Lecture 11- Populations/Species. Chapters 18 & 19 - Population growth and regulation - Focus on many local/regional examples

Transcription

1 Lecture 11- Populations/Species Chapters 18 & 19 - Population growth and regulation - Focus on many local/regional examples

2 Why Study Birds? From DNT

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6 Causes of the Decline Temperate? Tropical?

7 Potential causes for trends Changes in forest area, types, or configurations on the breeding grounds Increased predation rates on breeding grounds Events on the wintering grounds or migratory areas Pollution, disease, bird feeding, etc. Climate change

8 Importance of Tropical Habitats for Neotropical Migrants? What happens to their stopover and winter habitats is as important to their survival as what happens on their breeding areas. - Rappole (1995, p. 151) Recent concern that declines among many North American birds stem primarily from habitat loss on Neotropical winter grounds is poorly substantiated, and this is unlikely for most species. - Stotz et al. (1996, p. 65)

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10 itat the most critical sue for populations!! he main threat humans se to the diversity of life is r destruction of natural bitat (Primack 2002, p. 4) e cumulative impacts of > illion people are ormous primarily the pacts of where people live d what they consume

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23 Homework Google Why are the birds disappearing?

24 Piping Plover

25 Population Analysis Population analysis is concerned with the numerical attributes of a population - numbers, sex ratio, rate of increase and so on - together with the properties of the animals and the properties of the environment that determine these values. Graeme Caughley, Analysis of Vertebrate Populations

26 Population Regulation

27 Definitions r m - intrinsic rate of increase, exponential rate of increase of a population where: stable age distribution no resource is in short supply K - carrying capacity; maximum number of individuals supported

28 Logistic Growth Model Relates population density to: Survival Fecundity Carrying capacity of environment (K) dn dt = r m N (1 N K )

29 N t Year (t) r = 0.5 K = 250

30 N Year (t) r = 0.1 K = 250

31 Limitations of Logistic Equation Applicable only when limiting resource is being produced at rate independent of number of animals using it Most wildlife populations do not fit this assumption, BUT Still provides general form for discussing population regulation/growth

32 Limitations (cont) Logistic equation assumes equilibrium state (i.e., stable state) Recent research suggests that many populations exhibit CHAOS unpredictable, but with repeatable patterns

33 Factors Regulating Density Population Density intra- & interspecific permanent residents Natural Factors Habitat Climate Food resources Disease

34 Age Age Distributions Increasing Stable Decreasing Frequency

35 Dispersal Movement of individuals between local populations (immigration / emigration) Reduces genetic inbreeding Colonizes new sites

36 What Processes Generate the Patterns of Distribution and Abundance We Observe? Why are there so many species of birds? Why are there so few species of birds? Why are species found where they are? Why are some species rare and some species abundant? These are some of the key questions in the mystery of life fascinating.

37 Abundance vs Distribution 1.2 Proportion of Sites Occupied Mean Abundance (log-transformed)

38 Review of major paths of speciation 1. Allopatric model 2. Dispersalist model 3. Sympatric model including hybridization

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40 Geological Time Scale Yrs BP Periods Epochs Life Forms Quaternary Recent Pleistocene Human civilization oic 2 Tertiary Pliocene Age of Mammals Miocene, etc. 65 Birds Evolved Here 130 Cretaceous Dinosaurs, 1 st angiosperms oic 160 Jurassic Dinosaurs & other reptiles 210 Triassic Reptiles including thecodonts

41 Early Jurassic Late Jurassic From Brown and Lomolino (1998)

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44 - Now Fig 19-7

45 There are at least nine discrete populations or types of Red Crossbill

46 Speciation by hybridization Peter Grant (Princeton University) - paper in Science 256: , had completed many detailed studies of Darwin s finches on the Galapagos Found hybridization among the finches to be common Found hybrids often to be more fit than parental species phenotypes - e.g., between Geospiza fortis and fuliginosa; Galapagos climate fluctuates widely and, hence, a balance of species and hybrids i likely to be maintained under highly varying environmental conditions; Noted that about 10 % of all bird species are known to hybridize - produces novel combinations of genes and thereby creating favorable genetic conditions for rapid and major evolutionary change to occur Recent work (Science 283: 1255, 1999) - analysis of 16 microsatellite markers on genomic DNA from Darwin finches blood - confirmed the speciation process in exactly the correct time scale - ancestral finch is pointy-beaked warbler finch

47 Sibley 2000

48 Now Fig. 19-3

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