Aedes (Ochlerotatus) vigilax (Skuse)

Harbach, Ralph E. & Wilkerson, Richard C., 2023, The insupportable validity of mosquito subspecies (Diptera: Culicidae) and their exclusion from culicid classification, Zootaxa 5303 (1), pp. 1-184 : 43-46

Aedes (Ochlerotatus) vigilax (Skuse)

subspecies ludlowae ( Blanchard, 1905) —original combination: Culex ludlowi [sic] (subspecific status by Knight & Hull 1951 b). Distribution: Philippines ( Blanchard 1905).

subspecies vansomerenae Mattingly, 1955 (in Mattingly & Brown,1955)—original combination: Aedes (Ochlerotatus) vigilax subspecies vansomerenae . Distribution: Seychelles ( Mattingly & Brown 1955).

subspecies vigilax ( Skuse, 1889) —original combination: Culex vigilax . Distribution: Australia, Fiji, Indonesia (Java, Flores, Kalimantan, Sulawesi, Sumatra), Malaysia, New Caledonia, New Hebrides, Papua New Guinea, Solomon Isl., Taiwan, Thailand, Timor, Tonga, Vanuatu, Vietnam ( Wilkerson et al. 2021, incorrectly listed from the Philippines and the Seychelles).

Summary. Aedes vigilax sensu lato is a species complex. A key indicator for us was the report of two molecularly identified species-level taxa that occur throughout coastal Australia, with co-occurrence at the type localities of the nominotypical form (see below). It is not yet known if one or both extend northward into Indonesia and Southeast Asia, or which one should bear the name vigilax . Neither do we know for certain the identity of Ae. vigilax sensu lato north of Australia. The subspecies ludlowae and vansomerenae are geographically isolated in the Philippines and Seychelles, respectively, and can be morphologically characterized. Also known are one or two unnamed taxa in New Caledonia and the New Hebrides. Researchers have usually treated the nominotypical form as a single entity for purposes of discussion and identification, which makes definition of other putative OTUs problematical. See Mattingly (1961) for an example of mixing life stages from different geographical areas to define vigilax . Also, the extensive biological and disease transmission literature (reviewed by Lee et al. 1984) consists of an array of variable attributes, which would be expected when multiple species are lumped together.

The taxa considered here are exclusive members of the Empihals Group of Wilkerson et al. (2015), formerly Ochlerotatus subgenus Empihals Reinert et al., 2008 . In the comprehensive infrasubgeneric classification of the subgenus Ochlerotatus , the taxa are members of the Vigilax Subgroup ( Marks 1949; Vigilax Section of Marks 1957; Empihals Group in part of Wilkerson et al. 2015) of the Taeniorhynchus Group ( Edwards 1932a, in part; Culicelsa Group of Wilkerson et al. 2015). The larvae are primarily adapted to coastal brackish-water marshes and mangroves. Keys and descriptions to nominal vigilax are included in Belkin 1962 (South Pacific), Tanaka et al. 1979 (Ryukyu Archipelago, Japan), Lee et al. 1984 (Australasia), Rattanarithikul et al. 2010 ( Thailand) and Becker et al. 2020 (Asia, Australia). Subspecies vansomerenae is compared by Le Goff et al. (2012) to other species found in the Seychelles, and subspecies ludlowae is included in the key of Knight & Hull (1951) to species of Aedes in the Philippines.

Based on morphological characters included in the keys and individual descriptions contained in the publications cited above, Wilkerson et al. (2021) characterized the adult female and larva of nominal vigilax , paraphrased below. The characters of the male genitalia are from ( Harbach 2022a).

Adult. Decumbent scales of vertex mostly narrow, erect scales cover most of dorsal surface; basal 0.67 of proboscis with midventral pale scaling. Scutum without distinctive markings, sometimes with pale brown scales along acrostichal line and an entirely white scale-patch just anterior to scutellum. Scale-patches on antepronotum, proepisternum and paratergite, broad whitish scales on postspiracular and prealar areas; subspiracular area without scales; lower mesepimeron without setae. [Postpronotal scale patterns are not noted here but we believe they are diagnostic for four of the taxa discussed below, i.e. vigilax sensu lato, ludlowae , vansomerenae and the “ Celebes Form”.] Tarsomeres of all legs with distinct white basal bands, hindtarsus with basal pale bands ≥ 0.25 length of tarsomeres. Wing with small areas of white scaling. Abdominal terga with white basal bands of uniform width.

