Native and Invasive Plants

Invasive plant Ability to spread aggressively outside its natural range Especially in new habitat

Invasive plant Lack insects, diseases and foraging animals

Where are they a problem? Disrupted habitats Thrive on disturbed sites like construction areas and road cuts

Why are they a problem? Threaten native plants and animals Insects, micro-organisms, birds, etc… Alter habitats and reduce biodiversity

Native Plants Plants growing here for a long time >500 years ◦ Christopher Columbus (1492)

Native Plant Databases ection.php?start=0&collection=SC&pagec ount=10&pagecount=100 ection.php?start=0&collection=SC&pagec ount=10&pagecount=100

Biodiversity The diversity of animals is linked to the diversity of plants ◦ Greater number of plant species means less competition and increased niches

Biodiversity 2.5 acres of Amazonian rainforest supports 473 species of trees Only 134 species of trees in Pennsylvania

Biodiversity Trophic level is the position an organism occupies in food chain. First trophic level: Plants Plants capture sun’s energy and turn it into food for the rest of us

Biodiversity Second trophic level: Herbivores Transfer energy from plants to predators and parasites in higher trophic levels ◦ Mainly insects

Biodiversity Worldwide, 37% of animal species are herbivorous insects Pound for pound, insects contain more protein than beef 96% of birds rely on insects and spiders to feed young

Keystone Species Keystone species essential role in maintaining diversity ◦ Robert T. Paine research Tidal pool on Pacific Coast ◦ Simple ecosystem

Keystone Species Simple Ecosystem ◦ Rivet example Some rivets on airplane more important than others ◦ Seat versus engine

Keystone Species Simple Ecosystem Removing some species had little effect on populations of remaining species But removal of a predatory starfish (Pisaster ochraceus) caused a collapse of half the remaining species’ population

Keystone Species Complex System No central players ◦ Jenga example How vital a block’s role to the tower’s stability is based on the presence of other blocks

Keystone Species Complex System Every time block is removed, role and importance of other blocks changes Almost any species can be a keystone species depending on circumstances

Trophic Cascades The impact on other species when removing a keystone species ◦ Predator example Yellowstone wolf population reduced Moose spend less time looking around ◦ More time grazing Overgrazing led to erosion, impacting streams, fish, plants, etc.

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Non-Native (Alien) Aliens colonize areas faster than natives Alien plants minimally interact ◦ Pass along very little energy  Plants 1 st trophic level  Herbivores (Insects) 2 nd trophic level

Non-Native (Alien) “Pest-free” ornamentals are primarily selected for landscape It takes time for insects to adapt to specific chemical composition of leaves

Non-Native (Alien) Paperbark tea tree introduced to Everglades in 1900 Presently, 8 species of arthropods feed on leaves, opposed to 409 back in Australia

Non-Native (Alien) 90% of herbivorous insects are specialists that have evolved with a specific plant

Non-Native (Alien) Insects develop ability to overcome physical and chemical defenses of host, but limited to feed on that host only ◦ Mainly due to leaf chemistry Insects develop enzymes that detoxify chemistry

Non-Native (Alien) Tannins in oak leaves would bind protein if we eat them, starving us Lima beans contain cyanide unless boiled Cucumber leaves are lethal

Seeds from a plant commonly called wild potato, known to botanists as Hedysarum alpinum. According to my hypothesis, a toxic alkaloid in the seeds weakened McCandless

Seeds from a plant commonly called wild potato, known to botanists as Hedysarum alpinum [caused slow-developing severe weakness that brought about starvation].

Non-Native (Alien) 10% of insect herbivores are generalists that eat several types of plants Ability to produce very powerful gut enzymes called mixed-function oxidases Feed on many alien plants, but not enough

Non-Native (Alien) Compare diversity and biomass of insects on 4 woody natives versus 5 aliens Native plants produce 4x more biomass Supported 3.2x more species

Non-Native (Alien) Compare diversity and biomass of insects on 4 woody natives versus 5 aliens In terms of caterpillars (most important to birds), 35x more than alien plants Natives produced 2x as many generalists

Non-Native (Alien) A plant can become native regardless of origins Norway maple introduced from Europe in 1756 Still has few insect feeders Compare to 80 millions years of coevolution, 250 years isn’t much

Non-Native (Alien) Native applies to local regions Human influence is too rapid for adaption

Non-Native (Alien) Birds eat fruit after reproduction Most species depend on insect protein for egg laying and feeding young and nesting

Non-Native (Alien) Non-invasive qualities of alien does not make it native Clematis vitalba introduced 100 years ago Supports 40 herbivores in homeland but only 1 after 100 years since introduction here

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