Platynectes submaculatus (Laporte, 1835)

Short, Andrew Edward Z., Benetti, Cesar J. & Gustafson, Grey T., 2020, New records of Platynectes (s. str.) diving beetles from South America with description of two new species (Coleoptera: Dytiscidae: Agabinae), Acta Entomologica Musei Nationalis Pragae 60 (2), pp. 437-447 : 446

Key to the species of the P. submaculatus species group

1 Elytra with 10 distinct yellow maculae. ....................... 2

– Elytra with fewer than 10 distinct yellow maculae. ... 6

2 Body length usually greater than 6.6 mm. .................. 3

– Body length less than 6.6 mm, rarely more than 6.5 mm. .................................................................................. 4

3 Pronotal lateral bead broad, anteriorly ca. 2× wider than anterior epipleural carina; median lobe with apex strongly pointed and triangular. Brazil, Suriname and French Guiana. ............. P. decemnotatus (Aubé, 1838)

The new collection records presented here provide insights into the range sizes of both individual species as well as the clade as a whole. In particular, the new data provides evidence that (1) some species of Platynectes Clade II have extremely broad ranges, in some cases spanning almost 2000 km, and (2) species of the clade are much more broadly distributed across the Guiana and Brazilian shields that was previously known.

– Pronotal lateral bead narrow, similar in size to anterior epipleural carina throughout its length; median lobe with apex rounded, not triangular. Colombia. .............. ................................................... P. colombicus sp. nov.

4 Total body length at most 5.0 mm, oflen smaller; WC/ WS = 5. Venezuela (Amazonas State). ............................ .................... P. meru Gustafson, Short & Miller, 2016

Several species, previously thought to be regional or microendemics, are now known from substantially larger ranges. Platynectes garciai was previously known from a few closely situated localities along the Venezuela /Guyana border that were not more than 125 km apart (Fig. 12). Our new collections expand the distribution more than 500 km southwest, to the very edge of the Guiana Shield in the state of Pará, Brazil. Despite this seemingly large range expansion, the specimens are morphologically and genetically identical to the original populations (e.g. Fig 1 ). Even more unexpected was the dramatic range expansion of P. tafelbergensis . This species had been suspected to be a putative microendemic of Tafelberg tepui in central Suriname, from where it was originally described (GUඌτΑΓඌƟΝ et al. 2016). In 2017, we collected a single specimen from a stream in Brownsberg Nature Park in northern Suriname confirming that it was not a tepui endemic taxon. But in 2018, we collected additional specimens in Manaus, at the extreme edge of the Guiana Shield, as well as in the Brazilian state of Rondônia on the northern edge of the Brazilian Shield ( Fig. 14 ). The assignment of the Rondônia populations to P. tafelbergensis is strongly supported by both morphology and genetic data ( Fig. 1 ). This is the first species of the genus with a distribution that spans the Amazon, known from both the Brazilian and Guiana Shields.

– Total body length greater than 5.0 mm; WC/WS = 4. ........................................................................................ 5

5 Body form parallel-sided and elongate; larger, body length = 6.1–6.5 mm; antennae filiform. Venezuela (Bolivar State). ................................................................... ...... P. elaskanaima Gustafson, Short & Miller, 2016

– Body form more evenly rounded and not elongate; smaller, body length = 5.3–5.9 mm; antennae subserrate. Suriname and French Guiana. ........................... ................................. P. submaculatus (Laporte, 1835)

6 Larger, body length = 6.6–6.7 mm; brown, usually with two distinct parascutellar maculae. Brazil, Suriname, and Venezuela. ................................................................... ................. P. garciai Gustafson, Short & Miller, 2016

– Smaller, body length = 5.8–6.5 mm; less brown, darker, never with parascutellar maculae. Suriname and Brazil. ........................................................................................ ..... P. tafelbergensis Gustafson, Short & Miller, 2016

Figures

Fig. 1. Maximum Likelihood phylogeny of sequenced Platynectes (s. str.) specimens based on the gene COI.

Figs 12–16. Distribution of Platynectes ‘Clade II’ sensu TƟUඌඌΑιΝτ et al. (2017) in South America. Circles represent previously published localities; stars represent localities newly reported in this paper.