Ambrysus signoreti Stål

Reynoso-Velasco, Daniel & Sites, Robert W., 2022, Revision of the Ambrysus signoreti Stål species complex (Heteroptera: Naucoridae Ambrysinae). Section 1., Zootaxa 5214 (3), pp. 421-439 : 422-424

Ambrysus signoreti Stål species complex

Discussion. It was Usinger (1946: 203) who first made reference to the signoreti complex when describing 16 new species in Ambrysus . It was in the description of his A. sonorensis that he stated the species belonged to this complex. Unfortunately, he did not provide a list of the group's unifying features nor the constituent species. The succeeding mention of the complex was by La Rivers (1951), in his work on the genus Ambrysus in the United States, where he designated seven additional complexes to accommodate the North American species in the genus. This author also failed to list the diagnostic features and members of the complex, except for A. mormon Montandon , which he considered to be the most distinctive element of the complex. Regarding the signoreti complex, La Rivers (1951) stated without specifics:

" is the most complex unit of the entire genus and the largest in point of species"

"is difficult on purely technical grounds to sharply characterize"

"displays a homogeneity of form and coloration, which is unmistakable"

Later, La Rivers (1957) described A. drakei , from northwestern Mexico, and assigned it to the signoreti complex. In this work, La Rivers finally listed the group's unifying attributes, which included: 1) broad body shape, 2) wide embolia, 3) prominent maculation, and 4) species often with spinose posterolateral corners of abdominal segments. Even with this list, La Rivers failed to explicitly mention the constituent species; only A. signoreti Stål , A. sonorensis Usinger , A. mormon , and A. drakei La Rivers were known to belong to the complex. Based on the current concept of the signoreti complex, we know that at that time, at least 13 species belonging to the complex (most of them authored by La Rivers) had been already described.

It is only based on the recent studies that have focused on the characterization and circumscription of the genus Ambrysus and its nominotypical subgenus ( Reynoso-Velasco & Sites 2021), as well as the species complexes in this subgenus ( Reynoso-Velasco & Sites 2016a, 2016b, 2018a, 2018b), that we know that based on characteristics of the male phallosoma the signoreti complex includes 24 species distributed in North America (see Table 1 ). In addition to the morphological data, molecular evidence also supports a close relationship of species in this complex (see Reynoso-Velasco & Sites 2021). La Rivers (1951, 1957) assigned A. mormon and A. drakei to the signoreti complex; also, the former species was preliminarily assigned to this complex by Reynoso-Velasco (2021a), but characteristics of the phallosoma clearly indicate the two species belong to the A. guttatipennis species complex.

For convenience, the species-rich A. signoreti complex is herein organized into three sections (see Table 1 ). This organization is artificial and does not necessarily indicate a close relationship among the species. It is based on conspicuous characteristics of the female subgenital plate: 1) posterolateral corners extending posteriorly slightly further than the central lobe ( Fig. 1A ), 2) central lobe extending posteriorly further than the posterolateral corners ( Fig. 1B ), and 3) posterolateral corners and central lobe almost at the same level ( Fig. 1C ).

Diagnosis. Similar to other species complexes, the most reliable unifying feature among species in the A. signoreti complex is the male phallosoma and includes the presence of small protuberances (pointed or rounded), referred to as "denticles," on the sclerotized and variously shaped endosomal sclerites (e.g., Fig. 2E ). In a few species, the right sclerite is reduced, greatly reduced ( Fig. 5E ) or absent; nonetheless, the protuberances are present on the left sclerite, which can also be reduced. Only one species, A. signoreti , lacks both sclerites and in consequence the protuberances; notwithstanding, molecular evidence clearly supports the inclusion of the species in this complex ( Reynoso-Velasco & Sites 2021). Additionally, the great majority of species in this complex, including A. signoreti , exhibit a characteristic maculation, as suggested but not described by La Rivers (1957). This feature includes extensive light-colored markings (sometimes spotted) at the lateral and posterior margins of the corium (e.g., Fig. 10A ). In some species, the marking on the posterior margin extends along the posterolateral angle of the corium (e.g., Fig. 2A ).

