Invasion Dynamics of Amur Honeysuckle in Southwest Ohio

David L. Gorchov, Dept. of BiologyMary C. Henry, Dept. of GeographyMiami University, Oxford, OH

Lonicera maackii• Native to east Asia• Introduced to U.S. in 1897; naturalized in 24 eastern states• Partly self-compatible (Goodell and Iler 2007)• Seeds dispersed by birds (Bartuszevige & Gorchov 2006) &

deer (Castellano & Gorchov 2013, Guiden unpubl.)• Seedlings establish in sun or shade (Luken & Goessing 1995)• Extended leaf phenology (can find all individuals)

1. Importance of stand invasibility vs. propagule pressure in invasions

40 woodlots in agricultural landscape

Darke and Preble counties, OH

Lonicera maackii cover weakly correlated with some woodlot measures

Correlation coeff. (r)

Stand age -0.40

tree cover in 1938 aerial photo -0.38

tree cover in 1962/63 aerial photo -0.37

Woodlot area

Perimeter : area ratio

Tree basal area

Woodlot L. maackii cover correlated with land cover in 1500 m buffer

land cover in 1500 m buffer r

% Crops -0.69

% Developed 0.44

% Forest 0.62

%Pasture 0.68

% Recreational Grass

% Water 0.36L. maackii cover not correlated with road density, latitude, or composition of woodlot perimeter in 1938 or 1962/3

Stepwise regression of woodlot L. maackii cover on predictors: % crop in 1500 m buffer was first predictor to enter; no other variable improved fit

1. ConclusionsLandscape, more than woodlot characteristics, determine cover of this invaderPropagule pressure more important than stand invasibilityL. maackii invasion impeded by cropland

Absence of propagule sources?Deterrent to movement of seed dispersers?

2. Relative importance of diffusion vs. long-distance dispersal in invasion of exotic species

Fragmented habitat (forested patches in agricultural matrix)

Diffusion (expanding front)

Diffusion: subsequent recruitment from outside the patch

propagule pressure

Long-distance dispersal

Long-distance dispersal

Long-distance dispersal

Long-distance dispersal: Subsequent recruitment from within patch

Founder effect

Understanding of dispersal can inform management of invasives

• Diffusion: target edge of current range• Long-distance dispersal: patrol for colonists

X

X

X

Age structure of 28 populations in s. Darke Co.14 pops.: all shrubs or 30 largest X-sections of stemsRings counted by 2-3 persons689 shrubs; >1200 stems

8

1616

121619

15

151812

8121121

713

81314

13

14

9

8

7

19

1113

13

Oldest shrub in each woodlot

Long-distance dispersal, followed by diffusion

4428500

4429500

4430500

4431500

4432500

4433500

4434500

4435500

4436500

689000 690000 691000 692000 693000 694000 695000 696000 697000

1992

1992

• X and Y axes correspond to UTM coordinates of woodlot centers in south-central Darke County Size of bubble corresponds to # of L. maackiishrubs in a woodlot in a given year

4428500

4429500

4430500

4431500

4432500

4433500

4434500

4435500

4436500

689000 690000 691000 692000 693000 694000 695000 696000 697000

1997

1997

Long-distance dispersal, followed by diffusion

4428500

4429500

4430500

4431500

4432500

4433500

4434500

4435500

4436500

689000 690000 691000 692000 693000 694000 695000 696000 697000

2002

1997

2002

Long-distance dispersal, followed by diffusion

Early phase of invasion: long distance dispersal

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

1988 1990 1992 1994 1996 1998 2000 2002 2004

Dis

tanc

e to

clo

sest

sour

cec

(m)

Establishment Year

Closest pop. ≥ 4 yrs older

after ~ 8 yrs: diffusion

Who is dispersing L. maackii seeds 4 km?

Peter Guiden, MS thesis (Miami U)

Do later-establishing pops. to grow faster? (expected if diffusion important)

Year pop. established

Σ oldest 9 years

NO

Age structure expected under diffusion vs. long-distance disperal

predicted age structure

age

num

ber o

f ind

ivid

uals

N(long)

N(short)

Immigration rate for a population (xi)# shrubs in oldest 3 age classes / 3

Agex145=0.67/yr

Mean of xi for 28 pops. used as ‘global’ immigration rate X = 0.87/yr

Regression of pop. imm. rate vs. year of establishment not sig.

xi

yi = ni - X

Recruitment from parents within the population assumed to equal total recruitment - immigration

Age

For pop. 145, within pop. recruitment accounts for 34% of recruits in years 5-7 and 83% in years 8-9 On avg. (14 pops.), within-pop. recruitment accounts for 46% of recruits in years 5-7 and 77% in years 8-9

yrs 5-7yrs 8-9

Early growth of new populations is due to both immigration (propagule pressure) and reproduction within the pop., but after 8 years is due mostly to within-pop. recruitment

2. ConclusionsLong-distance dispersal important early in invasionImmigration rates are low, and soon exceeded by recruitment from within pop.

• Management: patrol for colonists

X

Thanks!• USDA NRI Competitive Grants Program, Mary

Henry (MU) & Oscar Rocha (Kent State), co-PIs• Peter Frank, Steve Castellano, Doug Noe, Sujan

Khanal, Holly Andrews, Charlotte Freeman