Sandracottus vijayakumari (Coleoptera: Dytiscidae), a new aquatic beetle species from landslide hit area of Nelliyampathy Forest Range, Western Ghats, Kerala, India

The present study deals with the description of a new species Sandracottus vijayakumari from Nelliyampathy forest range, southern Western Ghats, Kerala, India with a comparative key of closely related species S. dejeani Aube, 1838. Only one species is known from the genus Sandracottus Sharp, 1882, from southern Western Ghats, Kerala. The Nelliyampathy forest areas are hilly and the altitude of the hills range 40–1,530 m. The region experiences several types of landslides especially during the monsoon (August to September 2018). The new species was discovered in one of the worst landslide hits area in Nelliyampathy forest, Kundrachola region. The new aquatic beetle species is moderately large in size and often very attractively marked dorsally with complex maculations. Additionally, the new species shows a strong synapomorphy along with Eretini, Hydaticini, and Aubehydrini tribes.

The adephagan beetles are one of the most successful groups of insects, distinguished by their adaptive nature in diverse ecological and geographical ranges. Most aquatic beetles are considered ecological indicators and their diversity is directly correlated with the ecosystem (Hutchison 1959;Boughey 1968;Benetti et al. 2003;Benetti & Regil-Cueto 2004). The factors like wave action, wind velocity, and scarcity of emergent vegetation presumably discourage the colonization of aquatic beetles. The abundance of macrophytic vegetation provides necessary shelter, shade, and substrate for colonization of aquatic beetles in the rainy and post-rainy season (Fernando 1968). Seasonal variation of the insect community in the rain pools, biotic patterns, some physical and meteorological variables were analyzed and found that the maximum taxonomic richness was observed at the end of summer (Fischer et al. 2000).
In India, the aquatic beetle diversity is poorly known. Dytiscidae is a large family of aquatic beetles, harbouring over ~300 species in India and adjacent countries. The Indian dytiscids have been chiefly studied by Vazirani (1968Vazirani ( -1977 where he dealt with 233 species from J TT India, out of which 69 species are from southern India. Till date, the majority of southern Indian species have been recorded from Tamil Nadu including Nilgiri Hills (Mukherjee & Sengupta 1986). During the biodiversity documentation of the flood and landslide hit area of Nelliyampathy, the authors came across a new species of Sandracottus Sharp, 1882 to science which has been described here and its comparison with the closely related species S. dejeani Aube, 1838 is also provided along with identification keys.

Study area
The present study was conducted at various locations in the Nelliyampathy Hills, Western Ghats, Kerala, India in view of the floods and landslides that occurred as a result of the heavy downpour of August and September 2018 that resulted in heavy damage in Kerala, India.

Specimen collection
Specimens were collected from a small rock of pool habitat in the landslide hit area of Nelliyampathy forest range in Kundrachola region (515m, 10 0 30'58''N & 76 0 37'51"E) of southern Western Ghats (Image 1, 2). An aquarium hand net (Miller & Bergsten 2016) was used to collect the samples during the cool dry season from January to March 2019; a total of seven specimens were collected from the field and preserved in 80% Image 1. Nelliyampathy forest with holotype collection locality (red colour).
ethanol prior to mounting. The holotype and paratype is deposited in the Department of Zoology, University of Calicut (DZUC). Specimens were imaged with a Canon EOS 5D Mark IV camera with MP-E 65mm lens, f/2.8 1-5X. Morphological terminology is according to Miller & Bergsten (2016). Identification was done based on available literature and taxonomic keys (Regimbart 1899;Mukherjee & Sengupta 1986;Nilsson 2001;Miller & Bergsten 2016).

