Liu et al., 2023).
With most of the (re)discovered plant taxa being assessed as
nationally Critically Endangered (Middleton et al., in press), conserva-
tion action is clearly needed. Moreover, most of these taxa lack
regional and global conservation assessments, indicating gaps in
knowledge of how threatened they might be outside of Singapore.
Species recovery work is especially needed for the taxa endemic to
Singapore, most of which are only known from a very small number of
individuals and could represent an extinction debt (Niissalo
et al., 2017; Tilman et al., 1994). For example, current known popula-
tions of the endemic ginger Zingiber singapurense have been found to
be highly relictual, susceptible to inbreeding and unlikely to persist in
the long term (Niissalo et al., 2018). For these reasons, the National
Parks Board of Singapore has launched a national species recovery
programme, under which staff carry out the monitoring of endemic
and nationally threatened taxa to better understand their population
sizes and dynamics, and actively collect propagation materials to grow
these taxa for ex-situ conservation, research and future reintroduction
into natural habitats (see Lim et al., 2019).
In some cases, cities may be our last chance to conserve plant
species (Soanes & Lentini, 2019). Singapore as a case study demon-
strates that plant rediscoveries and new discoveries are still possible
in cities where remaining fragments of original forest are reserved for
species conservation, other green spaces are maintained for ecological
connectivity, and there is continued investment in comprehensive
botanical surveys and taxonomic research. A concerted effort to cou-
ple surveys and research (both by trained professionals and by citizen
scientists) with conservation efforts and species recovery programmes
can support the persistence of rare native plant species and provide
opportunities for conservation in cities.
AUTHOR CONTRIBUTIONS
Louise Neo, Kwek Yan Chong, Stuart Lindsay, David J. Middleton,
Puay Yok Tan and Kenneth Boon Hwee Er contributed to the con-
cept, writing and review of this article. Louise Neo, Stuart Lindsay,
David J. Middleton and Kwek Yan Chong primarily compiled the data
for this study. Louise Neo and Kwek Yan Chong conducted the data
analyses and the preparation of figures and tables.
ACKNOWLEDGEMENTS
We acknowledge the expertise and assistance of many of our
colleagues who made the plant discoveries reviewed in this article or
who otherwise contributed to the compilation of the data used in this
study.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interest.
DATA AVAILABILITY STATEMENT
The data used in this study are available in the supporting information
of this article (Data S1).
ORCID
Louise Neo https://orcid.org/0000-0002-8185-3288
Kwek Yan Chong https://orcid.org/0000-0003-4754-8957
Stuart Lindsay https://orcid.org/0000-0002-9364-6542
David J. Middleton https://orcid.org/0000-0003-3754-1452
Puay Yok Tan https://orcid.org/0000-0003-0378-590X
Kenneth Boon Hwee Er https://orcid.org/0000-0003-4485-7260
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SUPPORTING INFORMATION
Additional supporting information can be found online in the Support-
ing Information section at the end of this article.
How to cite this article: Neo, L., Chong, K. Y., Lindsay, S.,
Middleton, D. J., Tan, P. Y., & Er, K. B. H. (2024). A botanical
oasis rather than a biological desert: Rediscoveries, new
species and new records in a tropical city. Plants, People,
Planet,113. https://doi.org/10.1002/ppp3.10482
NEO ET AL.13
... Until the collection from the Nee Soon Pipeline in 2011, the species was not recorded from Singapore. Despite Singapore being comparatively very well collected within Malesia (see Middleton et al., 2019), activities toward the Flora of Singapore programme, including additional fieldwork, collecting and critical re-appraisal and identification of herbarium material, has resulted in 150 additional species added to the flora of the island in a 14-year period from 2009-2023 (Neo et al., 2024). Climbing taxa, especially lianas reaching the canopy, were highlighted by Neo et al. (2024) as one of the groups previously overlooked by previous botanists and requiring specialist attention. ...
... Despite Singapore being comparatively very well collected within Malesia (see Middleton et al., 2019), activities toward the Flora of Singapore programme, including additional fieldwork, collecting and critical re-appraisal and identification of herbarium material, has resulted in 150 additional species added to the flora of the island in a 14-year period from 2009-2023 (Neo et al., 2024). Climbing taxa, especially lianas reaching the canopy, were highlighted by Neo et al. (2024) as one of the groups previously overlooked by previous botanists and requiring specialist attention. In the Icacinaceae, a new monotypic genus of canopy climber has been described relatively recently from material from primary rainforest in Borneo (Utteridge et al., 2005). ...
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Two species of Phytocrene Wall. are recorded for Singapore: the widespread and commonly collected species P. bracteata Wall., and P. oblonga Wall., known from a single collection from Nee Soon Swamp Forest in the Central Catchment Nature Reserve. Phytocrene bracteata is also cultivated in Singapore Botanic Gardens. The typification of each name is addressed, and a key to the two species, descriptions, an illustration of P. oblonga as well as photographs of both species are provided.
