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APS 276- Symbiosis > 9 + 10: parasitic plants and multipartite symbiosis > Flashcards

9 + 10: parasitic plants and multipartite symbiosis Flashcards

1
Q

what is the defining feature of a parasitic plant?

A

haustorium which grabs the host root/shoot, penetrating root cortex to access vascular system

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2
Q

give 7 points about Rhinanthus minor

A
  • root hemiparasite of northern temperate grasslands
  • can induce shifts in species composition of communities it lives in
  • key stone species
  • ecosystem engineer so can boost biodiversity
  • broadly grasslands reduced in presence of parasite and forb abundance promoted
  • variation in magnitude of response
  • can reduce total community productivity
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3
Q

what is a forb?

A

non leguminous perennial dicots

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4
Q

what did cameron et al 2006 discover about Rhinanthus minor

A

potted plant- when infected with the hemiparasite grasses loos significant biomass but legumes and forbs dont loose as much

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5
Q

what did cameron et al 2005 discover about Rhinanthus minor? (3)

A
  • shifts in host community structure induced by hemiparasite can be highly variable but polarity is conserved within the functional groups
  • grasses suppressed and forbs promoted at community level
  • forbs can flourish due to reduced competition with grasses
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6
Q

what did cameron et al 2009 experiment discover about Rhinanthus minor? (7)

A
  • grass dominates until parasite introduced
  • grass population crashes and forb pop increases
  • shifting cloud hypothesis: hemiparasite moves around in unpredictable shifts to attack grassland not yet infected
  • community is a mosaic with patches of different parasite densities and stage of regeneration
  • parasitic plants affect growth, metabolism, reproduction of hosts so cal alter structure of host communities due to competitive interactions
  • 2 nutrient levels with 3 grass species and 3 forb species
  • outcomes are sensitive to initial spatial pattern
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7
Q

what did lotka volterra suggest?

A

the predator prey interaction

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8
Q

what did cameron et al 2008 experiment discover about Rhinanthus minor and suppression of host photosynthesis? (7)

A
  • infestation of grasslands can lead to reduced community productivity
  • parasites grown on forb and grass host
  • found missing biomass in the grass
  • parasite reduces competitive ability of grass relative to forbes
  • parasitism decreased host and total biomass in the grass species but no growth repression in the forb species
  • grass suggested as superior host to forb
  • suppressed host photosynthesis affects total biomass production
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9
Q

what are the 2 competing hypotheses for why R.minor reduces competitive ability of grass relative to forbs

A
  1. active host choice (parasite selects one species over another)
  2. differential host resistance
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10
Q

what evidence is there for the active host choice hypothesis and what is a negative to this?

A
  • other parasitic plnats actively select host such as cuscuta
  • field trial suggest rhinanthus selects plantago laceolate and L.vulgare
  • BUT associations can be lethal to the parasitic plant
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11
Q

what does it mean that rhinanthus is a facultative parasite?

A

does not rely on the host to complete its life cycle but it benefits from finding one

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12
Q

unusually what may rhinanthus grow on?

A

inorganic material such as perspex

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13
Q

Cameron et al suggested the differential host resistance hypothesis, when and what was said about it?

A

2006
grasses can’t defend themselves against parasite
forbs induce successful resistance mechanisms

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14
Q

what did cameron et al discover for the differential host resistance hypothesis in 2007? (7)

A
  • forb haustorium less well developed
  • vulgare produce lignin at interface between host and parasite
  • xylem blocked with lignin to stop parasite gaining nutrients from xylem
  • Lanceolata will kill own tissues in contact with parasite by apoptosis and block vascular system
  • N isotope in petri dish under potted plant taken up by roots
  • parasite can divert flow of N from host root
  • Forb species gave up little/no N to prevent parasite stealing resources
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15
Q

what 2 species of root hemi parasites did Quested study in 2003 and what was compared in the study?

A

B.apina
P. lapponica
compared nutrient composition between parasitic plants and surrounding plants

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16
Q

what did Quested 2003 discover? (5)

A
  • lots of N in parasitic plants, more than surrounding vegetation
  • parasitic plants may induce nutrient cycling with litter acting as local fertiliser
  • parasitic plants have low C:N ratio so likely decompose quickly
  • parasite litter nutrient rich so host plants grew quicker
  • phytoassays show it benefits seedlings
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17
Q

what did Press study/find in 1998

A

effect of parasite litter in natural communities not previously investigates
- parasite steals nutrients from grasses, dies leaves litter so may be the grass that then benefits from the nutrients

18
Q

what was fisher et al 2013 study discoveries?

A
  • grass biomass higher in control and litter plits compared to rhinanthus
  • litter had fertilisation effect so grass biomass higher
  • forb response found in controls found litter suppressed growth but increased growth when there was litter and parasite present
19
Q

litter may have a wide zone of influence, what can this mean?

A
  • in complex ecosystems overlapping areas of influence

- parasites may be infected by more than one parasite or maybe just only gain benefits from being in the litter zone

20
Q

what is the scientific name for the salt marsh dodder?

A

cuscuta salina

21
Q

give points about cuscuta? (5)

A
  • actively seeks out and selects host plant in a predatory way
  • sucks nettle sap by inserting tube to gain enough nutrients to flower
  • haustoria produced in parasite stem entering host tissue by pressure and digestive enzymes forming vascular connections
  • attack xylem and phloem
  • stem waves around the air by circumnation to find host to spiral around
22
Q

what did Shen et al 2005 discover about the effect of cuscuta parasite on the host over time?

