Biological Interactions. Stenophagy: common in plant-eating insects. Biological Interactions. Biological Interactions. Stenophagy: examples in mammals

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1 Stenophagy: common in plant-eating insects 1 2 Slide courtesy C. Still Stenophagy: examples in mammals Giant panda (Ailuropoda melanoleuca) Koala (Phascolartus cinereus) Abert s squirrel (Sciurus aberti) Asia/China/photo1084.htm Free/Koala-Wallpapers.htm enlarged.asp?imageid=

2 Lotka-Volterra model Classic study of Canada lynx (Lynx canadensis), snowshoe hare (Lepus americanus) Note: more recent studies show the influence of plant-hare cycles w/o lynx 4 So, any evidence of predator controls on prey distribution? Yes, under certain circumstances Artificial exclusion experiments: Prey species before: 15 Prey species after: 8 Smith and Smith, Predator controls on prey distribution? invasive generalist predator (euryphagous) Figure 4.2, MacDonald 6 Slide courtesy C. Still 2

3 Competition Allelopathy: chemical warfare Casuarina equisetifolia litter completely suppresses germination of understory plants as shown here despite the relative openess of the canopy and ample rainfall (>120 cm/ yr) at the location en.wikipedia.org/wiki/allelopathy Toxins inhibit seed germination 7 Allelopathy or competition for resources (nutrients)? Scott et al., Competition Interspecific competition controlling species distributions similar, closely related species similar ecological niches no range overlap Suggestion: interspecific competition controlling species distributions 9 Slide courtesy C. Still 3

4 Competition Caution: correlation is not causation Sharp range limits do not always mean competition is the reason Other factors may be at work: 10 Competition Interspecific competition controlling species distributions less aggressive, require less and resources: outcompetes at higher, forested elevations where there are plenty of resources and it is more difficult to defend territories more aggressive, defend territory better, but more energy used and resources required But, habitat (% forest cover) also controls distributions 11 Evidence of competition controlling morphological traits => ability of species to expand/shift habitat or prey to avoid competition? Lomolino et al

5 Competition Invasive species are, by definition, superior competitors More on this later in the semester Cheatgrass (Bromus tectorum) Slide courtesy C. Still Pollination symbiosis example Obligate mutualism 15 5

6 Symbiotic mutualism example Clark s nutcracker (Nucifraga columbiana) 16 Five-needle pines large (nutritious), wingless (not dispersed by wind) seeds high fat, high-energy food source Whitebark pine (Pinus albicaulis) Limber pine (Pinus flexilis) esp.cr.usgs.gov/data/atlas/little/ 17 Caches thousands of pine seeds each year Photo by Michael G. Shepherd Has a tremendous memory: can remember where to find most of the seeds it hides 6 months later, under 3 of snow en.wikipedia.org/wiki/clark%27s_nutcracker 18 6

7 Caches by nutcracker (and squirrels) result in multiple stems in close proximity ( cache-mates ) Biology+Faculty/Dr.+Diana+Tomback.htm 19 Whitebark pine is a keystone species Reliance by animal species Key is the mutualistic relationship with the nutcracker 20 Symbiosis: 2. Commensalism Clownfish are impervious to anenome s poison => protection for clownfish Some clownfish are anenome-specific Clownfish may attract predators, which serve as prey for anemone => mutualism

8 Symbiosis: 3. Parasitism 22 Example of controls of parasites on host geographic distribution: invasive species 30 species of Hawaiian honeycreepers (Drepanididae) endemic to Hawaiian islands on Oahu, 6 species extinct by 1900 declines in lower elevation species but not higher elevation tied to introduction of Culex mosquitoes in 1820s by Europeans carriers of avian malaria lack of evolution in presence of mosquitoes => lack of defense in honeycreepers limited in elevation extent by temperature 23 Symbiosis: 4. Mimicry Müllerian mimicry Smith and Smith,

9 Symbiosis: 4. Mimicry Batesian mimicry Smith and Smith, Example of combined physical, biological controls Smith and Smith, Biological interactions and gradients Method of determining impact of competition: examine abundance of different species along environmental gradient Danger: inferred, not determined 27 9

10 Species distributions along an environmental gradient in the Sierra Nevada Two possibilities for range limits 1. environmental gradient 2. competition 3-needle pines Question 1: P. sabiniana at greatest growth rate and density at (A). Thus, which of above two possibilities defines upper limit of P. sabiana range? (A) Question 2: Which species occur the same niches? 5-needle pines Lomolino et al., Biological interactions and niches Additional concepts: when species face significant competition, they will have a more restricted or fragmented distribution than when no competition summer: wide range of habitats winter: limited to coastal sites and islands formed by mangroves Where is the yellow warbler s competition greatest? 29 10