Transcript Landcare: Hearing Presentation (x)

Application to release Lathronympha
strigana & Chrysolina abchasica into
NZ for biological control of Tutsan
Hypericum androsaemum
Topics
1. Need for biocontrol – already covered by Craig
2. Why two agent species?
3. Risk of non-target attack on native Hypericum spp.
I won’t discuss ecosystem effects (e.g. indirect
competition mediated by parasitoids) as we feel they
have been adequately covered in the
application/response to submissions
Why two agent species?
Increased chance of success:
• Weed biocontrol agent establishment
rate =~84%, so releasing 2 spp.
increases chance of getting 1 agent sp.
established from 84% to ~97%
• Main reason: complementary feeding =
potentially more impact
– Georgian populations of Lathronympha
strigana larvae bore into fruits/eat seeds;
– Chrysolina abchasica defoliates plants
Complementary feeding
Seed-feeding agents rarely destroy enough seeds to
reduce densities of existing weed infestations
BUT simulation modelling1 & field studies2 indicate that
reducing seed production can reduce the rate that weeds
spread into novel (previously uninvaded) habitats or
reinvade following control (e.g. by herbicides)
L. strigana probably won’t control tutsan on its own, but
can potentially slow tutsan invasion, making infestations
easier to contain & control using conventional means &
may be particularly useful if outlying plants escape attack
by Chrysolina abchasica (complementary impact)
1Coutts,
SR et al. 2011. Biological invasions, 13, 1649-1661
2Norambuena, H., & Piper, G. L. (2000). Biological Control, 17(3), 267-271
Complementary feeding
Good reason to believe Chrysolina
abchasica has excellent potential
to control existing infestations:
Closely-related Chrysolina hyperici
(introduced in 1943) successfully
controlled St John’s wort
Hypericum perforatum in NZ
NZ’s most successful biocontrol
programme1 & an almost identical
weed/agent combination
1Hayes,
L. et al., 2013. Biocontrol of weeds: Achievements to date and future outlook.
Ecosystem services in NZ–conditions & trends. Manaaki Whenua Press, Lincoln, NZ, 375-385.
Potential for non-target attack
Host-range testing
Species closely-related to the target weed are at
biggest risk of non-target attack1
Modern host-range testing, therefore, follows a
“centrifugal” phylogenetic approach (i.e. testing the
most closely-related spp., then more distantly related
plant spp. until the host-range is circumscribed2)
Track record of host-range testing is good
1Pemberton,
RW, 2000. Oecologia 125, 489-494
2Briese, DT & Walker A 2002. Biological control, 25, 273-287.
Track record host-range testing
No significant non-target attack on native plants or on
economically important exotic spp. in NZ1,2
Of 512 weed biocontrol agent spp. released worldwide
only 4 (0.8%) have serious non-target impacts: all were
on thistles or cacti & within the same genus as the
target host plant & with predictable outcomes that
resulted from an earlier era of lower standards of
biosafety than prevail today3.
Host-range testing works! Testing has been improved
to reduce potential risks still further1,2
1Paynter
et al. 2004 New Zealand Plant Protection 57 102-107
et al. 2012. J. Appl. Ecol. 49 307-310
3Suckling, D. M., & Sforza, R. F. H. 2014. PloS one, 9, e84847.
2Fowler
Predicting non-target attack
• Problems associated with agents that are capable
of developing on a potential non-target plant,
where they perform relatively poorly on that plant
• Such plants are termed “physiological” hosts,
because they support development, but they may
or may not be field hosts in natural conditions
• A Gung-ho approach to releasing such agents
risks non-target attack, but not releasing such
agents risks rejecting a safe & effective agent
Example: Longitarsus jacobaeae in NZ
No-choice starvation tests: NZ
native Senecio wairauensis is a
(poor) physiological host1
No evidence of non-target attack in
the field since 1983 release2
Rejecting this agent would have
needlessly prevented a highly
successful programme
1Syrett
1985. NZ J. Zool. 12: 335-340
et al. 2004. NZ Plant Prot. 57:102-107
2Paynter
Predicting non-target attack on
“physiological” hosts
• Ideally, field tests would be performed in agent native
range, but it is often impossible to grow NZ native plants
in other countries
• A recently developed scoring system predicts non-target
attack based on relative performance of agent on test
plant versus target plant1
• e.g. if an ovipositing ♀ lays 20% of the normal no. eggs on
a test plant & subsequent larval survival is 30% of that on
the host plant then the relative performance on that test
plant (expressed in proportions) is 0.2 Χ 0.3 = 0.06
1Paynter,
Q., et al. 2015. Biological Control 80, 133-142.
