Heying lect 2-FTTS Fall 2004 (H3)1Species Concepts1. What is evolution?2. What is a species?3. Three species concepts to consider4. In-class workshop on species concepts1. What is evolution?…And, it is the single, unifying theory of biology. As famous biologist TheodosiusDobzhansky said: "Nothing in biology makes sense except in the light of evolution.”Evolution’s two main branchesIn 1859, Darwin proposed natural selection as a unifying principle to explain two things:the origin of species, and the adaptation of organisms to their environment.• Systematics is the study of speciation (the origin of species), a.k.a. macroevolution.• Evolutionary ecology is the study of the adaptation of organisms to theirenvironment, a.k.a. microevolution. This includes the study of interactions withmembers of their own and other species (the biotic environment) as well as thephysical (abiotic) environment.What do the prefixes macro- and micro- refer to…?Hierarchical classificationOrganisms are grouped by increasing similarity due to common ancestry (unobviousplural forms are in parentheses):Kingdom Phylum (phyla) Class Order Family: typically ends in -eae Genus (genera) Species (species)Some basic rules of namesThe scientific (or Latin) name of a species includes the genus and species, in that order.Both words are italicized, the genus name is capitalized, the species name is not. (For agood rules summary, read Pielou chapter 2.)E.g.: Homo sapiens. Acer macrophyllum. Rhyacotriton olympicus.Heying lect 2-FTTS Fall 2004 (H3)2After a reference has been made to a particular species, the genus may be abbreviated.E.g. R. olympicus.The scientific names of species change sometimes, but they are more reliable than“common names,” because in different parts of a region, more than one species may becalled by the same common name. Common names for the organisms listed above are…?2. What is a species?Are species purely a human construct, used by us as a necessary semantic tool so that wecan discuss the diversity that exists on this planet? Or are species a “real” thing? That is,do “species” exist as entities apart from human involvement? Put another way: When alineage evolves in a forest, and there’s nobody there to name it — is it a new species?3. Species ConceptsThere are almost as many species concepts as there are people who have tried to definespecies. The problem is, none of them work for all evolved life forms. A few of the mostwidely used species concepts include:• Morphological Species Concept• Biological Species Concept• Evolutionary Species ConceptMorphological Species ConceptMorphological similarity (or dissimilarity) is the sole criterion for determining species.This concept involves subjectivity in the definition through the degree of difference.Different species are organisms that look different.Some problems with the morphological species concept include:Biological Species Concept“Groups of actually or potentially interbreeding natural populations which arereproductively isolated from other such groups" (Mayr ‘40).Criteria include: interbreeding among conspecific populations and reproductiveisolation from non-conspecific populations. Morphological distinctness is not a criterion.This is the dominant species concept in evolutionary literature today, at least amongzoologists. The biological species concept posits that a species is a reproductivecommunity, an ecological unit (interacting as a unit with other members of the sameHeying lect 2-FTTS Fall 2004 (H3)3species), and a genetic unit (individuals are seen as temporary vessels that contain aportion of the species’ gene pool).Problems:Evolutionary Species ConceptAn evolutionary species "is a single lineage of ancestor-descendant populations oforganisms which maintains its identity from other such lineages [in space and time] andwhich has its own evolutionary tendencies and historical fate” (Wiley 1981).Developed (by G.G. Simpson) as a response to the biological species concept, whichcan not be applied to asexual organisms or extinct species. In theory, the evolutionaryspecies concept deals with these problems.Problems:Does our inability to fix upon a single, always applicable species concept put the conceptof species at risk?4. In-class workshopAs a group, pick a species concept and defend it. You should address at least thefollowing points:1. Does this species concept have wide applicability? If not, on what basis have youchosen it?2. Are there any types of organisms that are excluded by your definition? How do youjustify excluding these organisms?3. What are the problems with your species concept?4. Are species delineated by your species concept likely to be replicated by theknowledge of local people? That is, will it allow you to come up with the same wayof classifying the natural world as do the people who rely on that world for theirlivelihoods?5. Would you feel comfortable handing this species concept over to a legislator whowould use it to make policy