Lecture 2 - Weed Characteristics Flashcards
what does the evolutionary success of any organism depend on
- # of individuals in existence
- extent of reproductive output
- area of the world’s surface they occupy
- range of habitats they can enter
what determines the evolutionary success of a weed
- they are persistent
- they can defy/avoid extermination to a large extent
what is a plant’s weediness greatly affected by
affected by the environment in which it grows and the nature of the community where it grows
what do weed traits affect
seed dormancy and longevity
phenology
ecophysiology
reproductive biology
fecundity (reproductive success)
response to stress
1st principle of weeds
weeds are highly heterogeneous, with considerable variation in traits contributing to their success
2nd principle of weeds
while weeds may be inherently competitive and/or invasive, their success is modulated by community structure
weeds are often specialized in ________________
non-specialization
weeds are widely adapted and able to ……..
- invade new areas
- suppress/displace desirable species
- dominate disturbed sites
- resist eradication or control measures
3 general characteristics of weedy species
ability to invade, dominate, persist
weed traits contributing to invasion
wind dispersal
high seed production
vegetative spread
good seed survival/viability
ability to germinate on surface
weed traits contributing to domination
high competitive ability (rapid growth)
resistant to management practices
perennial weed traits contributing to persistence
long lived
ability to tolerate stress (already established)
ability to form a persistent seed bank
what traits affect a weeds ability to form a persistent seed bank
dormancy
viability
high seed production
what is range of any weed species limited by
-extent of suitable habitat
-location of suitable habitats in relation to dispersal capabilities
the ‘ideal’ weed characteristics (1-11/22)
- annual with high seed production
- perennial with vigorous vegetative reproduction
- high seed output under favourable conditions
- seeds of great longevity and able to withstand bad conditions
- short-lived annuals that germ at wide range of conditions
- self controlled/induced germ
- rapid seedling growth
- short vegetative phase
- continuous seed production (indeterminate growth)
- Self-compatible but not chronically asexual production
- pollination by a non-specialized vector or wind
the ‘ideal’ weed characteristics (12-22/22)
- large, odiferous flowers that reflect and absorb UV
- high phenotypic plasticity and variability of form
- high genotypic plasticity with large variability in populations
- high resistance to bad conditions and high growth under wide range of conditions
- high potential growth rate
- high competitive ability
- strong and intensive root growth
- allelopathic
- unpalatable to livestock/resistant to grazing
- resistant to herbicides
- produce seeds same size and shape as domestic crops
what traits of a seed can contribute to longevity
hard seed coat or chem protectants
example of weed with seed longevity
wild mustard (85% of seed germed after 10yrs, some viable after 60)
what is rapid seed growth typically a function of
seed size, with larger seeds supporting more rapid growth
there is a compromise between seed ______ and seed ___
number, size
another word for seeds
propagules
what parts of large odiferous flowers reflect or absorb light
outer portion reflect UV/blue light
inner portion absorbs wavelengths
what does high phenotypic plasticity and variability of form contribute to in weeds
enables population to survive and produce seeds in a wide range of environments (ex: dwarf or giant individuals)
what does high genotypic plasticity and variability in populations contribute to in weeds
optimum for both opportunistic settlement and occupation of diverse/complex habitats (often favored by polyploidy)
