BIOL General Ecology Dr. Fisher

Ecology Defined Ecology is the study of the relationship between an organism and its environment Environment includes both the chemical / physical and biological components of an organism’s surroundings Relationship includes an organism’s interaction with its physical environment and other organisms

Ecology – term coined by Ernst Haeckel in 1866 Same root as economy: oikos = “house” (Greek) Haeckel conceptualized ecology as the “economy of nature”

“…in a word, ecology is the study of all those complex interrelationships referred to by Darwin as the conditions of the struggle for existence.”

Evolution and Ecology Natural selection and evolution form the foundation of ecology Evolutionary theory provides a framework for posing and testing ecological hypotheses

Ecology can be studied at many levels, from the individual to the biosphere environmental relationships can be studied at multiple spatial and temporal scales

INDIVIDUAL How do bobtail squid avoid predation?

POPULATION How does bobtail squid population size vary from year to year? What factors control population size?

INTERACTIONS Is the Vibrio-squid symbiosis beneficial to both species?

COMMUNITY How does exposure to waves affect the species composition of coral reefs?

ECOSYSTEM How does human settlement affect nutrient availability in coral reef ecosystems?

LANDSCAPE How does island age influence the composition of squid species within the Hawaiian archipelago?

REGION How do currents and ocean temperature affect the distribution of squid species throughout the Pacific basin?

BIOSPHERE What role does ocean temperature play in the global carbon cycle?

Ecologists use the scientific method

How can nutrient poor soils of rain forests support such abundant life? hypothesis: a majority of the nutrients / energy are stored in the rainforest canopy test: observation and direct measurement of nutrient levels in epiphyte mats

High nutrient content in epiphyte mats true in both tropical and temperate rainforests

rainforest trees grow adventitious roots from branches to absorb nutrients from epiphyte mats

Models simplification of reality based on our understanding of nature allow us to predict outcomes, estimate values can be used to generate hypotheses or to test hypotheses

Model example: using allele frequencies to estimate past population size

Mullerian Mimicry Heliconius erato (above), and H. melpomene (below), a pair of Müllerian mimics from different areas of Ecuador and Northern Peru.

In what context did this mimicry evolve? Hypothesis 1: both species were split up into many isolated populations during the last glacial period, and divergence / co- evolution of wing patterns occurred simultaneously in each species. Hypothesis 2: One of the Heliconius species diversified first (the “model” species); then a less abundant second species later evolved to mimic the wing patterns of the model species.

In what context did this mimicry evolve? Hypothesis 1 – Prediction: past population sizes, age of different wing pattern races are similar for both species Hypothesis 2 – Prediction: One of the Heliconius species had a larger past population size, and wing pattern races of this species have occupied geographic areas since before the last glacial period. The other species had a small population size in the past and underwent wing pattern diversification more recently.

Methods / Modeling researchers sequenced two genes from multiple co-occurring H. erato and melpomene races with matching wing patterns using a model of gene sequence evolution and how frequencies of gene mutations are affected by demographic factors, researchers estimated past effective population sizes and the ages of the different wing pattern races.

Results Small populations of H. melpomene have diverged to mimic H. erato populations at various times since the last glacial maximum H. erato had very large population sizes in the past, and had occupied geographic areas much longer than H. melpomene.

SUMMARY Ecology can be studied at multiple spatial and temporal scales: – individual – population – community – ecosystem – landscape – region – biosphere Ecology is the study of the relationship between an organism and its environment

SUMMARY Ecological studies follow the scientific method Ecology is an integrated and multidisciplinary field – uses tools from population genetics, chemistry, mathematics, physiology, geology, etc. Ecologists generate and test hypotheses using several different approaches – fieldwork – laboratory experiments – modeling / simulations