A new species of the characid genus Hollandichthys Eigenmann from coastal rivers of southern Brazil (Teleostei: Characiformes) with a discussion on the diagnosis of the genus

Abstract

A new species of the characid genusHollandichthys taramandahy, new species, is described from the rio Tramandaí, rio Mampituba, and rio Araranguá basins, coastal drainages of Rio Grande do Sul and Santa Catarina States, Brazil. The new species is distinguished from H. multifasciatus, the single recognized species of the genus, by the presence of a small black spot covering the base of median caudal-fin rays, by the lower number of dorsal and ventral procurrent caudal-fin rays, by the absence of a black spot located along anterior half of adipose-fin, and by the absence of humeral spot in specimens larger than 60 mm of standard length. Comments about the geographic distribution and diagnosis are provided for the genus.Hollandichthys taramandahy, espécie nova, é descrita para as bacias dos rios Tramandaí, Mampituba e Araranguá, drenagens costeiras dos estados do Rio Grande do Sul e Santa Catarina, Brasil. A espécie nova distingui-se de H. multifasciatus, a única espécie reconhecida do gênero, pela presença de uma pequena mancha preta cobrindo a base dos raios medianos da nadadeira caudal, pelo menor número de raios procorrentes dorsais e ventrais da nadadeira caudal, pela ausência de uma mancha preta na metade anterior da nadadeira adiposa e pela ausência de mancha umeral em exemplares maiores de 60 mm de comprimento padrão. Comentários sobre a distribuição geográfica e diagnose são apresentados para o gênero.

Genomic signatures of paleodrainages in a freshwater fish along the southeastern coast of Brazil: genetic structure reflects past riverine properties

“…Of the populations of Hollandichthys studied here, individuals from paleodrainage 11 ( Figure 1) have recently been described as a putative new species, H. taramandahy (Bertaco and Malabarba, 2013). The strong structuring of genetic variation in Hollandichthys may be indicative of a putative species boundary, and consequently, suggest that paleodrainages may be responsible for long-term isolation that culminates in speciation.…”

“…Nonetheless, it might be argued that this mechanism (i.e., dispersal across drainages via past connections that opened during periods of low sea level) may be relatively species-specific (Waters and Burridge, 2016) unlike river capture and vicariance, which tends to affect communities as a whole (Burridge et al, 2007;Albert et al, 2011). For example, Hollandichthys is associated with the presence of riparian forest (Bertaco and Malabarba, 2013), and consequently is distributed in lower land tributaries, which might make downstream dispersal more likely during the cycles of sea-level retreat, given the geographic proximity to the temporary river connections that existed among drainages in the past. However, for fish inhabiting different portions of the rivers (i.e., headwaters, as opposed to lowland tributaries), such temporary connections forged by sea-level retreat might not have been accessible.…”

“…However, the degree of genomic differentiation for this putative species is similar to those observed between the populations from other paleodrainages in Hollandichthys, as is estimates of its divergence (i.e.,~24 ky, Figure 3). It is unknown whether any of a set of geographically isolated regions/populations will become new species (Sukumaran and Knowles, 2017), but the clear morphological characters (Bertaco and Malabarba, 2013) of the proposed new taxon may suggest that this lineage has preceded beyond what might be expected from geographic isolation at the microevolutionary level (i.e., population isolation; Rosenblum et al, 2012). Further analyses that tests for morphological differences across individuals in the other paleodrainages are required to determine whether the differentiation observed in the new putative species H. taramandahy (Bertaco and Malabarba, 2013) is statistically equivalent to other divergences separating paleodrainage populations that are not recognized as different species (for example, Solis-Lemus et al, 2014;Huang and Knowles, 2016).…”

Common barriers, but temporal dissonance: Genomic tests suggest ecological and paleo‐landscape sieves structure a coastal riverine fish community

“…A community-wide effect supporting alternative scenarios have been suggested based on inferred congruence of population histories associated with Pleistocene climatic changes in the Atlantic Forest (Carnaval et al, 2009;Leite et al, 2016;Paz et al, 2018; but see Thomé, Zamudio, Haddad, & Alexandrino, 2014 The ramifications of the variation in the ephemerality of isolation across space, and among taxa, can be extended to consideration of the speciation process and distribution of diversity. For example, one of the oldest and one of the youngest divergence estimates (i.e., the northern division in H. boulengeri and the southern division in Hollandichthys, respectively; Figure 3) correspond to the proposed boundaries of putative species recognized by morphological data (Bertaco & Malabarba, 2013;Carvalho, 2006). In addition, for Bryconamericus, one species boundary corresponds to the southern division inferred in our study (Hirschmann, Fagundes, & Malabarba, 2017); however, we note the lack of a correspondence between the designation of two other species within this taxon and the regional structure inferred here (i.e., north clusters: populations 40 and 41 for B. ornaticeps and population 42 for B. tenuis -see Supporting Information S1), which results in a paraphyletic species under the currently proposed nomenclature.…”

“…In addition, for Bryconamericus , one species boundary corresponds to the southern division inferred in our study (Hirschmann, Fagundes, & Malabarba, ); however, we note the lack of a correspondence between the designation of two other species within this taxon and the regional structure inferred here (i.e., north clusters: populations 40 and 41 for B. ornaticeps and population 42 for B. tenuis – see Supporting Information ), which results in a paraphyletic species under the currently proposed nomenclature. It is also notable that the old divergences associated with the central division are not correlated with any obvious morphological differentiation (Bertaco & Malabarba, ; Camelier, Menezes, Costa‐Silva, & Oliveira, ). The variation observed among taxa and geographic divisions could be viewed as evidence of divergence along a speciation continuum, where differentiation might be observed in a limited set of characters in some cases or across multiple traits, as expected as isolation persists (see Huang & Knowles, ).…”