A

uninfected hosts do better in terms of growth and performance (more leaves, longer stem length and higher dry weight)

23
Q

what did Runyon et al 2006 do using filter paper and discover about cuscuta? (4)

A
  • cuscuta can dominate host plant
  • it can detect host using volatile cues released by stomata of host plant
  • germinated seed in middle of filter paper with host nearby
  • 24/30 would grow towards tomato host but also 22/30 would grow towards just the volatile chemicals produced by tomato host
24
Q

what did Kelly discover in 1992 when growing hawthorn at different N levels, about cuscuta? (6)

A
  • N content in host plant increased with fertilisation with parasite and more stems accepted the host
  • cuscuta parasite european dodder
  • cuscuta would attack hosts with more N
  • it can select and accept hosts with the greatest nutritional quality for the greatest gain
  • shows its acceptance response before taking up food from host
  • stems of dodder transplanted onto host plants of varying nutritional status
25
Q

what is an ecotone?

A

abrupt change in vegetation with intense competition

- part where 2 species can both survive

26
Q

what did Pennings and Callaway discover 1998? (6)

A
  • habitat graduated by saline conc and zoned depending on this
  • Salicornia is more salt tolerant than Arthrocnemum
  • Salicornia found to be the prefered host
  • looked at how often species were infected with parasite cuscuta salina in a removal experiment
  • if removed cuscuta arthrocnemum declined and Salicornia increased
  • parasite is regulating position of the ecotone on the shore
27
Q

what are 2 examples of multitrophic interactions between parasitic plants and their host?

A
  • mistletoe- juniper - frugivore interactions

- indian paintbrush -lupin - herbivore -pollinator interactions

28
Q

what is juniper mistletoe reliant on, what also benefits from this and how are mistletoe seeds spread?

A

avian frugivores
host juniper
- fruit digested by birds who defecate sticky substance with seed in it and wipe it onto branches of other trees

29
Q

what did Ommeren and Whitham 2002 say that the clear parasitic relationship of mistletoe on juniper is confounded by?

A

both share common seed dispersing mutualists

30
Q

what does it mean that juniper is masting?

A

it mass fruits, producing vast quantities of fruit irregularly

31
Q

what did Ommeren and Whitham 2002 discover about juniper seedling recruitment and what did they do?

A
  • counted birds and avian frugivores with and without mistletoe
  • more than 2 fold increase in juniper seedling recruitment in mistletoe infected areas as these had a higher reproductive success
32
Q

what did Ommeren and Whitham 2002 find for the multitrophic interaction involving mistletoe density and nature of interaction? (2)

A
  • low mistletoe density avian frugivores interact with juniper in 2 way interaction
  • high: 3 way interaction (host, parasite, bird) as mistletoe alternate food resource
33
Q

what did Ommeren and Whitham 2002 find for the multitrophic interaction involving mistletoe density and effect on juniper? (6)

A
  • low mistletoe density infected juniper has negative impact
  • base mistletoe densities provide no indirect benefit to uninfected juniper
  • high density increases juniper reproductive success until a point
  • uninfected and infected juniper both indirectly benefit at increasing mistletoe density
  • -ve effect on host fitness at very high mistletoe densities outweigh seed dispersal benefits
  • uninfected juniper in the same community can benefit with no costs
34
Q

what did Ommeren and Whitham 2002 find for the multitrophic interaction involving nature of interaction and variability in juniper berry crop? (2)

A
  • increased variability enhances role of mistletoe as alternate resource for avian frugivores
  • action shifted from 2 way to 3 way
35
Q

what did Ommeren and Whitham 2002 find for the multitrophic interaction involving mistletoe density and effect of avian frugivores on juniper? (3)

A
  • when 2 way or 3 way relationship between avian frugivores and juniper mutualistic
  • antagonistic relationship at very high mistletoe density when birds are acting as a vector for mistletoe spread
  • at low mistletoe density frugivores have a high beneficial effect on juniper
36
Q

what species and family does the indian paintbrush parasite belong to?

A

castilleja

orobanchaceae

37
Q

what does the indian paintbrush depend on?

A

external pollinators

38
Q

lupin accumulates lots of N- what often are legumes and why?

A

poisonous to avoid N being taken by herbivores

39
Q

lupin produces alkaloids

  • what are they
  • give 2 examples
  • what are the 2 morphs
A
  • complex secondary metabolites with antifeedant properties to deter herbivore attack and are often bitter
  • Sparteine, Lupinine
  • some alkaloids defer but others are sweet which is cheating as herbivores associate the plant with bad taste so the sweet morph is saving resources by not producing the bitter alkaloid
40
Q

what did alder 2000 discover about the multitrophic interaction involving Castilleja indian paintbrush species? (6)

A
  • castilleja attached to bitter hosts high in alkaloids reduces herbivory relative to parasites attached to sweet hosts low in alkaloids
  • herbivory and % plants visited similar for those sprayed with pesticides and bitter hosts
  • pollinators prefer castilleja individuals not attacked by herbivores so increased fecundity of parasites attached to bitter hosts
  • bitter plants more attractive to pollinators as aren’t damaged so increased reproductive success
  • pollinators help prevent herbivory and increase lifetime seed production
  • parasite steals lupin alkaloids to increase plant fitness directly by reducing herbivory and indirectly by increasing pollinator visitation

APS 276- Symbiosis (29 decks)

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