Host availability hypothesis: complex interactions with abiotic factors and predators may best explain population densities of cicada species

Figures & data

Table 1. Sampling localities for the measurement of cicada density in this study.

Habitat	Locality	Site	Latitude (°N)	Longitude (°E)	Area (m^2)
Metropolitan	Samsung	SS1	37°31′12″	127° 3′34.10″	1230
		SS2	37°31′17″	127° 3′44.35″	5825
	Apgujeong	AG1	37°31′26″	127° 2′4.72″	7341
		AG2	37°31′46″	127° 1′57.39″	926
	Nonhyeon	NH1	37°30′56″	127° 1′31.49″	8203
		NH2	37°30′40″	127° 0′37.81″	1422
	Daechi	DC1	37°29′55″	127° 4′1.32″	3673
Suburban	Jungang C1	GC11	37°25′53″	126°59′33.75″	1506
		GC12	37°25′51″	126°59′49.17″	2015
	Jungang C7	GC21	37°25′55″	126°59′59.61″	4736
Country	Yangpyeong	YP1	37°29′40″	127°29′32.10″	1813
		YP2	37°29′46″	127°29′27.21″	3353
		YP3	37°29′40″	127°29′39.88″	2532
	Pocheon	PC1	37°54′16″	127°12′7.87″	13869
		PC2	37°53′52″	127°11′33.12″	3380
		PC3	37°53′59″	127°12′2.75″	1476
		PC4	37°53′32″	127°12′38.80″	8213
	Gapyeong	GP1	37°50′3″	127°30′20.83″	3103
		GP2	37°50′7″	127°30′40.21″	5085
		GP3	37°49′50″	127°30′28.69″	3486
		GP4	37°49′45″	127°30′47.20″	13261
	Yeoju	YJ1	37°17′38″	127°38′28.60″	13171
		YJ2	37°17′32″	127°38′13.59″	8039
		YJ3	37°17′35″	127°38′20.25″	1911
		YJ4	37°17′44″	127°38′40.42″	4339

Note: All metropolitan localities are within the city of Seoul, and all suburban localities are within the city of Gwacheon, which is located south of Seoul. All country localities are found in the province of Gyeongi-do, which surrounds Seoul and Gwacheon.

Table 2. Percentages of land cover types for three habitats using the GIS analysis.

Radius	Habitat	Urban	Road	Agriculture	Forest	Plain	Swamp	Empty	Watery
100 m	Metropolitan	81.0 ± 25.0	13.1 ±14.8	0 ± 0.0	0 ± 0.0	4.8 ± 11.2	0.4 ± 1.1	0.7 ± 1.2	<0.1 ± 0.0
	Suburban	67.7 ± 26.4	1.0 ± 1.4	1.5 ± 2.6	9.5 ± 13.5	7.4 ± 5.3	0 ± 0.0	12.9 ± 22.4	0 ± 0.0
	Country	60.9 ± 29.3	6.5 ± 4.9	10.2 ± 14.0	11.9 ± 23.9	8.6 ± 13.2	0 ± 0.0	1.9 ± 4.0	0 ± 0.0
1000 m	Metropolitan	65.2 ± 15.3	14.7 ± 1.5	0.1 ± 0.3	1.3 ± 1.5	5.1 ± 4.7	0.4 ± 0.8	1.1 ± 0.9	12.1 ± 13.8
	Suburban	44.8 ± 0.8	11.7 ± 0.8	4.9 ± 1.9	27.4 ± 1.4	8.6 ± 1.0	0.3 ± 0.1	2.4 ± 0.5	<0.1 ± 0.0
	Country	32.4 ± 5.6	6.0 ± 2.1	22.4 ± 5.6	22.4 ± 11.1	8.8 ± 4.5	0 ± 0.0	4.0 ± 3.5	4.0 ± 4.4

Note: Radii of 100 m and 1000 m were used for the analysis. The GIS analysis was conducted for all localities for all three habitats (see Table 1). Mean and standard deviation of GIS data are shown for the three habitats: metropolitan (n = 7), suburban (n = 3), and country (n = 15).

Figure 1. The area-weighted densities for cicada species based on enumeration of exuviae. Collection of exuviae was conducted twice to estimate cicada densities: the first period between 3 and 5 August 2010, and the second period between 14 and 16 August 2010. The first sampling period was preceded by a pre-sampling exercise to remove all exuviae from the study area. Area-weighted density was estimated by counting the number of exuviae divided by the area of a site. The same character in a species indicates no statistical difference between habitats (Table 5).