Relative performance
• all plants with a combined
risk score > 0.33 were
attacked;
• no plants attacked when
the risk score was < 0.33
All attack(including spill-over)
1.00
Probability of non-target attack
Relative risk score
(combining oviposition &
starvation test results)
from past NZ biocontrol
programmes shows a
clear-cut threshold:
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.00
Paynter, Q., et al. 2015. Biological Control 80, 133-142.
0.50
1.00
1.50
2.00
Combined risk score (R1 x R2)
Host-range testing L. strigana & C. abchasica
Phylogenetic approach predicts biggest risk of undesirable
non-target feeding is to 4 native NZ Hypericum spp., - H.
rubicundulum; H. minutiflorum; H. pusillum & H. involutum
(formerly H. gramineum).
Three of these were tested - H. minutiflorum was not tested
(hard to obtain & notoriously difficult to grow). According to
Peter Heenan (Landcare Research, pers. comm.), H.
rubicundulum & H. minutiflorum are genetically almost
identical1, so we would expect almost identical test results.
These 2 spp. are ecologically similar too, so the risk profile for
these spp. is almost identical – essentially H. rubicundulum can
be considered a surrogate for H. minutiflorum.
1Heenan,
PB 2008 Three newly recognised species of Hypericum (Clusiaceae) from NZ, NZ J.
Botany, 46:4, 547-558
Phylogeny of genus Hypericum: Meseguer et al. /
Molecular Phylogenetics & Evolution 67 (2013) 379–403
A
NZ natives
B
C
34 MYA
H. androsaemum
D
H. calycinum
E
H. perforatum
27 MYA
NZ native Hypericum spp. belong to clade B; H. androsaemum belongs to clade C.
Other commonly naturalised Hypericum spp. in NZ included in testing belong to
clades D & E.
• Clade B diverged from Clades C-E ~34 MYA
• Clades C, D & E diverged ~27 MYA,
• Closest relatives to H. androsaemum in NZ in order of relatedness are exotic H.
perforatum & H. calycinum, then NZ natives
Summary of host-range testing
Lathronympha strigana:
– Oviposition & larval development restricted to Genus Hypericum.
– Both oviposition & no-choice development/larval starvation tests
indicate little risk to native Hypericum spp. (no or v few eggs laid; no
larval development).
Chrysolina abchasica:
– Oviposition & larval development restricted to Genus Hypericum.
– No oviposition or larval development on native H. involutum (not a
host).
– Significantly lower oviposition & larval survival on native H. pusillum
& H. rubicundulum compared to H. androsaemum (tutsan) & low
survival of resulting adults indicate these spp. are very poor hosts.
Host-range testing Chrysolina abchasica
All attack(including spill-over)
1.00
Probability of non-target attack
Relative risk score for C.
abchasica ranged from
0.01-0.06 for H. pusillum &
H. rubicundulum – well
below threshold for nontarget attack - i.e. predicts
that C. abchasica
populations will not colonise
& persist on native NZ
Hypericum spp. & even spillover (incidental feeding on
non-target plants that does
not persist or only occurs in
the presence of the target)
is unlikely
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.00
0.50
1.00
1.50
2.00
Combined risk score (R1 x R2)
Risk to native Hypericum spp.
