TimeFISH: Long-term assessment of reef fish assemblages in a transition zone in the Southwestern Atlantic.

The TimeFISH database provides the first public time-series dataset on reef fish assemblages in the southwestern Atlantic (SWA), comprising 15 years of data (2007-2022) based on standardized Underwater Visual Censuses (UVCs). The rocky reefs covered by our dataset are influenced by pronounced seasonal cycles of ocean temperatures with warm tropical waters from the Brazil Current in the summer (~27°C) and colder waters from the La Plata River Plume discharge and upwelling from the South Atlantic Central Water in the winter (~18°C). These oceanographic conditions characterize this area as the southernmost tropical-subtropical climatic transition zone in the Atlantic Ocean. As a result, reef fish assemblages are comprised of both tropical and subtropical species. All records included in TimeFISH were collected using UVCs, a nondestructive method that allows the estimation of fish species richness, abundance, and body size distributions. UVCs were performed through 40 m2 belt transects by scuba diving in nine locations along the southern Brazilian coast (25-29°S). Four of these locations lie within the boundaries of the no-entry Arvoredo Marine Biological Reserve, where fishing and recreational activities are forbidden, and the remaining locations are unprotected from these activities. During each belt transect, a diver swam at a constant depth above and parallel to the reef, identifying fish species, counting the number of individuals, and estimating the total body length (Lt in cm) of all detected individuals. All fish individuals in the water column (up to 2 m above the substratum) and at the bottom were targeted. In total, 202,965 individuals belonging to 163 reef fish species and 53 families were recorded across 1857 UVCs. All survey campaigns were funded by either public or mixed capital (private-public) sources, including seven grants from the Brazilian federal and Santa Catarina state governments. Part of the data has already been used in multiple MS.c. and Ph.D. theses and scientific articles. TimeFISH represents an important contribution for future studies aiming to examine temporal and spatial variations of reef fish assemblages in transition zones. No copyright restrictions apply to the use of this data set, other than citing this publication.

Phylogeography of the banded butterflyfish, Chaetodon striatus, indicates high connectivity between biogeographic provinces and ecosystems in the western Atlantic

Among the four butterflyfishes of the genus Chaetodon present in the western Atlantic, the banded butterflyfish Chaetodon striatus has the largest distribution range, spanning 44 degrees of latitude (from Massachusetts, USA to Santa Catarina, Brazil). Although the ecology of the banded butterflyfish has been well studied over its entire range, nothing is known about its phylogeography and how biogeographic barriers structure its populations. To assess the level of genetic connectivity among populations from distinct biogeographic provinces and environmental conditions, we collected samples from seven localities: Puerto Rico, in the Caribbean, and Tamandaré, Salvador, Abrolhos, Trindade Island, Arraial do Cabo and Florianópolis, in Brazil. One nuclear (rag 2) and two mitochondrial (control region and cyt b) molecular markers were sequenced. Our findings are consistent with a recent population expansion, around 30-120 thousand years ago, which was found for all populations. Haplotype network analyses point to the Caribbean as a refugium before the population expansion. Results show no geographic pattern of genetic diversity. Indeed, a lack of population structure was found and no isolation was observed across oceanographic barriers, as well as between coral and rocky reef ecosystems. Furthermore, no directionality in the migration pattern was found among populations. Since ecological and environmental characteristics are very diverse across such a vast geographic range, the lack of genetic differentiation suggests that C. striatus evolved ecological plasticity rather than local adaptation in the western Atlantic.(AU)

O peixe-borboleta listrado, Chaetodon striatus, possui a maior distribuição geográfica dentre as quatro espécies de peixes-borboleta do gênero Chaetodon presentes no Oceano Atlântico Ocidental, abrangendo 44° de latitude (entre Massachusetts, EUA até o sul do Brasil). A ecologia alimentar desta espécie é bastante conhecida, considerando a ampla distribuição, porém, pouco se sabe sobre a filogeografia e como as barreiras biogeográficas estruturam as populações. Para acessar a conectividade genética entre as populações de diferentes províncias biogeográficas e diferentes condições ambientais, foram coletadas amostras de sete localidades: Porto Rico, no Caribe, e Tamandaré, Salvador, Abrolhos, Ilha da Trindade, Arraial do Cabo e Florianópolis, no Brasil. Foram sequenciados um gene nuclear (rag 2) e dois genes mitocondriais (região controle e cit B). Para todas as populações, foi identificada uma expansão populacional recente, em torno de 30-120 mil anos atrás. A análise de rede de haplótipos sugere que o Caribe serviu como refúgio antes desta expansão populacional. Os resultados indicam que não há padrão geográfico de diversidade genética. Apesar da existência de barreiras oceanográficas e diferenças na constituição dos recifes (rochosos e coralíneos), não foi encontrada estruturação populacional. Também, não encontramos padrão na direção de migração entre as populações. Os resultados sugerem que C. striatus apresenta plasticidade ecológica, uma vez que não há diferenciação genética entre as populações que habitam ecossistemas tão diferentes ao longo da ampla distribuição no Atlântico Ocidental.(AU)

Diet and diversification in the evolution of coral reef fishes.

The disparity in species richness among evolutionary lineages is one of the oldest and most intriguing issues in evolutionary biology. Although geographical factors have been traditionally thought to promote speciation, recent studies have underscored the importance of ecological interactions as one of the main drivers of diversification. Here, we test if differences in species richness of closely related lineages match predictions based on the concept of density-dependent diversification. As radiation progresses, ecological niche-space would become increasingly saturated, resulting in fewer opportunities for speciation. To assess this hypothesis, we tested whether reef fish niche shifts toward usage of low-quality food resources (i.e. relatively low energy/protein per unit mass), such as algae, detritus, sponges and corals are accompanied by rapid net diversification. Using available molecular information, we reconstructed phylogenies of four major reef fish clades (Acanthuroidei, Chaetodontidae, Labridae and Pomacentridae) to estimate the timing of radiations of their subclades. We found that the evolution of species-rich clades was associated with a switch to low quality food in three of the four clades analyzed, which is consistent with a density-dependent model of diversification. We suggest that ecological opportunity may play an important role in understanding the diversification of reef-fish lineages.