The genus Basilichthys (Teleostei: Atherinopsidae) revisited along its Chilean distribution range (21º to 40º S) using variation in morphology and mtDNAEl género Basilichthys (Teleostei: Atherinopsidae) analizado a lo largo de su distribución en Chile (21º a 40º S), utilizando rasgos morfológicos y variabilidad del ADN mitocondrial ABSTRACTThere is still doubt as to the number of species of the freshwater Chilean ichthyofauna, 64 % of which have conservation problems. One of the groups is that of the silversides of the genus Basilichthys. Three morphological species of this genus have been described in Chile with disjoint distributions: Basilichthys semotilus, B. microlepidotus and B. australis; the latter two overlap in distribution only in the Aconcagua River and are not easily distinguishable by morphological and meristic characters. In order to evaluate the effi cacy of identifi cation of these species by molecular techniques, we analyzed the sequence of 9 % of the mitochondrial DNA (Control Region and COI) of individuals from the Loa River (21º41' S) to the Valdivia River (39º50' S), adding meristic features for B. microlepidotus and B. australis in order to study population variation to clarify the taxonomy of the native species of the genus. The phylogenetic analysis showed that the individuals of Basilichthys semotilus form an haplogroup separated from the other species of the genus; however, B. australis and B. microlepidotus form a monophyletic group that shares the most common haplotypes. An analysis of meristic information showed no statistically signifi cant differences in the number of lateral line scales or number of rays in the fi ns between B. microlepidotus and B. australis. These results do not support the current classifi cation for the latter two species; there appears to be one group in the extreme north of the country (Basilichthys semotilus) and a second group in central Chile which should be called B. microlepidotus. This information will be useful to review the conservation status of the Chilean fauna.Key words: COI, Control Region, drainages, mtDNA, Silverside fi sh. RESUMENSi bien aún existen dudas sobre el número de especies descritas en el país, se reconoce que el 64 % de la ictiofauna dulceacuícola chilena se encuentra en alguna categoría de peligro de conservación. Uno de los grupos categorizados como vulnerable y en peligro de extinción es el de los pejerreyes del género Basilichthys. A lo largo Chile, este género posee tres especies morfológicas con distribución disjunta: Basilichthys semotilus, B. microlepidotus y B. australis. Las dos últimas sobreponen su distribución en el río Aconcagua y no son fácilmente diferenciables morfológicamente. Para evaluar la efi cacia en la identifi cación de estas especies al utilizar marcadores moleculares, se analizó el 9 % del ADN mitocondrial (Región Control y COI) de organismos obtenidos desde el río Loa (21º41' S) al río Valdivia (39º50' S) y adicionando un análisis merístico en organismos pertenecientes a las especies B. microlepidotus ...
Top-down and bottom-up mechanisms have been proposed as potential regulators of the phytoplankton biomass of aquatic ecosystems. We evaluated the effect of nutrient enrichment and planktivorous fish predation through a mesocosm experiment conducted at a polimictic system (Penuelas reservoir, Chile). Results show that phytoplankton biomass increased, while diversity decreased, in nutrient-enriched treatments. Planktivorous fish predation did not have a significant effect on phytoplankton biomass but led to a reduction of bigger zooplankton abundance. These results are an indication that these reservoir systems would be preferentially influenced by resource availability in short-term manipulations
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