Leptocera angulispina, Buck & Marshall, 2009

Buck, Matthias & Marshall, Stephen A., 2009, Revision of New World Leptocera Olivier (Diptera, Sphaeroceridae), Zootaxa 2039 (1), pp. 1-139 : 72-74

Leptocera fontinalis species group

Species included. Nearctic: L. angulispina sp.n., L. finalis (Collin) , L. fontinalis (Fallén) , L. kanata sp.n., L. neofinalis sp.n., L. parafinalis Papp , L. tenuispina sp.n., L. neovomerata sp.n. Neotropical ( L. cymatonota subgroup): L. cymatonota sp.n., L. hexadike sp.n.

Description. Body length ca. 2.0– 3.3 mm. Dark brown species with very restricted reddish markings (i.e., frons at anterior margin and sometimes facial tubercle obscurely reddish), some areas paler brown (e.g., some thoracic sutures, tarsi). Wing pale greyish to slightly infuscated (especially in anterior third). Head with lower orbital bristle only slightly shorter than upper one. Inner orbit lacking setulae behind level of upper orbital bristle. Palpus slender. Arista short- to medium-pubescent, long-pubescent in L. cymatonota subgroup. Prosternal membrane usually bare, in L. cymatonota subgroup with 1–2 setulae on each side of midline. Mesonotum thinly pruinose, subshining, in L. cymatonota subgroup with more or less developed pattern of stripes and spots. Mesoscutum with five dorsocentral bristles, first one often just slightly longer than surrounding hairs; ca. 5–7 paramedian acrostichals near middle of mesoscutum moderately to greatly enlarged (anterior ones paired, posterior one usually only developed on one side), longest acrostichal in some species as long as or even longer than orbital bristles ( L. cymatonota subgroup). Prescutellar bristles usually slightly to moderately enlarged. Mid tibia with typical chaetotaxy but posteroapical bristles relatively long, extending at least 3/4 the distance towards socket of ventrobasal bristle of metatarsus ( Figs. 24–28 ). Mid tibia with longest bristle of proximal posterodorsal series clearly shorter than longest bristle of anterodorsal series; bristle above distal dorsal bristle short to moderately long, very long in L. cymatonota subgroup.

Male terminalia: Sternite 5 with simple desclerotized posteromedian area, lacking fringe of large, black scales (e.g., Fig. 151 ). Sternite 8 separated from epandrium by distinct suture except at extreme right. Epandrium saddle-shaped, with bristles fairly evenly distributed, neither very numerous nor very long (e.g., Figs. 148, 149 ; except for L. cymatonota sp.n. which has bristles longer than other species). Cercus commashaped (e.g., Fig. 170 : ce), basal portion inflated and with several bristles, apical portion slender and bare, directed ventrally and posteriorly, its apex rounded in lateral view. Surstylus (e.g., Fig. 170 ) with posterior section elongate and straight, dorsal (posterior) surface setose; apex with two stout bristles; anterior section with variably shaped and bristled ventral lobe and microtrichose anterior process. Postgonite produced posteriorly at base, with deep notch in lateral view ( Figs. 199–205 ).

Female terminalia: Tergite 7 short and wide, only laterally with long bristles, usually with dark, transverse, central band. Sternite 7 simple, usually with straight hind margin, in some species medially produced (apex of produced part often forming a short overhang); in the L. cymatonota subgroup hind margin with a conspicuously microtrichose posteromedial tab ( Figs. 217 , 224 ). Tergite 10 and cerci well-developed, fused, often with a more or less developed crease indicating limit between them. Tergite 10 with one pair of setae (in aberrant specimens with 0, 2 or three pairs or odd numbers). Spermathecae usually pear-shaped to subcylindrical (e.g., Fig. 153 ), lemon-shaped in L. cymatonota subgroup (e.g., Fig. 216 ), with or without apical invagination, surface spiculate, sculpture otherwise weak, if present striate.

Taxonomy. The species of this group are very uniform externally, and species identifications usually require genitalic dissections. Females of some species pairs cannot be separated with certainty. External characters (length of acrostichal bristles, posteroapical bristles and bristle above distal dorsal bristle of mid tibia) are subtle and do not show distinct morphological gaps between certain species. The most important diagnostic characters include: shape of anterior process of anterior section of surstylus, shape and chaetotaxy of ventral lobe of anterior section of surstylus, chaetotaxy of posterior section of surstylus, shape of female sternite 8, hind margin of female sternite 7.

