Table 4.

Comparison of mean observed niche overlap and expected niche overlap employing Pianka's index, expressed as a percentage, for four null models of niche (RA1–4) breadth and resource suitability (‘zero states’) implemented in Ecosim v7 (Gotelli and Entsminger, 2001)

		Mean niche overlap and variance
		Observed	RA1	RA2	RA3	RA4
36 visited plant species	Mean	16·96	75·24 (<0·0001)	33·80 (<0·0001)	7·62 (0·96)	8·38 (0·93)
	Variance	3·71	0·25 (>0·9999)	1·19 (0·9996)	2·42 (0·7405)	2·55 (0·7223)
22 Palaearctic plant species	Mean	14·34	75·36 (<0·0001)	32·24 (<0·0001)	28·49 (<0·0001)	30·24 (<0·0001)
	Variance	0·56	0·40 (0·8052)	1·83 (0·0203)	2·79 (0·0025)	1·95 (0·0194)
14 non-Palaearctic plant species	Mean	14·98	75·63 (<0·0001)	36·07 (<0·0001)	29·92 (<0·0001)	31·90 (<0·0001)
	Variance	3·09	0·63 (>0·9999)	3·70 (0·367)	4·98 (0·1073)	5·39 (0·0746)
26 visited garden plant species	Mean	12·63	75·30 (<0·0001)	34·82 (<0·0001)	6·87 (0·8732)	7·34 (0·8461)
	Variance	3·96	0·34 (>0·9999)	2·27 (0·9588)	3·41 (0·6489)	3·52 (0·6410)
12 Palaearctic garden plant species	Mean	15·07	75·74 (<0·0001)	34·13 (0·0005)	13·78 (0·6455)	14·65 (0·6143)
	Variance	6·70	0·73 (>0·9999)	3·74 (0·9658)	6·72 (0·5215)	6·84 (0·5303)

Model RA1 relaxed niche breadth/relaxed zero states; RA2 relaxed niche breadth/fixed zero states; RA3 retained niche breadth/relaxed zero states; RA4 retained niche breadth/fixed zero states.

Values in parentheses represent the randomization test probability that observed value ≤ expected value.

Values in bold indicate that observed mean or variance in niche overlap is significantly lower than model expectation at the P value shown.