Beetle community responses to grey willow (Salix cinerea) invasion within three New Zealand wetlands

Figures & data

Figure 1  Map of the study area in the Waikato, North Island, New Zealand, showing the locations of the three wetlands (Whangamarino, Toreparu and two Horsham Downs peat lakes—Lake Kaituna and Lake Tunawhakapeka) in which beetle communities were sampled using Malaise traps.

Table 1  Number of plots in each vegetation type within the Waikato wetlands.

				Horsham Downs peat lakes
Vegetation type	Total number of plots per vegetation type (n=14)	Whangamarino	Toreparu	Lake Kaituna	Lake Tunawhakapeka
Native wetland vegetation	4	2	2
Removed willow, restored native vegetation	2			2
Invading willow	2		2
Willow-dominated vegetation	6	2	2		2

Table 2  Akaike information criterion (AIC) values for three possible models fitted to beetle abundance data.

Models	AIC
Wetland+vegetation type	115.76
Vegetation type	124.85
Wetland	322.24
The model with the smallest AIC value was chosen as the best model.

Figure 2  Total abundance of beetles collected from a Malaise trap within two plots at each vegetation type in the Waikato wetlands. N, native wetland vegetation; R, restored native wetland vegetation; I, native wetland vegetation undergoing grey willow invasion; W, dense grey willow-dominated vegetation; WH, Whangamarino; TO, Toreparu; HD, Horsham Downs peat lakes.

Table 3  General linear model (GLM) of beetle abundance at the four vegetation types and wetland sites.

Vegetation type; Wetland	Estimate (±SEM)	Abundance	Z-value	P-value
Native; Toreparu	0.09 (0.13)	61.56 [=exp(4.03^a+0.09)]	0.71	0.4750
Restored native; Horsham Downs	0.44 (0.12)	87.36 [=exp(4.03^a+0.44)]	3.67	0.0002
Invading willow; Toreparu	0.34 (0.12)	79.04 [=exp(4.03^a+0.34)]	2.77	0.0055
Willow; Whangamarino	1.01 (0.11)	154.47 [=exp(4.03^a+1.01)]	9.21	<0.0001
Willow; Toreparu	0.84 (0.11)	130.32 [=exp(4.03^a+0.84)]	7.47	<0.0001
Willow; Horsham Downs	1.15 (0.10)	177.68 [=exp(4.03^a+1.15)]	10.74	<0.0001
Beetle abundance at each vegetation type within a wetland was compared with the abundance of beetles sampled from native wetland vegetation at Whangamarino.
^a4.03 (0.09) was an estimate of beetle abundance in log scale (real number = 56.26) for the native vegetation in Whangamarino, which was treated as reference site. Standard error of mean estimates is given in brackets.

Table 4  Akaike information criterion (AIC) values for three possible models fitted to beetle species richness data.

Models	AIC
Wetland+vegetation type	82.81
Vegetation type	79.38
Wetland	90.90
The model with the smallest AIC value was chosen as the best model.

Figure 3  Beetle species richness sampled from a Malaise trap and plant species richness recorded from the sampling plot within each vegetation type. Closed circles, beetle species richness; open circles, plant species richness; Native, native wetland vegetation; Restored, restored native wetland vegetation; Invaded, native wetland vegetation undergoing grey willow invasion; Willow, dense grey willow-dominated vegetation.

Table 5  General linear model (GLM) of beetle species richness at the four vegetation types.

Vegetation type	Estimate (±SEM)	Abundance	Z-value	P-value
Restored native wetland (R)	0.39 (0.19)	22.87 [=exp(2.74^a+0.39)]	2.02	0.0426
Invading willow (I)	0.32 (0.20)	21.33 [=exp(2.74^a+0.39)]	1.64	0.0992
Willow (W)	0.57 (0.14)	27.39 [=exp(2.74^a+0.39)]	3.89	<0.0001
Beetle species richness within each vegetation type was compared with the beetle species richness sampled from native wetland vegetation.
^a2.74 (0.12) was an estimate of beetle species richness in log scale (real number = 56.26) for the native vegetation, which was treated as reference category. Standard error of mean estimates is given in brackets.

Figure 4  Proportion of native and introduced taxa sampled from each vegetation type. A, Proportion of beetle species caught per vegetation type. B, Proportion of beetles caught per vegetation type. C, Proportion of plant species sampled per vegetation type. Black bars, native species; light grey bars, introduced species; dark grey bars, status unknown. Note: n, the number of plots/Malaise traps per vegetation type (Table 1).

