Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 October 2023 | 15(10): 24148–24150
ISSN 0974-7907 (Online) | ISSN 0974-7893
(Print)
https://doi.org/10.11609/jott.8646.15.10.24148-24150
#8646 | Received 04 July 2023 | Final
received 09 September 2023 | Finally accepted 04 October 2023
Threats faced by Humboldtia bourdillonii
Prain (Magnoliopsida: Fabales: Fabaceae), an endangered tree endemic to the
southern Western Ghats, India
Jithu K. Jose 1
&
K. Anuraj 2
1 Karakkadayil House, Nazareth Hill P.O,
Kottayam, Kerala 686633, India.
2 Karakkath Veedu,
Anamangad, Aliparamba P.O.,
Malappuram, Kerala 679357, India.
1 jithukjose1@gmail.com
(corresponding author), 2 kanuraj684@gmail.com
Editor: Aparna Watve,
Biome Conservation Foundation, Pune, India. Date
of publication: 26 October 2023 (online & print)
Citation: Jose, J.K.
& K. Anuraj (2023). Threats faced by Humboldtia bourdillonii
Prain (Magnoliopsida: Fabales: Fabaceae), an endangered tree endemic to the
southern Western Ghats, India. Journal of Threatened Taxa 15(10): 24148–24150. https://doi.org/10.11609/jott.8646.15.10.24148-24150
Copyright: © Jose & Anuraj 2023. Creative Commons Attribution 4.0
International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: None.
Competing interests: The authors declare no competing interests.
Forests cover nearly a third of
the world’s surface (Lee & Jarvis 1996), containing almost 60,000 tree
species (BGCI 2022). According to the first Global Tree Assessment Report in
2021, almost 1/3rd of these tree species are threatened with
extinction, of which 142 have already recorded as ‘Extinct’ (BGCI 2021). Of all
the tree species 58% are single-country endemics (Beech et al. 2017). The
report says that there are 2,603 tree species in India, of which 650 are
endemic and 469 are under the threat of extinction (BGCI 2021). Western Ghats
is one of the biodiversity hotspots in India with high floristic diversity and
endemism (Jose et al. 2023).
The genus Humboldtia
comprises nine species (Kumar et al. 2022), all of which are endemic to the
Western Ghats, except H. laurifolia which is
endemic to Sri Lanka. Humboldtia bourdilloni Prain is an
Endangered species (World Conservation Monitoring Centre 1998) endemic to the
southern Western Ghats, India. It is locally known as ‘Adimundan’
and belongs to the family Leguminosae and subfamily Caesalpinioideae.
It is a medium-sized tree that grows up to 20 m in evergreen forests in the
altitudinal range of 200–1,250 m. The species was first described by David Prain, based on the collections of T.F. Bourdillon
from Peermede Ghats in 1894, then for the next 108
years there was no report or data about this species. In 2002, the Kerala
Forest Research Institute (KFRI) research team rediscovered this species from
the Periyar Tiger Reserve. Now this species is facing
serious ecological and man-made threats in its natural habitat.
We conducted extensive forest
surveys in the southern Western Ghats region from June 2021 to March 2023 to
study the population and ecology of H. bourdillonii
in its natural habitat (Image 1). The information from floristic literature and
herbariums helped us to plan the field surveys. The major population sites
located were Kulamavu, Vagamon,
and Arjunankotta-Poonkavanam forests in the Periyar Tiger Reserve of the Peermede
plateau. The population studies showed that H. bourdillonii
has an area of occupancy of less than 0.06 km2 and an area of
occurrence is approximately 2 km2. The number of mature trees is
less than 200.
There are irregularities observed
in the flowering and fruiting of H. bourdillonii
mainly owing to climate change. Generally, the flowers are produced in
November–January, and fruiting is observed in January–May (Balan et al, 2019).
The flowers are pollinated by wind, ants, and honey bees Apis
indica. However, the intensity of pollinators has
recently decreased. Young fruits are largely consumed by the Malabar Giant
Squirrel Ratufa indica,
which is also endemic to the Western Ghats. Insect infestation heavily affects
the reproductive biology of H. bourdillonii.
Jumping thrips multiply and colonize the young
inflorescence and suck the sap of young fruits. Sixty percent of seeds are lost
due to the damage caused by the weevils. Weevils penetrate the fruit wall and
lay eggs in the cotyledons of the young embryo. The larvae grow at the expense
of the cotyledons and the adults emerge out as the seeds get dispersed. The
entire metamorphosis of the insect occurs within the fruit. The attack of
weevils is more prominent during the months of April and May. The seed
dispersal is carried out by dehiscing pods, the blasted seeds are scattered
around the mother tree indicating the short-distance gene flow within the
population. This short-distance gene flow has affected the genetic diversity of
this species (Rathmacher et al. 2010). The
pre-monsoon rainfall is beneficial to seed establishment but recent abnormal
monsoon flooding (started in 2018) wipes the seeds and hinders the soil seed
bank of the species. The recalcitrant nature of the seed is also a cue factor
affecting the regeneration of the species.
The conversion of forest areas in
Vagamon and Peermede Ghats
into tea and cardamom plantations has heavily affected the populations of H.
bourdillonii. This conversion was started during
the 19th century British rule. Vagamon is
a major tourist spot in Kerala, so tourism development has also negatively
affected this species. The impact of recent abnormal flooding in Kerala
triggered a number of landslides that affected the Vagamon
Hill population of the species. Both locations (Vagamon
and Peermede) of this species are identified as
landslide-prone areas by the Kerala State Disaster Management Authority (KSDMA;
Balan et al. 2019). In Kulamavu forest areas,
commissioning the Idukki Dam reservoir may submerge the populations of the
target species. So, the conservation of this endangered, endemic species is the
need of the hour.
For
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