Biogeog, Williams et al. 2007

Analog communities

Communities that are compositionally unlike any found today

Where are novel climates expected to arise by 2100?

Primarily in tropical and subtropical regions

What is a key characteristic of future novel climates?

They are warmer than modern climates

What is uniformitarianism?

The principle that the present is the key to the past

What appears to drive the formation and dissolution of no-analog communities?

Climate change

How does moving further from the present affect ecological models?

The present becomes a less adequate model for past and future system behaviour

What happened to terrestrial species ranges and abundances during the last deglaciation?

They shifted dramatically

Did communities migrate as intact units during climate change?

No, species shifted individually

What drove Quaternary vegetation dynamics?

Orbitally controlled glacial-interglacial climate cycles

How can no-analog communities be explained conceptually?

Through a niche-based conceptual framework

What is a fundamental niche?

The environmental envelope within which a species maintains viable populations

How can climate change allow species to expand their niche?

New climate combinations may allow species to occupy previously unrealized portions of their fundamental niche

Why do no-analog communities form according to niche theory?

Because climates develop that lack modern counterparts

In the niche framework, what remains static and what changes?

Species niches remain static while the environment changes

Is the assumption of static niches always correct?

No

What suggests a common atmospheric driver for Alaska and eastern North American no-analog communities?

Their similar timing despite separation by ice sheets

What are no-analog communities?

Communities consisting of species combinations not found together today

How are temperate tree taxa in eastern North America explained in highly seasonal Late Glacial climates?

They occupied climates at the edge of the current North American climate envelope

What do paleoecologists study?

Ecosystems from the past

What do global-change ecologists study?

Future ecosystems under climate change

Is no-analog an ecological or evolutionary phenomenon?

It is an ecological phenomenon

How are species reorganized in no-analog communities?

Existing species are reshuffled into new combinations rather than evolving anew

How does climate affect species distributions?

Species shift individually rather than as intact communities

What are Gleason’s ideas about communities?

Species respond independently to climate shifts rather than migrating as unified ecosystems

What does the fundamental niche concept suggest about modern climates?

Not all possible climate combinations exist today, so some niches are unrealized

How stable are species niches over short geological timescales?

They are mostly stable

What evidence documents Late Glacial no-analog communities in North America?

Fossil pollen and other fossil evidence from plants, mammals, beetles, mollusks, and marine microfossils

What are characteristics of Late Glacial no-analog communities?

High abundance of unusual species, coexistence of species now geographically separated, and low abundance of common modern species

Which species pair coexisted in Late Glacial no-analog communities despite being separated today?

Spruce and ash

Which currently common species had low abundance in Late Glacial no-analog communities?

Pine

Where were no-analog communities especially common in North America?

Alaska and eastern interior North America

What is Fraxinus?

An ash tree genus

Where do modern ash trees occur relative to today’s climate envelope?

Near the edge of the climate envelope

What does the ash tree niche suggest about past climates?

Their niche extends into climates more seasonal than any modern climate

What are other possible causes of no-analog communities besides climate?

Lower atmospheric CO2, megaherbivores, and low human populations

What organization provides future climate modelling scenarios?

The IPCC

What is the A2 emissions scenario?

A high-emissions scenario where CO2 reaches about 850 ppm by 2100

What is the B1 emissions scenario?

A lower-emissions scenario where CO2 stabilizes near 550 ppm

Which regions are most at risk of developing novel climates under the A2 scenario?

Amazon Basin, southeastern US, Sahara and Sahel, Arabian Peninsula, India, southeast China, Indo-Pacific, and northern Australia

Why are tropical regions especially vulnerable to novel climates?

They are already warm, so additional warming pushes them outside modern climate conditions

Besides temperature, what other climate factor is important in creating novel climates?

Precipitation

Why might species fail to occupy future novel climates?

They may not migrate fast enough naturally

What are regionally novel climates?

Climates similar to past no-analog climates that species cannot reach quickly enough

Why may current ecological models fail under future climate change?

They are based on modern climate conditions and may not predict responses to entirely new climates

What is a likely consequence of continued global warming?

The creation of more no-analog ecosystems