Figures

FIGURE 1. Representative female subgenital plate of each of three sections in the Ambrysus signoreti Stål complex (terminal abdominal segments removed; solid line indicates level of posterolateral corners and dashed line level of central lobe). (A) posterolateral corners extending posteriorly further than central lobe in Ambrysus cosmius La Rivers, (B) central lobe extending posteriorly further than posterolateral corners in A. inflatus La Rivers, (C) posterolateral corners and central lobe almost at the same level in A. signoreti Stål. sgp = subgenital plate.

FIGURE 2. Structures of Ambrysus cosmius La Rivers. (A) dorsal habitus of male (yellow arrow indicates light mark at lateral margin and white arrows light mark along posterolateral angle of corium), (B) sternum VI and subgenital plate of female (terminal abdominal segments removed), (C) 6th and 7th abdominal terga of male (inset indicates angles measured on the accessory genitalic process), (D) 8th abdominal tergum of male, (E) ventral surface of male phallosoma, (F) genital capsule of male (phallosoma removed). agp = accessory genitalic process, cl = central lobe, les = left endosomal sclerite, ll = lateral lobe, pct = proctiger, plc = posterolateral corner, pmc = posteromesal corner, pp = pseudoparamere, pr = paramere, pyg = pygophore, res = right endosomal sclerite, sgp = subgenital plate.

FIGURE 5. Structures of Ambrysus morelosensis Reynoso & Sites n. sp. (A) dorsal habitus of female holotype, (B) sternum VI and subgenital plate of female holotype (terminal abdominal segments digitally removed), (C) 6th and 7th abdominal terga of male, (D) 8th abdominal tergum of male, (E) ventral surface of male phallosoma, (F) genital capsule of male (phallosoma removed). al = apical lobe, res = right endosomal sclerite.

FIGURE 10. Structures of Ambrysus variegatus Usinger. (A) dorsal habitus of female paratype (yellow and white arrows indicate light marks at lateral and posterior margins of corium, respectively), (B) sternum VI and subgenital plate of female (terminal abdominal segments removed), (C) 6th and 7th abdominal terga of male, (D) 8th abdominal tergum of male, (E) ventral surface of male phallosoma, (F) genital capsule of male (phallosoma removed). al = apical lobe.

Tables

TABLE 1. Checklist of species in the Ambrysus signoreti Stål complex*

Species	Distribution
Section 1 Ambrysus cosmius La Rivers, 1953 A. morelosensis Reynoso & Sites new species A. schuhi Reynoso & Sites, 2019 A. variegatus Usinger, 1946	Mexico Mexico Mexico Costa Rica
Section 2 A. brailovskyi Reynoso & Sites, 2019 A. harmodius La Rivers, 1962 A. henryi Reynoso & Sites, 2019 A. inflatus La Rivers, 1953	Mexico Costa Rica Mexico Mexico
A. lunatus Usinger, 1946 A. lundbladi Usinger, 1946	Mexico and United States Mexico
Section 3 A. altiplanus Reynoso, 2021 A. cayo Sites & Shepard, 2015 A. colimanus Polhemus & Polhemus, 1981 A. dyticus La Rivers, 1953 A. hydor La Rivers, 1953 A. magniceps La Rivers, 1953	Mexico Belize Mexico Guatemala Mexico Mexico
A. occidentalis La Rivers, 1951 A. portheo La Rivers, 1953 A. quadracies La Rivers, 1976 A. rotundus La Rivers, 1962 A. scalenus La Rivers, 1953 A. signoreti Stål, 1862	Mexico and United States Mexico Mexico Mexico Mexico Mexico
A. sitesi Reynoso, 2019 A. sonorensis Usinger, 1946	Guatemala and Mexico Mexico

* Sections are based on characteristics of the female subgenital plate:

1 - posterolateral corners extending posteriorly further than central lobe.

2 - central lobe extending posteriorly further than posterolateral corners.

3 - posterolateral corners and central lobe at same level

.