The Amazonian dwarf cichlid Apistogramma agassizii (Steindachner, 1875) is a geographic mosaic of potentially tens of species: Conservation implications

Abstract

1. Assessing biodiversity and understanding how it works is a prerequisite for species conservation. The Amazon basin is one of the main biodiversity hotspots where fish are heavily exploited for ornamental purposes.2. The ornamental trade heavily exploits the genusApistogramma, which is one of the most species-rich among Neotropical cichlids with 94 formally described species. This number is certainly underestimated owing to the limitations of conventional taxonomy, which is still too often based solely on morphological criteria and sometimes on few individuals.3. Most species of this genus have a high degree of endemism and are highly prized on the ornamental market, which could put them at risk. A few species are supposed to have extensive distributions, and in particularApistogramma agassizii, present from the Amazon estuary up to the Ucayali and Maranon rivers in Peru.Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.5. According to the molecular calibrations, these three species would have diverged during the Plio-Pleistocene. Two of them seem to be endemic from small sub-basins, one from the Nanay River and the other from the Apayacu/Ampiyacu systems. A possible scenario that may explain the evolutionary history of these species is proposed.6. The conservation implications of these results on the estimation of the diversity ofA. agassizii, ofApistogrammaspecies in general, and of other Amazonian cichlids are discussed.

Epigenetic Regulation and Environmental Sex Determination in Cichlid Fishes

“…In the model, when the evolution of novel color morphs was combined with strong assortative mating, it would promote speciation when both sex reversal and suppressor genes are incorporated. Empirical data support the connection between color morphs, assortative mating, and rapid speciation for species in the genus Apistogramma [Estivals et al, 2020]. It could be argued that ESD could speed up or inhibit such speciation via sex reversal.…”

Reproductive aspects of the dwarf cichlid Apistogramma agassizii under captive conditions

“…According to Estivals et al (2020) and Souza (2021), the intense coloration in the caudal and anal regions of A. agassizii indicates a possible relationship with characteristics that can be sexually selected and act as a signal, making individuals more attractive. As observed in this study and according to Maan and Sefc (2013), Apistogramma sp.…”

“…According to Estivals et al (2020), the Apistogramma genus includes about 94 species. These fish normally reach between 20 and 60 mm in standard length and have accentuated sexual dimorphism, where males are larger, more colorful, and more adorned than the females (Römer, 2001;.…”

River Reorganization Affects Populations of Dwarf Cichlid Species (Apistogramma Genus) in the Lower Negro River, Brazil

“…The dwarf cichlids from the genus Apistogramma have over a hundred described species, which are well known to have either allopatric or sympatric geographic distributions (Kullander and Ferreira, 2005;Römer, 2006;Costa et al, 2019). It is estimated that many Apistogramma species still need to be described and thus species richness is probably underestimated (Estivals et al, 2020). The dwarf cichlids occur in all types of river waters (clear, black, and white) found in the Brazilian Amazon, though are rarely found in the main channels of the major rivers, which is a reflection of their ecology and restricted habitat requirements (Kullander, 2003).…”

“…The dwarf cichlids occur in all types of river waters (clear, black, and white) found in the Brazilian Amazon, though are rarely found in the main channels of the major rivers, which is a reflection of their ecology and restricted habitat requirements (Kullander, 2003). Nonetheless, most of them present a high endemic level (Estivals et al, 2020). The life history of cichlids includes parental care and territorialism, which explains their high rates of endemism.…”