A geographical cline in craniofacial morphology across populations of Mesoamerican lake-dwelling fishes.

Together, the complex geological history and climatic diversity of Mesoamerica create a rich source of biodiversity from which evolutionary processes can be studied. Here, we discuss highly divergent morphs of lake-dwelling fishes distributed across Mexico and Central America, originally recognized as members of different genera (Astyanax and "Bramocharax"). Recent phylogenetic studies, however, suggest these morphs group within the same genus and readily hybridize. Despite genetic similarities, Bramocharax morphs exhibit stark differences in cranial shape and dentition. We investigated the evolution of several cranial traits that vary across morphs collected from four lakes in Mexico and Nicaragua and discovered an ecomorphological cline from northern to southern lakes. Northern populations of sympatric morphs exhibit a similar cranial shape and tooth morphology. Southern populations of Bramocharax morphs, however, showed a larger disparity in maxillary teeth, length and frequency of unicuspid teeth, an elongated snout, and a streamlined cranium compared to Astyanax morphs. This divergence of craniofacial morphology likely evolved in association with differences in trophic niches. We discuss the morphological differences across the four lake systems in terms of geological history and trophic dynamics. In summary, our study suggests that Bramocharax morphs are likely locally adapted members derived from independent Astyanax lineages, highlighting an interesting parallel evolutionary pattern within the Astyanax genus.

Variabilidade de microssatélites e geometria alar em Aedes aegypti / Variability of microsatellites loci and wing geometry in Aedes aegypti

The Aedes (Stegomya) aegypti (Linnaeus, 1762) is a Culicidae with high geographical coverage, restricted only on the poles. Due to its bond with several arboviruses, it is one of the most important mosquitoes species for global public health. It reproduces easily in Brazil because of its favorable climate to the species. Many control methods have been proposed to it, but the rapid microevolution of these mosquitoes turns into a limiting factor, compromising the efficacy of most of them. Molecular markers as DNA SSR (microsatellites) demonstrate great results in the investigation of populations and microevolution studies but demands a high financial value. In parallel, studies with morphological markers such as wing geometry have been proposed as a cheap and sensitive tool for detecting the same kind of data. In this study, both markers were used aiming to distinguish two populations based on its variability index. The first one, original from the Santos city - SP (SAN), and the second one, highly endomorphic and originated by a Higgs strain (COL) by the Instituto Butantan. With the molecular marker, we successfully had a standardization of PCR (Polymerase Chain Reaction) in situ of four loci. Another fourteen microsatellite loci were ex-situ genotyped. Data from that were analyzed by this study author and demonstrated higher genetic variability in the SAN population. The morphological marker reinforced SAN as the most variated population and indicated a possible ancestral polymorphism in the COL population, demonstrating once again the capacity of allelic maintenance of the Aedes aegypti species and the sensibility of wing geometry as a morphological marker. With this study, we could describe a pattern of variability of endogamic population to genetic marker as microsatellite DNA and morphological marker as wing geometry. This is the possible first study to describe the biological variability of an endogamic population.

O mosquito Aedes (Stegomya) aegypti (Linnaeus, 1762) é um Culicidae de alta abrangência geográfica, restringindo-se apenas nos polos. Por possuir afinidade com diversos arbovírus, tornou-se uma das espécies mais importantes para a saúde pública global. Reproduz-se com facilidade no Brasil devido ao clima favorável à espécie. Diversos métodos de controle do inseto vêm sendo propostos, entretanto a rápida microevolução do mosquito compromete a eficácia de grande parte deles. Marcadores moleculares como DNA SSR (microssatélites) apresentam bons resultados na investigação de populações e microevolução, mas demandam um valor financeiro elevado. Paralelamente, estudos com marcadores morfológicos do tipo morfometria de asa vêm se mostrando sensíveis para detectar variações do mesmo tipo, e com valor financeiro muito reduzido. Neste trabalho, ambos marcadores foram utilizados para diferenciar duas populações quanto aos seus índices de variabilidade. A primeira, proveniente da cidade de Santos – SP (SAN), e a segunda originada de uma colônia de cepa Higgs altamente endocruzada e cedida pelo Instituto Butantan (COL). Quanto ao marcador molecular, houve padronização de PCR (Polymerase Chain Reaction) in situ para 4 loci. Outros 14 loci microssatélites foram genotipados externamente. Os dados provenientes desta genotipagem foram analisados pela autora deste trabalho e indicaram maior variabilidade genética na população de SAN. O marcador morfológico reforçou SAN como a população mais variada e indicou possível polimorfismo ancestral na população COL, demonstrando mais uma vez a capacidade de manutenção alélica da espécie e a sensibilidade da morfometria de asas como marcador morfológico. Com este estudo conseguimos ainda descrever um padrão de variabilidade de população endogâmica para marcador genético do tipo DNA microssatélite e marcador morfológico do tipo geometria de asas. Este é possivelmente o primeiro trabalho a descrever tal relação.

Parasitic copepods affect morphospace and diet of larvae of a temperate reef fish.

The effects of ectoparasites on larvae of the clingfish Gobiesox marmoratus were evaluated at the dietary and morphometric levels. The larvae and ectoparasites were collected by nearshore plankton samplings during October, November and December 2013 off El Quisco Bay, central Chile. The standardized abundance of total larvae and those ectoparasitized larvae (PL) was positively related and high parasite prevalence was found throughout the sampling period (up to 38%). Geometric morphometrics analyses indicate main changes in the shape through early ontogeny and subtle but significant variations between PL and non-parasitized larvae (NPL). Prey composition varied between PL and NPL; small size (<6 mm standard length, LS ) parasitized larval G. marmoratus ate mostly gastropod larvae, whereas small non-parasitized specimens ate mainly cirripede nauplii. All larger (>8 mm LS ), pre-settlement stages parasitized by Trifur and, or Caligus copepods had content in their gut, suggesting that ectoparasites did not diminish prey capture in host with larger size. Morphometric and dietary changes occurring during larval development were decoupled, both for PL and NPL. The maintenance of a slender, more hydrodynamic body through pelagic development and the ingestion of less-mobile prey in PL suggests non-lethal effects of ectoparasitism on rocky-reef fish larvae.