Biogeography. This species group is Holarctic except for the Central American L. cymatonota subgroup, and some undescribed species from Nepal which probably also belong here. In the New World most species are restricted to northern-temperate, arctic and montane regions, ranging from Canada and the northern United States (including Alaska) south to California and New Mexico along the mountain ranges of the western United States. The species of the L. fontinalis group are usually rarely collected, with several species known from only a few specimens. The fauna of the western United States remains poorly known, and new species might be discovered there in the future (in this study several unassociated females from isolated localities could not be identified with certainty). The Nearctic fauna shows strong affinities to the eastern Palaearctic fauna. One species, L. parafinalis , has a trans-Beringian distribution, i.e. it occurs in the western Nearctic and the eastern Palaearctic region. Other species form intricate clusters with members distributed on either side of the Pacific: L. vomerata (eastern Palaearctic) with L. neovomerata sp.n. (western Nearctic), L. boruvkai Roháček (eastern Palaearctic) with L. kanata sp.n. (Nearctic), and L. equispina Papp (eastern Palaearctic) with L. angulispina sp.n., and L. tenuispina sp.n. (both western Nearctic). Leptocera finalis has a trans-Holarctic distribution and a highly similar Nearctic sister species, L. neofinalis sp.n. The western Palaearctic/eastern Nearctic distribution pattern of Leptocera fontinalis is probably due to introduction by early North American settlers. Surprisingly, the L. fontinalis group also includes two members in mountain regions of Central America (southern Mexico to Panama). These two species, L. cymatonota sp.n. and L. hexadike sp.n., differ in a number of apomorphic characters from all Holarctic species and undoubtedly form a monophyletic group (see below).

Phylogeny. The L. fontinalis group was provisionally established by Roháček (1982) to include eight Palaearctic species ( L. alpina Roháček , L. caenosa (Rondani) , L. equispina Papp , L. finalis (Collin) , L. fontinalis (Fallén) , L. oldenbergi (Duda) , L. parafinalis Papp , L. spinitarsata Papp ), with later additions ( Roháček & Papp, 1983; Roháček, 1993) of three subsequently described Palaearctic species ( L. boruvkai Roháček , L. dyscola Roháček & Papp , L. vomerata Roháček & Papp ). Leptocera caenosa has its affinities with a speciose clade of New World (mostly Neotropical) species and is here referred to the newly established L. caenosa group (see above). The monophyly of the L. fontinalis group in this revised sense remains to be demonstrated. The L. fontinalis group plus the largely Old World/Australasian L. nigra group (sensu Roháček, 1983, see below) and several other Oriental species ( L. nigrolimbata Duda and related species) probably form a monophyletic group, which can be defined based on the peculiar, apomorphic, “comma”-shaped, male cercus. However, the L. fontinalis group in the present, revised sense shows no obvious, exclusive, apomorphic characters, and only a thorough phylogenetic analysis can substantiate or refute its monophyly. The two newly described Neotropical species L. cymatonota sp.n. and L. hexadike sp.n. form a distinct monophyletic subgroup (here called the L. cymatonota subgroup). It is characterized by a pruinose pattern of the mesonotum, distinct surstylus structure, microtrichose tab-like posteromedial process of female sternite 7, and lemon-shaped spermathecae.

Biology and habitat. There are no previously published Nearctic rearing records for this species group except numerous references to L. fontinalis ( Howard, 1900; Usinger & Kellen, 1955; Kilpatrick & Schoof, 1957; Walker, 1957; Reed, 1958; Johnson, 1975) which are without doubt based on misidentifications (see discussion under L. fontinalis ). Among the material examined we found two specimens of L. neofinalis sp.n. from Alaska that were bred from turnip according to label data. This record is probably rather exceptional, but we strongly suspect that various types of decaying vegetation (e.g., drift in river beds and along shorelines) or soil with a high content of organic matter are utilized as breeding substrates by Nearctic species of the L. fontinalis group. In fact, Leptocera fontinalis has been reared from decaying grass and nest litter from rodent burrows in Europe ( Okely, 1974; Hackman, 1967). Other larval habitats include dead snails ( Richards, 1930; Joswig, 1985), outhouses ( Skidmore, 1978), and sewage filter beds ( Hawkes, 1951; Skidmore, 1978; Learner, 2000). A small but significant number of Nearctic specimens were collected on carrion or in carrion traps ( L. kanata sp.n., L. neofinalis sp.n., L. parafinalis ), in mushroom traps ( L. angulispina sp.n., L. cf. kanata sp.n. ♀♀, L. neofinalis sp.n., L. parafinalis ), and on dung or in dung traps ( L. kanata sp.n., L. neofinalis sp.n.). Similar to their Palaearctic relatives, Nearctic species of the L. fontinalis group prefer riparian habitats (edges of rivers and streams, lake shores, floodplains, springs) as well as other damp places like wet deciduous and coniferous forests, willow and alder thickets (northern localities), sedges, and to a lesser degree marshy meadows, swampland and bogs. Several species have been collected at beaver ponds or beaver dams ( L. angulispina sp.n., L. neofinalis sp.n., L. neovomerata sp.n.) and in mammal runs ( L. cf. kanata sp.n. ♀♀, L. cf. neofinalis sp.n. ♀♀, L. parafinalis ). In Europe, L. fontinalis has occasionally been found in caves ( Bährmann & Weber, 2008). One species ( L. neofinalis sp.n.) has been collected at lights. The two Neotropical members of the L. cymatonota subgroup occur in montane forests from 1,400 to 2,850 m. Both species are attracted to dung, L. hexadike sp.n. also to carrion. A sizeable series of the latter was swept from downed bromeliads, indicating a possible phytosaprophagous lifestyle of the larva.

