Species composition and distribution of rotifers in Chihua-huan Desert waters of Mexico: is everything everywhere?

摘要

For nearly 100 years (ROUSSELET 1909), investigators have as-sumed rotifers are cosmopolitan because they have stages that can disperse easily, either abiotically (wind and rain) and/or biotically (epi- or endozoochory). Monogononts may be trans-ported as diapausing embryos (resting eggs), while bdelloids disperse as xerosomes (anhydrobiotic adults and eggs; WAL-LACE & Small 2009). Rotifers also mature rapidly and have a high reproductive potential. These features presumably result in a wide distribution and allow rapid colonization of suitable habitats, thereby following the Baas Becking Principle (BBP): "Everything is everywhere, but nature selects" (DE WIT & Bou-VIER 2006). While cosmopolitanism does characterize organ-isms of ≤ mm (FINLAY 2002) and many monogononts are re-ported to be cosmopolitan (e.g., KOSTE 1978), this feature has been rejected as a characteristic of the phylum (DuMONT 1983, DUMONT & SEGERS 1996, WALLACE et al. 2006, WALSH et al. 2007). However, bdelloids seem to follow the BBP, at least in part (FONTANETO et al. 2005, 2006). Therefore, for rotifers the puzzle remains: can everything get everywhere, with nature determining the outcome of colonization?We examined the BBP as it relates to rotifers by collecting species richness (S) data from a large group of geographically dispersed waters in the Mexican Chihuahuan Desert (CD). We chose the CD because it is widely recognized as one of the most biologically diverse ecoregions in North America (DINERSTEIN et al. 2000). This contribution represents part of a larger proj-ect that is investigating the phylogeography of micrometazoans in the waters of the CD.