Ngirhaphium caeruleum, Grootaert & Puniamoorthy, 2014

Samoh, Abdulloh, Satasook, Chutamas & Grootaert, Patrick, 2019, NGS-barcodes, haplotype networks combined to external morphology help to identify new species in the mangrove genus Ngirhaphium Evenhuis & Grootaert, 2002 (Diptera: Dolichopodidae: Rhaphiinae) in Southeast Asia, Raffles Bulletin of Zoology 67, pp. 640-659 : 642-644

Ngirhaphium caeruleum species complex

The original described population of N. caeruleum consisted of large flies with a blue shine on the thorax and the abdomen and they were accordingly named caeruleum , which means blue in Latin. Actually a large population was found on the island of Semakau ( Fig. 1 ). However green metallic shining specimens of N. caeruleum were found in southern Thailand, Brunei, Cambodia and on some small islands around Singapore. Apart from their green body colour, their morphology and the male terminalia resemble the original population from Semakau Island in Singapore, but differ in details. Here we paid attention to the shape and the bristling of the surstyli that are clasping organs. We compared it with the haplotypes based on the NGS barcodes (313 bp).

Fig. 2D represents the original blue population from the type locality on Semakau. On the inside of both right and left surstyli there are small bristles, that are black on the inside but pale on the border of the plate. A few small protuberances are also visible on the border of the plates.

The populations from Brunei (localities Tutong, Berambang, and Labu, Fig. 1 ) have the inside of the surstyli and the border covered with small black bristles without any tubercles. Both surstyli are comparatively wide and the tips are bluntly rounded ( Fig. 2A ). The populations on Pulau Tekong and Pulau Ubin ( Fig. 2B, C ) have similar shaped surstyli as in Brunei with short black bristles.

In the Thai and Cambodian population both surstyli are distinctly more pointed ( Fig. 2E, F ) and the tubercles on the border and sometimes on the inside of the surstyli are more pronounced. The inside of the plates are covered with short yellow bristles.

This distinct morphology and since the genetic distance of the Thai/Cambodian population is 4.2% apart from the Singapore and Brunei population let us decide to consider the Thai and Cambodian population as a different species. Considering it just as a variable species would only lead to loss of information linked to its ecology. The new species is described here below. If we consider the bio-species concept it might well be that the blue N. caeruleum from Semakau represents a distinct bio-species from the green specimens from the surrounding islands of Singapore and the populations on Brunei. However, the short genetic distance of 1–2% difference and the similar morphology except for the general body colour would render this species unrecognisable.

Haplotype network. Number of sequences used: 114

Total number of sites (excluding sites with gaps / missing data): 311

Number of haplotypes, h: 31.

There are seven haplotypes of the caeruleum complex in Thailand and one in Cambodia. They are all unique as can be seen on Fig. 1 . There is no connection shown on the figure between the Thai and the Singaporean population because the genetic distance (4.2%) is too far. The original blue caeruleum population is found on the island of Semakau. On Semakau Island there are only 2 haplotypes: 1 huge population and a very small one. The Semakau population is connected to the Pulau Ubin population where 5 haplotypes occur. One haplotype is shared with Semakau. Pulau Tekong, which is very close to Pulau Ubin has an own unique haplotype. This population seems to be connected to the populations on Brunei. Remarkable is that the connection is by haplotypes occurring in the bay of Brunei (Berambang and Labu) and not the population in Tutong that is closer to Singapore. That population is well separated from the 2 sites in the Bay of Brunei.

Figures

Fig. 1. Haplotype network of the Ngirhaphium caeruleum-complex. Brunei: Berambang, Tutong, Labu; Singapore: Pulau Ubin, Pulau Tekong, Semakau Island; Thailand: Chumphon, Surat Thani, and Cambodia.

Fig. 2. Ngirhaphium caeruleum-complex. View of inside of the dorsal surstylus of the left side and the fused dorsal and ventral surstyli of the right side. Scale = 0.1mm. A, green caeruleum from Tutong, Brunei (ZRCBDP0066395) at 1.6 % from the Semakau population; B, green caeruleum from Pulau Tekong, Singapore (ZRCBDP0001462) at 0.6% from the Semakau population; C, green caeruleum from Pulau Ubin, Singapore (ZRC_BDP_0084430) at 0.6% from the Semakau population; D, blue caeruleum from the type locality on Semakau Island, Singapore (ZRCBDP0118762); E, green thaicum, new species from Surat Thani, Thailand (24-018) at 4.2% from the Semakau population; F, green thaicum, new species from Cambodia (JP3C_Ngi-cambodiensis_Misc002) within the variability of the southern Thailand populations.