Common Slope Tests for Bivariate Errors-in-Variables Models

Warton, David I.; Weber, N. C.

doi:10.1002/1521-4036(200203)44:2<161::aid-bimj161>3.0.co;2-n

Cited by 290 publications

(233 citation statements)

References 20 publications

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“…The bivariate log-log scaling relationships among the functional traits and stoichiometric ratios across species of the two groups were calculated using the standardised major axes approach (Warton et al 2006). We also followed the method from Warton and Weber (2002) to test the differences in the log-log regression slopes between the two groups of bryophytes and to calculate the common slope when the homogeneity of the slopes was justified. Furthermore, the shifts in elevation (i.e.…”

Section: Discussionmentioning

confidence: 99%

Higher photosynthetic capacity and different functional trait scaling relationships in erect bryophytes compared with prostrate species

2015

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photosynthetic capacities than prostrate species. Furthermore, erect bryophytes invest more nitrogen in chloroplast pigments to improve their light-harvesting ability, while the structure of prostrate species permits more efficient light capture. This study confirms the effect of growth form on the functional trait levels and scaling relationships of bryophytes. It also suggests that bryophytes could be good models for investigating the carbon economy and nutrient allocation of plants at the shoot rather than the leaf scale.

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Section: Discussionmentioning

confidence: 99%

Higher photosynthetic capacity and different functional trait scaling relationships in erect bryophytes compared with prostrate species

2015

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“…The slopes and y intercepts of log-log regressions (i.e., the scaling exponents and allometric constants, respectively), as well as their 95 % confidence intervals were calculated using the protocols of Warton et al (2006). The heterogeneity of regression slopes and the common slopes were tested following (Warton and Weber 2002). (S)MATR were used to estimate the parameters for the regressions ).…”

Section: Discussionmentioning

confidence: 99%

Testing the packing rule across the twig–petiole interface of temperate woody species

Chen

Niklas

Sun

2012

Trees

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Theories that incorporate the area-preserving rule of Leonardo da Vinci predict that the sum of the crosssectional lumen area of xylem conduits (vessels or tracheids) is constant across different levels of branching. If true, this rule obtains the packing rule, according to which (1) vessel cross-sectional lumen area (A) will negatively and isometrically scale to vessel number per unit area (N) and (2) the distal to proximal vessel diameter ratio (DR = D n?1 /D n ) should scale as the -1/2 power of the distal to proximal vessel number ratio (NR = N n?1 /N n ), i.e., DR = NR -1/2 . Using data collected from the terminal twigs and the petioles of 60 temperate (27 evergreen and 33 deciduous) woody species from southwestern China, we determined the scaling relationships for A versus N and for DR versus NR. Analyses of the data revealed contrasting scaling exponents and normalization constants for A versus N and for DR versus NR and no consistent trend across the two species groupings or between the two organ types (as predicted by the area-preserving and packing rules). These results caution against applying these rules ubiquitously to all species or to different organ types (even on the same plant).

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“…Confidence intervals for individual regression slopes were calculated following Pitman (1939). We followed the methods of Warton and Weber (2002) to test for the heterogeneity of regression slopes and calculated the common slopes when homogeneity of the slopes was demonstrated. Differences in the elevation of regression slopes (y-intercept) and in shifting along the common slope were tested by ANOVA (and post hoc Tukey tests where appropriate).…”

Section: Discussionmentioning

confidence: 99%

Testing the generality of the ‘leafing intensity premium’ hypothesis in temperate broad-leaved forests: a survey of variation in leaf size within and between habitats

Sun

2009

Evol Ecol

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Because leaf size scales negatively and isometrically with leaf number per shoot size (leafing intensity) in woody species, and because most tree and shrub species have small leaves, Kleiman and Aarssen (J Ecol 95:376-382, 2007) recently proposed that natural selection favors high leafing intensity resulting in small leaves, i.e., the leafingintensity-premium hypothesis. However, empirical evidence for or against this hypothesis is still lacking. In addition, this hypothesis has not been examined in the context of how leaf size varies among habitats. To fill this void, we investigated leaf size frequency distributions of woody species from temperate China and explored the relationships among leaf mass, leaf number, and stem mass of current-year shoots of 133 woody species at low and high altitudes of three mountain ranges. The scaling relationships between leaf size and leafing intensity (leaf number per stem mass) were determined using both standardized major axis regression analyses and phylogenetically independent comparative techniques. In light of the leafing-intensity-premium hypothesis, we made three predictions: (1) leaf size frequency distributions should be right-skewed for each local study area and for the entire study region, (2) leafing intensities at different altitudes at different sites should differ while leafing intensities at comparable altitudes should be similar baring large taxonomic differences among sites, and (3) that leafing intensity should be higher for any given leaf size in habitats with small-leaved species. Significant negative and isometric scaling relationships between leaf size and leafing intensity were found to be consistently conserved independent of habitat type, both across species and across correlated evolutionary divergences. Within each mountain range or across the entire study region, leaf size frequency distributions were right-skewed, in accordance with our prediction. However, leafing intensity was smaller for any given leaf size at the altitude with smaller leafed 123Evol Ecol (2010) 24:685-701 DOI 10.1007 species than for altitudes characterized by large leafed species, i.e., altitudes characterized by species with small leaves did not have consistently higher leafing intensities than other altitudes on each mountain range. Our analyses therefore indicate the direct adaptive value of leaf size but not the selective advantage in high leafing intensity as posited by the leafing-intensity-premium hypothesis. We suggest that this hypothesis explains less about the variation of leaf size among different habitats as it does about variation within habitats, i.e., the relative importance of the adaptive significance of leafing intensity and leaf size can and does vary with habitats.

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Common Slope Tests for Bivariate Errors-in-Variables Models

Cited by 290 publications

References 20 publications

Higher photosynthetic capacity and different functional trait scaling relationships in erect bryophytes compared with prostrate species

Higher photosynthetic capacity and different functional trait scaling relationships in erect bryophytes compared with prostrate species

Testing the packing rule across the twig–petiole interface of temperate woody species

Testing the generality of the ‘leafing intensity premium’ hypothesis in temperate broad-leaved forests: a survey of variation in leaf size within and between habitats

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