Significant habitat effects influence protist fitness: evidence for local adaptation from acidic mining lakes

Abstract

Abstract. It is currently controversially discussed if the same freshwater microorganisms occur worldwide wherever their required habitats are realized, i.e., without any adaptation to local conditions below the species level. We performed laboratory experiments with flagellates and ciliates from three acidic mining lakes (AML, pH ;2.7) to investigate if similar habitats may affect similar organisms differently. Such manmade lakes provide suitable ecosystem models to test for the significance of strong habitat selection. To this end, we analyzed the growth response of three protist taxa (three strains of the phytoflagellate Chlamydomonas acidophila, two isolates of the phytoflagellate Ochromonas and two species of the ciliate genus Oxytricha) by exposing them to lake water of their origin and from the two other AML in a crossfactorial design. Population growth rates were measured as a proxy for their fitness. Results revealed significant effects of strain, lake (¼habitat), and strain 3 habitat interaction. In the environmentally most adverse AML, all three protist taxa were locally adapted. In conclusion, our study demonstrates that (1) the same habitat may affect strains of the same species differently and that (2) similar habitats may harbor ecophysiologically different strains or species. These results contradict the 'everything is everywhere' paradigm.

Systematics and species-specific response to pH of Oxytricha acidotolerans sp. nov. and Urosomoida sp. (Ciliophora, Hypotricha) from acid mining lakes

“…The binomen Oxytricha acidotolerans was already used by Weisse et al (2011). However, it was disclaimed for nomenclatural purposes referring to Article 8.3 of the ICZN (1999) and therefore the name O. acidotolerans in Weisse et al (2011) is not available and consequently it is not a homonym of the name introduced above.…”

“…Obviously, similar habitats can be inhabited by closely related, but unequivocally different protist species. Since AML are man-made, isolated water bodies with reduced rates of dispersal, compared to natural lakes, the chances for local adaptation and ecological speciation are particularly high in such environments (Weisse et al 2011). Although AML are of limited global significance, the findings from our case study add to the rapidly growing evidence that biodiversity of aquatic microorganisms is higher, and maybe even orders of magnitude higher, than assumed until recently (Caron et al 2009; Finlay et al 2006; Hahn 2006; Weisse 2006b).…”

Molecular evidence for the polyphyletic origin of low pH adaptation in the genus Klebsormidium (Klebsormidiophyceae, Streptophyta)

“…Variance around the parameter estimates were verified in order to ensure that they were effectively modelled. Bootstrap analyses were performed by maximum likelihood (ML) and weighted parsimony (wMP) criteria using GARLI, version 0.951 (Zwickl 2006) and PAUP*, version 4.0b10 (Swofford 2002), respectively. ML analyses consisted of rapid heuristic searches (100 pseudo-replicates) using automatic termination (genthreshfortopoterm command set to 100,000).…”

“…More often, however, the low pH is the result of human influence, mostly in the form of acid mine drainage released by mining activities (Lukešová 2001, Sabater et al 2003, Novis & Harding 2007. The extent of these effects is usually localized, and consequently the distribution of highly acidic habitats is patchy and fragmented (Gross 2000, Weisse et al 2011. However, sites with low pH exist in all continents and the overall extent of these habitats on global scale is not negligible; for example, in the recent past it was considered that approximately 15,000 km of streams in the U.S. were affected by acid mine drainage (Gross 2000).…”

Multiple environmental stressors confine the ecological niche of the rotifer Cephalodella acidophila

“…, 2010; Moser & Weisse, 2011b). The present investigation is part of a larger project investigating whether the pelagial of acidic mining lakes is primarily colonised by pH specialists or generalists (Moser & Weisse, 2011a,c; Weisse et al. , 2011) and to determine what factors control these plankton communities.…”