Potamocoris robustus La Rivers, 1969

Peralta-Argomeda, Jorge Luis, Rodrigues, Juliana Mourão Dos Santos, Huamantinco-Araujo, Ana & Moreira, Felipe Ferraz Figueiredo, 2024, Checklist of the aquatic and semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha, Leptopodomorpha & Nepomorpha) of Peru, Zootaxa 5467 (1), pp. 1-72 : 43-47

Potamocoris robustus La Rivers, 1969

Geographic distribution. Peru ( La Rivers, 1969).

Distribution in Peru. Loreto (Sites, in litt.), Ucayali (J. Polhemus & D. Polhemus 1983b; D. Polhemus & Carrie 2013), Huánuco ( La Rivers 1969; D. Polhemus & Carrie 2013).

General geographic distribution of represented species

A total of 233 species has been recorded from Peru. Among them, 51 (22%) are endemic from the county; 112 (49%) occur in Peru and other South American countries, especially in Brazil; 49 (21%) are distributed throughout the Neotropical Region; and 18 (8%) are widely distributed in America, including the United States and Canada ( Table 1, Figure 1 ). Some of the species in the last category have also been reported from other regions, including Mesovelia mulsanti in the Hawaiian Islands and Merragata hebroides in the Hawaiian and Canary Islands ( Moreira et al. 2011). The oceanic species Halobates sericeus , H. sobrinus and H. splendens ( Cheng & Mishra 2022) have been excluded from Table 1 because of their distinct distribution patterns.

The three infraorders, Gerromorpha ( Figure 2 ), Leptopodomorpha ( Figure 3 ) and Nepomorpha ( Figure 4 ) show similar percentages of species distributions. When comparing their richness, there is a slight predominance of Gerromorpha over Nepomorpha (48% vs. 46%), and both are much more speciose than Leptopodomorpha , which is a tendency observed in other South American countries such as Colombia (51% Gerromorpha; Aristizábal 2017) and Ecuador (59% Gerromorpha; Froeschner 1981; Buzzetti & Cianferoni 2011). The opposite is true in other countries of the region, with lower proportions of Gerromorpha in Brazil (39%; Moreira et al. 2011), Argentina (28%; Coscarón 2017) and Chile (21%, Damgaard & Moreira 2021).

Most of the widely distributed species represented in Peru belong to Gerromorpha, especially to Gerridae and Veliidae . In Nepomorpha, only Notonectidae includes widely distributed species. However, some of these species have several described synonyms and at least some are believed to represent complexes of morphologically similar species (e.g., Mesovelia mulsanti , Microvelia pulchella , Platyvelia brachialis ).

Geographic distribution of represented species in Peru by hydrographic slope

According to the division of Peru into three hydrographic slopes (Geo GPS Perú 2014), most aquatic and semiaquatic bugs recorded from the country are present in the Atlantic slope (198 species, 92%), followed by the Pacific slope (34 species, 16%) and the Titicaca slope (4 species, 2%) ( Table 2, Figure 5 ).

The greatest species richness in the Atlantic slope can be explained by its large area (74.5% of the Peruvian territory), as well as by the wide elevational and thermal ranges, from the high Andean zone to the permanently flooded Amazon plains. These characteristics favoured the diversification not only of aquatic and semiaquatic Heteroptera in Peru, but also of other insect orders such as Odonata ( Hoffmann 2009) , Hymenoptera ( Rasmussen & Asenjo 2009) and Lepidoptera ( Lamas 1997) . This high diversity of insects has generated great interest in studying the region, leading to expeditions like the one organized by the Catherwood Foundation ( Roback 1966) and to biological inventories of the Parque Nacional del Manu and the Reserva Nacional de Tambopata, both in Madre de Dios department ( Chaboo & Catenazzi 2015).

