ISSN 2816-6531

The first record of an alien aquatic plant, Egeria najas Planch. (Hydrocharitaceae), in Malaysia

Andrey  
Efremov  
authors orcid
Tags: Alismatales, Angiospermae, Egeria najas, Hydrocharitaceae, Malaysia, Monocotyledones, Plantae, Tracheophyta
Number 41, 
13 February 2025

Introduction

The genus Egeria Planch. encompasses three species: Egeria densa Planch., E. heterostemon S. Koehler & C.P. Bove and E. najas Planch. (Cook & Urmi-König, 1984; Koehler & Bove, 2001). Sometimes this genus is included in the genus Elodea Michx. (GBIF, 2024). Egeria heterostemon is endemic to Central Brazil, E. densa is considered to be native to Northeast Argentina, Bolivia, South Brazil and Uruguay, but has now formed a nearly cosmopolitan secondary range (Cook & Urmi-König 1984; GBIF, 2024).

Egeria najas is an autochthonous species for Northeast Argentina, Bolivia, Brazil, Paraguay and Uruguay (Cook & Urmi-König 1984; GBIF, 2024; see also Material), which began to spread in tropical, subtropical and temperate regions of western and central Europe and Asia. In Asia, it is currently found in Hong Kong and Singapore (GBIF, 2024). It lacks morphologically specialized hibernacula and vegetative dispersal organs (Cook & Urmi-König 1984), which limits its ability to spread in temperate regions. The plant easily reproduces vegetatively (non-specialized morphological disintegration); seed reproduction is often limited by sexual segregation. This is the first presentation of the information on a new species of aquatic plant, E. najas, which is alien to Malaysia.

Results and Discussion

Information about a new record and herbarium specimens: Malaysia, Wilayah Persekutuan Kuala Lumpur, Titiwangsa, Taman Tasik Titiwangsa, East Lake, 03°10′46″ N, 101°42′33″ E, depth 0.2-0.3 m, sandy bottom soil, phytocenoses of Thalia geniculata L. ‒ Egeria najas and Egeria najas, total protective cover (PC) 50-60%, 04.I.2024, A.N. Efremov, IBIW 74397.

Only female plants were found in the coenopopulation (Fig. 1). They formed two types of shallow-water communities in the East Lake: Thalia geniculata (PC 30%) ‒ E. najas (PC 40-50%) and pure thickets of E. najas (Fig. 2). Beside the dominants, Hymenocallis speciosa (L.f. ex Salisb.) Salisb., Ludwigia sp., Fimbristylis dichotoma (L.) Vahl were also discovered. The water characteristics were measured using a multifunctional tester Megeon 17002 (Russia) in accordance with the instructions. The water in the habitat had a temperature of 26.6 ˚С, pH of 8.65, salinity of 92 ppm, conductivity of 275 μS/cm.

In Indonesia, the proportion of introduced, naturalised or invasive aquatic species is 10.1-20.0% (Lobato-de Magalhães et al. 2022). The Harmonia+ protocol (Belgian Biodiversity Platform, 2024) was used for the invasion risk assessment. The invasion risk proved to be moderate (0.39), which requires monitoring the spread of E. najas. For Malaysia, the probability of finding the invasive species E. densa, which is widespread in neighboring regions and significantly transforms local aquatic vegetation communities, is extremely high. The identification key for both species is given below (Cook & Urmi-König 1984, amended and augmented).

Leaves mostly in whorls of 4, usually spreading, averagely 22.6 ± 6.4 × 3.1 ± 0.6 mm; leaf edge slightly serrate; filaments club-shaped, constricted below the anther, strongly papillose; staminodia of female flowers almost club-shaped …………………………........................ Egeria densa

Leaves mostly in whorls of 5, usually recurved, averagely 14.5 ± 4.8 × 1.5 ± 0.4 mm; leaf edge with large prickles, serrate; filaments elongate, not constricted below the anther, weakly papillose above; staminodia of female flowers elongate ……..........................……………..…… Egeria najas

Acknowledgments

The author thanks the staff of the University of Malaya (KLU) and the Papanin Institute for Biology of Inland Waters (IBIW) for help during the work with herbarium specimens, and Ilia Kibishevand and Sergey Morozov for assistance during field studies.

Material

References

1.

Belgian Biodiversity Platform. 2024. Available: http://ias.biodiversity.be/protocols/form (accessed 2024.11.22).

2.

Cook, C.D.K. and K. Urmi-König. 1984. A revision of the genus Egeria (Hydrocharitaceae). Aquatic Botany, 19(1-2) :73-96. https://doi.org/10.1016/0304-3770(84)90009-3

3.

GBIF.org (29 November 2024) GBIF Occurrence Download for Egeria Planch. https://doi.org/10.15468/dl.ru33u4

4.

Koehler, S. and C.P. Bove. 2001. Hydrocharitaceae from Central Brazil: a new species of Egeria and a note on Apalanthe granatensis. Novon, 11(1):63-66. https://doi.org/10.2307/3393209

5.

Lobato-de Magalhães, T.,·Murphy K., Efremov A., Davidson Th.A., Molina-Navarro E.,·Wood K.A., Tapia Grimaldo J., Hofstra D.,·Fu H. and I. Ortegón-Aznar. 2022. How on Earth did that get there? Natural and human vectors of aquatic macrophyte global distribution. Hydrobiologia, 850: 1515-1542. https://doi.org/10.1007/s10750-022-05107-0

6.

Planchon JÉ. 1849. Synopsis specierum Anacharidis et Apalanthes. Annales des Sciences naturelles. 3e Série. Botanique, 11: 73-82. https://www.biodiversitylibrary.org/page/47175182

Figures

Fig_1

Fig 1. Female plants of Egeria najas.

Fig_2

Fig 2. Community of Egeria najas.