Browsing by Author "Muñoz, AA"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Biogeographic patterns of Chilean littoral fishes
    (2000) Ojeda, FP; Labra, FA; Muñoz, AA
    In this study, we analyzed the biogeographic patterns of the Chilean littoral fish fauna, including latitudinal trends in teleost and chondrichhyan 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 40 degrees S, declining south of this latitude. We detected two biogeographic regions along the Chilean coast, with a break between them at 40 degrees 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.
  • No Thumbnail Available
    Item
    Diversity and host tree preferences of vascular epiphytes and vines in a temperate rainforest in southern Chile
    (2003) Muñoz, AA; Chacón, P; Pérez, F; Barnert, ES; Armesto, JJ
    Vines and epiphytes contribute importantly to the biodiversity of temperate rainforests of southern South America. However, compared with their tropical counterparts, these functional groups have received less attention. We evaluated diversity, floristic composition and relative abundance of vascular epiphytes and vines within a humid temperate forest in northern Chiloe Island, southern Chile. We assessed whether epiphyte and vine species exhibit preferences among host tree species and tested whether species richness on tree hosts differs from that expected by chance, by comparing observed frequencies of occurrence (FO) and species richness with randomly simulated frequency distributions generated under the assumption of no epiphyte preferences. Finally, we tested for associations of epiphyte and vine species with host tree size ( trunk diameter at breast height). Eleven species of ferns and nine angiosperms ( seven vines, one epiphytic angiosperm and one shrub) were recorded growing epiphytically in a sample of 499 trees. The most abundant species were three vines, Luzuriaga polyphylla (Hook.) Macbr., Griselinia racemosa (Phil.) Taub. and Mitraria coccinea Cav., and five species of filmy ferns (Hymenophyllaceae). Most epiphytes and vines (65%) showed preference for one or two tree species, with seven species being overrepresented on Podocarpus nubigena Lindl. hosts and 10 underrepresented on Drimys winteri J.R. et G. Forster. Epiphyte and vine species richness was significantly lower than expected by chance on D. winteri and higher than expected on Nothofagus nitida ( Phil.) Krasser. Three epiphytic ferns showed preferences for large-sized trees, while frequency of occurrence of three common vines was independent of host tree size.
  • No Thumbnail Available
    Item
    Feeding selectivity of the herbivorous fish Scartichthys viridis
    (1999) Ojeda, FP; Muñoz, AA
    The ecological importance of fish herbivory was examined in a temperate rocky intertidal zone along the central Chilean coast. In this system, the blenny Scartichthys viridis is the most abundant and only herbivorous fish. We describe its diet, determine its field food selectivity (gut contents vs macroalgal field availability comparison), and report on its laboratory dietary preferences in a multiple-choice feeding experiment. Finally, we evaluate the relative effects of fish herbivory and grazing invertebrates on macroalgal abundance, distribution and diversity patterns in the field, using replicated exclusion cages to manipulate grazing intensity. S. viridis was found to be a selective grazer; its diet was dominated by 2 macroalgae: the green Ulva and the red Gelidium, representing 32.6 and 41.4% of its total gut content biomass, respectively. Ulva was consumed much above its field availability while Gelidium was selected only during fall-winter. In the laboratory, S. viridis selected the green macroalgae Ulva rigida and Codium dimorphum and avoided Gelidium chilense. We suggest that Gelidium may be included in its diet due to the limited availability of Ulva in the field. Experimental exclusion of this fish from rocky surfaces resulted in increased abundance of green foliose macroalgae (U. rigida and Enteromorpha linza), and, to a much lesser extent, of the red foliose macroalgae G. chilense, Porphyra columbina, and Mazzaella laminarioides, and of the brown macroalgae Colpomenia phaeodactyla and Petalonia fascia, as well as an extension of the distribution of P. columbina from the high intertidal to the mid intertidal zone, where it normally does not occur. Exclusion of grazing invertebrates resulted in a decrease in foliose macroalgal species richness, but had no effect on biomass. To our knowledge, this is the first experimental demonstration of the effect of an herbivorous fish on macroalgal community structure in a temperate rocky intertidal area. The selective feeding displayed by S, viridis, its high numerical abundance, and the results of the herbivore exclusion experiment suggest its importance in maintaining the low abundance of foliose macroalgae and the high relative cover of brown and red crustose macroalgae, characteristic of many low to mid rocky intertidal areas along the coast of central Chile.
  • No Thumbnail Available
    Item
    Ontogenetic changes in the diet of the herbivorous Scartichthys viridis in a rocky intertidal zone in central Chile
    (2000) Muñoz, AA; Ojeda, FP
    Scartichthys viridis maintains a herbivorous diet following recruitment to rocky intertidal areas, where it consumes almost exclusively macroalgae. The sheet-like green macroalgae Ulva and Enteromorpha were the main items consumed by individuals <130 mm L-T. The tough branching red macroalga Gelidium made the bulk of the gut contents of specimens >220 mm L-T, Ulva being consumed to a much lesser extent. Further, Gelidium increased in importance in the total gut contents during ontogeny. In contrast, both small (70-120 mm L-T) and medium-sized (140-210 mm L-T) S. viridis individuals preferred Ulva in the laboratory. It is suggested that the increasing consumption of Gelidium along the ontogeny of S. viridis results from the limited availability of Ulva in the field. Large S. viridis individuals possessed longer guts relative to their body length, in comparison with small individuals. (C) 2000 The Fisheries Society of the British Isles.