Figure 2. The tree-weighted densities for cicada species based on enumeration of exuviae. Collection of exuviae was conducted twice to estimate cicada densities: the first period between 3 and 5 August 2010, and the second period between 14 and 16 August 2010. The first sampling period was preceded by a pre-sampling exercise to remove all exuviae from the study area. Tree-weighted density was estimated by counting the number of exuviae divided by the number of trees in a site. The same character in a species indicates no statistical difference between habitats (Table 5).

Table 3. The resource-weighted densities of cicada species for three habitat types.

	Metropolitan	Suburban	Country
(A) Tree density (#/m^2)	0.0500	0.1284	0.0810
(B) Area-weighted density – first (#/km^2)
C. atrata	18869	13761	1147
H. fuscata	44877	68855	5806
Meimuna spp.	1904	3794	733
G. nigrofuscata	0	23409	319
(C) Area-weighted density – second (#/km^2)
C. atrata	5676	3930	395
H. fuscata	30801	21912	7833
Meimuna spp.	1114	2213	1816
G. nigrofuscata	0	3836	330
(D) Tree-weighted density – first (# of exuviae/tree)
C. atrata	0.46	0.19	0.02
H. fuscata	0.78	0.42	0.23
Meimuna spp.	0.04	0.03	0.02
G. nigrofuscata	0.00	0.19	0.01
(E) Tree-weighted density – second (# of exuviae/tree)
C. atrata	0.12	0.05	0.00
H. fuscata	0.50	0.11	0.06
Meimuna spp.	0.02	0.01	0.02
G. nigrofuscata	0.00	0.04	0.00

Note: Both area-weighted and tree-weighted densities were estimated for cicada species. We estimated the densities of cicada species twice, each at the end of an 11-day interval after exuviae removal. First represents the first sampling period, 3 and 5 August 2010, and second denotes the second sampling period, 14 and 16 August 2010.

Table 4. The results of univariate GLM on area-weighted densities of cicada species.

Source	Variable	df	Mean square	F	P
Habitat	C. atrata	2	6.698E-04	14.916	0.000
	H. fuscata	2	5.809E-03	3.723	0.037
	Meimuna spp.	2	1.170E-05	3.821	0.034
	G. nigrofuscata	2	6.014E-04	5.605	0.009
Locality	C. atrata	3	6.254E-05	1.393	0.266
	H. fuscata	3	7.738E-03	4.959	0.007
	Meimuna spp.	3	1.282E-05	4.186	0.014
	G. nigrofuscata	3	1.715E-05	0.160	0.922
Site (locality)	C. atrata	3	7.174E-05	1.598	0.212
	H. fuscata	3	3.422E-03	2.193	0.111
	Meimuna spp.	3	8.722E-06	2.848	0.055
	G. nigrofuscata	3	5.920E-05	0.552	0.651
Date	C. atrata	1	7.381E-04	16.439	0.000
	H. fuscata	1	7.219E-03	4.626	0.040
	Meimuna spp.	1	5.754E-06	1.879	0.181
	G. nigrofuscata	1	2.599E-04	2.422	0.131
Error	C. atrata	28	4.490E-05
	H. fuscata	28	1.561E-03
	Meimuna spp.	28	3.063E-06
	G. nigrofuscata	28	1.073E-04

Note: The results of multivariate GLM on the area-weighted densities of cicada species and post hoc analyses were reported in the Results. The predictor variables of multivariate GLM were habitat, locality, site, and date. Site was nested within locality

Table 5. Post hoc comparisons of cicada densities among three habitat types.

			Area-weighted density			Tree-weighted density
Species	Habitat I	Habitat J	I–J	SE	P	I–J	SE	P
C. atrata	Metropolitan	Suburban	0.0014	0.00365	0.704	0.1701	0.13133	0.210
	Suburban	Country	0.0098	0.00353	0.012	0.1034	0.12688	0.425
	Country	Metropolitan	−0.0112	0.00267	0.000	−0.2736	0.09591	0.010
H. fuscata	Metropolitan	Suburban	−0.0141	0.01708	0.420	0.3762	0.22887	0.116
	Suburban	Country	0.0444	0.01650	0.014	0.0679	0.22111	0.762
	Country	Metropolitan	−0.0304	0.01247	0.024	−0.4441	0.16714	0.015
Meimuna spp.	Metropolitan	Suburban	−0.0018	0.00071	0.023	0.0118	0.00944	0.227
	Suburban	Country	0.0023	0.00069	0.004	0.0012	0.00912	0.899
	Country	Metropolitan	−0.0005	0.00052	0.336	−0.0129	0.00689	0.075
G. nigrofuscata	Metropolitan	Suburban	−0.0175	0.00573	0.006	−0.1129	0.03022	0.001
	Suburban	Country	0.0172	0.00553	0.005	0.1079	0.02919	0.001
	Country	Metropolitan	0.0003	0.00418	0.943	0.0050	0.02207	0.935

Note: Multivariate GLM were conducted to determine factors critical for area-weighted density (Table 4) and tree-weighted density (Table 6). Habitat was a significant factor for both analyses. Densities of each cicada species was compared for three habitat types using LSD.

