Table 1.

Results of PCA of cell size in amphibian, bird and mammalian tissues (on raw data and phylogenetic contrasts). (Loadings in bold are greater than 0.5. n is the number of species used.)

group	cell type	raw data			phylogenetic contrasts
		PC1	PC2	PC3	cPC1	cPC2	cPC3
birds (Nitecki) n = 6	hepatocytes	0.990	0.123	−0.001	0.977	0.179	−0.007
	proximal kidney tubules	0.997	−0.028	0.058	0.989	−0.085	−0.100
	duodenal epithelium	0.988	0.139	0.067	0.976	0.187	−0.108
	skin epithelium	0.991	0.005	−0.132	0.976	0.051	0.210
	tracheal chondrocytes	0.957	−0.290	0.022	0.898	−0.438	−0.004
	thyroid follicles	0.997	0.042	−0.013	0.992	0.072	0.010
explained proportion of variation		0.97	0.02	0.004	0.94	0.05	0.01
amphibians (TG) n = 8	kidney (nephron)	0.974	−0.118	−0.193	0.911	−0.266	0.315
	intestinal epithelium	0.966	−0.200	0.164	0.912	−0.262	−0.316
	epidermis	0.945	0.325	0.031	0.798	0.602	0.002
explained proportion of variation		0.93	0.05	0.02	0.77	0.17	0.07
mammals (Morgado) n = 9	adipocytes (skin)	0.729	−0.064	−0.580	0.013	−0.650	0.723
	cerebellar granule neurons	0.925	−0.173	0.283	−0.676	0.482	0.533
	cerebellar Purkinje neurons	0.932	−0.054	0.338	−0.430	0.651	0.573
	fibroblasts	−0.256	−0.809	0.496	−0.789	0.228	−0.513
	fibrocytes	0.285	−0.636	−0.682	−0.566	−0.697	0.298
	glomerular epithelium	−0.085	−0.946	0.236	−0.917	−0.201	−0.223
	goblet cells	0.800	0.319	−0.118	0.468	−0.246	0.705
	Henle-loop cells	−0.225	−0.560	−0.216	−0.002	−0.718	−0.164
	hepatocytes	−0.400	0.162	0.483	0.320	−0.008	−0.228
	proximal convoluted tubules	0.586	−0.780	0.173	−0.966	−0.080	0.159
	sebaceous gland cells (skin)	0.699	0.416	0.466	0.211	0.870	0.216
explained proportion of variation		0.37	0.29	0.17	0.34	0.27	0.20
mammals (TG) n = 8	hepatocytes	0.343	−0.914	0.206	0.128	−0.972	−0.164
	proximal kidney tubules	−0.065	0.418	0.903	0.056	−0.117	0.989
	duodenal epithelium	0.800	0.542	−0.002	0.883	0.358	0.119
	skin epithelium	0.878	0.328	−0.248	0.891	0.329	−0.191
	thyroid follicles	0.861	−0.442	0.242	0.780	−0.614	0.039
explained proportion of variation		0.46	0.32	0.20	0.44	0.31	0.21
mammals (Levi) n = 8	Purkinje cells (cerebellum)	0.843	0.445	−0.076	0.917	−0.205	−0.001
	neuron (small ganglion)	0.829	0.311	−0.372	0.807	−0.207	−0.466
	hepatocytes	−0.354	0.628	0.551	0.622	0.544	0.413
	adrenals fascicular zone	−0.313	0.710	−0.546	0.316	0.749	−0.460
	pancreas	−0.705	0.593	−0.133	0.012	0.838	0.142
	tongue epithelium	0.507	0.454	0.595	0.794	−0.290	0.332
explained proportion of variation		0.40	0.29	0.19	0.44	0.29	0.12