Although the scoring system predicts that
spill-over attack is unlikely, we nevertheless
examined this risk in more detail:
2 scenarios how spill-over might occur:
1. Larvae dispersing from defoliated tutsan plants
might feed on native Hypericum plants (C.
abchasica larvae are not very mobile so this could
only occur in v close proximity to the source plant)
2. High adult densities may result in oviposition on
native Hypericum plants growing near tutsan, with
subsequent larval feeding. The risk of damage
would fall off rapidly with distance, so is also likely
to be relatively localised (few beetles likely to
disperse > a few hundred m).
Risk of spill-over attack
Significant spill-over can only occur if:
1. The host plant & the non-target species co-exist
regionally
2. The non-target plant could attract & arrest the dispersal
of adult C. abchasica
3. Non-target damage to plants affects their survival status
4. There is spill-over risk from host plants spp. other than
tutsan (e.g. other invasive Hypericum spp.)
1. Do host plant & non-target spp. co-exist
regionally
• Tutsan is a common weed in higher rainfall areas, esp N &
W NZ, but is less suited to, or absent from drier & cooler
eastern or upland regions
• H. pusillum has closest range overlap with tutsan, but
tolerates a wider range of habitats & is commonly found
where tutsan is absent.
• H. rubicundulum occurs in dry areas of the S Island (& 1
site in Hawkes Bay). Range overlap with H. androsaemum
minimal.
• H. minutiflorum almost exclusively grows on pumice soils
in the Taupo basin & central volcanic plateau where tutsan
is rare. Range overlap with H. androsaemum also minimal
2. Could non-target plants attract dispersing
adult C. abchasica?
During oviposition tests, adult beetle feeding was recorded as
well as the no. eggs laid
Species exposed
Percent of tests in which adult feeding was observed
Tutsan present
Tutsan absent
Hypericum androsaemum
100
-
Hypericum pusillum
40
70
Hypericum rubicundulum
0
0
Hypericum involutum
0
10
Adults did not feed/only trivial feeding on H. involutum & H.
rubicundulum indicating that adults encountering these spp.
in the field would likely re-disperse rather than settle & feed.
Hypericum minutiflorum was not tested, but a similar
response is probable.
3. Damage to non-target plants affected survival
status of the non-target species
Photographs were taken following
the completion of larval
starvation/development tests
•
Larvae caused heavy damage on H.
androsaemum (top)
•
Barely discernible damage by 11
larvae on H. rubicundulum (middle)
& ditto for
•
12 larvae on H. pusillum (bottom)
4. Spill-over risk from host plants species other
than tutsan
The most closely-related plant to tutsan in NZ is hybrid H. x
inodorum (clade C; parent plants: tutsan & H. hircinum).
Given it’s derivation, it is likely to be a host. Not included in
testing as it is rarely naturalised (Mainly Auckland &
Northland: little overlap with native Hypericum spp.)
Hypericum canariense is another naturalised sp. belonging to
clade C. It is restricted to a roadside near Gisborne (almost
no overlap with native Hypericum spp.)
St John’s wort (H. perforatum) is a fundamental host for C.
abchasica, but performance scores (0.17-0.21) predict that it
will not be field host in NZ – backed up by field surveys in
Georgia, where tutsan & St John’s wort co-occur that indicate
St John’s wort is not a host there.
Relative performance
Finally, it is noteworthy that retrospective testing performed
on Chrysolina hyperici & C. quadrigemina, which have trivial
impacts on H. pusillum & H. involutum in NZ1, indicates much
higher equivalent combined risk scores than for C. abchasica
– further evidence that C. abchasica is likely to be safe
Test plant
Beetle species
Combined risk score
Hypericum involutum
Hypericum involutum
Hypericum involutum
Chrysolina quadrigemina
Chrysolina hyperici
Chrysolina abchasica
1.135
0.631
0
Hypericum pusillum
Hypericum pusillum
Hypericum pusillum
Chrysolina quadrigemina
Chrysolina hyperici
Chrysolina abchasica
0.537
0.307
0.01-0.06
Groenteman, R., et al. 2011. St. John's wort beetles would not have been introduced to NZ now: A retrospective host range test
of NZ's most successful weed biocontrol agents. Biological Control 57, 50-58.