Larva. Seta 4-C short, nearer level of 6-C than 5-C; setae 11,12-C short. Seta 5-P single or double, lateral spine of plate bearing setae 9–12-M,T small and lightly pigmented. Most abdominal setae comparatively short; seta 1- III–V short, branched; seta 6-III branched. Comb scales in 1–3 irregular rows; saddle incomplete; anal papillae shorter than 0.5 length of saddle; seta 3-X single; siphon short, index <2.0; pecten spines evenly spaced, not inserted beyond seta 1-S.

Male genitalia. “Ninth tergal lobes with flattened setae; gonocoxite with scales, with setose dorsal basomesal lobe, mesal surface membranous; gonostylus attached at apex of gonocoxite, with apical gonostylar claw; claspette a long narrow columnar stem with an *apical seta (claspette filament) [hooked in subspecies ludlowae and vigilax and not hooked in subspecies vansomerenae ], *stem ≤ 0.85 length of aedeagus; aedeagus tube-like, widest at mid-length; cercal setae present.” [* = diagnostic character for subgenus Empihals of Reinert et al. 2009]

The nominotypical form was described by Skuse (1889) from specimens collected at four localities in southeastern Australia: Gosford, Kiama and National Park [unclear what this represents], New South Wales; and Brisbane, Queensland. Lee et al. (1984) cited Hahn (1962) [not seen by us] for the deposition of female syntypes [number not given] and a type female of vigilax in the Macleay Museum of Natural History, University of Sydney, Sydney, Australia. The Macleay Collection is now housed in the Chau Chak Wing Museum on the same campus. Many insects from the Macleay Collection were transferred to the Australian National Insect Collection in Canberra, but vigilax does not appear in their inventory of primary types. It is assumed that the type specimens of vigilax remain in the Macleay Collection.

Puslednik et al. (2012) used comprehensive collection records and multiple DNA sequences from 66 vigilax females from Australia and New Caledonia to test the validity of the Carpentaria Barrier, which is one of “a number of important biogeographical barriers [that] have been identified and are thought to have played a pivotal role in speciation events of Australian fauna...”. Aside from partially answering in the affirmative, their primary question concerning the influence of past patterns of change having resulted in the Carpentaria Barrier, they stated that “Within Ae. vigilax we have identified three distinct and divergent lineages that may well represent cryptic species. Sequence divergence between the three distinct lineages of Ae. vigilax was higher than between other Aedes species (Cook et al., 2005). Furthermore, total genetic divergence within the COI barcoding region was 4.23%, which is higher than the cutoff suggested by proponents of DNA barcoding ( Hebert et al., 2003).” We think this is clear indication of three species, two of which are sympatric in eastern Australia (Clades II and III of Puslednik et al. 2012). Specimens of Clade III were from eastern and western Australia and those of Clades II and III were found in sympatry near the type localities of nominotypical vigilax . The third taxon, Clade I, was found in New Caledonia, nearly 1,400 km from the Australian mainland.

The results of Puslednik et al. (2012) raise many questions, such as: What are the distributions of Clades II and III outside of Australia? Does Clade II or Clade III correspond to vigilax sensu stricto? To which clade(s) do the three current synonyms correspond?— Culex marinus Theobald, 1901a (eastern Australia), Culicelsa pseudovigilax Theobald, 1907 (eastern Australia) or Culicelsa uniformis Strickland, 1911 (western Australia). The type specimens of the three synonyms are in the Natural History Museum, London. In addition, an older name, Culex albirostris Macquart, 1850 (eastern Australia), was suppressed by the International Commission on Zoological Nomenclature 1972, Opinion 979, and is available to represent one of the two clades, as long as it is not vigilax sensu stricto. The type of albirostris is in the Muséum National d’Histoire Naturelle, Paris. And lastly, does Clade I already have a name, or is it undescribed? Answers to these questions could be possible with further molecular analyses.

