Ecological niche models reveal the importance of climate variability for the biogeography of protosteloid amoebae

Abstract

Habitat availability and environmental preferences of species are among the most important factors in determining the success of dispersal processes and therefore in shaping the distribution of protists. We explored the differences in fundamental niches and potential distributions of an ecological guild of slime moulds-protosteloid amoebae-in the Iberian Peninsula. A large set of samples collected in a north-east to south-west transect of approximately 1000 km along the peninsula was used to test the hypothesis that, together with the existence of suitable microhabitats, climate conditions may determine the probability of survival of species. Although protosteloid amoebae share similar morphologies and life history strategies, canonical correspondence analyses showed that they have varied ecological optima, and that climate conditions have an important effect in niche differentiation. Maxent environmental niche models provided consistent predictions of the probability of presence of the species based on climate data, and they were used to generate maps of potential distribution in an 'everything is everywhere' scenario. The most important climatic factors were, in both analyses, variables that measure changes in conditions throughout the year, confirming that the alternation of fruiting bodies, cysts and amoeboid stages in the life cycles of protosteloid amoebae constitutes an advantage for surviving in a changing environment. Microhabitat affinity seems to be influenced by climatic conditions, which suggests that the micro-environment may vary at a local scale and change together with the external climate at a larger scale.

Figure 1

Map of the Iberian Peninsula with selected localities for the analyses. Localities are represented as circles, and numbers correspond to information in Supplementary Tables S3 and S4.

Figure 2

Maxent predictive ecological models of protosteloid amoebae with more than 10 occurrences. Probabilities of presence >0.5 are represented using different shades of grey.

Figure 3

CCA using species as dependent variables and climatic and microhabitat variables as independent variables. Each species point in the diagram is at the centroid (weighted average) of the sites in which it occurs. Diameters of circles around the points are proportional to the logarithm of the species' absolute abundances. Environmental variables are represented by arrows that run from the origin to the weights that each variable has in the linear combinations that form the axes. A, aerial litter; G, ground litter; B, bark; AM, annual mean temperature; IT, isothermality; PS, precipitation seasonality; PCQ, precipitation of the coldest quarter; PWQ, precipitation of the warmest quarter; Ca, C. apophysatum; Cr, Clastostelium recurvatum; Ea, E. amerosporum; Eb, E. bisporum; Eo, E. oligospora; Ez, E. zonatum; Mp, M.paxillus; Ng, N. gracile; No, N. ovatum; Partic, P. articulatum; Pbisp, P. bisporum; Pa, P. arachisporum; Pm, P. mycophagum; Pn, P. nocturnum; Ppyr, P. pyriforme; Sa, S. amoeboidea; Sm, S. micropunctata; Sps, S. pseudoendospora; Sr, S. reticulata; Sv, S. vulgaris; Sc, S. cavostelioides; Si, S. irregulare; Ta, T. acutostipes.