2000. Biogeographic patterns of Chilean littoral fishes

ABSTRACT In this study, we analyzed the biogeographic patterns of the Chilean littoral fish fauna, including latitudinal trends in teleost and chondrichthyan fish species richness, their distribution range patterns, and their level of endemism, both to the Chilean coast and the Southeastern Pacific. We determined the number and percentage of fish taxa within four different groups based on their biogeographic affinities. This was done, both for teleost and chondrichthyan fishes, at the species, genus and family level. In order to recognise the existence ofbiogeographic regions, we applied cluster and ordination analyses to the distribution data, using objective boots trapping techniques at the three taxonomic levels used. We found that littoral fish diversity remains fairly constant along the coast down to around 40° S, declining south of this latitude. We detected two biogeographic regions along the Chilean coast, with a break between them at 40° S. These results lend support to previously recognized biogeographic provinces or faunistic units. These two biogeographic regions are a reflection of the mixed origin of the Chilean littoral ichthyofauna, consisting of northern warm-temperate fishes of subtropical origin and southern cold-temperate fishes of subantarctic origin. While the percentage of fishes endemic to the Chilean coast is not high (18%), a large percentage ofteleost species inhabiting Chilean littoral waters are endemic to the Southeastern Pacific (44%). Dispersal and evolutionary history, rather that other factors, seem to explain the observed patterns of distribution of this particular fish fauna. This study represents a necessary first step towards understanding the biogeography of Southeastern Pacific marine fishes

Distributed under Creative Commons CC-BY 4.0 Nonlinear temperature effects on multifractal complexity of metabolic rate of mice

ABSTRACT Complex physiological dynamics have been argued to be a signature of healthy physiological function. Here we test whether the complexity of metabolic rate fluctuations in small endotherms decreases with lower environmental temperatures. To do so, we examine the multifractal temporal scaling properties of the rate of change in oxygen consumption r(VO 2 ), in the laboratory mouse Mus musculus, assessing their long range correlation properties across seven different environmental temperatures, ranging from 0 • C to 30 • C. To do so, we applied multifractal detrended fluctuation analysis (MF-DFA), finding that r(VO 2 ) fluctuations show two scaling regimes. For small time scales below the crossover time (approximately 10 2 s), either monofractal or weak multifractal dynamics are observed depending on whether T a < 15 • C or T a > 15 • C respectively. For larger time scales, r(VO 2 ) fluctuations are characterized by an asymptotic scaling exponent that indicates multifractal anti-persistent or uncorrelated dynamics. For both scaling regimes, a generalization of the multiplicative cascade model provides very good fits for the Renyi exponents τ (q), showing that the infinite number of exponents h(q) can be described by only two independent parameters, a and b. We also show that the long-range correlation structure of r(VO 2 ) time series differs from randomly shuffled series, and may not be explained as an artifact of stochastic sampling of a linear frequency spectrum. These results show that metabolic rate dynamics in a well studied micro-endotherm are consistent with a highly non-linear feedback control system

Biogeographic patterns of Chilean littoral fishes Patrones biogeográficos de los peces litorales de Chile

In this study, we analyzed the biogeographic patterns of the Chilean littoral fish fauna, including latitudinal trends in teleost and chondrichthyan fish species richness, their distribution range patterns, and their level of endemism, both to the Chilean coast and the Southeastern Pacific. We determined the number and percentage of fish taxa within four different groups based on their biogeographic affinities. This was done, both for teleost and chondrichthyan fishes, at the species, genus and family level. In order to recognise the existence of biogeographic regions, we applied cluster and ordination analyses to the distribution data, using objective bootstrapping techniques at the three taxonomic levels used. We found that littoral fish diversity remains fairly constant along the coast down to around 40º S, declining south of this latitude. We detected two biogeographic regions along the Chilean coast, with a break between them at 40º S. These results lend support to previously recognized biogeographic provinces or faunistic units. These two biogeographic regions are a reflection of the mixed origin of the Chilean littoral ichthyofauna, consisting of northern warm-temperate fishes of subtropical origin and southern cold-temperate fishes of subantarctic origin. While the percentage of fishes endemic to the Chilean coast is not high (18%), a large percentage of teleost species inhabiting Chilean littoral waters are endemic to the Southeastern Pacific (44%). Dispersal and evolutionary history, rather that other factors, seem to explain the observed patterns of distribution of this particular fish fauna. This study represents a necessary first step towards understanding the biogeography of Southeastern Pacific marine fishes<br>En este estudio, analizamos los patrones biogeográficos de los peces litorales chilenos, incluyendo las tendencias latitudinales en riqueza de especies de peces teleosteos y condrictios, sus rangos de distribución, y nivel de endemismo, tanto para la costa de Chile, como para el Pacífico Suroriental. Determinamos el número y porcentaje de taxa de peces pertenecientes a cuatro grupos según sus afinidades biogeográficas. Esta asignación a grupos se hizo al nivel de especie, género y familia, tanto para teleosteos como condrictios. Con el fin de determinar la existencia de regiones biogeográficas, utilizamos análisis de conglomerados y ordenación en conjunto con técnicas de aleatorización, para los tres niveles taxonómicos estudiados. Se determinó que la diversidad de peces litorales se mantiene relativamente constante a lo largo de la costa, hasta alrededor de los 40º S, disminuyendo hacia el sur. Detectamos dos regiones biogeográficas a lo largo de la costa chilena, con un quiebre entre ellas a los 40º S. Estos resultados apoyan la existencia de las provincias biogeográficas o unidades faunísticas reconocidas previamente en la literatura. Estas dos regiones biogeográficas reflejan el origen mixto de la ictiofauna litoral chilena, la que consiste de especies de peces de origen subtropical y subantartico. Aunque el porcentaje de peces endémicos a la costa chilena es bajo (18%), un alto porcentaje de las especies de teleosteos presentes en aguas chilenas es endémico al Pacífico Suroriental (44%). Procesos relacionados con fenómenos de dispersión y la historia evolutiva de los componentes de esta fauna explicarían de mejor manera los patrones de distribución observados más que otros factores sugeridos en la literatura. Este estudio representa un primer paso hacia una mejor comprensión de la biogeografía de los peces marinos del Pacífico Surorienta