Subspecies ludlowae (replacement name for Culex annulifera Ludlow, 1903 , not Culex annuliferus Blanchard, 1852 ) was described as a species from the Philippines. Ludlow stated: “The female was described from a lot (28) [a “lot” apparently means “many specimens”], all females, sent... from Mangarin, Mindoro: the males from a lot (234)... from Dagupan, Pangasinan, Luzon.” A female lectotype of annulifera was designated by Knight & Hull (1951) and is in the National Museum of Natural History, Washington, D.C..

Regarding ludlowae, Knight & Hull (1951) stated: “Not known from outside the Philippines.” “DISCUSSION: The Philippine form is treated here as a distinct subspecies of vigilax (Skuse) on the basis of the scaling of ppn [postpronotum] in the female. In v. vigilax this area [postpronotum] is covered with flat-lying slightly elongate broad scales; except for a fringe of narrow dark scales dorsally. The broad scales are dark except for a small ventral posterior patch of pale ones. The type of v. vigilax has not been seen by us, but the types of the synonyms uniformis Strickland [type locality: Perth, Western Australia ] (female) and marinus (Theobald) [Queensland] (male, female), which are in the British Museum, have been.”

Since ludlowae is only found in the Philippines and it has a distinctive postpronotal scale pattern, we believe this is evidence of genetic isolation. Because of these factors (morphology and distribution) we think ludlowae merits return to its original species status: Aedes (Ochlerotatus) ludlowae ( Blanchard, 1905) . Aedes ludlowae is not currently included as a species in the Encyclopedia of Life and should be added to the list of species of the genus.

Subspecies vansomerenae Mattingly, 1955 (in Mattingly & Brown 1955) was described from “a holotype ♁ and allotype ♀ from Anse Lascar, Silhouette I....3 ♁ and 4 ♀ paratypes with the same data as the holotype and 2 ♁ and 1 ♀ paratypes from Dennis I. ...”. This differs somewhat from what Townsend (1990) found in the Natural History Museum, London: “ Holotype male [Pe on slide] ‒ Seychelles: Silhouette I., Anse Lascar. Paratypes (17) ‒ Seychelles: 5 male, 6 female, 6L. ” “Pe & Le of some paratypes in alcohol.”

Mattingly prefaced his description of vansomerenae as follows: “Adults of this subspecies differ from type form Aë. vigilax Skuse ... and from ssp. ludlowae (Blanch.) ... in having a greater proportion of the scales on the posterior pronotum [postpronotum] pale, in the presence of strongly developed lateral prolongations of the pale tergal bands on the abdomen of the male and in not having the terminal appendage of the male claspette hooked. The larva differs in usually having more branches in the antennal tuft [seta 1-A], in having more teeth in the mentum [dorsomentum] and, apparently, in having the comb spines [scales] more delicately fringed with less tendency to thickening of the median denticle. The males also differ from the description of ssp. ludlowae given by Knight & Hull in having the lateral patches of broad pale scales on the vertex narrowly interrupted by dark scales. A similar condition is, however, shown by a male of ssp. ludlowae , from Manila, in the British Museum. The present form differs from Knight & Hull’s description of the Philippines subspecies in usually having 6 instead of 3–4 bristles [setae] on each lobe of the male ninth tergite [tergum IX].”

Additionally, in his description: “Posterior pronotum [postpronotum] with a conspicuous patch of broad white or whitish scales posteriorly and ventrally, rather smaller flat blackish scales forming a patch in the middle and narrow golden scales along the upper margin.” And for the larva, Mattingly noted that “Mouth brushes [palatal brushes] with serrated teeth of inner bristles [filaments] very strongly developed.” This is a character not mentioned in other descriptions of vigilax sensu lato.

The above comparisons by Mattingly, along with the at least 5,000 km of distance to the nearest member of the Empihals Group (sensu Wilkerson et al. 2021), lead us to conclude that vansomerenae is a distinct and independently evolving species, and is raised here to specific rank: Aedes (Ochlerotatus) vansomerenae Mattingly, 1955 . The proximity to Madagascar even suggests that it might be more related to species in that region, rather than to the other species discussed here. Aedes vansomerenae is currently listed as a species in the Encyclopedia of Life.

Aedes vigilax has three synonyms, which we retain: Culex marinus Theobald, 1901a , Culicelsa pseudovigilax Theobald, 1907 and Culicelsa uniformis Strickland, 1911 .