3)What makes a species invasive?

An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77:

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Of species that make it to the wild, only ~10% become naturalized

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Only ~10% of species that make it to the wild become naturalized Of species that become naturalized, only ~10% become pests

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Only ~10% of species that make it to the wild become naturalized Only ~10% of naturalized species become pests

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Only ~10% of species that make it to the wild become naturalized Only ~10% of naturalized species become pests Example: 1000 imported species

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Only ~10% of species that make it to the wild become naturalized Only ~10% of naturalized species become pests Example: 1000 imported species 100 escape to wild

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Only ~10% of species that make it to the wild become naturalized Only ~10% of naturalized species become pests Example: 1000 imported species 100 escape to wild 10 become naturalized

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Only ~10% of species that make it to the wild become naturalized Only ~10% of naturalized species become pests Example: 1000 imported species 100 escape to wild 10 become naturalize 1 becomes pest

3)What makes a species invasive? An observation: “Tens Rule” From Williamson & Fitter (1996) Ecology 77: Only ~10% of imported species escape to wild Only ~10% of species that make it to the wild become naturalized Only ~10% of naturalized species become pests Example: 1000 imported species 100 escape to wild 10 become naturalize 1 becomes pest If so few species become invasive, does a plant species become invasive because it has certain characteristics?

3)What makes a species invasive? Species characteristics: Nevada’s Coordinated Invasive Weed Strategy: Invasive weeds often share characteristics such as: Highly competitiveCause environmental degradation ExoticEasily spread Highly aggressiveAre difficult to control Cause economic lossAugment wildfires Davis & Thompson (2000): 8 ways to be a colonizer, but only 2 ways to be an invader Richardson et al. (2000): Invasive plants are naturalized plants that produce reproductive offspring (often in large numbers) at considerable distance from parent plants

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system Dioecious (male & female flowers on separate plants) vs. Monoecious (on same plant)

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system Dioecious vs. Monoecious Self-incompatible pollen vs. Self-compatible pollen

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system Dioecious vs. Monoecious Self-incompatible pollen vs. Self-compatible pollen Some type of asexual reproduction Apomixis – produce viable seed without fertilization Vegetative reproduction – regenerate from stem or root fragments Clonal propogation – new individuals produced through rhizomes

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible monoecious w/ asexual reproduction)

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible monoecious w/ asexual reproduction) 2.Flowering & fruiting periods Short vs. Long flowering period

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible monoecious w/ asexual reproduction) 2.Flowering & fruiting periods Short vs. Long flowering period Short vs. Long fruiting period

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible & monoecious w/ asexual reproduction) 2.Flowering & fruiting periods (tend to be: long) 3.Juvenile period Short vs. long

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible & monoecious w/ asexual reproduction) 2.Flowering & fruiting periods (tend to be: long) 3.Juvenile period (tend to be: short) 4.Seed production Low vs. high

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible & monoecious w/ asexual reproduction) 2.Flowering & fruiting periods (tend to be: long) 3.Juvenile period (tend to be: short) 4.Seed production (tend to be: high) 5.Germination cues Present vs. Absent

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible & monoecious w/ asexual reproduction) 2.Flowering & fruiting periods (tend to be: long) 3.Juvenile period (tend to be: short) 4.Seed production (tend to be: high) 5.Germination cues (tend to be: present) 6.Light requirements Low vs. High ability to capture and efficiently use

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible & monoecious w/ asexual reproduction) 2.Flowering & fruiting periods (tend to be: long) 3.Juvenile period (tend to be: short) 4.Seed production (tend to be: high) 5.Germination cues (tend to be: present) 6.Light requirements Low vs. High ability to capture and efficiently use High phenotypic plasticity for light & other resources

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible & monoecious w/ asexual reproduction) 2.Flowering & fruiting periods (tend to be: long) 3.Juvenile period (tend to be: short) 4.Seed production (tend to be: high) 5.Germination cues (tend to be: present) 6.Light requirements Low vs. High ability to capture and efficiently use High phenotypic plasticity for light & other resources High competitive ability for light & other resources

3)What makes a species invasive? Species characteristics: Plant Life History Traits (Chapter 3 of NRC 2002) 1.Reproductive system (tend to be: self-compatible & monoecious w/ asexual reproduction) 2.Flowering & fruiting periods (tend to be: long) 3.Juvenile period (tend to be: short) 4.Seed production (tend to be: high) 5.Germination cues (tend to be: present) 6.Light requirements (tend to be: highly efficient, plastic, & competitive)

3)What makes a species invasive? SUMMARY: Is it characteristics of the species?

3)What makes a species invasive? SUMMARY: Is it characteristics of the species? X

3)What makes a species invasive? SUMMARY: Is it characteristics of the species? If not simply a characteristic of the species, then is it a characteristic of the environment? X

3)What makes a species invasive? SUMMARY: Is it characteristics of the species? If not simply a characteristic of the species, then is it a characteristic of the environment? Or both species and environment? X

3)What makes a species invasive? SUMMARY: Is it characteristics of the species? If not simply a characteristic of the species, then is it a characteristic of the environment? Or both species and environment? 10 hypothesis: (order subject to change) Vacant niche hypothesis Environmental change hypothesis Microevolutionary change hypothesis Escape from biotic constraints hypothesis BCW hypothesis Variable resource availability hypothesis Competition hypothesis Biodiversity hypothesis Disturbance and land use hypothesis Anthropogenic hypothesis X

3)What makes a species invasive? a) Vacant Niche Hypothesis “Niche” concept first developed by Grannell in Found that could differentiate species of thrushes on the basis of a resource (in his case, microhabitats)

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche formalized by Hutchinson in = theoretical limits of existence for a species along n resource axes

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche formalized by Hutchinson in = theoretical limits of existence for a species along n resource axes Realized niche = actual limits of existence for a species

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche – Species A Resource axis #1 Success

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche – Species A Resource axis #1 Success Resource axis #2 Success

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche – Species A Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche – Species A Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche – Species A, Species B Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche – Species A, Species B Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Fundamental niche – Species A, Species B Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Realized niche – Species A, Species B Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Realized niche – Species A, Species B Fundamental niche: Invader – Species C Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Realized niche – Species A, Species B Fundamental niche: Invader – Species C Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis New realized niche – Species A, Species B Realized niche: Invader – Species C Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Realized niche – Species A, Species B Realized niche: Invader – Species C Fundamental niche: Invader – Species D Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis Realized niche – Species A, Species B Realized niche: Invader – Species C Fundamental niche: Invader – Species D Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis New realized niche – Species A, Species B Realized niche: Invader – Species C Realized niche: Invader – Species D Resource axis #1 Resource axis #2

3)What makes a species invasive? a) Vacant Niche Hypothesis SUMMARY: Vacant niches May have some utility for tropical oceanic islands BUT Actual demonstration of “vacant” niche is nearly impossible Many potential invaders lack pollinators, symbionts, etc.