Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints

Knowledge about how species richness varies along spatial and environmental gradients is important for the conservation and use of biodiversity. The Ericaceae is a major component of alpine and subalpine vegetation globally. However, little is known about the spatial pattern of species richness and the factors that drive that richness in Ericaceae. We investigated variation in species richness of Ericaceae along an elevational gradient in Yunnan, China, and used a variation partitioning analysis based on redundancy analysis ordination to examine how those changes might be influenced by the mid-domain effect, the species-area relationship, and climatic variables. Species richness varied significantly with elevation, peaking in the upper third of the elevational gradient. Of the factors examined, climate explained a larger proportion of the variance in species richness along the elevational gradient than either land area or geometric constraints. Species richness showed a unimodal relationship with mean annual temperature and mean annual precipitation. The elevational pattern of species richness for Ericaceae was shaped by the combined effects of climate and competition. Our findings contribute to a better understanding of the potential effects of climate change on species richness for Ericaceae.

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Worldwide patterns in species richness of falconiformes: analytical null models, geometric constraints, and the mid-domain effect

Brazilian Journal of Biology ◽

10.1590/s1519-69842004000200016 ◽

2004 ◽

Vol 64 (2) ◽

pp. 209-308

Author(s):

T. F. L.V. B. Rangel ◽

J. A. F. Diniz-filho

Keyword(s):

Species Richness ◽

Primary Productivity ◽

Net Primary Productivity ◽

Empirical Support ◽

Null Models ◽

Geometric Constraints ◽

Global Level ◽

Spatial Gradients ◽

Available Energy ◽

Surrogate Variable

Recently, the hypothesis that the geographic distribution of species could be influenced by the shape of the domain edges, the so-called Mid-Domain Effect (MDE), has been included as one of the five credible hypotheses for explaining spatial gradients in species richness, despite all the unsuccessful current attempts to prove empirically the validity of MDE. We used data on spatial worldwide distributions of Falconiformes to evaluate the validity of MDE assumptions, incorporated into two different sorts of null models at a global level and separately across five domains/landmasses. Species richness values predicted by the null models of the MDE and those values predicted by Net Primary Productivity, a surrogate variable expressing the effect of available energy, were compared in order to evaluate which hypothesis better predicts the observed values. Our tests showed that MDE continues to lack empirical support, regardless of its current acceptability, and so, does not deserve to be classified as one possible explanation of species richness gradients.

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Biodiversity and conservation of terricolous lichens and bryophytes in continental lowlands of northern Italy: the role of different dry habitat types

Biodiversity and Conservation ◽

10.1007/s10531-020-02034-1 ◽

2020 ◽

Vol 29 (13) ◽

pp. 3533-3550

Author(s):

Gabriele Gheza ◽

Silvia Assini ◽

Chiara Lelli ◽

Lorenzo Marini ◽

Helmut Mayrhofer ◽

...

Keyword(s):

Species Richness ◽

Vegetation Dynamics ◽

Biodiversity Loss ◽

Northern Italy ◽

Environmental Drivers ◽

Dry Grasslands ◽

Species Of Conservation Concern ◽

Terricolous Lichens ◽

Landscape Scales

Abstract In dry habitats of European lowlands terricolous lichens and bryophytes are almost neglected in conservation practises, even if they may strongly contribute to biodiversity. This study aims at (a) testing the role of heathlands, acidic and calcareous dry grasslands for lichen and bryophyte diversity and conservation in lowland areas of northern Italy characterized by high human impact and habitat fragmentation; (b) detecting the effect of environmental drivers and vegetation dynamics on species richness and composition. Lichens, bryophytes, vascular plants, and environmental variables were recorded in 287 circular plots for 75 sites. Our results indicate that heathlands, acidic and calcareous dry grasslands host peculiar terricolous lichen and bryophyte communities that include several species of conservation concern. Thus, each habitat provides a complementary contribution to lichen and bryophyte diversity in continental lowland landscapes. Furthermore, in each habitat different factors drive species richness and composition with contrasting patterns between lichens and bryophytes. In terms of conservation, our results indicate that management of lowland dry habitats should act at both local and landscape scales. At local scale, vegetation dynamics should be controlled in order to avoid biodiversity loss due to vegetation dynamics and wood encroachment. At the landscape scale, patches of all the three habitats should be maintained to maximize regional diversity.