Figure 5  Trophic structure of beetles caught from Malaise traps in each vegetation type. A, Proportion of beetle species caught per vegetation type. B, Proportion of beetles caught per vegetation type. Black bars, detritivores; light grey bars, predators; dark grey bars, herbivores. Note: n, the number of plots/Malaise traps per vegetation type (Table 1).

Figure 6  Two-dimensional semi-strong hybrid multidimensional scaling (SSH) ordination of beetles caught in 14 Malaise traps (symbols) and significant (P<0.01) environmental variables (arrows). Four vegetation type groupings identified by the FUSE clustering analysis have been superimposed as ellipses around plots with similar species composition: (Group I) plots dominated by native wetland species, (Group II) restored native wetland plots, (Group III) native wetland plots undergoing grey willow invasion and (Group IV) grey willow-dominated plots. The vegetation type and wetland sampled are: open circles, native wetland vegetation at Whangamarino; open triangles, native wetland vegetation at Toreparu; grey filled squares, restored native wetlands at a Horsham Downs peat lake; grey filled triangles, invading grey willow plots at Toreparu; closed squares, grey willow-dominated vegetation at a Horsham Downs peat lake; closed circles, grey willow-dominated vegetation at Whangamarino; closed triangles, grey willow-dominated vegetation at Toreparu. See Table 6 and text for environmental codes. The angle between environmental arrows indicates the degree of intercorrelation in their effects on beetle community composition.

Table 6  Environmental variables and their correlations with vectors in ordination space.

Environmental variable	Code	Correlation coefficient
Vegetation type	VEG	0.823
Total grey willow cover (%)	%SC	0.794
Canopy density	CD	0.781
Canopy height	CH	0.760
Total vegetation cover (%)	%TC	0.698
Amount of coarse woody debris	CWD	0.675
Plant species richness	SPP	0.512
All Principal Component Correlation coefficients presented were significant at P<0.01.

Appendix Abundance of beetle species sampled using Malaise traps at each vegetation type within each wetland between 21 November 2007 and 17 January 2008.