... This is in spite of the fact that Singapore is probably the most botanically densely collected tropical country in the world . Comparing between two national plant checklists from 2009 and 2023 (i.e., Chong et al., 2009based on Lindsay et al., 2022, Neo et al. (2024) showed that there have been 173 rediscoveries and 155 new records documented after 2009, including 22 species new to science and five endemic species. Among the rediscoveries and new records, the Orchidaceae was one of the best represented families, with 26 rediscovered and eight new taxa. ...
... With the exception of the dip in orchid species between Ridley and Holttum, which was due to the fact that Holttum did not specifically mention Singapore in the orchid descriptions, it is evident that the number of native orchid taxa recorded for Singapore continued to increase (Fig. 1). Additions of new records from 2009 to 2023 could be attributed largely to taxonomic revisions and new discoveries in the field ( Fig. 2; Neo et al., 2024). More significantly, the number of native orchids recorded for Singapore does not appear to have plateaued. ...
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The conservation status of orchids in the city-state of Singapore mirrors the worldwide decline of this group of plants, one of the largest families of flowering plants. Despite this, the number of extant native orchids has been revised from 45 to 76 in the last 15 years largely due to taxonomic revisions and (re-)discoveries. Building on the history of orchid taxonomic research in the Singapore Botanic Gardens and the revival of plant systematics in Singapore, these recent successes reflect efforts in establishing resident taxonomists and field ecologists, embracing integrative taxonomy, undertaking comprehensive botanical surveys, and developing an opportunistic instinct to discover orchids in the field. Coupled with ongoing species recovery efforts, this provides a sense of optimism for conservation and suggests that small habitat fragments characteristic of cities could continue to be refugia for native orchids. This also further illustrates the important role that botanic gardens play in the conservation of endangered plant species.
... Urban green spaces (UGSs), which include all vegetation-covered areas in the city, ranging from natural to artificial ecological systems with vegetation, play a crucial role in urban sustainability. They offer multiple benefits to humans, such as climate regulation [3][4][5], air quality improvement [6,7], biodiversity conservation [8][9][10], carbon sequestration [11], waterlogging control [12], and positive effects on the physical and mental health of urban residents [13][14][15]. Consequently, UGSs have been recognized as a key factor in promoting urban sustainability. ...
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Urban green spaces (UGSs) are integral to urban ecosystems, providing multiple benefits to human well-being. However, previous studies mainly focus on the quantity or quality of UGSs, with less emphasis on a comprehensive analysis. This study systematically examined the spatiotemporal UGS dynamics in the Pearl River Delta urban agglomeration (PRDUA) in China from the perspectives of the area, spatial configuration, and quality, using the high spatial resolution (30 m) Landsat-derived land-cover data and Normalized Difference Vegetation Index (NDVI) data during 1985–2021. Results showed the UGS area in both the old urban districts and expanded urban areas across all nine cities in the PRDUA has experienced a dramatic reduction from 1985 to 2021, primarily due to the conversion of cropland and forest into impervious surfaces. Spatially, the fragmentation trend of UGSs initially increased and then weakened around 2010 in nine cities, but with an inconsistent fragmentation process across different urban areas. In the old urban districts, the fragmentation was mainly due to the loss of large patches; in contrast, it was caused by the division of large patches in the expanded urban areas of most cities. The area-averaged NDVI showed a general upward trend in urban areas in nearly all cities, and the greening trend in the old urban districts was more prevalent than that in the expanded urban areas, suggesting the negative impacts of urbanization on NDVI have been balanced by the positive effects of climate change, urbanization, and greening initiatives in the PRDUA. These findings indicate that urban greening does not necessarily correspond to the improvement in UGS states. We therefore recommend incorporating the three-dimensional analytical framework into urban ecological monitoring and construction efforts to obtain a more comprehensive understanding of UGS states and support effective urban green infrastructure stewardship.
... Thus, we hope that our paper motivates others to report cases of, e.g., more orchid or lichen species not only from the Americas, but from anywhere else on the globe. Finally, our study should also be seen as an important contribution to the growing literature on plants in urban settings [9,[45][46][47]. In a world with increasing dominance of Homo sapiens, many plants take advantage opportunistically of structural resources such as fences, walls, roofs, or power lines, but the study of this phenomenon is far from complete. ...
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There are a number of rather anecdotal reports of plant growth on power cables in the Americas, but until now there has been no systematic attempt to gauge the geographical extension of this phenomenon nor a documentation of the diversity of species found there. Using observations from the participatory science data platform iNaturalist and the scientific literature, we document almost 700 occurrences of more than 40 species of vascular plants and three lichen species on power cables with a geographical distribution over 7000 km from the southern United States to northern Argentina. Based on these observations we discuss the ecological conditions of plant growth on power cables in terms of climate; elevational distribution; and the morphological, physiological, and life history traits that allow the observed set of species to thrive on this anthropic structure.
... These areas have higher human activity levels, and human activities have a more coordinated relationship with HQ. These remaining fragments of natural habitats are crucial refugia and stepping stones for maintaining urban biodiversity (Neo et al., 2024). They can also serve as buffer zones for urban development, preventing further construction land expansion. ...
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