Spatial gradients in species diversity of microscopic animals: the case of bdelloid rotifers at high altitude
Articolo
Data di Pubblicazione:
2006
Citazione:
Spatial gradients in species diversity of
microscopic animals: the case of bdelloid rotifers at high altitude / D. Fontaneto, C. Ricci. - In: JOURNAL OF BIOGEOGRAPHY. - ISSN 0305-0270. - 33:7(2006), pp. 1305-1313.
Abstract:
Aim Organisms smaller than 2 mm appear not to follow the spatial patterns in
richness and diversity commonly observed in macroscopic organisms. We
describe spatial patterns in species diversity in a group of microscopic organisms,
bdelloid rotifers, living in moss and lichen patches, in order to test the hypotheses
of no relationship between species richness and composition and spatial
gradients, suggested by previously published patterns in microscopic organisms.
Location Moss and lichen patches as habitats for bdelloids, on high-elevation
peaks at altitudes between 2984 and 4527 m a.s.l. across the Italian, French and
Swiss Alps, with distances among sample sites ranging from 1 m to 420 km, in
comparison with lower-elevation samples at altitudes from 850 to 1810 m a.s.l.
Methods We sampled species assemblages of bdelloid rotifers living in isolated
moss and lichen patches in 47 sites. We described the observed a, b and c
diversities; the heterogeneity of species assemblages; and the estimated number of
species (incidence-based coverage estimator). Patterns in species distribution
were analysed at three different levels: (1) habitat, comparing species richness on
moss and lichen substrates, testing differences in a diversity and heterogeneity
(anova), species composition (analysis of similarities test), and c diversity
(rarefaction curves); (2) altitude, comparing the observed richness with
previously published data from locations well below 2000 m; and (3) distances
between sites, correlating the matrix of Jaccard dissimilarities and the matrix of
geographical distances with a Mantel test.
Results Both species richness and species composition of bdelloid rotifers
differed significantly between mosses and lichens at high elevations, but no
difference was found in the heterogeneity of species assemblages. Alpha diversity
was significantly lower at high-elevation than at low-elevation sites, but the
estimated number of species was not reduced when compared with sites at low
elevations. Geographical distance between sites had no effect on species
composition in either mosses or lichens. The distribution of species was highly
heterogeneous, with a low similarity among assemblages.
Main conclusions As expected, bdelloids appear to occupy habitats selectively.
The altitudinal gradient in species richness for bdelloid rotifers is limited to a
decrease in a diversity only; such a decrease is not caused by a lower number of
species (low c diversity) being able to tolerate harsh conditions, and high-altitude
species are not a subset of species living at lower elevations. The observed values
of a, b and c diversity at high altitudes in the Alps are compatible with the
scenario of a very low number of available propagules because of the low density
of patches of favourable habitat. Our results suggest that the geographical
distribution of animals, and therefore biodiversity patterns, may be strongly
influenced by animal size, as small organisms such as bdelloids appear to show spatial patterns that differ from those known in larger animals. Differences in
body size should be taken into account carefully in future studies of biodiversity
patterns.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
β diversity; Alpha diversity; Alpine environment; Bdelloidea; Community dispersal; Europe; Rotifera; Species richness
Elenco autori:
D. Fontaneto, C. Ricci
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