ecology claude final

Humans are primarily responsible for most of climate warming.
Main sources: greenhouse gases (CO₂ & methane) from burning fossil fuels and livestock/land use.

Approximately 1.4 – 5.8°C increase in global temperatures by 2100.

Tree rings, ice cores, corals, and direct measurements (Fig. 11.1).
The graph shows Medieval Warm Period → Little Ice Age → Industrial Revolution spike.

Ranges shift toward poles / higher latitudes. Study: >100 bird species in Great Britain over 30 yrs showed a ~2 km/yr northward shift; similar pattern in 55 N. American bird species since the 1960s.

Shifts are upslope. Temperature changes faster with elevation than latitude. Examples: amphibians in Madagascar moved 65–400m upslope; small mammals in Yosemite shifted upslope 500m during past century with 0.10–0.39°C warming.

They are more sensitive to shifting because lower range limits move up more than upper limits → range contraction. Lower limit of range moves up ~3.7°C worth, more than upper limit.

Shorebirds feed on mudflats, which will flood. In Florida, sea-level rise increases probability of extinction of snow plovers.

Sea turtles use beaches for breeding; those beaches will be reduced in size with sea-level rise.

Spring has advanced by 1–2 days per decade in the Northern Hemisphere.

The flycatcher breeds in Europe but winters in Africa. Peak food abundance (caterpillars) advanced 7.5 days/decade, but egg-laying advanced only 5 days → mismatch between food peak and chick hatching.

Emergence delayed 0.47 days/yr due to frequency of late winter storms → reduces reproductive rates → population declines. Note: migration timing is fixed by photoperiod, NOT temperature.

Species with high dispersal rates and broad habitat tolerances/preferences are favored.

Body size is increasing in response to climate variability; larger-sized buffered individuals can better handle temperature extremes.

Black morphs are adapted to warmer temps. There has been a decrease of striped morphs by ~60% over this century as temperatures warm.

Polar bears depend on sea ice for hunting seals. Ice breaks up earlier each year → reduces hunting success → reduces winter fat → reduces survival & reproduction.

Warming increases cloud formation elevation → decline in mist → decline in humidity → population declines & increased human conflict with amphibians over non-water sources.

Phytoplankton & zooplankton blooms advance in time at different rates with warming → lack of synchrony across trophic levels.

Pines produce seeds that support birds, rodents, and bears. Warming → reduction in range of pines → limits food availability → causes a shift in prey base.

Larvae of moths hatch earlier, before oak leaves open → mismatch in timing disrupts food chain.

1. Physical constraints to range expansion (mountains not tall enough for elevation shift).
2. Habitat loss can exacerbate shifts (no other place to go).
3. Biotic effects – species become more vulnerable to biotic factors (e.g., chytrid fungus in amphibians).

Determine how high tides during warm periods affect avian predation; elevated water levels are analogous to future sea-level rise caused by climate change.

Used water level loggers to track changes in water depth across study sites; conducted surveys for raptors & ardeids (egrets/herons) abundance and foraging behavior.

1. More raptors observed during high tides than low.
2. Most prey strikes occurred during high tides (lots of variation across sites).
3. Predation pressure maximized at mid-range water levels for raptors and at higher water levels for ardeids.

High tide flooding (up to 1.4m) is analogous to sea-level rise projections (up to 3.0m). Increased predation with rising water levels could have community-level impacts on protected species and the prey base. Understanding predator-prey relationships under climate change is critical.

For a large, randomly mating population, in the absence of evolution, genotype frequencies do NOT change between generations. Conditions: p + q = 1; p² + 2pq + q² = 1. Allows prediction of genotype frequencies given allele frequencies.

Changes in allele frequencies over time due to: natural selection, mutation, genetic drift, gene flow.

Fitness = success at surviving and reproducing → mating success + fecundity (# of offspring). It is the mechanism by which phenotypes allow some individuals to survive and reproduce more effectively.

R = S × h². R = change in average trait value from one generation to the next. S = selection differential (measures strength of selection; difference between trait values of reproductive individuals vs. population mean). h² = narrow-sense heritability.

Trophy hunting targets bigger, older males → results in early onset of reproduction at expense of growth & survival → decline in body size and horn length over time.

Selection on size (minimum size limit) intended to allow smaller fish to survive. But small fish become reproductive at younger ages and at smaller body sizes → decline in body size & born length over time.

Lizards transplanted to experimental islands; lizard density manipulated (competition) or predators controlled → variation in density (competition) caused selection on body size, limb length, and endurance — not predation.

Decline in heterozygosity → decline in fitness when deleterious recessive alleles occur in populations.
Occurs when populations become small → increases inbreeding. Reduces fecundity & increases mortality.

Average # of individs in a population that contribute genes to the next generation. Generally smaller than actual pop. size. Small Nₑ → (1) increase in genetic drift, (2) more mating between close relatives → exposes lethal recessive alleles.

Need effective pop. size of at least 50 to avoid inbreeding depression. Need minimum of 500 to maintain long-term evolutionary potential. Rule of thumb assumed for small/endangered populations.

Habitat patches are destroyedemoved → isolation of small numbers of patches → 'habitat islands' → result in small, isolated populations.

A network of subdivided populations with growth.
Proportion of occupied patches: P = 1 − (e/c), where e = probability of extinction, c = probability of colonization. High extinction risk if e > c.

Sources: habitat patches that sustain positive population growth & supply 'sinks'.
Sinks: patches that experience high mortality. Sources balance extinction with high colonization rates.

Corridors create connectivity/pathways between habitat patches to facilitate dispersal & gene flow.
Factors: (1) biology & ecology of species; (2) habitat suitability; (3) location in landscape; (4) type of disturbance; (5) suitability of surrounding area.

Advantages: (1) increase immigration → more species richness, lower extinction prob., more gene flow; (2) increase foraging area; (3) escape cover from predators; (4) creates 'greenbelt'. Disadvantages: (1) spread of disease/pests/invasive species; (2) facilitates spread of fire; (3) increases predator/poacher access to prey; (4) cost & land use conflicts.

Examine roles of population structure & landscape features in shaping gene flow in the salt marsh harvest mouse (SMHM) — especially critical given habitat destruction & fragmentation.

Trapped & released mice; collected hair samples for DNA analysis; used PCR to amplify microsatellites; computed population genetics statistics: heterozygosity, Fst, effective population size (Nₑ).

Not lots of differentiation among populations in northern marshes. But Ryer Island pop. is distinct due to isolation & small size (= genetic drift & reduction of genetic diversity). Nₑ is largest in northern marshes, lowest in Ryer Island.

Water bodies & land elevation are most important for restricting gene flow & animal movement in Suisun Marsh SMHM populations. Good connectivity due to network of managed marshes that provide 'corridors'. Populations separated by open water & by >2 meters elevation create barriers & genetic differentiation.

1. Ryer Island represents a distinct population segment under the Endangered Species Act. 2. Each population of SMHM should be considered separately for delisting & management actions (delisting = removing species from the endangered species list).