Recognition of biotic components is a key element for understanding evolution in space-time. Panbiogeography represents a biogeographic approach that may be applied to identify these biotic components. A revision of the panbiogeographic approach is provided herein, including definitions of basic concepts individual and generalized tracks, nodes, baselines, and main massings and methods manual, connectivity and incidence matrices, track compatibility, and parsimony analysis of endemicity. As an example of this approach, 70 biotic components of Latin America and the Caribbean are identified, briefly characterized, and arranged in a biogeographic system of three regions, seven subregions, and two transition zones. The relevance of the recognition of biotic components and transition zones is discussed. Keywords: Biogeography; evolution; Neotropics; nodes; parsimony analysis of endemicity; tracks.
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ABSTRACT For almost a century, a number of authors have analyzed the distribution patterns of the marine fauna and flora in the South American Pacific and particularly along the coast of Chile, with the purpose of determining the number of existing biogeographical units.
Although the general, present day patterns are relatively well known, most studies have focused on distributional breaks and classification proposals rather than on the factors and dynamic processes that formed the identified spatial units.
Even in the case of biogeographical classifications, published conclusions are based mainly on the analysis of one or few selected groups, exhibiting important differences in their criteria for selecting groups, the number of species involved, and their methodology. On the other hand, diverging conclusions among particular studies tend to obscure the more relevant, large-scale phenomenon of biota dynamics, one of the less known biogeographic aspects in Chile.
Within that context, this paper presents a literature review on the marine biogeography of Chile and related subjects, with the following objectives: a to summarize the oceanographic, climatic and geomorphologic characteristics of the Chilean continental coast; b to discuss 27 biogeographic classifications published for the Chilean coast, analyzing both the procedures and criteria used by their authors, along with their main conclusions and agreements; c to assess the vicariant and dispersal processes associated with the displacement and modification of the regional biotas, regarding the available antecedentes on the prevailing conditions and main events during the Tertiary and Quaternary periods; and d to propose a scenario of biogeographic change based on historical determinants and their influence on the formation, character, and dynamics of biotas along the Chilean coast, emphasizing the identification and biogeographic nature of the main spatial units.
From the preceding information, I propose a hypothesis of biogeographic classification for the level of biotas, not necessarily coincident with prior studies at lower levels such as flora or fauna. This classification identifies three major spatial units: a southern area which comprises an austral biota Magellan Province , a northern area which comprises a warm-temperate biota Peruvian Province , and a non transitional, Intermediate Area including mixed components of biota and exhibiting a poor biogeographic definition of both its character and hierarchical rank.
I also discuss the different nature of two transitional zones located at the boundaries of the Intermediate Area, a southward induced transition and a northward contact transition, likely produced by the migration of biotas and glacial-tectonic events, respectively.
Key words: biogeographical classification, Chile, dynamics, marine biota, provincialization, tectonic and glacial events. En similar perspectiva, Castilla e. Destaca el llamado "codo" de Arica ca. Outline of the main oceanic circulation patterns along the coast of Chile based on Bernal et al. Entre ca. Viviani ha estimado que la temperatura del mar en el extremo norte es ca.
Alveal et al. Sketches of biogeographical classifications horizontal lines of the Chilean continental coast proposed in 27 studies during the last century. Due to its variety, the names of biogeographical areas have been omitted for clarity. Closed dots: divisions among major biogeographical units; vertical lines: subdivisions of a major unit; in some cases, divisions were approximated to the closest degree of latitude.
La Fig. Frequency distribution of the number of proposed biogeographical limits for a given latitude according to the classifications shown in Fig. As the data sets used in some works are not independent, and studies differ in the type and specificity of their criteria for selecting organisms taxa of varying hierarchy, flora, fauna, environments, etc.
Para ciertos taxa, el efecto puede ser indirecto. Algo similar ocurre con la riqueza de macroalgas Santelices , Con respecto al sector chileno entre ca.
Como se observa en la Fig. Frequency distribution of the number of biogeographic limits documented by the studies analyzed in this work. The curve represents a normal distribution fitted to the data, evidencing a strong right-skewness due to the conservative criteria used by most authors.
Larrain , o se apoyan en interpretaciones que hoy han sido descartadas. Especialmente para la zona austral de Chile, algunos autores e. Por ello, Crisci et al. Similarmente, Alveal et al. Hedgpeth , cf. La Deriva del Oeste es un mecanismo potencial relevante, pero es poco probable que sea un mecanismo generalizado.
La bipolaridad y los patrones anfitropicales han sido en general un tema conflictivo, ya que implican el cruce de la banda tropical que representa una barrera efectiva para muchas especies marinas. Por otra parte, hay otras interpretaciones alternativas que plantean la existencia de supercontinentes distintos y anteriores a Pangaea, y que implican una historia de relaciones espaciales muy distinta entre las actuales biotas boreales, tropicales y australes.
Aun cuando Crisci et al. En este sentido, los diversos trabajos realizados por Moyano e. Possible evolution of the physical-climatic scenario of the coast of Chile; A and B represent alternative interpretations in the literature about the situation prior to the installation of the cold Humboldt system during the Tertiary period. A : Warm-temperate conditions along the whole coast with a moderate latitudinal gradient of sea temperature.
Dominance of a northward oceanic flow FN , likely of cold-temperate nature, with a weak influence of a southward warm flow FCS. B : Warm-temperate conditions along the coast, with dominance of a southward warm flow FCS and weak infkuence of a northward flow FN.
C : After the opening of the Drake passage PD , with a steeper latitudinal gradient of sea temperature and dominance of a cold northward flow Humboldt system; SH with moderate influence of a southward warm flow FCS. Conditions roughly similar to modern ones, probably acting since the Neogene. Beginning of the circumantarctic current CCA.
Figure 1 shows the Holocene-recent scenario, with a fragmented southern coast due to glacial-tectonic processes.
Covacevich , cf. En contraste, Ortlieb et al. Ortlieb et al. De este modo, es probable que ca. En este sentido, Jerardino et al. Esto sugiere que poco antes del posible evento del 9. Alternativamente, si el episodio de 9.
Posteriormente, Rollins et al. Como se desprende de la Fig. En base a lo anterior, siguiendo un criterio conservativo es factible sugerir la presencia de dos unidades espaciales mayores en Chile Fig. Hypothesis of biogeographic classification for the continental coast of Chile, developed for the level of biota see details in text and Table 1. Este criterio implica reconocer discontinuidades distribucionales al nivel de flora-fauna surgidas al interior de una unidad mayor por cualquier factor, siempre en la perspectiva de las biotas.
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