PROBLEMS OF BIOLOGICAL SPECIES CONCEPT

1. Systematics PROBLEMS OF BIOLOGICAL SPECIES CONCEPT GHULAM JILANI HASHMI

2. Contents: • Species • Types of Species • Biological Species Concept(BSC) • Principles of BSC Application • Problems • Solutions

3. Species The most inclusive group of individuals that actually or potentially interbreed and can produce fertile off spring is called species.

4. Types of species concept • Evolutionary SC (EvSC) • Ecological SC (EcSC) • Cohesion SC (CSC) • Genotypic Cluster SC (GCSC) • Genealogical Species Concept (GSC)

5. Biological-Species Concept species are groups of interbreeding natural populations that are reproductively isolated from each other • Functions of Each Species • It forms a reproductive community i.e., the individuals of an animal species recognize each other as potential mates and seek each other for the purpose of reproduction. The species specific genetic programmers of every individual ensures intraspecific reproduction.

6. Conti… • It is an ecological unit regardless of the individuals composing it, interacts as a unit with other species with which it shares the environment. • It is also a genetically unit consisting of a large intercommunicating gene pool, whereas the individual is merely a temporary vessel holding a small portion of the contents of gene pool for a short period.

7. Criteria of application • Principles: • Asexual organisms form clusters similar to those in sexual, so SC must apply to asexualspecies. • We need to be able to compare species in asexual and sexual organisms, so SC must apply to sexual species. • Species are populations, so SC must be grounded in population/evolutionary genetic theory.

8. Conti… • If there were only one cluster, there would be no species, so SC must explain gaps as well as clusters. • SC must not allow gaps due to drift. • SC must define evolutionarily independent lineages; species must be independent arenas for mutation, selection, and drift. This requires that speciation events be completed and the species be reciprocally monophyletic

9. Problems: • 1.Fossil record: It is unidirectional concept dealing with only living species but not with extinct species. There are certain species which are in the fossilized form. We can not recognize them and it is difficult to place them in a single species. • 2. Biological species concept can only be applied in the case of a species which are found together in nature in a breeding condition both in time and space. • 3. This concept is not applicable to immature and old population of a species because they can not breed.

10. Conti… • 4. This concept can not be applied on the asexually reproducing species such as rotifers and aphids because they are parhenogenetic. • 5. In a laboratory condition, if allopatric groups in a controlled condition or brought together not only different species but also different genera can reproduce with each other. • 6. In natural conditions different species can inter breed but it happen rarely e.g. horse and donkey interbreed to produce mule. Similarly horse and zebra can interbreed. It does not mean that they can interbreed, so they are same species.

11. Solution: • First, it retains the element common to all concepts and definitions of species by adopting the general concept of species as separately evolving meta population lineages. • Second, it eliminates the conflicts among rival concepts by treating this property, existence as a separately evolving meta population lineage, as the only necessary property of species. The most inclusive group of individuals that actually or potentially interbreed and can produce fertile off spring.

12. THANKS