Table 6. The results of univariate GLM on tree-weighted densities of cicada species.

Source	Variable	df	Mean Square	F	P
Habitat	C. atrata	2	0.386	6.272	0.006
	H. fuscata	2	1.726	4.963	0.014
	Meimuna spp.	2	2.304E-03	5.009	0.014
	G. nigrofuscata	2	2.702E-02	9.175	0.001
Locality	C. atrata	3	7.694E-02	1.250	0.310
	H. fuscata	3	0.929	2.671	0.067
	Meimuna spp.	3	2.035E-03	4.423	0.011
	G. nigrofuscata	3	1.989E-03	0.675	0.574
Site (locality)	C. atrata	3	7.968E-02	1.295	0.296
	H. fuscata	3	0.448	1.287	0.298
	Meimuna spp.	3	1.488E-03	3.234	0.037
	G. nigrofuscata	3	1.645E-03	0.559	0.647
Date	C. atrata	1	0.375	6.097	0.020
	H. fuscata	1	0.964	2.771	0.107
	Meimuna spp.	1	1.215E-03	2.641	0.115
	G. nigrofuscata	1	5.083E-03	1.726	0.200
Error	C. atrata	28	6.153E-02
	H. fuscata	28	0.348
	Meimuna spp.	28	4.600E-04
	G. nigrofuscata	28	2.944E-03

Note: The results of multivariate GLM on the tree-weighted densities of cicada species and post hoc analyses were reported in the results. The predictor variables of multivariate GLM were habitat, locality, site, and date. Site was nested within locality.

Table 7. Organism-weighted density (A), percentage of trees without exuviae (B), and percentage of preferred trees (C) for three habitats: metropolitan, suburban, and country.

Species	Metropolitan	Suburban	Country	Habitat	Locality
(A) Organism-weighted density (individuals per tree)
C. atrata	4.27	4.66	0.94	F 2,28 = 3.806, P = 0.035	F 7,28 = 1.458, P = 0.223
H. fuscata	4.92	9.70	2.61	F 2,28 = 1.451, P = 0.251	F 7,28 = 1.903, P = 0.107
Meimuna spp.	0.83	1.42	1.04	F 2,28 = 0.099, P = 0.906	F 7,28 = 0.743, P = 0.638
G. nigrofuscata	0.14	4.42	0.50	F 2,28 = 11.457, P < 0.001	F 7,28 = 0.483, P = 0.839
(B) Percentage of trees without exuviae (%)
C. atrata	81.5	89.7	98.8	F 2,28 = 6.703, P = 0.004	F 7,28 = 0.480, P = 0.841
H. fuscata	67.3	84.5	90.9	F 2,28 = 2.130, P = 0.138	F 7,28 = 0.643, P = 0.717
Meimuna spp.	96.9	96.1	98.8	F 2,28 = 2.061, P = 0.146	F 7,28 = 2.112, P = 0.075
G. nigrofuscata	99.8	85.1	99.8	F 2,28 = 13.530, P < 0.001	F 7,28 = 0.306, P = 0.945
(C) Percentage of preferred trees (%)
C. atrata	10.32	12.87	9.56	F 2,15 = 0.077, P = 0.927	F 7,15 = 0.776, P = 0.617
H. fuscata	7.77	8.00	11.54	F 2,15 = 0.236, P = 0.793	F 7,15 = 0.327, P = 0.930
Meimuna spp.	0.68	0.00	0.04	F 2,15 = 6.651, P = 0.009	F 7,15 = 10.432, P < 0.001
G. nigrofuscata	4.81	11.02	3.85	F 2,15 = 5.533, P = 0.016	F 7,15 = 1.239, P = 0.342

Note: To test whether these three variables differed among the three habitats, multivariate analyses of variance (MANOVA) with habitat and locality as predictor variables were conducted. The results of univariate ANOVA are shown in the table. Results of MANOVA: (A) habitat: Wilks' λ = 0.224, F_8,50 = 6.963, P < 0.001; locality: Wilks' λ = 0.186, F_28,92 = 1.943, P = 0.010; (B) habitat: Wilks' λ = 0.233, F_8,50 = 6.697, P < 0.001; locality: Wilks' λ = 0.309, F_28,92 = 1.259, P = 0.206; (C) habitat: Wilks' λ = 0.237, F_8,24 = 3.158, P = 0.014; locality: Wilks' λ = 0.046, F_28,45 = 2.144, P = 0.011.

