2011-09_Dive - EVOLUTION (11:704-486) - BIODIVERSITY SMOUSE...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
EVOLUTION (11:704-486) - BIODIVERSITY S MOUSE – SPRING 2011 1 B IODIVERSITY AND E VOLUTION Motivation: That there is an incredible variety of life on the planet is a trite statement, at this point in the course. The question is why? And there are other questions: Why is it that we have more diversity at the equator than at the poles? Why do we have more diversity in tropical rainforest than in the deserts? And how much has it changed over evolutionary time, and why? Ecological vs Evolutionary Measurements – There are two approaches to the biodiversity issue, one ecological, the other evolutionary. They are related but not the same. An ecologist is concerned with what is out there now, and how it changes in contemporary time, as a consequence of the ecological forces that are operative. An evolutionary biologist is concerned with what has happened over the last 3.5 billion years, and why (in some larger sense) it has. Ecological – An ecologist goes out to a pond, a lake, a forest inventory plot (a hectar or so), and simply counts all the different species within a certain group, say insects or fungi, or trees or orchids, or whatever. There are problems of finding everything, and the taxonomic challenge is terrifying – that’s a lot of taxa for one person to know, but it’s basically a counting exercise. One can compare the biodiversity of different places and situations. Evolutionary – A student of evolution has to be more indirect. Both the time and spatial coverage are much larger, so one ends up collecting records of the taxa that have been found from musea, herbaria, and published reports in several different literatures. The catalogue is always incomplete and imperfect, and there are several different taxonomic styles involved. Ecological Approaches – Let’s start with the ecological approach, because that is driven by its own set of interests. In a given locality, the species present are some subset of those available from the immediate region, providing the potential colonizers. That species pool is determined by the range of ecological opportunity in the region, as well as the history of that biota. Influential factors – The factors that can drive a species to local extinction are: (a) severe climatic events, (b) rapid changes in the habitat, (c) an overdose of predation, parasitism or disease, (d) competition, (e) loss of food or other resources, on which the organism depends, or (f) demographic randomness (in small populations). Wallace (1878) took the view that climatic evenness would promote species persistence, but later data don’t support that view very closely. In fact, a modicum of local disturbance is beneficial to biodiversity, because it allows the habitat to support species at different stages of ecological succession. Either total disruption or total stasis lead to reduced biodiversity.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/18/2011 for the course ECOLOGY 301 taught by Professor Staff during the Spring '11 term at Rutgers.

Page1 / 9

2011-09_Dive - EVOLUTION (11:704-486) - BIODIVERSITY SMOUSE...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online