Figures

FIGURES 16–29. Leptocera mid tibiae and basitarsi. Mid tibia, dorsal: (16) L. neocurvinervis (Chile); (17) L. duplicata (Juan Fernández Is.). Apical half of mid tibia and basitarsus, posterior: (18) L. parallelipennis sp.n. (Juan Fernández Is.); (19) L. ellipsipennis (Juan Fernández Is.); (20) L. erythrocera (Honduras); (21) L. sphaerotheca sp.n. (Mexico); (22) L. plax sp.n. (Ecuador); (23) L. tapanti sp.n. (Costa Rica); (24) L. cymatonota sp.n. (Mexico); (25) L. parafinalis (Canada); (26) L. neofinalis sp.n. (Canada); (27) L. kanata sp.n. (Canada); (28) L. fontinalis (France); (29) L. nigra (South Africa). d ad—distal anterodorsal bristle, d d—distal dorsal bristle, d pa—dorsal posteroapical bristle, l ad—lowermost bristle of proximal anterodorsal series, l pd—lowermost bristle of proximal posterodorsal series, mv—midventral bristle, pa v—preapical ventral bristle, vb—ventrobasal bristle of basitarsus, v pa—ventral posteroapical bristle.

FIGURES 148–154. Leptocera angulispina sp.n. (U.S.A., except 153: Canada). Male terminalia (phallus and postgonites omitted): (148) lateral; (149) posterior; (150) ventral; (151) sternite 5. Female terminalia: (152) dorsal; (153) spermathecae; (154) ventral. aps—anterior process of anterior section of surstylus, ce—cercus, cp—ventral process of cercus, ep—epandrium, fm—field of dense microtrichia, ha—hypandrial apodeme, hy—hypandrium, pa—phallapodeme, pss—posterior section of surstylus, S—sternite, se—subepandrial sclerite, T—tergite (female tergite 8 divided into two halves), vls—ventral lobe of anterior section of surstylus.

FIGURES 170–176. Leptocera neofinalis sp.n. (Canada). Male terminalia (phallus and postgonites omitted): (170) lateral; (171) posterior; (172) ventral; (173) sternite 5. Female terminalia: (174) dorsal; (175) spermathecae; (176) ventral. as—sclerotized anterolateral angle of surstylus, ce—cercus.

FIGURES 199–209. Postgonites and aedeagal complex of Leptocera fontinalis group (excluding L. cymatonota subgroup). Postgonites of (199) L. angulispina sp.n. (Canada), (200) L. finalis (Canada), (201) L. kanata sp.n. (Canada), (202) L. neofinalis sp.n. (Canada), (203) L. parafinalis (Canada), (204) L. neovomerata sp.n. (U.S.A.), (205) L. tenuispina sp.n. (Canada). Aedeagal complex of L. fontinalis (Spain): (206) posterior; (207) anterior; (208) lateral; (209) dorsal. bcp—basal connection between postgonites, bp—basiphallus, dp—distiphallus, ea—ejaculatory apodeme, pa—phallapodeme, pg—postgonites.

FIGURES 211–217. Leptocera cymatonota sp.n. (Guatemala). Male terminalia (phallus and postgonites omitted): (211) lateral; (212) posterior, right cercus omitted; (213) ventral; (214) sternite 5. Female terminalia: (215) dorsal; (216) spermathecae; (217) ventral. i vls, o vls—inner and outer ventral lobes of anterior section of surstylus.

FIGURES 218–224. Leptocera hexadike sp.n. (Panama). Male terminalia (phallus and postgonites omitted): (218) lateral; (219) posterior; (220) ventral; (221) sternite 5. Female terminalia: (222) dorsal; (223) spermathecae; (224) ventral.