Nonlinear temperature effects on multifractal complexity of metabolic rate of mice

Complex physiological dynamics have been argued to be a signature of healthy physiological function. Here we test whether the complexity of metabolic rate fluctuations in small endotherms decreases with lower environmental temperatures. To do so, we examine the multifractal temporal scaling properties of the rate of change in oxygen consumption r(VO2), in the laboratory mouse Mus musculus, assessing their long range correlation properties across seven different environmental temperatures, ranging from 0 °C to 30 °C. To do so, we applied multifractal detrended fluctuation analysis (MF-DFA), finding that r(VO2) fluctuations show two scaling regimes. For small time scales below the crossover time (approximately 102 s), either monofractal or weak multifractal dynamics are observed depending on whether Ta  15 °C respectively. For larger time scales, r(VO2) fluctuations are characterized by an asymptotic scaling exponent that indicates multifractal anti-persistent or uncorrelated dynamics. For both scaling regimes, a generalization of the multiplicative cascade model provides very good fits for the Renyi exponents τ(q), showing that the infinite number of exponents h(q) can be described by only two independent parameters, a and b. We also show that the long-range correlation structure of r(VO2) time series differs from randomly shuffled series, and may not be explained as an artifact of stochastic sampling of a linear frequency spectrum. These results show that metabolic rate dynamics in a well studied micro-endotherm are consistent with a highly non-linear feedback control system

Rivers as a potential dispersing agent of the invasive tree Acacia dealbata

Background: The silver wattle Acacia dealbata is a fast-growing tree from Australia that has become naturalised in different regions of the world, attaining invasive status in most of them. In Chile, A. dealbata reaches large abundances along banks and floodplains of invaded fluvial systems, suggesting that rivers may act as a vector for seed dispersal. As hydrochory has not been documented previously in this species, the aim of this study is to evaluate the potential for water dispersal of seeds of this invasive tree along rivers. Methods: Seed samples from rivers were collected at three sites along two A. dealbata-invaded rivers within the Cachapoal basin, central Chile. Number of seeds collected was contrasted versus hydraulic and local conditions with RDA. Seed buoyancy and sedimentation velocity were determined and compared between sites with an ANCOVA. Finally, the probability of seed germination after long periods of immersion in water was assessed, simulating transport conditions in the flow. Germination results were tested with a GLM. Results: Results indicate that increasing abundance of A. dealbata seeds in the flow is related to the level of turbulence of the flow. Seeds display high floatability but their sedimentation velocity is high when they do sink. Finally, silver wattle seeds can germinate after long periods (many weeks) of immersion in water; however, their probability of germination depends to a large extent on whether seeds are scarified or not. Conclusions: Based on the evidence collected, we suggest that the seeds of A. dealbata have the necessary traits to be dispersed by rivers, this being the first research testing this hypothesis. The success of hydrochory of A. dealbata would depend on river flow turbulence, and whether there are natural mechanisms for scarifying the seeds either before or during transport. The proposed methodology can be used to assess river hydrochory for any tree species

Changes in body size spectra of benthic caridean shrimps (Decapoda: Caridea) and snails (Gastropoda) as response to seasonal variability

"Ecologists have been largely interested in the description and understanding of the power scaling relationships between body size and abundance of organisms. Many studies have focused on estimating the exponents of these functions across taxonomic groups and spatial scales, to draw inferences about the processes underlying this pattern. The exponents of these functions usually approximate -3/4 at geographical scales, but they deviate from this value when smaller spatial extensions are considered. This has led to propose that body size-abundance relationships at small spatial scales may reflect the impact of environmental changes. This study tests this hypothesis by examining body size spectra of benthic shrimps (Decapoda: Caridea) and snails (Gastropoda) in the Tamiahua lagoon, a brackish body water located in the Eastern coast of Mexico. We measured water quality parameters (dissolved oxygen, salinity, pH, water temperature, sediment organic matter and chemical oxygen demand) and sampled benthic macrofauna during three different climatic conditions of the year (cold, dry and rainy season). Given the small size of most individuals in the benthic macrofaunal samples, we used body volume, instead of weight, to estimate their body size. Body size-abundance relationships of both taxonomic groups were described by tabulating data from each season into base-2 logarithmic body size bins. In both taxonomic groups, observed frequencies per body size class in each season were standardized to yield densities (i.e., individuals/m3). Nonlinear regression analyses were separately performed for each taxonomic group at each season to assess whether body size spectra followed power scaling functions. Additionally, for each taxonomic group, multiple regression analyses were used to determine whether these relationships varied among seasons. Our results indicated that, while body size-abundance relationships in both taxonomic groups followed power functions, the parameters defining the shape of these relationships varied among seasons. These variations in the parameters of the body size-abundance relationships seems to be related to changes in the abundance of individuals within the different body size classes, which seems to follow the seasonal changes that occur in the environmental conditions of the lagoon. Thus, we propose that these body size-abundance relationships are influenced by the frequency and intensity of environmental changes affecting this ecosystem.