Family	Species	Status	Trophic group	N, WH	N, TO	R, HD	I, TO	W, HD	W, WH	W, TO
Anobiidae	Anobium punctatum	Introduced	D				2	7	5
Anthicidae	Sapintus deitzi	Introduced	D			1	10		3	3
Anthicidae	Sapintus pellucidipes	Native	D					2		1
Anthicidae	Trichananca fulgida	Introduced	D	2			3	1
Anthribidae	Androporus discedens	Unknown	D					1	5	3
Anthribidae	Araeocerodes sp. 1	Native	D			2		3	2
Anthribidae	Etnalis spinicollis	Native	D		3	1	1
Anthribidae	Euciodes suturalis	Native	D		1					4
Anthribidae	Eugonissus conulus	Native	D				2
Anthribidae	Liromus pardalis	Native	D						1
Anthribidae	Micranthribus atomus	Native	D	1		1
Anthribidae	Pleosporius bullatus	Native	D		4			5	2	1
Anthribidae	Sharpius brouni	Native	D		1	1		4
Cantharidae	Asilis sp. 1	Native	P	24					1
Carabidae	Cicindela parryi	Native	P		1	3
Carabidae	Cicindela spilleri	Native	P	1		3
Carabidae	Cicindela tuberculata	Native	P	4	2
Carabidae	Euthenarus promptus	Introduced	P			8	1
Carabidae	Lecanomerus atriceps	Introduced	P			1	2			11
Carabidae	Notagonum lawsoni	Native	P			1		100	10
Carabidae	Paratachys crypticolus	Introduced	P			1	2			1
Carabidae	Scopodes fossulatus	Native	P					5
Cerambycidae	Coptomma lineatum	Native	H		9
Cerambycidae	Hybolasius sp.	Native	H	2		4			1
Cerambycidae	Microlamia pygmaea	Native	H		1	2
Cerambycidae	Oemona hirta	Native	H		1			1
Cerambycidae	Somatidia antarctica	Native	H		1	1
Cerambycidae	Zorion guttigerum	Native	H			2		15
Chrysomelidae	Arnomus sp. 1	Native	H	1
Chrysomelidae	Eucolaspis sp. 1	Native	H					1
Chrysomelidae	Peltoschema sp. 1	Introduced	H	1			1
Chrysomelidae	Pleuraltica cyanea	Native	H	2		1				1
Ciidae	Ciidae sp. 1	Native	D		2			1
Coccinellidae	Adalia bipunctata	Introduced	P	2		1		1	6
Coccinellidae	Coccinella undecimpunctata	Introduced	P		1		3		5
Coccinellidae	Diomus sp. 1	Unknown	P	2	1	1	3
Coccinellidae	Halmus chalybeus	Introduced	P			1	3	4	2	8
Coccinellidae	Rhyzobius fagus	Introduced	P			2	4	11	1	11
Coccinellidae	Rhyzobius forestieri	Introduced	P				3			4
Coccinellidae	Scymnus loewi	Introduced	P		4	3	3			7
Coccinellidae	Coccinellidae sp. 1	Unknown	P					1
Corylophidae	Arthrolips oblongus	Native	D					1	1
Corylophidae	Holopsis sp. 1	Native	D	3	11	1		2		4
Corylophidae	Sericoderus sharpi	Native	D	1					1	2
Corylophidae	Sericoderus sp. 1	Introduced	D				2	3
Cryptophagidae	Micrambina sp. 1	Native	D			4			2
Curculionidae	Cossoninae sp. 1	Native	H			1				1
Curculionidae	Hoplocneme squamosa	Native	H	10	2		6		9	1
Curculionidae	Listronotus bonariensis	Introduced	H			3	1		2	2
Curculionidae	Naupactus leucoloma	Introduced	H				1			4
Curculionidae	Notacalles sp. 1	Native	H	2					8	1
Curculionidae	Phloeophagosoma sp. 1	Native	H	2				1
Curculionidae	Praolepra sp. 1	Native	H			1			3
Curculionidae	Psepholax sp. 1	Native	H				1			1
Curculionidae	Sericotrogus subaenescens	Native	H	1	1		3	24	5
Curculionidae	Sitona lepidus	Introduced	H		3	11		6	1	12
Curculionidae	Stephanorhynchus lawsoni	Native	H							1
Dytiscidae	Rhantus suturalis	Introduced	P				2	2	4
Elateridae	Agrypnus variabilis	Introduced	H	1					2	23
Elateridae	Conoderus sp. 1	Unknown	H		3	1	7	9	2
Elateridae	Elateridae sp. 1	Native	H	2					3	1
Erotylidae	Loberus depressus	Native	D			5
Eucnemidae	Dromaeolus nigellus	Native	D	1		2
Eucnemidae	Eucnemidae sp. 1	Native	D			1
Hydrophilidae	Cercyon sp. 1	Introduced	D					3	4	2
Hydrophilidae	Enochrus maculiceps	Introduced	D				2	7	11	9
Latridiidae	Aridius bifasciatus	Introduced	D					4	5
Latridiidae	Aridius costatus	Introduced	D					2	3	18
Latridiidae	Corticariinae sp. 1	Unknown	D			1	1	12		2
Latridiidae	Enicmus sp. 1	Native	D				1	2	1
Latridiidae	Enicmus sp. 2	Native	D				1
Melyridae	Melyridae sp. 1	Native	H	10	2
Mordellidae	Stenomordellaria neglecta	Native	H	4		1	1		1	2
Mordellidae	Zeamordella monacha	Native	H	1		1	2	2
Mycetophagidae	Triphyllus sp. 1	Native	D				4		1
Mycetophagidae	Typhaea stercorea	Introduced	D				1	3	11	25
Nitidulidae	Homepuraea amoena	Native	H				1
Oedemeridae	Selenopalpus cyaneus	Native	H	9	22		3
Oedemeridae	Thelyphassa lineata	Native	H		1	1
Oedemeridae	Oedemeridae sp. 1	Native	H	1		3
Scarabaeidae	Costelytra zealandica	Native	H		2	1		5		31
Scarabaeidae	Odontria sp. 1	Native	H						3
Scirtidae	Byrrhopsis gravidus	Native	D				3			19
Scirtidae	Scirtidae sp. 1	Native	D	23	45	96	74	104	143	32
Staphylinidae	Carpelimus sp. 1	Unknown	D					1
Staphylinidae	Scaphisoma funereum	Introduced	D					1	39	10
Staphylinidae	Sytus sp. 1	Native	D			1			1
Staphylinidae	Philonthus sp. 1	Unknown	P				2	3
Staphylinidae	Xantholinini sp. 1	Unknown	P					1
Tenebrionidae	Tanychilus sophorae	Native	D							4
N, native wetland vegetation; R, restored native vegetation; I, native wetland vegetation undergoing grey willow invasion; W, dense grey willow-dominated vegetation; WH, Whangamarino; TO, Toreparu; HD, Horsham Downs peat lakes; D, detritivore; P, predator; H, herbivore. Nomenclature follows Klimaszewski & Watt (1997) and species are ordered alphabetically by Family.