An addition to the alien flora of Java: the first record of adventive Costus

*Corresponding Author: Wendy A. Mustaqim, Program Studi Biologi, Fakultas Teknik, Universitas Samudra, Langsa, Aceh, Indonesia; Email: wamustaqim@unsam.ac.id; wendyachmmadm@gmail.com Abstract: More than 6000 plant species, native and introduced, have been recorded in Java that includes the Costaceae family. In the last few years, several additions of alien Costus species have been published from Java. In 2019, a set of specimens of wild Costus sp. was collected from Institut Pertanian Bogor, Bogor, West Java Indonesia. This species is not similar to any previously recorded wild Costus in Java. Therefore, this research aims to identify the collected specimen and provide a taxonomic account for the species. The morphological description was made from the living plant and the collected herbarium. The description was used to identify the species, supported by field notes and photographs. The result showed that the recently collected specimen belongs to Costus dubius. Before this finding, the plant was only known in cultivation in the Bogor Botanical Garden. Therefore, this finding represents the first record of the adventive population of C. dubius in Java and increases the number of wild Costus in Java into seven species. Further researches on Costus in Java are suggested such as the ecological impact due to the presence of several non-native species.


Introduction
The publication of the Flora of Java by Backer and Bakhuizen van den Brink (1963;1965;1968) is one of the most monumental works to the flora of Java. More than 6000 species native and introduced have been reported. With the gap of more than a half century ago, many new discoveries either new taxon (Mahyuni et al., 2018) or new records of native (Puspitaningrum et al., 2017) or alien plants (Irsyam & Mountara, 2018;Irsyam et al., 2019aIrsyam et al., , 2019bIrsyam et al., , 2020 have been published. Costaceae is one of the plant families that can be found in Java. The latest taxonomic account on the Costaceae of Java has been published by Backer & Bakhuizen van den Brink (1968). Later, no more published accounts are available until the 2000s and only Maas (1979) who provided an updated account for all Malesian species where Javan species are also discussed.
Costus is a genus with perhaps as many as 81 to 95 species (Specht, 2006;Specht and Stevenson 2006) and according to POWO (2021), there are 100 accepted species. This genus can be found from the tropics to subtropic regions of the world (POWO, 2021;Wu & Larsen, 2000). In 2013, a nomenclatural changes was made in the genus Costus, where some species was transferred to Hellenia (Govaerts, 2013), but this concept seems not acceptable except in some database like Co's Digital Flora of the Philippines (Pelser et al., 2011-onwards). Many species of Costus have been cultivated as ornamental in Java (Nisyawati and Mustaqim, 2017;Skinner, 2016) and some of them possess medicinal properties like in Costus afer Ker-Gawl (Boison et al., 2019).
After the 2000s, further records of Costus species in Java were provided by Sari et al. (2010), Nisyawati & Mustaqim (2017), Sari et al. (2010), and Irsyam et al. (2019). Sari et al. (2010) mentioned that C. dubius has been cultivated in Bogor Botanic Gardens based on the seed they brought in from The Netherlands. Nisyawati & Mustaqim (2017) Irsyam et al. (2019b) on Costus afer Ker Gawl. In this paper, we present a record for Costus dubius (Afz.) K. Schum. in Java based on an adventive population for the first time.

Material and Methods
Field collecting was conducted in the year of 2019 in IPB University campus area supported by previous botanical explorations by both authors since 2017 ( Figure 1). According to our field explorations, only one wild population of the targeted species that has been found in IPB University area. Specimen was collected follwing the standar guideline from Bridson and Forman (1992). Morphological data of the species were prepared based on dried herbarium materials for the vegetative parts and fresh materials for the generative part including the inflorescence. The identification of the materials was done by using a comparison to descriptions and photographs to many published literatures including Backer & Bakhuizen van den Brink (1968), Maas (1979), Kramer et al. (2017), Mustaqim & Nisyawati (2017) and Irsyam et al. (2019).

B. Distribution and Ecology
This species is native to tropical Africa (Maas-van der Kamer et al., 2016). The previous record in Malesia was made by Maas (1979) from a cultivated plant in Singapore Botanic Gardens and Sari et al. (2010) from plants cultivated in Bogor Botanic Gardens. The adventive population in Java so far known only from the Western part of the island, but maybe also already become adventive elsewhere. The population was found on an abandoned land within a campus area. The plants have already become locally abundant in more or less shaded and humid situations. Flowering seems throughout the year.

C. Important Characters, Notes, and Key
Identification for Javan Costus Species In Java, this species can be recognized solely by the inflorescence that is borne on a separate leafless stem. The plants are strongly assumed to have become naturalized or maybe to a lesser extent, relict of cultivation. Compared to the description in Maas-van der Kamer et al. (2016), we did not find terminal inflorescences and two flowers per bracts in Javan materials. Besides that, we also found that the plants are clad with the minute and subspreading hairs that detached with age and becoming subglabrous. The upper dorsal sides of the bracts are also clad with some hairs. Such difference may be caused by the facts that Maas-van der Kamer et al. (2016) mostly describe the species based on dried materials, which we observed that indumentum is hardly recognized and only appears as powderlike materials. To facilitate the identification of Javan species of Costus, a key is presented below (partly adopted from Maas (1979) and Proctor (2005)

Conclusion
With the addition of C. dubius as an adventive or possibly also capable of become naturalized or even invasive in Java, the number of species for Costus in Java is now increased to seven. Further research in the taxonomy of genus Costus or Costaceae family, distribution and studies on some other aspects, such as the ecological impact of the adventive or naturalized species, are encouraged.