Chapter 53 Community Ecology Community all of the organisms living together in a place Similar communities differ in two main ways 1 Species richness 2 Relative abundance Niche Habitat is a place Niche is a pattern of living Fundamental Niche entire niche that an entire species they are capable of using Realized Niche Why the difference 1 Species Interact affects distribution and abundance of the species 2 3 Ongoing Interactions agents of natural selection Interspecies Interactions 1 Competition 2 Predation including hebivory 3 Symbiosis including parasitism Competition Interspecific Competition Principle of Competitive Exclusion o If two species are competing for the same limited resource efficient user wins and other leaves o No two species with the same niche can coexist when resources are limited o Over time can lead to Resource partitioning niche differentiation o This may lead to Character displacement Predation Carnivores eat animals Herbivores eat plants What about eating bacteria fungi protists form follows function Symbiosis Mutualism Commensalism N Parasitism o External Parasites Coevolution evolution of two or more interdependent species each adapting to changes in the other o Internal Parasites o Brook Parasites o Pathogens Defense Mechanisms book categorizes as constitutive or inducible 1 Coloration a Mullerian Mimics look dangerous 2 Chemical venom toxins yucky stuff 3 Structural porcupine quils 4 Behavioral 5 Cooperation 6 Mimicry Predation reduces competition Parasitism may counter competition o Anolis Lizards Rainforest Relationships Frugivorous bats seed dispersal jungle succession Hectare 10 000 square meters 100 ha 1km2 Forest Edge Edge created Natural regeneration permitted via succession Succession prevented edge affects Final Paper and Related Letter Fruit Bat Biology Fruit bats roots in hollow trees logging removes roots This disturbance reduces pollination service as well as seed dispersal Seed dispersal in forest is a critical factor Birds avoid open areas Bats are the primary dispersers for tropical plants they are nocturnal so open areas are safe under the cover of darkness helping reseed the forest Hypothesis Artificial roosts could attract frugivorous bats to disturbed areas with limited roosts This will increase seed rain and improve secondary succession Applied Research solve the problem to reseed the forest Study Site Highly fragmented forest o Regularly disturbed o Surrounded by pasture areas Old continuous forest Nest Roost Boxes Sawdust concrete slabs Single opening in bottom netting on ceilings Cheap and durable Methods Survey both areas determine roost densities group sizes species in a roost Artificial roosts places in both habitats but in the shade Captures bats with nets at dusk to ID species Study fecal samples to ID seeds fruits flower parts bug parts Install fecal collection stations below some next boxes Seed traps woods frames 1m2 with fine nets to catch seeds Approximately 23 per roost site arranged in a grid Control Seed Traps Grid of frams 50m from roost Pasture lands away from forest edges Seed traps checked and cleaned at dawn and dusk 4 sites inside forest areas 1 natural roost site in old forest All roots were colonized within a few weeks Most were permanently colonized Ten bat species were observed group sizes per species Bat species diversity was greater in forest than disturbed areas o 44 forest vs 22 disturbed Bats Fruits Rainforest Succession Why no roost free seed collection Their controls were 50m from roost dispersal can also be due to birds wind primates Why focus on feces only not larger seeds Seed number type per sample in 3 bat species of genus Carollia Comparable numbers and types between two areas Table 3 53 of plant species ID in feces were early successional plants 56 ID in seed rain were shrubs Tables 1 3 Together Bat diversity was lower in disturbed areas Diet diversity was higher in disturbed areas Strong preference for early succession species Figure 1 Seed Rain Data Seed rain greater at roost sites compared to controls Seed rain higher in forest than open pastures Numbers of bats in roosts correlated with seed rain around roosts but varied a lot Conclusions natural roots available There was very fast acceptance of artificial roosts indicating there are limited numbers of Yes instillation of bat roosts can aid reforestation efforts by increasing seed dispersal The distribution of early succession plant seeds may aid in recruitment of later succession plants Published Papers are not the End of the Story Generally a paper is the next step in an ongoing discussion o Follow up studies by same group o Parallel studies by other group who come to same conclusions o Parallel studies by other groups who come to different conclusions o Letters to journal o Rebuttal often offered as courtesy and to promote healthy discussion Letter Topic Placement of Roosts Seed Rain Seed Survivability Topic Placement of Roosts Seed Rain Seed Survivability Concern by Holl Only in areas with dense trees none in the open No data showing seed rain in open pastures or if that would cause regeneration Due to predation and competition even seed that reach abandoned pastures are unlikely to survive Rebuttal Rebuttal by Authors Roosts in the open would get too hot and primary goal of experiment was to attract seed dispersers Increased bat presence will undoubtedly increase seed rain but further study is needed to determine how much Pioneer shrubs are R strategists so low survivability of seeds is expected Primary Producers Plants Primary Consumers Herbivore Secondary Consumers Carnivore Tertiary Consumers Carnivore Quaternary Consumers Carnivore Ways to Manage Complexity Focus on one individual which may occupy many places in the web Focus on functional groups Focus on isolated portions of the food web As the number of trophic levels between individual and primary source Trend size decreases in number Why is there an upper limit on number or trophic levels Two Theories Energetic Hypothesis o The Ten s Rule Dynamic Stability Hypothesis Two Theories H herbivore hand and depleting the system a P H V N resources N you regulate the population a N V H P A combination of the two is probably the reality Disturbance and Community Structure Two Views 1 Top Down focus is on predators P preventing those below them from getting out of 2 Bottom Up focus is on the resources primary producers V rely on Regulate the 1 Stability the tendency of a community
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