The Atlantic slope includes 13 Peruvian departments ( Table 4, Figure 6 ), of which Huánuco and Junín have the highest number of recorded aquatic and semiaquatic Heteroptera (with 68 and 69 species, respectively). This might be because both share a wide elevational range and important ecological factors for the establishment of these insects, allied to an elevated collecting effort over the 20 th century (e.g., Kuitert 1942; Roback 1966). Although Pasco department is located between Huánuco and Junín, it has received less attention and many fewer species (22) have been recorded. Other departments potentially have a high diversity of aquatic and semiaquatic bugs due to the heterogeneity of local habitats. These include San Martín, Loreto, Ucayali, and Cusco, with richness values ranging between 32 and 36 species. Similarly, Madre de Dios department (40 recorded species so far) might also harbor a high diversity. An expedition focusing on these bugs in the local Reserva Nacional de Tambopata reported 67 taxa, with a potential richness of up to 135 taxa ( Peralta-Argomeda 2011). In contrast, only one species has been recorded from Huancavelica and Apurímac departments, possibly due to lower collecting effort, which is reflected in general inventories of their plants, birds and mammals ( Fajardo et al. 2014).

The Pacific slope, probably because of the smaller area (21.7% of the Peruvian territory) and the narrower elevational and thermal ranges in comparison with the Atlantic slope, has an intermediate richness of aquatic and semiaquatic bugs. Another factor contributing to this scenario is the low effort in conducting faunal inventories in the area, which leads to knowledge gaps on the fauna of the coastal desert ( Rodríguez & Young 2000, Fajardo et al. 2014).

The Pacific slope includes 10 departments ( Table 3, Figure 6 ), of which Lima has the most records of aquatic and semiaquatic bugs (24 species). This can be explained by the geopolitical importance of Lima as the capital of Peru and the main entrance for the scientific expeditions visiting the country in the 20 th century. Furthermore, Lima has a wide elevational range and important ecological features for the establishment of these insects, especially in the coastal wetlands ( Peralta-Argomeda & Huamantinco-Araujo 2014). In contrast, other departments, such as La Libertad and Ica, have important wetlands and high potential richness, but still lack studies. Other departments such as Piura, Moquegua and Tacna, in turn, are scarce in permanent rivers and are in the border between the Pacific coastal desert and the Atacama coastal desert. No species of any of the three infraorders have been recorded from those departments .

The Titicaca slope has the lowest richness of aquatic and semiaquatic bugs, with only four species. It is very likely related to its small area (3.8% of the Peruvian territory) and to the elevations above 4,000 m, where the rivers are cold and not favourable for the establishment of these insects. This slope includes only Puno department ( Table 5, Figure 6 ), where there has been low collecting effort, except for the Catherwood Bolivian-Peruvian Altiplano Expedition ( Roback et al. 1980).

Figures

FIGURE 6. Map showing the number of species of aquatic and semiaquatic Heteroptera recorded from each Peruvian department. Pacific slope (TU: Tumbes, PI: Piura, LA: Lambayeque, LL: La Libertad, AN: Ancash, LI: Lima, IC: Ica, AR: Arequipa, MO: Moquegua, TA: Tacna), Atlantic slope (CA: Cajamarca, AM: Amazonas, SM: San Martín, LO: Loreto, HU: Huánuco, PA: Pasco, JU: Junín, UC: Ucayali, HV: Huancavelica, AY: Ayacucho, AP: Apurímac, CU: Cusco, MD: Madre de Dios), and Titicaca Slope (PU: Puno).

FIGURES 1–5. Distribution of aquatic and semiaquatic Heteroptera recorded from Peru. 1. Percentages of recorded species according to their general geographic distributions (Peru: species recorded exclusively from this country; South America: species recorded from Peru and other countries in South America; Neotropical: species recorded from Peru and widespread along the Neotropical Region, including localities outside South America; Widely Distributed: species recorded from Peru, and that occur through a wide range in the Americas, including portions of the United States and sometimes Canada). 2. Percentages for Gerromorpha species. 3. Percentages for Leptopodomorpha species. 4. Percentages for Nepomorpha species. 5. Percentages of recorded species according to their geographic distribution in Peru at the hydrographic slope level (PS: Pacific hydrographic slope; AS: Atlantic hydrographic slope; TS: Titicaca hydrographic slope).