J TT
distinct organization of appendages (Image 3B). Structure: Large black color compound eye and cranium, not emarginated; scutellum clearly visible with elytra closed. Filiform antennae and antennomeres 11 (Image 3C); posterior margin of pronotum elevated with dark orange colored mark. Pronotum without lateral bead. In ventral part, distinct prosternal process and discrimen; elytral epipleuron ends in 4 th ventrites. Well distinct metatibial spur with numerous long setae present. Ventral surface of pro-and meso-tarsomeres broadly expanded into rounded palette with ventral adhesive setae; male median lobe symmetrical, protected by numerous spurs. Protarsi distinctly pentamerous, tarsomere IV is smaller than the others (Image 3C). Apices of both metatibial spurs bifid; series of bifid setae on posterior surface of metatibia oblique. Margins of sternites 6 & 7 are somewhat bordered. Mesotibiae with four natatorial setae (Image 3C); metatibiae is found without natatorial setae (Image 3D).
Female: Unknown Diagnosis: This species shows close relation with Sandracottus dejeani Aube, 1838 except in the case of presence of head with fine microreticulation and numerous small setiferous punctures.
Distribution: Known only from the type locality. Etymology: The species is named in honor of Mr. Vijayakumar PK (Aka. Vijayakumar Blathur), Popular science writer in Malayalam for his ardent passion towards insects.
Ecology: Most of the seven specimens of Sandracottus vijayakumari sp. nov. were collected in a partly shaded, shallow, ditch-like forest pool which was rich in decaying leaves and twigs; lentic habitat.

Discussion
Dytiscinae contains five tribes, and 12 genera in total. These are among the largest of all diving beetles in the world. They are characteristic of pond and lakes, but they can be found in different ecosystems, with extensive marginal vegetation. Many of the largest have been involved in predation on vertebrates, some of them may rarely act as competition in fish farming (Wilson 1923;Bishat & Das 1979, 1985Balke & Hendrich 1996;Adeyemo et al. 1997;Megna et al. 2019). In each biogeographic region, there are groups of Dytiscinae with main groups that are endemic to certain areas. They are well distributed in temperate and high altitude to tropical low land habitats .
Until now, one species of Sandracottus was known, i.e., S. dejeani Aube, 1838 from Silent Valley National Park, southern Western Ghats, Kerala, in 1979 (Mukherjee & Sengupta 1986). Sandracottus vijayakumari sp. nov. shows a high similarity with the other tribes, however, analyzing the morphological taxonomic characters of this species shows close affinity to the tribe Aciliini. The strong resemblance between the two species (S. vijayakumari and S. dejeani) can be explained by the multiple convergence arising from a similar shift in

J TT
habitat. Throughout most biogeographical regions, Aciliines are found worldwide with distinct fauna and sometimes uncommon genera, with the exception of Australia, where Aciliines comprises rare species of Sandracottus and the extremely common Rhantaticus congestus (Klug, 1833) (Balke & Hendrich 1996).
Historically, Dytiscinae has been placed under Cybistrinae, which share a number of synapomorphies in both adult and larvae (Alarie et al. 2011;. The tribe Aciliini may act as connecting link between other diving beetles. The new species S. vijayakumari, may play a vital role in the evolutionary lineage of Dytiscinae. Ribera et al. (2002Ribera et al. ( & 2008 suggested that either Eretesor Nottaticusis nested within Aciliini, but the current evidence shows that Eretini is sister to Aciliini (Bukontaite et al. 2014) and Aubehydrini (Notaticus) is sister to that clade . Sandracottus showed synapomorphy together with several other taxa such as Eretini, Hydaticini, and Aubehydrini, especially in the case of both metatibial spurs are apically bifid. Also, the line of bifid setae on the posterior surface of the metatibia is distinctly oblique with resected to the long axis of the tibia. More molecular and evolutionary studies are needed to assess the evolutionary origin and diversification of these taxa, and S. vijayakumari will help to the understand the convergent or divergent evolutionary pattern of Sandracottus genus. In past few years nobody studied the genus, and this genus is currently under revision .

Conclusion
Sandracottus vijayakumari sp. nov. shows close morphological similarity with S. dejeani; however the latter is from Silent Valley, which is north of the Palghat gap of the Western Ghats, where as the new species is from south of the Palghat gap.