Table 8. Results of multiple linear regressions for the exuviae occurrence in cicada species.

	C. atrata	H. fuscata	Meimuna spp.	G. nigrofuscata
	B, P	Coefs, P	Coefs, P	Coefs, P
Intercept	0.321, 0.001	0.558, <0.001	0.089, <0.001	−0.025, 0.589
Habitat 2	−0.347, <0.001	−0.287, <0.001	−0.002, 0.835	0.220, 0.000
Habitat 3	−0.469, <0.001	−0.683, <0.001	−0.029, <0.001	0.011, 0.486
Ulmus davidiana	−0.321, 0.599	−0.058, 0.951	0.411, 0.001	0.025, 0.932
Zelkova serrata	0.503, <0.001	0.230, 0.168	−0.061, 0.004	0.005, 0.922
Acer palmatum	0.192, 0.057	0.209, 0.180	−0.043, 0.034	0.015, 0.755
Acer pseudosieboldianum	0.160, 0.283	0.113, 0.624	−0.056, 0.061	0.125, 0.072
Berberis poiretii	−0.321, 0.310	−0.558, 0.254	−0.089, 0.158	0.025, 0.868
Zizyphus zizyphus	0.098, 0.436	0.076, 0.694	−0.011, 0.654	0.043, 0.460
Metasequoia glyptostroboides	0.075, 0.600	0.198, 0.368	−0.058, 0.043	0.778, <0.001
Magnolia kobus	0.495, <0.001	0.652, <0.001	0.007, 0.757	0.274, <0.001
Hibiscus syriacus	0.181, 0.101	0.253, 0.140	−0.026, 0.242	−0.025, 0.632
Prunus serrulata	0.124, 0.237	0.660, <0.001	−0.050, 0.016	0.019, 0.706
Prunus persica	0.051, 0.793	0.158, 0.601	−0.070, 0.074	0.008, 0.927
Deutzia crenata	0.258, 0.118	0.310, 0.223	−0.087, 0.008	−0.195, 0.011
Alnus firma	1.901, <0.001	5.664, <0.001	0.022, 0.713	0.025, 0.861
Euonymus japonicus	0.111, 0.368	−0.081, 0.671	−0.071, 0.004	−0.046, 0.427
Pinus densiflora	0.127, 0.230	0.080, 0.625	−0.061, 0.004	0.007, 0.883
Syringa oblate	0.033, 0.818	0.177, 0.429	−0.026, 0.361	−0.027, 0.687
Robinia pseudoacacia	0.087, 0.560	0.198, 0.388	−0.043, 0.150	0.020, 0.768
Ginkgo biloba	0.091, 0.400	0.479, 0.004	−0.048, 0.026	0.010, 0.844
Chionanthus retusus	0.133, 0.306	0.110, 0.585	−0.062, 0.017	0.014, 0.815
Betula platyphylla	0.149, 0.221	0.162, 0.389	−0.062, 0.011	0.014, 0.803
Taxus cuspidata	−0.321, 0.057	−0.558, 0.033	−0.089, 0.008	0.025, 0.756
Pinus koraiensis	0.072, 0.473	0.078, 0.617	−0.065, 0.001	0.000, 0.998
Rosa	0.093, 0.425	0.072, 0.689	−0.067, 0.004	−0.007, 0.904
Abies holophylla	0.136, 0.239	0.178, 0.320	−0.063, 0.006	0.011, 0.840
Ligustrum obtusifolium	0.145, 0.326	0.135, 0.554	−0.061, 0.039	0.010, 0.884
Rhododendron schlippenbachii	0.244, 0.043	0.063, 0.737	−0.050, 0.036	0.116, 0.039
Juniperus chinensis	0.069, 0.490	0.078, 0.616	−0.064, 0.002	−0.004, 0.932
Buxus koreana	0.271, 0.027	0.010, 0.957	−0.043, 0.076	0.004, 0.945

Note: Values in boldface are B > 0.1 and P < 0.05.