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Low predictive power of mid-domain effect to explain geographic species richness patterns in Palearctic songbirds

Contributions to Zoology ◽

10.1163/18759866-07603005 ◽

2007 ◽

Vol 76 (3) ◽

pp. 197-204 ◽

Cited By ~ 1

Author(s):

M. Aliabadian ◽

C. S. Roselaar ◽

R. Sluys ◽

V. Nijman

Keyword(s):

Species Richness ◽

Predictive Power ◽

Explanatory Power ◽

Null Model ◽

Species Range ◽

Geometric Constraints ◽

Diversity Patterns ◽

Distribution Maps ◽

Biogeographic Patterns ◽

Richness Patterns

In the study of diversity patterns, the Mid-domain effect (MDE), which explains gradients in diversity solely on the basis of geometric constraints, has emerged as a null-model against which other hypotheses can be tested. The effectiveness, measured by its predictive power, of these MDE models appears to depend on the size of the study area and the range-sizes of the taxa considered. Here we test the predictive power of MDE on the species richness patterns of birds and assess its effectiveness for a variety of species range sizes. We digitised distribution maps of 889 species of songbird endemic to the Palearctic, and analysed the emergent biogeographic patterns with WORLDMAP software. MDE had a predictive power of 20% when all songbirds were included. Major hotspots were located south of the area where MDE predicted the highest species-richness, and some of the observed coldspots were in the centre of the Palearctic, contradicting the predictions of the MDE. MDE had little explanatory power (3-19%) for all but the largest range sizes, whereas MDE performed equal or better for the large-ranged species (20-34%) compared to the overall model. Overall MDE did not accurate explain species-richness patterns in Palearctic songbirds. Subsets of larger-range species did not always have a larger predictive power than smaller-range species or the overall model. Despite their low predictive power, MDE models can have a role to play in explaining biogeographic patterns but other variables need to be included in the model as well.

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Bat Species Richness and Community Composition along a Mega-transect in the Okavango River Basin

Diversity ◽

10.3390/d12050188 ◽

2020 ◽

Vol 12 (5) ◽

pp. 188 ◽

Cited By ~ 1

Author(s):

Sina M. Weier ◽

Mark Keith ◽

Götz G. Neef ◽

Daniel M. Parker ◽

Peter J. Taylor

Keyword(s):

Species Richness ◽

Community Composition ◽

River Basin ◽

Total Activity ◽

Environmental Drivers ◽

Conservation Strategies ◽

Miombo Woodlands ◽

Human Land Use ◽

Functional Community ◽

Okavango River

The Okavango River Basin is a hotspot of bat diversity that requires urgent and adequate protection. To advise future conservation strategies, we investigated the relative importance of a range of potential environmental drivers of bat species richness and functional community composition in the Okavango River Basin. During annual canoe transects along the major rivers, originating in the central Angolan highlands, we recorded more than 25,000 bat echolocation calls from 2015 to 2018. We corrected for possible biases in sampling design and effort. Firstly, we conducted rarefaction analyses of each survey year and sampling appeared to be complete, apart from 2016. Secondly, we used total activity as a measure of sample effort in mixed models of species richness. Species richness was highest in the Angola Miombo Woodlands and at lower elevations, with higher minimum temperatures. In total, we identified 31 individual bat species. We show that even when acoustic surveys are conducted in remote areas and over multiple years, it is possible to correct for biases and obtain representative richness estimates. Changes in habitat heterogeneity will have detrimental effects on the high richness reported here and human land-use change, specifically agriculture, must be mediated in a system such as the Angolan Miombo Woodland.

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