Integrative taxonomy of the neotropical genus Omalonyx (Elasmognatha: Succineidae)

Abstract

The genus Omalonyx d'Orbigny, 1837, includes neotropical semi‐aquatic succineid slugs and comprises six recognized species to date. Field surveys across continental South America recovered five of the six recognized species. According to the morphological characters traditionally included in Omalonyx descriptions, the specimens were tentatively identified as O. matheroni, O. pattersonae, O. convexus, O. geayi and O. unguis. Employing sequences of mitochondrial cytochrome oxidase I (COI) alone or combined with the nuclear second internal transcribed spacer (ITS2) in discovery methods of species delimitation (GMYC and STACEY) led to species delimitation hypotheses that, except for unambiguously supporting O. convexus, have no correspondence to morphologically based assignments. To choose the delimitation model that best fit our data, the hypotheses recovered by GMYC, STACEY and morphology and created by merging species recovered by those methods had their marginal likelihood estimated and compared using the Bayes factors. The best‐supported hypothesis distinguished two species besides O. convexus: one widespread over most of South America and the other restricted to Rio de Janeiro State, Brazil. Furthermore, the pattern of genetic structuring supports pathways connecting the Amazonian and Atlantic forests. This pattern is similar to that observed in terrestrial taxa (e.g., forest‐dwelling small mammals) and is different from the pattern for fully aquatic taxa.

Single‐locus DNA barcoding and species delimitation of the sandfly subgenus Evandromyia (Aldamyia)

“…The members of the evandroi complex may be in an incipient sympatric speciation process, in which only a few loci involved in the differentiation of genitalia – the morphological structure that distinguishes between them – might be involved. Morphologically‐distinct taxa comprising a single molecular group have been previously observed in various organisms, including land snails (Stankowski & Johnson, 2014; Vidigal et al ., 2018), reef sponges (DeBiasse & Hellberg, 2015), octocorals (Ament‐Velásquez et al ., 2016) and lizards (Jin et al ., 2014).…”

First record of the semi-slug Omalonyx unguis (d’Orbigny, 1837) (Gastropoda, Succineidae) in the Misiones Province, Argentina

“…However, due to misconceptions and contradictions in Omalonyx systematics, those previous records should be interpreted with caution as they may include what today is recognized as O. convexus (Arruda and Thomé 2008a). Despite this, the records reported herein constitute the first anatomically and molecularly confirmed occurrences of O. unguis in Misiones and increase Vidigal et al (2018). Circles indicate the new localities where the specimens of O. unguis were found in Misiones Province, Argentina.…”

“…Our BLASTN searches of the COI sequences revealed that samples of O. unguis from Itá, Zaimán, and Garupá streams were identical (100% query coverage, 100% maximum identity) to Foz do Iguaçu, Brazil samples, whereas our sample from Mártires stream was identical (100% query coverage, 100% maximum identity) to sequences from a tributary stream of the Paraguay River, as well as with High Paraná River samples from locations situated before its confluence with the Paraguay River. On the other hand, DNA sequences from the remaining samples differed from the previously characterized by Vidigal et al (2018), thus representing new haplotypes. Further research is required to gain insights into the genetic background of the O. unguis populations in Misiones Province, as the molecular data presented here represent the first DNA sequences for the species in Argentina.…”

“…In addition, O. unguis differs from O. geayi, and the whole genus, in the shape and distribution of the inner penis surface papillae. Further information on the anatomical differences amongst Omalonyx species can be found in Arruda (2011) and Vidigal et al (2018).…”

“…To date, specific-identity of the Omalonyx species in Misiones Province is unknown. Recently, the first molecular data for Omalonyx in South America became available, which comprises DNA sequences for the mitochondrial COI gene, and the nuclear internal transcribed spacer 2 (ITS2) region (Vidigal et al 2018). Nonetheless, DNA sequences for Omalonyx from Argentina are still scarce, and are only available for O. convexus.…”